Catch and Release – Not quite perfect

This snook will probably survive after being released, but some don’t. In fact, we kill more of these fish with catch-and-release than we take home to eat.. Photo: Capt. John Merriwether

Catch and Release is an important conservation tool. Catch and release fishing helps to sustain native fish populations by allowing more fish to remain and reproduce in the ecosystem. This practice provides an opportunity for more people to enjoy fishing and to successfully catch fish.

But, catch and release fishing is not perfect. Some fish still die. Including some that swim away after being released. Caught and released fish can die for many reasons including: hook injury, handling practices, air exposure, and barotrauma (swim bladder trauma in deep water fish). Released fish sometimes die immediately, but in other cases mortality due to angling stress may take days.

How many fish are we talking about? Well, a 2001 study that evaluated catch and release mortality in snook found that 2.13% of all caught and released snook died with 24 hours of release. That doesn’t sound like a lot, but extrapolated out to the estimated number of snook caught and released it adds up. Based on an angler survey, an estimated 1.59 million snook were caught on the Gulf Coast in 2014, and of those, 99.1 percent were released. If 2.13 percent of them died, that’s 33,609 snook that dies after release — far more than the 13,851 that were intentionally harvested.

A 2013 study of redfish in Tampa Bay found catch and release mortality rates of 5.6% after 48 hours. The authors concluded higher water temperature (over 79 degrees) and anatomical hook position (higher mortality in gut hooked fish) were significant drivers in post release mortality.

These numbers, although small, can have significant consequences in fish populations, but that’s not it! There’s a whole host of non-lethal impacts. These stressors include altered blood chemistry, behavioral impairments, depressed growth and reproductive rates, and increased vulnerability to disease. These sub-lethal effects can be magnified due to other environmental stressors such as increased temperature or low dissolved oxygen levels.

To expand on just one sub-lethal effect, growth, first consider that fish in general have very simple life strategies: 1) get enough to eat, 2) don’t get eaten, and 3) reproduce. When fish forage, the food resources are allocated to various competing needs, namely maintaining bodily functions, growing, and reproduction. Think of these competing needs as a pie cut into three pieces. In order for you to get more pie, at least one of your two buddies is going to get less.

So how does this relate to fishing? Well, studies have shown that fish exposed to regular stress may respond by allocating food resources differently. For instance, some studies have shown that fish exposed to high fishing pressure, pink salmon as an example, divert less resources to growing larger so that they can reproduce sooner.

Stress responses vary by situation and amongst species. As an example, a 2005 study on rainbow trout found that juvenile trout raised in low-food lakes took high risks to grow rapidly so that they shortened the amount of time they would be exposed to high predation at a small size.

Just like humans and other animals, fish that survive stressful events may minimize their exposure to similar situations in the future through learned behavior modifications. In fact, a University of Florida study on largemouth bass found that fish caught on a lure can learn from the experience and not be as easily caught again.

Many anglers concerned about the fishing pressure in Charlotte Harbor have theorized that targeted fish (redfish in particular) may not feed (or at least bite) as much or they may be becoming more dispersed in learned response to the pressure. Fishing pressure is not unique to our little paradise. And, it’s on the rise virtually everywhere.

Many researchers say that angler passion and concern is why more information about the effects of catch and release is especially important. Scientists are certain that releasing fish helps sustain populations that would wane if those fish were harvested. But they know far less about how repeated releases may affect breeding, behavior and more. Getting at these types of questions requires very concerted research efforts; globally those efforts are increasing.

Catch and release is the greatest conservation measure available to recreational anglers. Using tackle heavy enough to land a fish quickly, keeping fish in the water whenever possible, and using wet hands when you must handle a fish are just a few best angling practices to help released fish survive. For more catch and release tips visit catchandrelease.com.

Sources:
Robert G. Muller, Alexis A. Trotter, and Philip W. Stevens. 2015. THE 2015 STOCK ASSESSMENT UPDATE OF COMMON SNOOK, Centropomus undecimalis, Fish and Wildlife Conservation Commission Fish and Wildlife Research Institute, In House Report: IHR 2015-004.

Kerry E. Flaherty, Brent L. Winner, Julie L. Vecchio1, and Theodore S. Switzer. 2013. SPATIAL AND SIZE DISTRIBUTION OF RED DRUM CAUGHT AND RELEASED IN TAMPA BAY, FLORIDA, AND FACTORS ASSOCIATED WITH POST—RELEASE HOOKING MORTALITY, Gulf and Caribbean Research Vol 25, 29-41.

Katja Enberg, Christian Jørgensen, Erin S. Dunlop, Øystein Varpe, David S. Boukal, Loïc Baulier, Sigrunn Eliassen, and Mikko Heino. 2012. Fishing-induced evolution of growth: concepts, mechanisms and the empirical evidence, Marine Ecology Volume 33, Issue 1, 1-25.

Ronald G. Taylor, James A. Whittington, and Douglas E. Haymans. 2001. Catch-and-Release mortality rates of common snook in Florida. North America Journal of Fisheries Management 21:70-75.

Nick Cole, Ed Camp, and Mike Allen. 2014. Yep, Bass learn to avoid lures, Water Works, June 2014 pg 2.

Mike Allen, Phil Stevens, Sarah Burnsed, and Courtney Saari. 2017. Personal communication.

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