Catch and release (C&R) angling is a useful fisheries management and conservation tool, and its popularity amongst anglers continues to rise. A 2015 survey of recreational anglers in Canada indicated over 184,000 adults went fishing in Manitoba and reportedly caught and released over 10 million fish. To fisheries biologists, this information is important because, at the population level, there is no such thing as a zero-mortality C&R fishery.
DO YOUR HOMEWORK
There is great information available in the angling community on how to properly handle and release fish to improve their survival rates. Proper gear selection, reduced time out of the water, and the use of release tools have given the average angler an edge in caring for their catch. Improved knowledge is raising the standard of fish care in the field. The application of best handling practices considerably improves survival rates for many fish species, but there will always be a percentage of fish (typically small) that will not recover from stress and injuries related to C&R.
ENSURING HIGH SURIVAL RATES
Why do some fish die after C&R? To frame some of the information available on best practices for releasing fish, it is useful to unpack some of the more common causes of post-release death in fish. Before we dive into the biological response of fish to angling stresses and injuries, it is important to note that these responses are species- and context-dependent. That means that no two C&R events are the same. Outcomes will vary by species, habitat, waterbody, season, water temperature, gear type, and angler experience.
PHYSICAL INJURY
When a fish is hooked, hook type and placement dictate the initial injury to the fish. Fish hooked in the jaw generally have the least injury whereas bleeding and tissue damage can occur with deep hooking in the gills or the oesophagus.
There are risks that severe wounds may result in fish bleeding out or wounds becoming infected, then leading to delayed mortality or long-term stress. Handling related injuries such as dropping the fish, removing slime, and poor hook removal increases the risk of trauma and infection.
Additionally, in deep water, barotrauma can occur when fish experience a rapid change in pressure that causes extreme inflation of the swim bladder. Fish in this state will suffer extensive physiological damage and often cannot be released successfully.
THE STRESS TEST
The initial hooking triggers the ‘fight or flight’ response in fish. The fighting that follows is forced and often strenuous on behalf of the fish against the angler. One useful comparison to consider when thinking about fish exercise and exhaustion during the fight is the response that humans have to running.
Light jogging is an aerobic exercise for most people, meaning our breathing is sufficient to provide the oxygen required to sustain that pace. However, if we begin sprinting, our breathing cannot keep up with the oxygen demands of our muscles.
Thus, a sprinter will rely on the body’s backup energy system, anaerobic metabolism, which produces energy during periods of oxygen debt. That burning, sore feeling in our muscles after a sprint is the result of lactic acid buildup, which needs to be cleared during recovery. This same process happens to fish during extended fights, and the harder and longer the fight, the longer fish take to recover.
FISH OUT OF WATER
After all this exercise and the fish is landed, the additional stressors a fish experiences out of the water will strongly influence its survival. Holding a fish out of water impedes its ability to breathe. Air exposure mixed with exhaustive exercise causes further buildup of lactic acid and leads to increasingly acidic blood.
Extended air exposure can also damage and cause the collapse of gill filaments, decreasing the fish’s ability to respire after it is released. Ideally, unhooking, measuring, and photographing fish should be done quickly and efficiently as an exhausted fish has much better odds of recovery the sooner it can resume normal respiration in the water.
Further, the physiological changes caused by capture can lead to behavioural changes in released fish. Temporary changes in movement patterns, feeding activity, and spawning may occur; and some fish might become more vulnerable to predators (e.g., pelicans, birds of prey, otters and larger predatory fish) while the fish is impaired.
MONEY IN THE BANK
One useful way to think about the energetic cost of C&R and recovery is to consider the amount of energy available to a fish as if it were money in a bank account. Under normal conditions, that fish is making deposits every day by feeding and turning that food into energy. Much of that energy goes into ‘regular expenses’ such as growth and reproduction, surplus energy accumulated beyond these immediate needs are invested into energy storage.
When the unexpected happens, and that fish needs to escape a predator or an angler, it’s going to have to dip into the savings to fuel that ‘fight or flight’ response. The energetic price tag associated with C&R then increases with the severity and duration of the challenges the fish faced.
In the end, a fish will die if the energetic cost of recovery exceeds what the income and savings are able to cover. To make matters more complicated, natural stresses will also dip into the savings, including spawning, disease, parasites, and poor environmental conditions (e.g., water quality, heat wave).
Under challenging conditions, fish will not have much more money to invest in their recovery, and it might not take much to tip them over the edge. This might explain why anglers sometimes have fish die and wonder, “why did that fish die? I did everything right!” In some cases, the condition of the fish leading into your fight will have a large bearing on its survival outcome.
THERE IS NO ZERO RISK
Ultimately, C&R is an amazing tool for conservation, but it is not a zero-risk game. There are factors we can control as anglers, and our responsibility is to handle every fish properly and quickly to maximize the odds of post-release survival.
Going forward, further research on the effects of C&R fishing on Manitoban fish species will be vital to continue to improve our understanding of those fisheries.
These studies provide fisheries managers with the best possible information to develop regulations and promote best handling practices to the angling community. Taken together, science-based fisheries management, combined with the efforts of conservation-minded anglers, will play a crucial role in protecting our fisheries for the future.
WATER TEMPERATURE AND RECOVERY
Many anglers have heard that fish typically release better in colder water, as compared to the high water temperatures of the summer months. Several studies have documented the effect of temperature on the survival of various species. For example, a study of walleye on Mille Lacs conducted by the Minnesota Department of Natural Resources estimated a 5.6 percent average C&R mortality for walleye during the open-water season.
WARM WATER STRESS
Interestingly, high water temperatures (above 20˚C) during the months of June and July caused 12.2 percent mortality, whereas cooler water temperatures in May and October produced zero percent mortality. Similarly, a recent study from the University of Winnipeg by Jamie Card looked at the effects of C&R on Freshwater Drum in the Red River. Her study revealed a more pronounced stress response in summer-caught Drum compared to Drum caught in the spring when water temperatures were cooler.
THE REASON WHY?
Though the reasons for this phenomenon are not fully understood, several factors may play a role. Cold water holds more dissolved oxygen than warm water, meaning that fish that are in a physiological ‘oxygen debt’, due to angling stress, have more oxygen available to them in cooler water, which may speed their recovery.
Further, the internal metabolic rate and enzyme activity of fish increases with warming water temperatures, which may allow fish to exhaust their energy sources more rapidly during capture.
SHALLOW WATER FISH
Another consideration is that for some of our most popular species (walleye, northern pike, smallmouth bass), there is a tendency for movements into shallower depths in the spring and fall when surface temperatures are in their preferred range. This means that fish can be captured in areas where the risk of barotrauma and extended battles is lower than in deeper water.
Tips for releasing fish (Potentially another smaller side bar with bullet points to re-iterate ‘best practice’)
- Study the species you are targeting and look up specific tips for handling and release
- Use a rod, reel, fishing line, and terminal tackle that are well-suited for your target species
- Play the fish for as little time as possible
- Avoid C&R fishing in deep water, especially when targeting species that are vulnerable to barotrauma (e.g. Crappie, Walleye, Northern Pike, etc.)
- Use a large basket net to hold fish in the water while preparing for unhooking
- Have your gear ready for unhooking, measurements, and photographs
- Minimize air exposure time as much as possible (under 30 sec is ideal)
- Hold fish horizontally and provide solid support for the body