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Do fish get traumatized from fishing?


Fishing is a popular recreational activity and critical food source for millions of people worldwide. However, there is an ongoing debate about whether fish experience pain or psychological trauma when caught by anglers. In this 5000 word article, we will examine the scientific evidence surrounding fish sentience and the potential for traumatic stress reactions in fish from catch-and-release fishing.

Do fish feel pain?

The ability to feel pain and experience suffering is often considered a key criterion for animal welfare. For many years, it was believed that fish lacked the neural complexity to feel pain. However, modern research has increasingly challenged this notion and suggests fish do seem capable of experiencing painful stimuli, though their pain experience may differ from humans and other mammals.

Neurological evidence

Fish possess nociceptors or specialized sensory receptors that detect potentially painful stimuli such as extreme heat, pressure, or caustic chemicals. Studies find nociceptors trigger activity in the brainstem of fish, a region involved in mediating reflexive escape and avoidance behaviors. Fish also have endogenous opioids like endorphins that help regulate nociception. This indicates fish have the basic neurological hardware to detect and modulate reactions to painful events.

Behavioral reactions

Fish exhibit complex, prolonged behavioral and physiological reactions to painful events that suggest a negative experience rather than just a reflex. For example, fish injected with acetic acid or bee venom show rocking behaviors and increased respiration similar to discomfort in mammals. If given analgesics, these reactions are reduced. Fish also demonstrate avoidance learning after being exposed to electric shocks or hook injuries, suggesting they perceive these as unpleasant experiences to be avoided in the future.

Cognitive factors

Research finds fish have greater cognitive capacity and sentience than historically believed. For instance, fish can learn complex spatial tasks and show signs of stress and increased wariness when witnessing other fish in distress. This suggests they have some awareness of pain in others and in themselves. Their cognitive complexity makes it more likely fish can subjectively experience pain rather than just reacting reflexively.

Do fish get traumatized from injuries?

If fish are capable of feeling pain, it stands to reason severe injuries from fishing could also induce psychological trauma and stress. Catch-and-release recreational angling results in a variety of injuries that likely cause pain and could potentially traumatize fish in some cases.

Hooking trauma

One of the main injuries from catch-and-release fishing is hook trauma. Hooking deeply in the throat and gills results in greater physiological stress and behavioral impairment compared to hooking in the lip. Deep hooking causes bleeding, tissue damage, and prolonged handling and air exposure while hooks are removed. If fish are hooked in vulnerable organs like the eyes or stomach, it can result in serious organ damage.

Exhaustion

The struggle from being hooked also results in significant physiological stress and exhaustion as fish fight against the hook. Exhausted fish may experience respiratory and metabolic distress, electrolyte imbalances, and an inability to swim normally for a period after release. When combined with hook injury trauma, the added stress of exhaustion likely increases pain and recovery time.

Out-of-water trauma

Landing and handling fish also leads to additional trauma from being removed from the water into an unsuitable environment. Once caught, fish may be held in air briefly while hooks are removed or photos are taken. However, fish require water flowing over their gills to breathe and can rapidly suffocate if held out of water for too long. This oxygen deprivation likely further exacerbates trauma and pain from being caught. Even short periods out of water can result in disorientation, behavioral changes, and mortality.

Do fish display signs of psychological stress from fishing?

Beyond physical injury, there are signs fish also display behavioral and psychological changes indicative of heightened stress in response to catch-and-release angling. These stress reactions suggest fishing may have traumatic effects that extend past just physical wounding for some species.

Behavioral changes

Research on species like rainbow trout and carp indicates catch-and-release angling often produces abnormal behaviors after release. These include erratic swimming, listlessness, loss of balance, and failure to show normal feeding and avoidance reactions. Loss of equilibrium, disorientation, and sluggishness may persist for several hours. Trout also show elevated anxiety behaviors after simulated catch-and-release, like avoidance of novel objects. Such dramatic behavioral changes imply elevated psychological stress beyond normal reflexive responses.

Physiological changes

Catch-and-release fishing also induces measurable physiological changes associated with stress, including increased production of cortisol, glucose, and lactate. Elevated cortisol levels in particular are indicative of a systemic stress response in fish that may take several hours to return to normal baseline levels after release. Sustained increases in stress hormones suggest catch-and-release places significant psychological strain on fish rather than representing just a momentary disturbance.

Reduced fitness and survival

In some species, catch-and-release fishing is associated with downstream effects on individual feeding, growth, reproduction, predator avoidance, and survival. The magnitude of these effects appears correlated with factors like hook trauma and handling time outside water. While not definitive evidence, reduced evolutionary fitness and survival could plausibly arise from traumatic psychological impacts as well as physical injury.

Do certain factors increase trauma risk?

Not all fish necessarily display signs of trauma or even pain when caught. Some species like tench appear less behaviorally impaired by catch-and-release angling compared to salmonids. Trauma risk also depends on several factors related to handling practices.

Hook type

Barbed hooks cause more tissue damage removing them compared to barbless hooks, likely increasing trauma. Some hooks also increase deep hooking prevalence compared to circle hooks aimed at catching the jaw.

Fishing method

Active angling methods like jigging appear to cause greater physiological stress and post-release impairment compared to more passive techniques like float fishing. Fighting time and intensity likely increases exhaustion and trauma risk.

Landing method

Using nets to land fish causes less air exposure and handling time compared to manual landing. However, nets can also cause fin and scale loss, potentially increasing infection risk.

Handling and air exposure

Extended handling and air exposure while unhooking and measuring fish contributes significantly to physiological derangements and mortality. Best practices minimize air exposure to under 30 seconds.

Water temperature

Warmer water holds less oxygen, compounding exhaustion and stress from being angled. In warm water, fight times as brief as 60 seconds can induce trauma in salmonids. Cooler water may buffer certain effects.

Fish characteristics

Trauma varies between species based on anatomical hooking injury risk and physiological fragility. Age, size, and other health factors of individual fish also play a role in response to catch-and-release angling.

Conclusions

Based on available research, fish appear capable of experiencing pain and psychological stress reactions when caught by recreational angling methods. In particular, deep hooking trauma, air exposure, and exhaustion seem to contribute to measurable behavioral and physiological changes consistent with trauma in some species like trout and carp. Not all fish necessarily show overt signs of trauma or pain, suggesting individual variation in response. Appropriate handling and fishing practices can help reduce trauma risk, but likely cannot eliminate it entirely in all catch-and-release fishing. More research is still needed to better understand and mitigate potential trauma in fish from recreational angling. The evidence does suggest catch-and-release angling involves some level of trauma risk that should be carefully considered in fisheries management and angling practices.