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Hammerhead Sharks Most Vulnerable to Death from Catch-and-Release Fishing [VIDEO]

Jan 30, 2014 03:33 PM EST
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A shark fighting for its life against a fishing ling experiences a build-up of lactic acid in its muscles similar to how a human body would when it is overexerted, and some shark species exhibit high lactate build-up when presented with even minimal degrees of fighting on a fishing line, according to new research, which suggests that even if a shark swims away from an encounter with an angler, it may not survive.

The study, carried out by scientists at the University of Miami and the Rosenstiel School of Marine and Atmospheric Science, has implications on the sport of catch-and-release shark fishing.

Stress levels brought on by catch-and-release fishing were measures in five commonly fished shark species, and researchers found that hammerhead sharks were by far the most vulnerable on a fishing line.

The shark species studied included hammerhead, blacktip, bull, lemon and tiger sharks, all of which were caught and released in Florida and Bahamian waters.

To assess stress levels in sharks caught on fishing lines, researchers took blood samples to measure pH, carbon dioxide and lactate levels, as well as conducted tests of reflexes. After the tests, the sharks in the study were fitted with satellite tags so their survival post-release could be monitored.

According to the researchers, "even with minimal degrees of fighting on a fishing line, hammerheads exhibited the highest levels of lactic acid build of all species studied, followed by blacktip, bull, lemon and tiger sharks."

The satellite tags revealed that after release, hammerheads were more likely to die than the other shark species studied.

"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" said lead study author Austin Gallagher, a PhD candidate at University of Miami. "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."

Study co-author Neil Hammerschlag, a research assistant professor at University of Miami said: "Many shark populations globally are declining due to overfishing. Shark anglers are some of the biggest advocates for shark conservation. Most have been making the switch from catch and kill to all catch and release. Our study helps concerned fisherman make informed decisions on which sharks make good candidates for catch and release fishing, and which do not, such as hammerheads."

The research is published in the journal Marine Ecology Press, more on this research can be found at www.SharkTagging.com.

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