The Marine Ecology Progress Series of the Inter-Research Science Center has published a new study about the effects of catch-and-release fishing on five species of sharks.
The article, written by Austin J. Gallagher, Neil Hammerschlag, Joseph E. Serafy of the National Marine Fisheries Service in Miami and the University of Miami and Steven J. Cooke of the Ottawa-Carleton Institute of Biology and Institute of Environmental Science in Ontario, Canada, reports findings from a three-year study of sharks in South Florida and the Bahamas. The study examined the effects of catch-and-release sportfishing of blacktip, bull, hammerhead, lemon,and tiger sharks. Researchers studied stress effects on each type of shark following a fight with an angler.
The University of Miami R.J. Dunlap Marine Conservation Program has posted an interesting video about the research, as well.
Each of the tests revealed various responses from each of the kinds of sharks. Blood tests showed that lemon and tiger sharks recovered quite well after being hooked and released. Using satellite tagging and tracking, the researchers were able to determine that none of the caught tigers or lemons suffered post-release mortality.
On the other hand, that researchers found that hammerheads suffered the most from the stress of being caught. Blood tests showed hammerheads to have high levels of stress indicators–like concentrations of lactic acids–following a fight. Researchers found this to be indicative of the high energy disposition of large, powerful sharks like hammerheads. The post-release satellite tracking process also revealed that hammerheads had a higher rate of post catch-and-release mortality than the other species studied.
Researchers took blood samples to examine stress, including pH, carbon dioxide and lactate levels, conducted reflex tests, as well as used satellite tags to look at their post-release survival. Fighting on a fishing line significantly affected the blood lactate levels of sharks, similar to what happens to humans during intense or exhaustive physical exercise, which has been linked to mortality in many species of fish. The study revealed that even with minimal degrees of fighting on a fishing line, hammerhead exhibited the highest levels of lactic acid build of all species studied, followed by blacktip, bull, lemon and tiger sharks. Tagging results also suggested that, after release, hammerheads were also prone to delayed mortality.
Lead author and Abess Center Ph.D candidate Austin Gallagher comments that “Our results show that while some species, like tiger sharks, can sustain and even recover from minimal catch and release fishing, other sharks, such as hammerheads are more sensitive. Our study also revealed that just because a shark swims away after it is released, doesn’t mean that it will survive the encounter. This has serious conservation implications because those fragile species might need to be managed separately, especially if we are striving for sustainability in catch and release fishing and even in bycatch scenarios.”
Catch-and-Release, fish, Fishing, Shark, University of Miami
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