Do fish feel pain?

Fishing is cruel

Do fish feel pain?

Fishing is cruel

Fish feel pain when hooked, with pain sensitivity comparable to humans. They have nerve receptors that detect painful events, which then send pain signals to higher brain areas.

"Angling", "recreational fishing", "sport fishing", "big-game fishing", and "fishermen" are all terms used to describe the practice of hooking and dragging fish from the water for fun. There are probably about 118 million of them worldwide.(Arlinghaus)

Fishermen for a long time justified their "sport" by claiming that fish do not feel pain, therefore, they reasoned, tricking a fish into biting into a hook was harmless.

However, the scientific consensus now is that fish feel pain. They also suffer stress, begin to suffocate, are wounded, and may not survive the experience, with fishermen oblivious of the trauma caused. Fish suffer in silence, unable to scream, or otherwise signal their distress.

When being hooked, fish instinctively fight to stay in water. Tournaments are the greatest risk to them, as they may be repeatedly caught in the same day. As many as half of the fish may die.(Muoneke). Catch and release fishing is cruel.

cycle of catch and release

Whether inland or at sea, when a fish is "played", the line may break, leaving the hook embedded with the line attached. Sport fishing is cruel to the fish.

Injury caused by hooks

Deep hooking is where the hook penetrates further into the body. This can wreak havoc, lodging in gills, throats, heart, lungs, liver, stomach, oesophagus, eyes, and brain cavities.

In a study, The University of Maryland found that deep-hooking caused a third of the fish to die. The majority had major damage to the heart, stomach or liver.(Reiss,1)
They investigated complaints of dead and floating striped bass near fishing areas, and discovered fishing tackle left in the bodies of many fish.(Lukacovic,1)(Lukacovic,2)

Single hooks penetrate fish deeper, treble hooks entangle in gills, and barbed hooks on lures impale the oesophagus and gill arches. Fish hooked in vital organs usually die. A study found that nearly half of the salmon that died were hooked in the gut, and a quarter in the oesophagus. The overall death rate was 75%. Fishermen often say that hooks left in fish do not matter, as the hooks work their way out, or cause no harm. This is a self-deluding myth. A study with salmon found that over half of the fish died when hooks were left in place.(Muoneke)

fine line

Scientists at an American Fisheries Society Symposium reported their findings on deep-hooking of sailfish, caught off Guatemala and Florida. Nearly half of them had hooks lodged in their mouth, throat, gill arch, oesophagus, pharynx, or stomach. Several fish were hooked in the eye or eye socket. Hooks also penetrated the brain cavity.(Prince)

In another study, with bluefin tuna, one fish had a hook protruding through the stomach. The exposed hook point ripped the abdominal cavity, causing internal bleeding. Another tuna had a hook lodged between two gill arches in the throat, resulting in extensive bleeding from gill filament damage. Hooks damaged livers, and large hooks embedded in the jaws led to scraping of facial tissue. Smaller tuna did not easily swallow the larger hooks, but could still experience extensive damage to the gut, and eye socket, causing blindness, thereby impacting upon feeding and potentially causing death.(Skomal,1)

Fish learn to remember painful situations

Fish have demonstrated that they remember the circumstances of painful experiences and will afterwards seek to avoid the same situation. Fishing hurts fish.

Can fish feel pain when hooked? Dutch researchers used anglers for three days to fish for pike, which had never been fished before, with live bait or spinner hooks. The fish were then tagged and returned to the water. It was then found that pike previously only hooked once by a spinner, rarely took it again, and avoided spinners for the remaining five days.(Beukema,1)

spinner used to catch fish
The pike were fished again the next Summer, together with unfished carp. Individual fish, and then the whole population of the two pools learned, and then remembered, that the spinner was to be avoided. This memory lasted for at least one year.
Similar results were found with carp. This time, carp were able to remember their terrifying experience one year later, and, as with the pike, they were able to learn from the unfortunate experience of other previously hooked carp.(Beukema,2)

pike and perch learned to avoid fish hooks
Sticklebacks receive some protection from predator fish through their sharp spines. In 1957 at Oxford University, researchers found pike and perch initially snapped up, but then rejected, sticklebacks. Within a few experiences, the pike and perch learned to avoid the sticklebacks and the pain from the spines, altogether. It was found that when spines were removed from sticklebacks, their protection disappeared.(Hoogland)
fish avoid stickback spines


Most fishermen believe that the fish that they release swim away unaffected. But many fish will suffer and die, sometimes several hours later. Studies have found that a third, half, or even more fish can die at a fishing site. Catch and release is not humane.

After exhaustion brought on by fighting against being pulled out of the water, only one minute in the air caused in trout severe lactic acid imbalance. The fisherman, satisfied with himself, may be blissfully unaware that the fish’s life is endangered during the 12 hours that follow.(Ferguson)

fishing deliberate cruelty

Sport fishing is cruel. Damage by hooks, fatigue, and sometimes excessive internal pressure when the fish is brought to the surface, all contribute to loss of life. However, the mere trauma of capture, even for short periods, can herald death.(Pelletier)

A wide review of research into fish deaths at the hands of fishermen was made by Muoneke and Childress in 1994. They collected data from fisheries management agencies in all American states, the American government, all Canadian provinces, and a number of academic and research institutions. They found, on many occasions, shockingly high death rates. Most deaths occurred within 24 hours of the fish’s impalement on a hook. The percentage of deaths included: 64% Alaska salmonids (these include salmon and trout), 60% yellow bass caught on unattended bait, 30% tournaments, 77% black crappies in Texas, 56% spotted seatrout, and 45% for red drum.(Muoneke)

High numbers of recreational fishermen equate to high numbers of fish deaths around the world. There are then fewer fish which can reproduce, with abnormal changes in the population structure, and loss of genetic diversity.

The depth of water that fish are taken from affects their chance of death. A study found that a third of rainbow trout died when only taken at 1 to 3 metres, with this rising to half at 6 metres. Three-quarters of black crappies, when caught between 6 and 16 metres died. Eyes of blue rockfish were forced out of their sockets when caught at 76 meters.(Muoneke)

Temperature also affects mortality, for example a study showed that striped bass are more likely to die when out of water when caught in the spring and summer.(Muoneke)

The longer a fish is out of water, the greater its life is in danger. When trout were exposed to air for 30 seconds, a third of them went on to die. When fish were exposed to air for 60 seconds, three-quarters of them later died. However, it may take 12 hours for fish to perish, giving fishermen the false impression that released fish always survive. The research found that death after release was up to half for small mouth bass, and over three-quarters for largemouth bass.(Ferguson) (Cooke,1)

fishing fish die out of water

Fish often struggle so hard that they are seriously weakened, resulting in severe physiological disturbances. Fish battle for their lives when hooked. A significant number of them die, and the longer the struggle, the more likely it is that the fish will lose its life.(Julie). It is cruel to catch and release fish.

Fish may take 20 minutes to die on a warm day, or even longer on a cold one.

Fish may die from damage from hooks or be attacked by predators while they are helplessly held on the line. One study in this review found that, out of water, rainbow trout took 11 minutes to stop moving at room temperature, and an appalling 3½ hours at 2°C.(Davie)


Often fishermen feel that they are doing some sort of good deed by tagging the fish that they release. However, Danish scientists found that it causes tissue damage, decreased swimming capacity, reduced growth, increased predation, and an increased chance of death.(Niels)

fishing tagging

Harm caused by nets

Nets, used to scoop up fish out of the water (landing nets), and nets used to hold fish at the fisherman’s pleasure (keep nets), harm gills and scales, and severely erode fins. The outer protective mucous layer can be rubbed off, allowing in fungal infections which can later lead to death. Hooks often catch on nets, causing more distress, handling, and time out of the water.(Reiss,2)

Research found a 14% death rate for landing nets, with fish swimming erratically before dying. Most deaths took place 2 to 4 days after the fish were caught. The most lethal of the nets were knotted mesh, although all nets caused fin erosion. The study found fungal lesions across 5 to 15% of the body of the fish.(Barthel)


The enzyme cortisol, is produced in response to stress, in people and in fish. Hooking, time out of the water, and handling, all causes great stress for fish. Heart rate and breathing is increased, and may stay this way for as long as 3 days. Additionally, there may be unnatural behaviour, a fish may be less likely to reproduce and grow, and they may suffer permanent tissue damage, and are more likely to die.

In Finland, it was found that transferring trout between tanks, followed by restraining them for only 5 minutes, caused their heart rate and breathing to increase for up to 3 to 4 days. Their overall activity was reduced for up to 2 days.(Laitinen)

fishing fish stress immune system

American and Canadian scientists found that, even after being caught briefly, the heart beat of bass doubled. They reported that stress rises in bass when they are exposed to air, and it increases their chances of dying, especially if they have strenuously fought against being caught. The researchers were particularly concerned about tournament weigh-ins, where fish are repeatedly handled and kept out of water. Health remains affected when they returned to water, and they are likely to be less able to breed. The heart rate of a fish reaches its maximum after only a short period (1 minute for largemouth bass) of fishing.(Cooke,1)

In Norway, scientists found that salmon which had suffered any of the following:

  • increased playing time
  • repeated capture
  • hooking in the throat
  • bleeding from a hook wound
  • increased handling time

suffered from:

  • poor condition when released
  • increased stress
  • unusual behaviour

Further research found that, in other species, all of these harmful factors increased the chance of the fish dying.(Reiss,3)(Mekaa)

When largemouth bass were removed from the water, the fish’s breathing rate increased, indicating stress. Also, the level of the enzyme Alanine Aminotransferase (ATS) increased, indicating permanent tissue damage. When the bass were out of the water for long periods, they showed abnormal behaviour, and rather than leaving the release site normally, they tended to linger there. An absence means that eggs and young are not tended for, and predators are not deterred.(Thompson) In a field study in Lake Erie, the effects of catch-and-release fishing on rock bass were observed. After the fish were removed from the water, their heart beat went up severely. After just 30 seconds, the fish took 2 hours to recover. When they were taken out for 3 minutes, it took a full 4 hours.(Cooke,2)

Barotrauma - bursting at the surface

Fish that live in the depths match their internal pressure to that of the surrounding water. However, when hooked and taken to the surface, barotrauma results - their greater pressure can cause the swim bladder to burst, the stomach to be pushed out of the mouth, bulging eyes, and other organ rupture, as well as gas bubbles in the heart and brain. Fish suffer when they are dying.


Research, in Canada, recorded horrendous suffering to fish in a lake in Ontario during a fishing tournament. Three quarters had haemorrhaging or their swim bladder distended, and a third showed extreme bloating. A fifth of them later died. Fish with severe barotrauma were only slowly able to swim from the fishermen when released. Some of them floundered on the surface, or were on the point of death, and susceptible to being struck by a boat. Other fish floated upside down, with their gills still moving. All of these fish faced possible predators, burning from the sun, or being carried ashore or to hostile environments.

Even less severe injuries can mean long-term harm, and threaten survival. Fish hooked from the deep often cannot return after they are released, as their swim bladders will have become too buoyant. Although fish taken from the deepest water are the most vulnerable, fish plucked from relatively shallow depths are also susceptible - most, or perhaps all, fish with swim bladders can suffer harm.(Gravel)

A brochure, Bring That Rockfish Down (pdf), produced by the University of Southern California and the California Department of Fish and Game, says that when a Rockfish is caught at depth, its swim bladder rapidly inflates as it is dragged to the surface, even when reeled in slowly. The fish may die from temperature shock, and the longer at the surface, the greater the chance there is of the fish dying, with the odds doubling for every ten-minute increase in time at the surface.

Sometimes fishermen jab a needle or a tube into the fish to release pressure, and then throw the fish back. This procedure can cause serious injury to the already traumatized fish, with possible damage done to another organ, and then the risk of infection.(Casselman)(Kerr)

Fish in danger after release

Suffering at the hands of fishermen often continues after fish are unhooked:

  • Damage to skin, allowing fungus and disease to take hold
  • Damage to eye, mouth, and internal organs
  • Difficulty in maintaining equilibrium
  • Hooks and line left in the body
  • Vulnerability to predators
  • Stress weakening the immune system which reduces growth, capability for breeding, and allows vulnerability to disease
fish in danger

Researchers deployed fishermen to catch over a thousand trout on 45 fishing trips, from the Bois Brule River in Wisconsin, United States. 3.5% of the fish died. Of these, 85% died immediately, and more than 90% within 24 hours. When trout were hooked in the gills, over a third of them died. Death was also caused by hooking in the eye, jaws and body, and by deep hooking in the mouth. Trout bled the most when resisting capture. Three quarters of the trout that died were bleeding noticeably. 10% of the fish suffered eye injury:

  • lens rupture
  • rupture of the external wall
  • internal bleeding
  • death of retina tissue
  • total removal of the eye
fishing hooking deaths

It was also discovered that the cornea lost its transparency with repeated contact with nets, cooler walls, and other fish.

Injuries to jaws were most commonly the tearing away of the jaw bone, often accompanied with tearing of the cheek.

In the Bahamas, bonefish were tracked using ultrasonic transmitters and small visual floats. When fishermen returned the fish back into waters with a high number of sharks, 39% of the traumatised fish were eaten within half an hour.(Cooke,3)

An independent panel of experts, who reported in the Medway Report in 1980 for The Royal Society for the Protection of Animals, said that the delicate outer skin and mucus layer of fish can be damaged by fishermen when they handle the fish. Normally it provides a barrier to disease-causing micro-organisms, found in water. If the harm done is severe, there could be infection of the skin, or circulatory failure, both of which could kill the fish.

Induced stress can lead to a weakened immune system, which makes the fish less resistant to disease.(Muoneke)

It was found that smallmouth bass grow less after they are hooked,(Clapp) and striped bass have poorer health.(Diodati)

Species of fish that make nests for their offspring, such as largemouth and smallmouth bass, which are worn out by being played on a line, take a long time to return to their nests, or abandon them completely.(Kieffer) (Cooke,1)

Blue sharks off the north-east coast of the USA are frequent victims. In a single two-day shark-fishing tournament off Massachusetts, over 2000 blue sharks were caught. 3% of the sharks still had hooks inside their bodies. It is not known how many died after release. Hooks were found in the oesophagus and gastric wall. Accompanying lesions included oesophagitis, gastritis, hepatitis and proliferative peritonitis. There can be mechanical trauma and persistent irritation by corroding hooks and bacterial infection causing severe, chronic peritonitis. Sharks can be left seriously weakened and dying.(Borucinska)

shark with hook

Targeted by fishermen off the east coast of America, are tuna and marlin. Researchers found extreme metabolic disruption, to causing the fish to be unable to function properly, or survive at all. After ten minutes of being hooked, tunas had significantly high levels of the stress hormone, cortisol, in their blood. Cortisol was measured in marlin - it was among the highest ever measured. A single bluefin tuna, angled for 42 minutes, died immediately after release. This fish had a depressed blood pH and high blood lactate levels, indicative of a severe acidemia (high levels of acid in the blood).(Skomal,2)

The strain of being caught by fishermen reduces the fish’s ability to reproduce and can affect its growth. For example, the growth of smallmouth bass was inversely related to the number of times hooked.(Muoneke)

A hole in a fish's mouth, caused by hook, handicaps a fish's capability to catch other fish. They are not able to suck in prey fish. Many species of fish feed this way, including bass, salmon, and trout.(Thompson,2)

Using live fish and other animals as bait

Some fishermen have the macabre practice of using live bait, such as other fish, frogs, salamander, and squid. This dooms these animals to be eaten, mutilated, or drowned. Hooks and line may be passed through parts of the fish, including the eyes. The fish may die when the target fish is caught, or eventually after time.

  • Live bait includes:
  • frogs, toads
  • tadpoles, salamanders
  • wasps, bees
  • caterpillars, cockroaches
  • crayfish, dragonflies
  • eels, grasshoppers
  • grubs, lamprey
  • leeches, minnows
  • moths, shrimps
  • sand dabs, squid
  • white suckers, worms
  • yellow perch, chub
  • jacks, mayflies
fishing frog bait

The Environment Agency in Britain pointed to the ecological harm caused by the use of live bait, through the introduction of disease and parasites, and use of rare or protected animals.(Environment Agency)

Ex-fisherman, Steve Hindi: I Was a Fish Killer

Often we bought large sucker minnows as bait.

The suckers were hooked just under and to the rear of the dorsal fin, in a way that would allow as much movement as possible, and would maximize their survival time.

Some fishers would run the hook through their eyes. The suckers were thrown out and suspended under a bobber, or were held close to the bottom by a lead sinker. The bobber was big enough to prevent the minnow from pulling it underwater, but small enough to be taken down by a larger predator as it grabbed the minnow.

Although we were told, and wanted to believe, that fish did not feel fear or pain, we almost always knew when a predator approached the sucker. The bobber would begin to bounce and move; although the sucker wasn’t big enough to sink the bobber, his or her panic was obvious.

The bobber jerked, pulsed, and slowly dragged across the water as the bigger fish approached.

Often the predator would only strike the sucker and let go, probably sensing that something was wrong. We would reel the smaller fish in to find him, or her, often still alive but ripped to shreds.

The Complete Guide To Coarse Fishing, Alan Wrangles

Remember to pass the hook through the top lip only; if both lips are caught on the hook the bait is prevented from breathing correctly and will therefore soon die.

Small fish should keep quite well for a few days in a large bath.

Although expensive, goldfish bought from a pet shop can be used for spinning or live baiting. The brilliant colour of the goldfish makes it a very attractive bait.

For pike spinning, mount the sprat on a tackle fitted with a body pin which is inserted right into the mouth of the fish. Secure the treble hooks to the sides of the sprat with several turns of thread.


Fish in the Mediterranean Sea learn to fear speardivers. They are able to discriminate if divers carry a speargun. They adjust their escape behaviour and keep a safe distance outside the shooting range.(Sbragaglia)

Many divers take advantage of their time of freedom in the sea to hunt down and kill almost any ocean creature they find there. Over 850,000 spearfishing kits are sold each year in the world. There are known to be over three million spearguns presently owned. It may take as little as one year for one single spear fisherman operating every day to practically annihilate the bustling fish life of a one-mile stretch of coral reef.
Jacques Cousteau, The Ocean World

Ecological harm

Fishermen reduce fish populations, including those of rare and endangered fish, introduce alien species and parasites, and harm habitat. They regularly discard hooks and monofilament line, which kills and maims dogs, birds, turtles, dolphins, and other marine animals. Significant harm is done by the killing of slow maturing sharks, as well as putting under pressure fish with low populations and ranges. Additionally, very large numbers of invertebrates are captured for use as bait.(Mcphee)(Environment Agency)

Fishermen catch billions of fish every year across the world. This generates a lot of profit, but because the industry is such a powerful lobby, damage to ecology is kept hidden, and fishing remains largely unregulated. California has about 2 million fishermen, making 6 million fishing trips a year. It has been estimated that a staggering 47 billion fish are caught by recreational fishermen every year.(Schroeder)

Fishermen often dodge criticism of plummeting fish populations by entirely blaming commercial fishing. While commercial fishing kills fish at lower levels of the sea, recreational fishermen kill at a higher sea level.. Failure to recognize the potential contribution of recreational fishing to fishery declines, environmental degradation, and ecosystem alterations places ecologically and economically important resources at risk.(Cooke and Cowx) Overall, they directly kill 4% of fish in the sea every year. Species such as red drum, bocaccio, and red snapper, are the most vulnerable.(Coleman)

anglers kill top of sea

Using data from four high-profile sources, Canadian researchers found dramatic reductions in fish populations over the last several decades, yet these declines have gone largely unnoticed by the public, even though fish suffer in proportion to how close they are to population centres. Predatory behaviour of fishermen is not self-regulating. This can only get worse, as the human population explosion continues. The large hatchery infrastructure only helps to hide the collapse of native fish, and reduce the natural gene pool.(Post)

Some countries have a closed season (a period where fishermen are banned), so wildlife, such as breeding fish, amphibians, birds, and vegetation can recover. Birds are at particular risk, as they may desert their eggs or young if disturbed. Wading fishermen can damage fish eggs buried in the gravel, invertebrates and water plants.(Environment Agency)

Technology makes life easier for the fisherman, but harder for the fish, with high quality echo sounders, global positioning systems (GPS), new types of low diameter high strength fishing lines, and chemically sharpened hooks. Additionally, there is greater information available through the media and the internet regarding "hot spots", the right seasons and the most efficient techniques for particular species, all aided by off-road vehicles. Modern technology makes it easier to wage war on fish, while simpler discarded technology, such as hooks and fishing line, and general litter, cause harm to many birds and mammals.

Anglers have a severe and cumulative impact on fish populations and rare or endangered fish.

cumulative impact

Fishermen, usually ignorant of the web of life, assume that adding more fish to a river, dam, or lake, is somehow helping nature. This practice has become so widespread that people often think that some of the invasive species are actually native ones.

Fish are transported around the world and dumped in waters without any risk assessment. Small native species lose out to larger fish used for fishing amusement, and indigenous native species have even been used as food for alien species. The release of non-native live bait adds to the problem, as local insects and tadpoles can be eaten in large numbers. An example is the Californian High Sierra lakes. Such small life became rare or absent in lakes containing introduced trout.(Cambray)

Populations of alien species in many parts of the world are now out of control. They contribute to the endangerment, or threatening, of one third of fish in the USA.

Alien species are added to make it easier for fishermen, but this causes losses to native fish, and other wildlife, through competition, predation and the introduction of disease and parasites. Wet nets and fishermen's boots can carry parasites and diseases, such as crayfish plague and spring viraemia of carp, the seeds of undesirable exotic plants, such as giant hogweed and Himalayan balsam, and root-fragments of the invasive Japanese knotweed.(Environment Agency) Introduced fish, popular with fishermen, such as trout and carp, reduce the natural gene pool of fish globally.

fishing alien fish

There are particular alien species that cause exceptional harm.

Salmonids (salmon, trout, char, etc), introduced into Australia and New Zealand in the 1800s, caused the decline of a range of native species, including the River Blackfish, galaxiids (a family of mostly small freshwater fish), the Tasmanian Mountain Shrimp, Crested Grebe, Blue Duck, New Zealand Grayling, Spotted Tree Frog, and possibly other frog species.

Ruffle and roach were introduced as live-bait for pike fishing, threatened vendance, whitefish, and Arctic Charr in the Lake District in Britain. The Environment Agency said that it was practically impossible to remove them; they can now only be managed by stopping any more being introduced. They stated that heavy fishing pressure had contributed to the decline in wild trout and salmon. Artificial stocking, such as bream and carp, meet the demand, but high densities reduced the diversity of native fish and plants.(Environment Agency)

Loch Lomond in Scotland is another good example of the problem of introducing new species of fish. In past years, ruffe settled in the loch. They had almost certainly been introduced there by fishermen using them as live bait for pike-fishing.(Environment Agency)

Introduced carp have had a negative impact across the globe in at least 32 countries. They are popular with fishermen, partially because they can grow quite large and therefore give the opportunity for fishermen to pose for the camera. However, carp push out other fish, such as perch, rudd and tench, and there is a subsequent decline in water clarity and plant growth. Even the introduced carp themselves can suffer, as they are more prone to parasites, can find it difficult to spawn, often do not reach full size, and risk introduced disease.

Largemouth bass, driven by the demands of fishermen, has also been artificially spread around the world. This has caused extreme harm to local fish and other wildlife, unable to suddenly cope with another species.(ISSG) They have affected populations of small native fish through predation, sometimes resulting in their decline or extinction. Their diet includes fish, crayfish, amphibians and insects. Studies have shown that they are quite capable of displacing native species - even predatory species such as northern pike.

Rainbow trout is another widely introduced species. They are the basis of many sport fisheries and are highly sought after by fishermen. Raised in hatcheries, they are released into rivers and streams. Native to western North America, from Alaska to the Baja Peninsula, they are regularly stocked in many locations where wild populations cannot resist the cope with their presence. In the United States, the introduction of rainbow trout into areas outside of their native range has caused problems due to their ability to hybridise with native salmonid species, affecting their genetic integrity. Some species, such as the Alvord cutthroat have become virtually extinct because of this. Other species known to be affected by hybridization include the Lahontan cutthroat trout; golden trout, and Gila trout. Invertebrates, frogs, toads, newts, and snakes have also squeezed.

Reared trout has caused outbreaks of Whirling disease. This is a condition caused by a protozoan that causes dysfunction in the nervous system of salmonids, and may result in curvature of the vertebral column. Fish lose the ability to maintain a proper orientation, causing them to swim in a spiral motion.

The brown trout is also blamed for reducing native fish populations, especially other salmonids, through predation, displacement and food competition.

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Arlinghaus Explaining participation rates in recreational fishing across industrialised countries R. Arlinghaus R. Tillner M. Bork, 2014 top
Barthel Effects of landing net mesh type on injury and mortality in a freshwater recreational fishery (pdf), Barthel, B Cooke, S, Suski, C, Philipp, D, Fisheries Research 63 275–282, 2003, Department of Natural Resources & Environmental Sciences, University of Illinois & Center for Aquatic Ecology, USA; Illinois Natural History Survey, Illinois, USA; Department of Biology, Queen’s University, Canada
In most cases, fish manifest few obvious immediate effects of the netting process, and when released, swim away in seemingly good condition. This leads fishermen and managers to conclude that the total costs of the fishing interaction for the fish consist of the energy expended in the struggle, the sub-lethal physiological disturbance from exercise, and associated hooking injury"
"To test this hypothesis, we used bluegill as a model species to examine the effects of different net mesh types (rubber, knotless nylon, fine knotted nylon, coarse knotted nylon) on injury and mortality following fishing at 26°C."
"A control group consisted of individuals that were angled and held out of the water but not netted. Retention in a landing net for 30 s resulted in increased pectoral and caudal fin abrasion relative to control fish."
"Furthermore, evidence of dermal disturbance (i.e. scale and/or mucous loss) was more prevalent in netted fish than in control individuals. No control fish died during a 168 hours holding period, whereas mortality rates ranged from 4 to 14% for fish landed with nets, and the majority of mortality occurred between 48 and 96 hours post-treatment."
"Fish that died exhibited impaired swimming behavior for approximately 24 hours prior to death that was attributable to the extreme caudal fin erosion. Fish that died also had Saprolegnian fungal infection lesions on the caudal peduncle that had begun to progress anteriorly toward the gills."
"Our results indicate that fish captured and landed by hand had lower injury rates than those fish landed using a net and experienced no mortality. Conversely, all net types resulted in heightened injury and mortality with the knotted mesh types being more injurious than the rubber or knotless mesh."
"Fish landed with knotless mesh and rubber mesh exhibited mortality rates of 6 and 4%, respectively. The highest levels of mortality were observed in fine knotted (14%) and coarse knotted (10%) mesh types. All mortality occurred between 48 and 120 hours post-treatment."
"Saprolegnian lesions were present on all fish that died and covered between 5 and 15% of the body of moribund fish. All fish that died exhibited extreme levels of caudal fin abrasion. In fact, most of the caudal fins had eroded to the caudal peduncle."
"All dead fish exhibited loss of scales and mucous and were observed to swim erratically for a period of ~ 12 hours prior to succumbing to their injuries."
"The mucous layer covering the dermal surface of the fish acts as a physical barrier to colonization by foreign organisms and possesses anti-fungal properties. Following an incident of dermal disturbance and infection, the fungal lesions spread across the surface of the fish. Saprolegnian lesions were present on all fish that died in our study and covered 5–15% of their bodies. The knotted mesh types have a higher incidence of dermal disturbance (i.e. loss of mucous and scales) that apparently promote fungal infection in netted fish."
Beukema,1 Acquired Hook-Avoidance in the Pike Esox Lucius L. Fished with Artificial and Natural Baits, Beukenia, J.J., Journal of Fish Biology, 2, 155-160, 1970, 1. Organization for the Improvement of Inland Fisheries, Utrecht, and Zoological Laboratory, 2. University of Groningen, The Netherlands
"The pike used, therefore, had no experience of angling."
"After an initial day of nearly equal catchability with either spinner or live bait of the previously unfished pike, catchability by spinner dropped quickly to very low levels during the succeeding days. This low catchability held during a week at least."
"It was difficult to capture pike more than once by spinning."
"The most likely cause of their lowered catchability is their experience of spinner-fishing."
"Evidently a pike captured once by spinning rarely takes a spinner again (at least during the first few days)."
"Any experience with a spinner hook, whether or not an actual landing follows, is sufficient for learning to avoid further capture by spinner."
"Analysis of the data in three ways yield results which consistently point to quick learning to avoid an artificial lure"
Beukema,2 Angling Experiments With Carp Decreasing Catchability Through One-Trial Learning
Beukema, et al, Netherlands Journal of Zoology 20(1): 81-92, 1970, Groningen University, Netherlands
"When high proportions of the fished carp were hooked and subsequently lost, the whole populations fished for (not only the captured parts) became nearly uncatchable."
Catchability of carp one year after being either captured or hooked and lost was some three times lower."
Borucinska Pathology associated with retained fishing hooks in blue sharks, Prionace glauca (L.), with implications for their conservation (pdf), Borucinska, J, Kohler, N, Natanson, Skomal, G, Journal of Fish Diseases 25, 515–521, 2002, USA
"The blue shark is also the primary pelagic shark species caught by recreational fishermen in the north-east USA from New Jersey to Maine. Although accurate estimates of total blue shark catch and release by the recreational sector are lacking, there is evidence from shark fishing tournament data that these numbers are high. In Massachusetts alone, a single 2-day shark fishing tournament in 1999 resulted in the catch of over 2000 blue sharks and 99% were released alive (G. Skomal, unpublished data)."
"We found fishing hooks retained from previous fishing interactions in six (2.84%) of 211 adult male blue sharks landed by recreational fishermen in the western North Atlantic. Considering the numbers of blue sharks caught and released alive each year in the North Atlantic alone, one can estimate the potential number of sharks with retained fishing hooks to number in thousands."
"The high number of blue shark releases results in an unknown number of fish that do not survive as a result of physiological and physical trauma associated with hooking."
"The hooks were embedded within the distal oesophagus (n=3), or perforated the gastric wall (n=3) and lacerated the liver (n=2). The hooks were surrounded by excessive fibronecrotic tissue which ablated the normal anatomical structures and in the three sharks with oesophageal hooks caused partial luminal obstruction. Accompanying lesions included oesophagitis, gastritis, hepatitis and proliferative peritonitis."
"The mechanical injury caused by the fishing hooks was similarly complicated by bacterial colonization of the oesophageal tissues and the peritoneum."
"The mesothelioma-like peritoneal proliferations found in all examined sharks in this study possibly arose from the mechanical trauma and persistent irritation by a foreign body (corroding hooks), and from bacterial infection leading to severe, chronic peritonitis."
"Active inflammation associated with the hooks and intralesional bacteria were present in each of these sharks, and thus progression of the disease leading to debilitation or death cannot be ruled out."
Cambray Impact on indigenous species biodiversity caused by the globalisation of alien recreational freshwater fisheries, Cambray, J.A., Hydrobiologia 500: 217–230, 2003, Makana Biodiversity Centre, South Africa

Casselman Catch-and-release fishing: A review with guidelines for proper fish handling practices, Casselman, S. J., Fisheries Section, Fish and Wildlife Branch, Ontario Ministry of Natural Resources,

Clapp Hooking Mortality of Smallmouth Bass Caught on Live Minnows and Artificial Spinners, Clapp, David, Clark, Richard, North American Journal of Fisheries Management, 9:1, 81-85

Coleman The Impact of United States Recreational Fisheries on Marine Fish Populations, Coleman, F Figueira, Ueland, J, Crowder, L, Vol 305, Science, 24 September 2004, (1) Florida State University, (2) Duke University, North Carolina
"We examined data from the National Marine Fisheries Service (NMFS) online databases."
"We developed a comprehensive landings database with data provided by the Marine Recreational Fisheries Statistics Survey, NMFS science centers and fishery management councils, multistate marine fisheries commissions, and state natural resource agencies."
"Recreational landings in 2002 account for 4% of total marine fish landed in the United States."
"It affects many of the most-valued overfished species - including red drum, bocaccio, and red snapper - all of which are taken primarily in the recreational fishery."
"Discards are not included in this analysis, so these results underestimate likely impacts. Current regulatory methods have done little to constrain recreational fisheries, and for some major fish populations, recreational landings in the United States outstrip commercial landings, notably for red drum in the South Atlantic (93% recreational), bocaccio on the Pacific Coast (87%), and red snapper in the Gulf of Mexico (59%)."
Top level predators are vital to the natural rhythm of life in the ocean.
"Commercial and recreational fishing have similar demographic and ecological effects on fished populations. They truncate size and age structures, reduce biomass, and alter community composition. Whereas commercial fisheries fish intensely on both lower levels (e.g., menhaden and anchovies) and upper levels (top-level predators) of the food web, the recreational sector concentrates on the latter. All these fishery removals can cause cascading trophic effects that alter the structure, function, and productivity of marine ecosystems."
"If the goal of fishery management is to sustain viable populations and ecosystems, then recreational as well as commercial fishing requires effective regulations."
Cooke,1 Physiological Impacts of Catch-and-release fishing Practices on Largemouth Bass and Smallmouth Bass, Cooke, S, Schreer, J, Wahl, D, Philipp, D, American Fisheries Society Symposium 31:489-512, 2000, (1) University of Illinois (2) University of Waterloo, Canada (3) Kaskaskia Biological Station, Illinois, USA
Delayed death
"Delayed mortality represents death from catch-and-release fishing at some point after the released fish swims away."
"Delayed mortality rates were highly variable for both species, 0–76.9 percent for largemouth bass and 0–47.3 percent for smallmouth bass."
"The intensity of the cardiac response did not increase with fishing duration, indicating that the cardiac response is maximized even with brief fishing duration. As a result, more severe fishing stress is not counterbalanced by a greater cardiac response, but rather by requiring a longer recovery period."
"Black bass spawn in shallow nests in the spring, and following egg deposition the males remain alone to provide all parental care for the brood."
"Because they likely only forage opportunistically while defending their nest and because parental care can be energetically costly physiological disturbances are particularly detrimental to parental male black bass."
"During the parental care period, which may last up to five to six weeks, males are particularly vulnerable to fishing because they vigorously defend their offspring from potential brood predators.
"When guarding males are removed by fishermen, even for short periods of time, predators such as other small centrarchids or percids may quickly consume the offspring with cumulative predation levels being proportional to the length of time the fish is absent from the nest."
"Recent studies, however, indicate that the behavioral and physiological effects of exhaustive exercise, such as catch-and-release fishing during the spawning period, may be stressful enough to cause abandonment of broods."
Cooke,2 The Influence of Terminal Tackle on Injury, Handling Time, and Cardiac Disturbance of Rock Bass, Cooke, S, Philipp, D, North American Journal of Fisheries Management 21:333–342, 2001, (1) University of Illinois, USA, (2) University of Waterloo, Canada
"Fish experienced severe bradycardia during air exposure, but after being returned to the water, all fish exhibited elevated cardiac output. Fish exposed to 30s of air exposure required 2h for full recovery, whereas those exposed to 180s of air required 4h."
Cooke,3 Behavior and mortality of caught-and-released bonefish (Albula spp.) in Bahamian waters with implications for a sustainable recreational fishery, Cooke, Steven and Philipp, David, Biological Conservation, Volume 118, Issue 5, August 2004, Pages 599-607
"Exhaustively angled fish exposed to air had problems maintaining equilibrium following release. These fish typically spent substantial periods of the first 30 min post-release remaining stationary."
Cooke and Cowx The Role of Recreational Fishing in Global Fish Crises, Cooke, Steven J, Cowx, Ian G, BioScience, Volume 54, Issue 9, Pages 857–859, 2004, Canada

Davie Physiology, behaviour and welfare of fish during recreational fishing and after release, Davie, P and RK Kopf, R, New Zealand Veterinary Journal 54(4), 161-172, 2006, Massey University, New Zealand, and Charles Sturt University, Australia
"Striking the cranium of a fish with a priest (club) can cause immediate death or unconsciousness and, if accurately administered, is humane. However, fish sometimes recover consciousness after percussive stunning."
"Hypothermia and asphyxia are not recommended for euthanasia of fish captured recreationally, due to variable and extended times required to cause insensibility and death."
"Kestin et al (1991) reported that rainbow trout took 11.5 min to lose all movement at 20°C and 197.6 min at 2°C."
Diodati Mortality of striped bass hooked and released in salt water, Diodati, P.J., and Richards, R.A, Transactions of the American Fisheries Society 125:300-307, 1996

Environment Agency (UK) Healthier Environment, Better Fishing Environment Agency, England
"There has also been an increase in the artificial stocking of rivers with both hatchery-reared brown and rainbow trout. This has been in response to declines in wild trout, probably due to a combination of habitat damage and heavy fishing pressure. Therefore, wild trout populations are becoming ... rarer."
Despite the continuing decline of salmon in Britain, nearly a tenth of fishermen continue to harry them.
"The number of salmon in our rivers has generally been declining in recent years." "Our Survey of Angling Rod Licence Holders (2001) showed that ... 7 per cent had fished for salmon."
"Many places produce good catches because they have artificially large stocks of fish, but these can harm local wildlife."
"By relying mainly on repeated artificial stocking, the vital link between sustainable wild fisheries and high environmental quality is lost."
"Stocking can be an easy and immediate way to meet fishermen’ demands for higher catches. Yet stocking above a certain level can have a damaging effect on a lake’s water and habitat quality. High densities of bream and, especially, carp can dramatically reduce the diversity of water plants, which will also affect other aspects of biodiversity. Without taking the necessary precautions, increasing numbers of fish may also increase the risk of disease, and could potentially kill fish."
"Some fishery owners may choose to have high densities of fish to meet their customers’ demands for higher catches, with little scope to manage the water for other forms of wildlife." "Stocking with farmed fish can threaten locally-adapted native salmon by posing serious genetic, disease, parasite, competition and predation risks. Exotic species such as rainbow trout can also cause problems."
"Where natural spawning is not available and a put-and-take fishery is the only option ... However, they do pose a significant predation risk to small native fish when introduced into natural lakes (or rivers)."
"Good perch, rudd, tench and crucian carp waters have become progressively less common as more and more lakes have been developed as carp waters. This has led to a corresponding decline in weed growth and water clarity. In these waters the carp themselves often have difficulty in spawning successfully, seldom reach large sizes and are prone to parasites. Stocking may also introduce diseases such as spring viraemia of carp, which ruin the fishery."
"Our National Fisheries Laboratory has found species of parasite that are new to the UK on fish examined during routine health checks. These were probably imported on fish from the European mainland."
"These parasites can have a devastating effect. For example, the parasitic fluke Gyrodactylus salaris wiped out salmon from several Norwegian rivers after it was accidentally introduced to that country. This had a huge impact on fishing and tourism."
"The important message is: introducing fish can spread diseases and parasites, and can have unforeseen and irreversible effects on fisheries through predation, competition or habitat damage."
"Parasites and diseases, such as crayfish plague and spring viraemia of carp, the seeds of undesirable exotic plants, such as giant hogweed and Himalayan balsam, and root-fragments of the invasive Japanese knotweed can all be carried on wet nets and boots."
"It is recommended that closed seasons are imposed where any wildlife, such as breeding fish, amphibians and birds, will benefit from not being disturbed as much."
"Wintering wildfowl flocks also benefit from less disturbance, especially at main sites where there are large numbers of birds. A closed season may also allow vegetation on the bankside to recover."
".. disturbance of vulnerable areas, such as concentrations of breeding birds or areas of bankside vegetation."
"Breeding birds depend upon their nests being quietly concealed and they may desert their eggs or young if they are disturbed. Fishermen can also force wintering and moulting wildfowl flocks out of important feeding and roosting areas. Rushes and reeds can be badly damaged by regular trampling."
"Never attempt to restrain an injured swan or any other large bird or animal by holding on to line it may be caught in or hooked to. This can cause severe injury and traumatise the animal even more."
"Wading can damage fish eggs buried in the gravel, invertebrates and water plants."
"Releasing live-baits could introduce new diseases and parasites to your fishery."
"We strongly discourage using larval or adult lampreys (brook, river or sea) for bait as these species are becoming rare across Europe. Native crayfish are now also a rare and protected species and you should not use them as live-bait."
"Stocking waters with fish carries the risk of introducing parasites and diseases that may harm the fish, and developing fish stocks that could damage the environment, either by changing habitats or competing with other species.
Loch Lomond is a good example of the problem of introducing new species of fish. In recent years, ruffe have settled in the loch. They have almost certainly been introduced there by fishermen using them as live bait for pike-fishing. These bottom-feeding fish may well be serious predators on the eggs and fry of powan, a rare whitefish living in the loch."
Ferguson Physiological Effects of Brief Air Exposure in Exhaustively Exercised Rainbow Trout (Oncorhynchus my kiss) - Implications for Catch and Release Fisheries, Ferguson, R and Tufts, B, Can. J. Fish. Aqua. Sci. 49:1157-1162, 1992, Queen’s University, Canada
62% of fish die after only 60 seconds out of water
"Survival after 12h was 100% in control fish and 88% in the exercised fish, but fell to 62 and 28% in fish which were air exposed for 30 and 60s, respectively, after exercise. These results indicate that the brief period of air exposure which occurs in many ’catch and release’ fisheries is a significant additional stress which may ultimately influence whether a released fish survives."
"One minute of air exposure following exhaustive exercise promotes more severe acid-base disturbances than does exercise alone."
"The amount of lactate accumulated was significantly greater than that seen following exercise alone."
"Exercise and brief exposure to air after exercise both had an impact on survival of the fish during the next 12h."
"Delayed mortality has been observed by other investigators and, in the wild, could give the false impression that released fish always survive."
Gravel Severity of Barotrauma Influences the Physiological Status, Postrelease Behavior, and Fate of Tournament-Caught Smallmouth Bass, Gravel, M and Cooke, S, North American Journal of Fisheries Management 28:607–61, 2008, Carleton University, Ottawa, Canada
"The decline in ambient pressure can have profound physiological and physical consequences... Beyond problems with swim bladder distention (which, in some species, includes stomach or anal eversion or swim bladder bursting), ... internal (peritoneum, kidneys, dorsal aorta)... and external (fins, gums, body surface) hemorrhaging; ocular pressure; formation of gas bubbles within the circulatory system, gills, heart, and brain... and general tissue damage."
"At a fall competitive fishing event on Rainy Lake in northwestern Ontario, we evaluated the incidence of barotrauma among tournament-caught smallmouth bass."
"Overall, 76% of fish had at least one sign of barotrauma (either hemorrhaging or swim bladder distention)"
"32% of fish had two or more indicators and were thus deemed to have severe barotrauma."
"Of our examined fish, 64% showed signs of hemorrhaging and 42% showed signs of extreme bloating."
left to suffer
"When telemetered fish were released at a common site, we determined that fish with negligible signs of barotrauma evacuated the release site more rapidly than fish with severe barotrauma did."
"Some fish with barotrauma floundered at the surface when released, and one of these fish was subsequently hit and killed by a boat."
"At the end of the monitoring period, 20% of fish with severe barotrauma had died; two additional individuals (20%) that were still at the release site were moribund"
"Stress indices were higher in fish with barotrauma and tended to be highest among fish with barotrauma that died after release."
"Outside of a laboratory environment, a significant proportion of fish with severe barotrauma may die after release."
"When released, fish that are unable to return to depth immediately because of the added buoyancy could face predation; ... solar radiation or thermal stress; involuntary transport to shore or undesirable habitats via waves, currents, tides, or wind; injury from impact with boats; or additional physiological disturbances as they struggle to return to depth."
"All fish with extreme bloating also had problems maintaining equilibrium and were floating on the water surface during observations. In addition, when placed in the live release boats, many of these same fish floated upside down but continued to ventilate their gills."
Hoogland Spines of Sticklebacks (Gasterosteus and Pygosteus) as Means of Defence Against Predators (Perca And Esox), Hoogland, et al, Behaviour 10, 205-236, 1957, Oxford University
"Sticklebacks are rejected when, after being snapped up, their spines hurt the predator’s mouth.
After very few experiences both Perch and Pike become negatively conditioned to the sight of sticklebacks and avoid them before they have made contact"
On a number of occasions a completely swallowed stickleback was regurgitated alive after some minutes.
Usually it was rejected immediately after it had been snapped up, and the Pike would make violent coiling movements, and would "cough" intensely several times.
After eating, the Perch frequently gulps, gapes, or belches, and we have even seen the whole body vibrate with rapid jerks after a stickleback had been swallowed. Sometimes a half-swallowed stickleback that has become lodged in the throat of the Perch may be dislodged by a combination of gaping movements and vigorous sideways shaking of the head."
Invasive Species Specialist Group of the International Union for Conservation of Nature
"Introduced around the world for aquaculture and stocked for sport fisheries. It (brown trout) is blamed for reducing native fish populations, especially other salmonids, through predation, displacement and food competition. It is a popular fishing fish."
"Brown trout have been implicated in reducing native fish populations (especially other salmonids) through predation, displacement, and food competition."
Julie Effects of Catch and Release on Physiological Responses and Acute Mortality of Striped Bass, Julie A. Thompson, Steven G. Hughes, Eric B. May, Wreginal M. Harrell, American Fisheries Society Symposium 31:489-512, 2002, Maryland, USA
"Targeted species must survive the trauma of catch and release. Fish caught by commercial or recreational methods often struggle to complete exhaustion. This can result in severe physiological disturbances, and a significant percentage may die."
"... Another cause of higher mortality in our study, however, was probably due to fighting the fish to exhaustion>, as indicated by the significant changes in pH, blood gas values, and increases in mortality as fish were angled for longer periods. Capture by hook and line induces a biochemical response, and muscular energy is expended, which produces acid metabolites. With severe stress from prolonged exercise, some of these anaerobic metabolites are discharged into the blood and disturb blood chemistry and hemalological parameters associated with respiratory gas transport."
Kerr A review of “fizzing”- a technique for swim bladder deflation, Kerr, S.J., Journal, 2001, Ontario Ministry of Natural Resources, Fisheries Section, Peterborough, Ontario

Kieffer Effects of Catch-and-Release Angling on Nesting Male Smallmouth Bass, Kieffer, J.D. et al, Transactions of the American Fisheries Society; 124: 70-76, 1995, Queen’s University Biological Station, Canada
"Smallmouth bass were hooked and then played either briefly (<20s) or to exhaustion (2 min)."
"Fish played to exhaustion took four times longer to return to their nests than did fish played briefly. As a result, offspring in the nests of fish played to exhaustion were exposed to more predation risk. The physiological and behavioral effects of exhaustive exercise induced by fishing indicate the potential for catch-and-release fishing of smallmouth bass during their spawning season to negatively affect reproductive success."
Laitinen Cardiovascular, ventilatory and total activity responses of brown trout to handling stress, Laitinen, M and Tapani Valtonen, T, Journal of Fish Biology 45, 933-942, 1994, University of Jyvaskyla, Finland
"The transfer and struggle both elevated the heart rate for 3 to 4 days. Ventilation rate was elevated to a maximum of about 30% above the nominal level and recovered within 3 to 4 days."
Lukacovic,1 Recreational Catch-and-Release Mortality Research in Maryland, Lukacovic, R, Maryland Department of Natural Resources
"Following will be a series of study summaries conducted by the Fisheries Service that have investigated various recreational fisheries and the release mortality that may be associated with them."
"Fishermen were asked to donate to the study any yellow perch they would normally have released."
"Deep-hooking was defined as being hooked past the gills. Yellow perch were observed for 48 hours in stream-side fiberglass tanks using a flow-through water system."
"Deep hooking rate was 5.8% and as expected these fish died at a higher rate (35.7&%;)"
"When Maryland’s spring trophy season ... The increased popularity of this fishing technique was followed by complaints of dead and floating striped bass near the fishing areas."
"Examinations of dead fish indicated terminal tackle left in many fish and physical trauma compatible with hook damage."
"Studies done here in Maryland have determined the deep hooking mortality rate of striped bass caught with conventional J-style bait hooks to be about 50% regardless of temperature, salinity or whether or not the hook is removed (57.7% in 1995; 41.0% in 1996, 56.3% in 1997, 53.1% in 1999 and 58.3% in 2000)."
"Fish subjected to abrupt increases in air temperature when removed from water prior to release (typically in June and July) were more likely to experience fatal disruption of their normal physiology."
Lukacovic,2 Striped Bass Circle Hook Study, Lukacovic, R, 1999, Maryland Department of Natural Resources
"Fifty striped bass was the target number for each day. Striped bass were caught by chumming and fishermen were instructed to hook, play and land the fish in a normal manner."
"The fish were placed in tanks on board DNR transport vessels. Oxygen, temperature and salinity measurements from surface, mid-water and bottom depths were taken at each site several times each day. The most optimal conditions for survival (lowest temperature and highest oxygen) found at each site were duplicated in the tank. When 25 fish were captured, they were transported to the net-pens. The striped bass were held for 72 hours and checked daily for mortality."
"The deep hooking rate for conventional bait hooks over the course of the entire study was 17.2%"
"The deep hooking mortality rate for striped bass caught with conventional bait hooks in this study was 53.1%."
"Studies done here in Maryland have consistently shown the deep hooking mortality rate of striped bass caught with conventional bait hooks to be about 50% regardless of temperature or salinity (57.7% in 1995; 41.0% in 1996 and 56.3% in 1997)."
"Post mortem examinations of deep hooked striped bass caught with conventional bait hooks showed hook points penetrating heart and/or liver in most dead fish, and severe internal hemorrhage in all dead, deep hooked fish, even when major organs had not been penetrated."
"Death in these studies is rapid. More than 75% of the fish that die, die in less than 6 hours and 95% die in less than 24 hours. Other catch-and-release studies with striped bass, shad and white perch show the same mortality pattern. This strongly suggests that mortality of these fish reflects hooking injury or fishing stress, not confinement because mortality is rapid and usually associated with severe internal damage from hook damage. Mortality from caging stress would be expressed over time as fish languished in confinement. All fish that survive in the net pens are extremely vigorous at release."
Mekaa Physiological response of wild rainbow trout to fishing: impact of fishing duration, fish size, body condition, and temperature, Mekaa, J, McCormick, S, Fisheries Research 72 311–322, 2005, (1) United States Geological Survey, Anchorage, USA (2) United States Geological Survey, Conte Anadromous Fish Research Center, Massachusetts, USA
"This study evaluated the immediate physiological response of wild rainbow trout to catch-and-release fishing in the Alagnak River, southwest Alaska. Information was recorded on individual rainbow trout (n = 415)."
"Levels of plasma cortisol and lactate in extended capture fish (fishing duration greater than 2 min) were significantly higher than levels in rapid capture fish (fishing duration less than 2 min). Rapid capture fish were significantly smaller than extended capture fish, reflecting that fish size influenced landing and handling times."
"Physiological disruptions from stress events can be considered cumulative; therefore, it is possible that fish caught and released several times during a fishing season may be more vulnerable to these types of sublethal effects."
"Approximately 30% of Alagnak River rainbow trout have at least one scar purportedly due to previous hooking, indicating that a substantial portion of the population is subjected to multiple fishing captures."
"Immediate mortality was observed in seven fish (2%, n = 7/415) that most likely died due to hooking injuries that produced significant bleeding."
"Increasing fishing duration produced a significant increase in levels of plasma cortisol and lactate during each year of the study."
"Capture by fishing is one of the most physically demanding forms of exercise stress in fish and the subsequent physiological response has been demonstrated to increase with the amount of time fish are on the hook, sometimes resulting in high mortality rates"
"Handling stress during the hook removal process is a concern among researchers examining the response of fish to fishing. We suggest that the initial slope of increase for levels of plasma cortisol and lactate in extended capture fish following landing and handling stress represents the early stages of a stress response that will continue to increase. Indeed, all of the physiological variables that we measured peaked some time after the stressor had been applied."
"In general, the amount of time required for plasma cortisol to recover to resting levels following an acute stress event is within 24 h."
Mcphee Swallowing the bait: is recreational fishing in Australia ecologically sustainable?, Mcphee, D.P Leadbitter, D., Skilleter, G, Pacific Conservation Biology Vol 8: 40-51, 2002, (1) University of Queensland, Australia (2) Marine Stewardship Council, United Kingdom
"Balon (2000) contests that the idea that recreational fishers and their organizations are instrumental in the conservation of natural resources is largely an unfounded myth."
"The environmental impacts from recreational fishing can be both ecologically significant and broad in scope and include: the removal of a considerable biomass of a wide variety of species; discarded by-catch; possible trophic cascades through the removal of higher order carnivores; impacts on habitat through bait harvesting; impacts of introduced and translocated species to support fishing fisheries; direct impacts on sea-birds, marine mammals and reptiles; and angler generated pollution."
"Management, for several reasons, has largely ignored these environmental impacts from recreational fishing. Recreational fishing impacts are cumulative, whereas. there is a tendency for consideration of impacts in isolation. Recreational fishing lobbyists have generally been successful in focusing public and political attention on other impacts such as commercial fishing".
"The most significant pollution problem from recreational fishing arises from discarded fishing line that can entangle a variety of animals including dolphins and several seabird species."
"An initial census by the Australian Seabird Rescue Group in the Richmond River (New South Wales) revealed that of the 108 resident Australian Pelicans, 37 were suffering injuries from being entangled or hooked by fishing tackle. Subsequent studies in the region have shown that of all the human induced injuries to the Australian Pelican, 92% were from entanglement in fishing line (Australian Seabird Rescue Group, unpubl. data). Wells et al. (1998) concluded that, although often overlooked, the number of deaths or serious injuries to Bottlenose Dolphins in Florida from recreational fishing, particularly entanglement in discarded fishing line, could exceed that from the region’s commercial net fisheries."
"Fishermen may interact with marine turtles, mammals and seabirds causing injury and sometimes death through ingestion of baited hooks and fishing line, entanglement in crabpots and fishing line, and being struck by recreational fishing vessels. Boat strike is the single biggest cause of marine turtle mortality in Queensland (Haines et al. 2001)."
"Recreational fishing as a rule is open access (i.e., there is no restriction on the number of fishermen participating) and effort is generally considered to be increasing in most of these fisheries throughout the world. Growing pressure on fish stocks from recreational fishing strongly suggests that managing only the effects of commercial fishing may be insufficient to prevent fish stocks from being over-exploited."
"For instance, areas and species in Australia, South Africa and the United States have been or are in the process of being declared recreational only fisheries with no independent consideration of the ecological consequences."
"Recreational fishing is an activity that has, for the most part, escaped close scrutiny from the community and governments in relation to impacts on aquatic biodiversity."
"While there is comparatively less known about the recreational harvest than the commercial harvest, it is generally considered to be substantially large. Kearney (1995) provides a preliminary estimate of the annual recreational harvest in Australia of approximately 50 000 tonnes."
"Although not quantified, the efficiency of recreational fishermen is also considered to be improving through the widespread use of technological improvements such as: high quality echo sounders; global positioning systems (GPS); new types of low diameter high strength fishing lines; and chemically sharpened fish hooks. Additionally, there is greater information available to fishermen through the media and the internet regarding "hot spots", the right seasons and the most efficient techniques for particular species."
"The increased usage of off-road vehicles is also considered to have increased the spatial extent of recreational fishing."
"For several species recorded by Steffe et al. (1996), the recreational harvest in absolute terms was small (< 1 tonne per year), yet even these small levels of mortality from recreational fishing may be enough to cause population decline in some of the harvested species. For instance, the populations of the various shark species (eg, Draughtboard Shark and Rusty Catshark) recorded in recreational catches by Steffe et al. (1996) may be susceptible to low levels of fishing mortality because of their life history characteristics which include low fecundity, slow growth rate, and late maturation."
"Finfish species such as Bluefish Girella cyanea, which are believed to have small population sizes and restricted ranges, may also be significantly impacted by the low rates of recreational fishing mortality (Steffe et al. 1996)."
"There is ample evidence that recreational fisheries discard large numbers of fish, retain substantial numbers of juvenile fish, interact with rare and threatened species and impact on aquatic habitats."
"While often overlooked in the context of fisheries management, the harvest of invertebrates for bait constitutes an important component of fishing’s ecological footprint."
Muoneke Hooking Mortality: A Review for Recreational Fisheries, Muoneke, Maurice and Childress, W. Michael, Reviews in Fisheries Science, 2(2): 123-156, 1994, Texas A&M University, and, Texas Parks and Wildlife Department
"We review studies on catch-and-release (hooking) mortality gathered from the existing fisheries literature and from a survey of fisheries management agencies in all 50 states, the U.S. government, all Canadian provinces, and selected academic and research institutions."
"We also solicited input from federal, state, and Canadian provincial agencies, Island Territories under U.S. Administration, and institutions across North America engaged in fisheries research."
"Hooking mortality information was available for 30 species and two interspecific hybrids representing both freshwater and marine species."
"Among salmonids, for which a number of hooking mortality studies were conducted under a range of conditions, mortalities ranged from 0 to 57% for brook trout, 0 to 28% for brown trout, 6 to 25% for chinook salmon, 6.8 to 69.3% for coho salmon, 0.3 to 48.5% for cutthroat trout, 6.98 to 14% for lake trout, and 1 to 95% for rainbow trout."
"Mortalities among centrarchids were relatively high on the average and ranged from 0 to 77% for crappies, 0 to 88% for bluegills, 3-2 to 38% for largemouth bass, and 0 to 47.3% for smallmouth bass."
"Chronically stressed fish may be less disease resistant as a result of weakened immune systems."
"Gotshall (1964) reported that blue rockfish brought from depths of 76.2 m suffered from a 'popeye' condition, in which gases in the skull expanded and forced the eyes out of their sockets. Insertion of a sharp object into the eye cavity at the juncture of the prefrontal and lacrimal bones usually relieved the condition, but caused greater mortality than nondeflation."
Gotshall, D. (1964), Increasing tagged rockfish (Genus Sebastodes) survival by deflating the swim bladder. Calif. Fish Game, 50:253-260.
"Hysmith et al. (in press) reported that striped bass mortality varied with seasons (temperature ranges unspecified) and was significantly greater in spring (69%) and summer (47%) than in fall (8%) and winter (13%)."
"Welborn and Barkley (1974) attributed differences in largemouth bass mortalities (15.7 vs. 75.6%) in two Mississippi tournaments to water temperature."
"Matlock and Dailey (1981) caught spotted seatrout with baited treble hooks and artificial lures and reported a mortality of 55.6% at temperatures of 27 to 33.5°C." Matlock, G. C. and J. A. Dailey, (1981) Survival of hook-caught spotted seatrout held in cages. Manage. Data Ser. No. 15. Texas Parks and Wildlife Department.
Welborn T. L, Jr. and J. H. Barkley, (1974) Study on the survival of tournament released bass on Ross R. Barnett Reservoir, April 1973 Proc. 271b Annu. Conf. Southeast. Assoc. Game Fish Commissioners, 27:512-519.
"Single hooks are generally swallowed deeper or penetrate the tissues farther."
"However, treble hooks (on lures especially) are most deadly when entangled in the gills." "Barbed hooks on lures were impaled mostly in the esophagus and gill arches, whereas barbless hooks (on artificial lures) were embedded in the lower jaw. However, hooking on vital organs was almost always fatal, regardless of hook type."
"When fish are hooked in vital organs (e.g., esophagus, gills), mortality is generally high. For example, Warner (1979a) indicated that 96% of the mortality among deeply hooked Atlantic salmon, from which hooks were removed, occurred within 24h."
"Using a variety of terminal gear (single and treble hooks, artificial flies, and worm-baited hooks), Warner (1979a) reported that 44% of Atlantic salmon that died were hooked in the gills, and 24% were hooked in the esophagus. Overall mortality was 73% (77 of 106) when worm-baited hooks were swallowed; it was 57% (32 of 56) when hooks were left in place and 90% (45 of 50) when they were removed. Loftus et al (1988) reported 71.4% mortality for lake trout hooked in vital organs (e.g., gills, esophagus) compared with 6.9% for those hooked in the lower or upper jaw. Milne and Ball (1956) reported 100% hooking mortality among coho salmon hooked in the gills."
"Nuhfer and Alexander (1992) observed that 6l% of brook trout hooked deep in the gills or esophagus died."
"Hulbert and Engstrom-Heg (1980) observed that brown trout that "suffered the greatest mortality were hooked in the esophagus or stomach (46.6%) or gills (39.6%). However, because mortality was 59% when hooks were removed and 17.5% when they were not, it was recommended that hooks be left in place among deeply hooked fish whenever possible."
"Hooking in other vital organs can also be lethal; mortality among Atlantic salmon was 76% for fish hooked in the eye and 12% for those hooked in the gills (Warner, 1976)."
Niels The use of external electronic tags on fish: an evaluation of tag retention and tagging effects, Niels Jepsen, Eva B. Thorstad, Torgeir Havn and Martyn C. Lucas, Jepsen et al. Anim Biotelemetry, 3:49, 2015, Denmark
"The most commonly reported problems with external tags are tissue damage, premature tag loss, and decreased swimming capacity."
"Reduced growth and survival have also been recorded."
"For PSATs (pop-up satellite archival tags), especially those that are large relative to fish size, there are particular problems with a high proportion of premature tag losses, reduced swimming capacity, and likely increased predation."
"Reduced swimming performance is one of the expected effects of attaching external tags to fish because of the additional drag exerted by the tag as the fish moves through the water. External tags will change the streamlined body shape that many fish species possess, disturb balance and, at worst, cause loss of equilibrium if the tag is too heavy compared to the mass of the fish. Predatory species that rely on speed to catch prey may be less successful and suffer reduced growth. For prey species dependent on escaping predators, the additional drag and weight of a tag may skew the balance between life and death."
"For migrating species, changes in swimming performance may delay or reduce migration success."
"In an early study, Shepherd reported a swim trial where the oxygen consumption rate of externally tagged wild cutthroat trout was compared with control fish. The study demonstrated a higher oxygen demand of tagged fish. A similar approach with small numbers of tagged and untagged cod showed a higher mass-specific oxygen consumption rate of tagged fish during swimming, indicating that there is a measurable drag effect from the tag, as predicted by Arnold and Holford. In a study of the effect of external tagging on juvenile rainbow trout, Lewis and Muntz used tail beat frequency, opercular beat rate, and drag measurements as indicators of swimming performance. All three indicators were elevated in tagged fish compared to controls, and a pannier-saddle-mounted tag, generating more drag than a single-side mount, caused a greater impact. Tests with a dorsal saddle-type tag on the same species showed that time to exhaustion was shorter for externally tagged fish than for surgically implanted and control fish. The same test with white perch showed large individual variation, but no difference was found between treatments."
"In general, these studies document a measurable effect on oxygen demand and swimming performance from fishes carrying an external electronic tag. This effect is most pronounced in relatively small fish, or when large buoyant tags have been applied."
"External tags may affect feeding and thus growth, because movement can be impaired by the presence of the tag. Furthermore, capture, handling, holding, and tagging may compromise the health of a fish, affecting the motivation and physical capability for feeding. External tags also involve additional mass and drag, which may result in increased energy expenditure and reduced growth, even if the fish is feeding normally. Thus, growth integrates a range of effects into one measurable parameter, because reduced performance will likely result in a reduced growth. Growth rate can, therefore, be a good indicator of long-term effects."
"Tank-reared barbel with side-mounted external dummy Tags (2% of body mass) lost an average of 10% of their body mass in the 60 days post tagging."
"Studies show negative effects on growth or body condition in Atlantic salmon juveniles, yellow perch, bluegill."
"A tagged fish might migrate a shorter distance and at a slower speed than an untagged fish."
"External tags are often attached with stainless steel wires or nylon filaments through the muscle at the dorsal fin, with the tag resting at the skin below the fin."
"Combined effects of capture and handling may be even more important for the welfare of the fish and the outcome of the study than tagging itself."
Pelletier Do Catch-and-Release guidelines from state and provincial fisheries agencies in North America conform to scientifically based best practices?, Pelletier, C, Hanson, Kyle, Cooke, Steven, Environ Manage, (2007) 39:760–773, 2006, Institute of Environmental Science, Carleton University, Ottawa, Ontario, Canada
“Many recreational fishermen practice catch and-release fishing, where fish are returned to the water with the presumption that they will survive. However, not all fish survive, and those that do often experience sublethal consequences including injury and stress."
Post Canada’s Recreational Fisheries: The Invisible Collapse?, Post, R, Sullivan, M, Cox S, Lester N, Walters, C, Parkinson, E, Paul A, Jackson, L, Shuter, B, Fisheries | | vol 27 no 1, 2002, Canada
"We reject the view that recreational and commercial fisheries are inherently different and demonstrate several mechanisms that can lead to the collapse of recreational fisheries."
"Data from four high profile Canadian recreational fisheries show dramatic declines over the last several decades yet these declines have gone largely unnoticed by fishery scientists, managers, and the public."
"Empirical evidence demonstrates that the predatory behavior of fishermen reduces fishing quality to levels proportional to distance from population centers. In addition, the behavior of many fish species and the fishermen who pursue them, the common management responses to depleted populations, and the ecological responses of disrupted food webs all lead to potential instability in this predator-prey interaction."
"We conclude that recreational fisheries are not necessarily self-regulating."
"The rainbow trout fishery in south-central British Columbia includes approximately 800 trout populations."
"Two populations for which time series are available show that over the last 3-4 decades, substantial increases in total angler effort are coupled with >6-fold reductions in catch rates."
"In Alberta, 21 of 27 walleye populations for which we have data have collapsed because of overfishing."
"Pike populations in Alberta also show strong evidence of over-exploitation leading to collapse; catch rates in the 1990s were only 15% of what they were two decades earlier in 9 pike populations for which we have data."
"Associated reductions in average age, size, number of age-classes in the catch, and failed year-classes all indicate severe overfishing of Alberta pike populations."
"The state of Alberta’s fisheries may be a precursor of what to expect in other jurisdictions as human populations continue to grow and the pressure on fish populations increase."
"Non-Canadian fishermen spent 5.3 million angler-days taking advantage of the perceived unlimited recreational fishing opportunities in Canada."
"Declines in populations of long-lived species can be slow, and poor intergenerational memory may lead to declining angler expectations as fish populations decline (coined the "shifting baseline" syndrome by Pauly 1995)."
"Indeed, the development of the huge hatchery infrastructure in North America in the second half of the last century may itself be credible evidence of the decline of native stocks (Pearse 1988; Hilborn 1992) and also one reason for the apparent invisibility of collapses. We stock a diversity of native and non-native species in waters containing native species despite a large literature on the negative ecological and genetic impacts of these stocking programs (Hilborn 1992)."
"Ontario lake trout are prized recreational fish, yet 60% of formerly viable natural lake trout populations in south eastern Ontario are now maintained partially or exclusively by hatchery propagation (Evans and Wilcox 1991)."
"Stocking on top of depleted wild stocks of lake trout leads to the loss of wild stocks because: (1) the number of artificially produced recruits can easily exceed the number of natural recruits at low natural stock densities, particularly in small lakes, (2) high fishing exploitation rates differentially reduces the reproductive potential of the wild stocks, and (3) juvenile hatchery-produced lake trout will cannibalize the smaller-bodied naturally produced juveniles (Evans and Wilcox 1991)." "Stocking is capable of maintaining exploitation rates well above that which is sustainable by wild stocks, thereby compounding the fishing effort imposed on natural stocks. From the standpoint of maintaining natural gene pools, stocking depleted populations is a management response that also acts in a depensatory manner and can hasten the collapse of native stocks."
"The large-bodied freshwater fish species that are the primary targets of many recreational fisheries are successful, in part, due to "cultivation effects," where they crop down forage species that are competitors and/or predators on the juveniles of their own species (Walters and Kitchell 2001)."
"We have evidence from food webs in which walleye populations have been reduced in abundance by exploitation that there has been a predatory release on small-bodied fishes (of the family Cyprinidae) and that these small-bodied fishes both eat and compete with larval and juvenile walleye."
"Since fisheries tend to reduce the abundance of the larger and more fecund individuals in a population, total population fecundity declines more quickly than numerical abundance. As a consequence of this decline in population fecundity, there is a substantially higher potential for predation by small-bodied fishes on eggs or juveniles of the targeted species."
"What is the prognosis for Canada’s recreational fisheries? We argue that if the collapses that we observe in some high profile recreational fisheries are real and general, and remain largely invisible, that many recreational fisheries are headed in the same direction as are the world’s commercial fisheries."
Prince Comparison of Circle Hook and "J" Hook Performance in Recreational Catch-and-Release Fisheries for Billfish (pdf) Prince, E, Ortiz, M, Venizelos, A, American Fisheries Society Symposium 30.
"Forty-six percent of sailfish caught on "J" hooks had them lodged inside the mouth, throat, gill arch, esophagus, pharynx, or stomach."
"Hooks found in the upper palate, throat, pharynx, esophagus, or stomach, and fish showing lacerations or bleeding from these areas, were considered potentially lethal."
"Several instances were documented where "J" hooks were foul hooked in the eye. If eye injuries result in blindness, then this injury could potentially affect survival because Istiophorids are highly dependent on daytime sight feeding in the upper portions of the water column".
"Blindness in one eye would negatively impact peripheral vision and could seriously inhibit the ability of these species to feed. Numerous instances were also documented where "J" hook injuries that were not foul hooked could have caused eye damage. For example, in some cases. "J" hooks caused deep lacerations to the upper palate, which, on occasion, affected the occipital orbit and resulted in hemorrhaging in the eye."
"These types of injuries can be deceptive and are particularly difficult to observe in fish at boat-side because, in most cases, the lack of tissue in the upper palate results in the hook dehooking from its initial location and rehooking in another area. Although these fish would appear lively alongside the boat, upper palate injuries could be potentially lethal, due to eye damage."
"Upper palate injuries can also affect the integrity of the cranial cavity by making this area susceptible to infection."
Reiss,1 Catch and Release Fishing Effectiveness and Mortality, Reiss et al, Journal, 2003, University of Maryland
"Deep-hooking (hooking in the gills or gullet) causes up to 35% mortality."
"Mortality is at its highest when fish are deep hooked. Necropsies performed on gut-hooked fish in a study by Grover, found that the majority had sustained major internal damage to the heart, stomach or liver."
Reiss,2 Catch and Release Fishing Effectiveness and Mortality (pdf), Reiss et al, Paper was written in response to a request by Brazilian Government, 2003, University of Maryland
"Nets can inflict varying degrees of damage to a fish’s sensitive fins, gills, slime coat and scales."
"Exposed hooks tend to snag in nets often exacerbating the time needed to remove hooks and release fish."
Reiss,3 Catch and Release Fishing Effectiveness and Mortality (pdf), Reiss et al, Paper was written in response to a request by Brazilian Government, 2003, University of Maryland
"Studies show that the longer the length of time that fish are removed from the water, the greater the ... increases are seen in the physiological indicators of stress."
"Minimizing time spent out of water, minimizes the risk of mortality, especially in smaller fish."
Rummer Physiological Effects of Swim Bladder Overexpansion and Catastrophic Decompression on Red Snapper, Rummer, J Bennett, W, Transactions of the American Fisheries Society 134:1457–1470, 2005, Department of Biology, University of West Florida

“In a landscape of fear humans are altering key behaviours of wild-living animals, including those related to foraging, reproduction, and survival. When exposed to potentially lethal human actions, such as hunting or fishing, fish, and wildlife are expected to behaviourally respond by becoming shyer and learning when to be cautious."
"Using a rich dataset collected in temperate rocky reefs, we provide evidence of spearfishing-induced behavioral changes in five coastal fish taxa, exposed to different levels of spearfishing exploitation, by using flight initiation distance (FID) as a proxy of predator avoidance. We detected a significant increase of mean and size effects of FID when the observer was equipped with a speargun.
"Such effects were more evident outside marine protected areas where spearfishing was allowed and was commensurate to the historically spearfishing pressure of each investigated taxon. Our results demonstrate the ability of fish to develop fine-tuned antipredator responses and to recognize the risks posed by spearfishers as human predators."
Schroeder Recreational Fishing and Marine Fish Populations in California (pdf), Schroeder, D and Love, M, CalCOFI Rep., Vol. 43, 2002, University of California
"Two species federally listed as over fished, cowcod and bocaccio, had 32-fold and 408-fold higher densities, respectively, in the de facto reserve than observed inside the recreational fishing area."
"For 17 nearshore fish species, we compared landings by recreational fishermen and commercial harvesters and found that, for 16 species, recreational fishing was the primary source of fishing mortality. We illustrate the potential damaging effects of mortality associated with catch-and-release programs on long-lived fish populations. Based on this information, we recommend that legislators and natural resource managers reject the assumption that recreational fishing is a low or no impact activity."
"By seeking to maximize fishery yields, traditional fisheries management places most of this risk burden onto fish populations (Dayton 1998). Such a tendency has been injudicious because (1) fisheries can be overexploited before managers and scientists have sufficient data to indisputably document declining population trends, and (2) over exploited fisheries rarely recover after collapse."
"We also illustrate how small increases in mortality associated with catch-and-release programs can affect long-lived fish populations."
"We extracted data from a six-year survey of fishes living on deep natural outcrops and around oil platforms within the Southern California Bight. To quantify fish abundance and associated habitat, we used the Delta, a two-person submersible."
"While performing fish surveys at the Footprint, we observed large amounts of gear debris (traps, longlines, trawl nets, and gill nets) from commercial fishing and many dislodged or damaged sponges. Evidence of recreational fishing activity (lead weights, artificial lures, monofilament line, and Budweiser beer cans) was also commonly encountered at the Footprint."
"Two alternatives frequently suggested by stakeholders as the primary cause of declining rockfish populations are high pollution levels and changing oceanographic conditions. There is no scientific evidence that pollutants in the Southern California Bight appreciably affect population dynamics of rockfishes."
"It remains clear that in the aggregate, recreational fishers impacted nearshore populations more than commercial harvesters."
"Recreational fishermen dominate other fisheries that show signs of depletion. Karpov et al. (1995) report that total surfperch landings from northern and central California during the period 1981–86 were 240 metric tons for recreational fishing and 56 metric tons for commercial harvesters."
"On localized rocky outcrops, depletion in olive rockfish populations has been described by Love (1978), who found a complete lack of mature individuals in areas heavily fished by recreational fishermen; lightly fished areas had many mature fish."
"Fish that have been hooked, landed, and released by fishermen may still die from tissue trauma, bacterial infection, or increased vulnerability to predation resulting from a catch-and-release event (Muoneke and Childress 1994)."
"After 25 years, 29 giant sea bass remained alive in the baseline population; the addition of any catch-and-release mortality changes this number considerably. A 20% catch-and-release mortality rate causes extinction of the giant sea bass population after 16 years."
"In California waters, the view that recreational fishing has no or little impact on marine populations is not supported by the best scientific information available. Our results agree with other reports that find recreational fishermen capable of measurably impacting marine resources (Buxton and Clarke 1991; Bennett 1993; Sluka and Sullivan 1998; Young et al. 1999; Jouvenel and Pollard 2001). California has the third largest number of recreational fishermen in the United States, with approximately 1.7 million fishermen making nearly 6 million fishing trips during 2000 (Marine Recreational Fisheries Statistical Survey database). With such large numbers of fishers pursuing limited numbers of fish, the results we present here are not unexpected."
"Our findings also suggest that recreational fishing may be incompatible with some common goals of spatial closures, such as protecting marine ecosystem structure, and establishing scientific control and marine wilderness areas. Large predators may disappear when a reef is fished even lightly, and this in turn may alter ecosystem structure through top-down, trophic cascades (Dayton et al. 1995; Boehlert 1996; Pinnegar et al. 2000). Local depletion of California sheephead and subsequent changes in sea urchin and giant kelp dynamics may be an example of this phenomenon (Pinnegar et al. 2000)."
"Many of California’s exploited marine species possess life history traits (e.g., long life or irregular juvenile recruitment) that may inhibit timely population recovery once overfishing occurs."
"34% of the fifty bluefin tuna caught on straight hooks were deep-hooked."
"One age-4 fish had a circle hook protruding through the lumen of the anterior stomach. The exposed hook point ripped tissue that supports viscera in the abdominal cavity and caused internal bleeding."
"An age-1 fish had a circle hook that lodged between two gill arches in the pharynx and caused extensive bleeding from gill filament damage."
"In most instances where hooks penetrated the abdominal cavity, tissues and blood vessels supporting viscera were damaged. Hooks positioned close to the transverse septum with the point lacing anteriorly would often tear the septum and sever the hepatic veins leading to the sinus venosus. Hooks positioned closer to the pylorus were observed to damage the anterior liver lobe."
"Large hooks embedded in the jaws of age-1 fish could result in scraping of facial tissue.... Nine of the 25 fish caught in the jaw with circle hooks larger than 10/0 had external damage caused by the hook point and barb."
"In two of these cases, the hook point caused severe damage to the eye socket."
"It was observed that these relatively smaller tuna (2-5 kg) did not easily swallow the larger hooks, but could still experience extensive damage anterior to the gut (gill filaments and eye socket)."
"Eye socket damage found in three of the bluefin sampled (two circle, one straight), could cause blindness, thereby impacting feeding and potentially causing mortality."
Skomal,2 The Physiological Effects of Angling on Post-Release Survivorship in Tunas, Sharks, and Marlin. Symposium on Catch and Release in Marine Recreational Fisheries, 2002, Skomal, G. B.
"Large numbers of tunas, sharks, and marlin are released annually by recreational and commercial rod-and-reel fishermen off the east coast of the United States."
"Angling practices result in increased anaerobic activity, muscular fatigue, and time out of water."
"Evidence supports the notion that high anaerobic muscular activity in fish causes extreme homeostatic disruptions that may impede normal physiological and behavioral function and, ultimately, reduce survivorship. Since blood reflects changes in muscle biochemistry, these perturbations can be measured and quantified."
"To quantify the physiological consequences of high anaerobic muscular exercise, blood was sampled from 312 fish comprising 12 species of tunas (230), sharks (77), and marlin (5), after exposure to rod-and-reel fishing."
"The primary response to stress included a significant elevation of blood cortisol in bluefin tuna, yellow fin tuna, and white marlin. In the tunas, a significant increase occurred 10 minutes into the fishing event."
"Cortisol levels measured in the white marlin were among the highest reported for any fish."
"A single bluefin tuna angled for 42 minutes died immediately after release. This fish had a depressed blood pH and high blood lactate levels indicative of a severe acidemia."
Thompson Physiology, Behavior, and Survival of Angled and Air-Exposed Largemouth Bass, Thompson, L, North American Journal of Fisheries Management 28:1059–1068, 2008, Carleton University, Ottawa, Canada
"A number of sublethal differences (e.g. physiological disturbances and behavioral impairments) were evident in the longer-air-exposure treatment group."
"In all instances, air exposure had a significant affect on the opercular rate of the largemouth bass." "... opercular rate is a good behavioral metric because of its sensitivity to stress."
"The baseline concentration of AST (an enzyme) for male largemouth bass was elevated significantly during the cool water treatment period."
"Because AST is an intracellular enzyme that is predominately located in the heart and liver, its appearance in plasma is a common and reliable indicator of permanent tissue damage in vertebrates."
"The fish exposed to air for longer durations tended to exhibit behavioral impairments and remained close to the release site longer than those exposed for short periods."
"Nesting males are extremely vulnerable to capture because they provide parental care for their brood by defending their nests against brood predators and fan their eggs to provide oxygen and keep them free of silt."
Thompson,2 Angling-induced injuries have a negative impact on suction feeding performance and hydrodynamics in marine shiner perch, Cymatogaster aggregata, Melissa Thompson, Sam Van Wassenbergh, Sean M. Rogers, Scott G. Seamone, Timothy E. Higham, Journal of Experimental Biology 2018 221: jeb180935 doi: 10.1242/jeb.180935, 2018, University of California, Riverside
University of California, Riverside Hook injury from catch-and-release can reduce fish feeding
“Fishing is a popular and lucrative sport around the world and, in some cases, may contribute to declining fish stocks.”
“Using high-speed video and computational fluid dynamics (CFD), we asked whether injuries around the mouth caused by fishing hooks have a negative impact on suction feeding performance (measured as maximum prey velocity) of the commonly angled marine shiner perch.”
Injury-induced hole in the buccal cavity wall reduced the pressure gradient during mouth expansion, thereby reducing the velocity of water entering the fish's mouth.
“Fishing injuries in nature are likely to depress feeding performance of fish after they have been released.”
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