The research team angles Tiger Shark up to the boat to begin samples.
It is obvious that any kind of living animal would respond to stress through catch-and-release fishing. Scientists at the University of Miami (UM) Abess Center for Ecosystem Science and Policy and the Rosenstiel School of Marine and Atmospheric Science investigated how several species of coastal sharks respond to these stresses as a result.
The five shark species being experimented on through catch-and-release fishing were the hammerhead, blacktip, bull, lemon and tiger sharks. This was taken place in South Florida and Bahamian waters. 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.
The blood lactate levels of sharks were hugely affected due to them resisting to be caught, which is similar to what happens to humans during intense or exhaustive physical exercise. This is linked to mortality in many species of fish. The study showed that the hammerhead exhibited the highest levels of lactic acid build out of all five species, followed by the blacktip, bull, lemon and tiger sharks. The study even showed that after release, hammerheads were prone to delayed mortality. Hence, the hammerhead sharks are more sensitive than the other sharks whereas tiger sharks can withstand or recover from even the minimal catch and release fishing a lot better.
This study not only shows the different effects on catch-and-release fishing on the different types of sharks but also conveys that it is not guaranteed that all of these species would survive from the encounter even if it swims away from the area. 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.
Many of the shark populations worldwide are declining due to overfishing. In order to conserve this population, the process of catch and killing is now slowly being switched to catch and releasing. Therefore this study helps fisherman make informed decisions on which sharks make good candidates for catch and release fishing, and which do not, such as the hammerheads.
Yuri Tomura
