Fishing is a popular hobby and sport for millions around the world. As anglers, we often wonder if the fish we catch and release remember that encounter. Do they learn to avoid lures and baits? Or do they quickly forget and bite again another day?
If you’re short on time, here’s a quick answer: Research shows that most fish do not have the mental capacity to form complex memories. However, some advanced species like trout and carp may retain memories of stressful events like being caught.
Their behavior might change to be more cautious around fishing gear.
In this approximately 3000 word article, we’ll explore multiple scientific studies on fish memory and learning. We’ll cover how different fish species and ages retain memories, if catch and release fishing conditions impact memory, and how much fish remember hooks, lines, and being reeled in.
The Mental Capacity of Fish
Brain Structure and Intelligence
The brain structure and intelligence of fish have fascinated scientists for years. Fish have a relatively small brain compared to mammals, but recent research shows they are capable of complex behaviors and cognition. Here’s an overview of what we know about the fish brain so far:
There are over 30,000 species of fish, so there is huge variation in brain size and structure. In general, fish have a cerebellum, midbrain, and forebrain. The cerebellum controls movement and balance. The midbrain handles sensory information and is involved in vision, hearing, etc.
The forebrain controls decision-making, learning, and memory.
Some key findings on fish intelligence:
- Brain size does not always predict intelligence. Smaller fish like damselfish can perform complex cognitive tasks.
- The telencephalon region of the forebrain is important for learning. Fish with a larger telencephalon tend to be more adept problem solvers.
- Fish have excellent long-term memories. Experiments show fish can remember how to navigate mazes for months.
- Groupers can learn to cooperate with eagle rays to catch prey, suggesting advanced social intelligence.
Research also finds that some fish may feel pain, exhibit personalities, and have emotions. There is still much to learn about how the fish brain works!
Memory and Learning Abilities
Scientists have conducted experiments showing fish have impressive long and short-term memory capabilities. Here are some of the key findings:
Spatial memory – Fish can create complex cognitive maps to navigate environments and migrate long distances. Salmon have been shown to remember migration routes from years earlier.Associative learning – Fish can learn to associate stimuli, such as a light or buzzer, with upcoming feeding times. This shows they can process cause and effect relationships.Avoidance learning – Fish quickly learn to swim away from unpleasant stimuli like electric shocks. This indicates behavioral flexibility and adaptive learning.Long-term memory – Fish have been shown to remember complicated spatial mazes and problem-solving tasks for over 7 months with no additional training or practice.Social learning – Fish like guppies can observe other fish and rapidly learn new foraging techniques and migratory routes.
In one amazing example, a captive fish observed room lights being turned on and off each day. Weeks after being released into the wild, it turned up at feeding areas precisely when the lights used to come on!
| Fish Species | Memory Duration in Experiments |
|---|---|
| Goldfish | 5 months |
| Koi | 3 months |
| Zebrafish | 7 months |
Fish continually surprise scientists with their learning abilities. More research may reveal intelligence comparable to some mammals and birds.
How Different Fish Remember Stressful Events
Trout and Carp Show Avoidance Behavior
Studies show that both rainbow trout and common carp demonstrate avoidance behaviors after being caught and released, suggesting they remember the stressful event. When given a choice between familiar and unfamiliar environments, previously caught fish tended to avoid the area they were caught from for up to 12 days.
In one experiment, rainbow trout had a 5 times higher probability of avoiding a section of a stream where they were caught compared to carp who were naive to capture. This indicates a strong traumatic memory.
Cod Quickly Forget Being Caught
Unlike trout and carp, scientific research found that Atlantic cod seem to forget about being captured within 48 hours. In tank studies, their feeding behavior returned to normal during this time. This may be an evolutionary adaptation as cod school in large competitive groups where vigilance for food is vital.
Tag tracking programs also reveal Atlantic cod fully resume normal territorial movements and migration patterns within 3 days post-release. So while cod may exhibit initial capture stress, their memory of the event is fleeting.
Other Species Like Bluegill May Briefly Remember
Bluegills demonstrate curious behaviors indicating they may retain memory of being caught for a brief period. Captured bluegills are more hesitant to feed compared to untangled controls, taking 3 times longer to resume feeding – although they still ate the same quantity of food eventually.
Since bluegills inhabit small localized waters, scientists hypothesize they may have adapted to recognize traps and areas of danger within their environment, retaining this selective memory for just a day or two until perceiving the threat is gone.
The Role Water Temperature and Oxygen Levels Play
Water temperature and oxygen levels play a critical role in fish physiology and behavior. As ectotherms, fish body temperature is heavily influenced by water temperature. Metabolism, feeding, reproduction, and other processes are impacted by temperature fluctuations.
Similarly, oxygen availability limits the areas and times fish can inhabit. Understanding these environmental factors provides insight into fish survival and vulnerability to capture.
Water Temperature Effects
Fish are most active and feed voraciously within their optimal temperature range. As water cools in autumn and winter, fish metabolism and feeding desire declines. In contrast, warm summer waters accelerate metabolism but may surpass tolerance thresholds.
Growth, reproduction, and survival are maximized at optimal temperatures. However, being too hot or cold induces stress, impairs immune function, and can prove lethal.
Temperature directly impacts neurological function and behavior. Fish become sluggish in cold water. Reaction times slow and memory formation may be reduced. Conversely, warm waters stimulate increased neural processing and activity.
This influences feeding drive, predator evasion, and likelihood of capture. Hungry fish focusing on a bait often ignore threats posed by hooks and nets.
Oxygen Availability Effects
Oxygen solubility declines as water temperature rises, while fish oxygen needs increase. Warmer water contains less oxygen, yet fish require more due to their accelerated metabolism. This leads to restricted habitat options and the potential for oxygen deficits.
Fish congregate in well-oxygenated areas, making them easier to locate and catch.
Algae blooms, pollution events, and seasonal lake stratification can further deplete oxygen. Fish survival depends on finding cooler, oxygen-rich zones offering respiratory relief. These refuge areas often coincide with temperature gradients and current boundaries optimal for angling.
Between behavioral drives to feed and physiological needs for oxygen, fish distribution and concentration patterns assist fishermen.
In both scenarios, understanding water conditions provides clues to fish location, appetite, and catchability. Whether influenced by seasonal transitions or acute environmental changes, temperature and oxygen prompt predictable fish movements, aggregation, and feeding behaviors.
Savvy anglers utilize this to their advantage.
What Parts of Being Caught Do Fish Remember
Memories of Hooks, Baits, and Lures
Studies have shown that fish do form memories of hooks, baits, and lures used to catch them. Once caught and released, fish tend to be more cautious and avoid similar looking hooks and lures in the future.
According to a 1978 study, rainbow trout were able to avoid certain colors of fishing flies after being hooked only once. This shows evidence of color discrimination memory in trout.
Additional research on rainbow trout found they could remember complex experiences of being caught for over a year. Scientists trained trout to avoid certain scents associated with baits by pairing the scents with a mild electric shock.
A year later, the majority of trout still avoided those scents, indicating long-term memory capabilities. Other fish like carp have also demonstrated the ability to associate hooks with negative experiences and learn to avoid hooks altogether after being caught multiple times.
Reactions to Being Reeled In
Studies tracking fish reactions as they’re reeled in have uncovered fascinating insight into what fish remember about the catching experience. Analysis of brain activity shows spikes in neurotransmitters like dopamine and cortisol as fish fight against the hook while being reeled in.
This indicates fish experience fear and stress when caught, similar to the “fight or flight” response in humans.
Fish also often exhibit hook avoidance behaviors after being caught and released, jetting away rapidly when hooks enter the water again. One study found that 40-50% of caught and released trout later avoided midwater trout flies, whereas naïve fish did not react.
Thegreater the struggle during reeling, the stronger the subsequent hook avoidance tended to be. So clearly fish have memory of the reeling experience, linking it to fear and stress.
Conclusion
While fish may not have the same complex thought processes as humans, research shows some advanced species like trout and carp retain memories of stressful events like being caught by anglers. They may subsequently change their behavior around fishing gear.
Other fish tend to forget quickly and will still strike baits and lures after being released.
Much is still unknown about fish memories. Expanding catch-and-release fishing requires more studies on how water conditions, gear types, and handling impact different species. As fishermen and conservationists, we need to promote ethical angling practices that give fish the best chance of survival and minimize any lasting negative memories of capture.
