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A new study that examined the survival rates of 12 different shark species when captured as unintentional bycatch in commercial longline fishing operations found large differences in survival rates across the 12 species, with bigeye thresher, dusky, and scalloped hammerhead being the most vulnerable. Image courtesy of Frank Gibson - Sharktagging.com
A new study that examined the survival rates of 12 different shark species when captured as unintentional bycatch in commercial longline fishing operations found large differences in survival rates across the 12 species, with bigeye thresher, dusky, and scalloped hammerhead being the most vulnerable. Image courtesy of Frank Gibson - Sharktagging.com

Vulnerability of Sharks in Commercial Fishing

New Study Reveals Vulnerability of Sharks as Collateral Damage in Commercial Fishing

UM Rosenstiel School and Abess Center-led study provides new information for shark conservation efforts

MIAMI –A new study that examined the survival rates of 12 different shark species when captured as unintentional bycatch in commercial longline fishing operations found large differences in survival rates across the 12 species, with bigeye thresher, dusky, and scalloped hammerhead being the most vulnerable. The study, led by researchers at the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science and UM Abess Center for Ecosystem Science and Policy, provides new information to consider for future conservation measures for sharks in the Northwest Atlantic.

The unintentional capture of a fish species when targeting another species, known as bycatch, is one of the largest threats facing many marine fish populations.

Researchers from UM and the National Marine Fisheries Service analyzed over 10 years of shark bycatch data from the western Atlantic Ocean and Gulf of Mexico tuna and swordfish longline fisheries to examine how survival rates of sharks were affected by fishing duration, hook depth, sea temperature, animal size and the target fish. Some species, such as the tiger shark, exhibited over 95% survival, whereas other species survival was significantly lower, in the 20-40% range, such as night shark and scalloped hammerheads.

“Our study found that the differences in how longline fishing is actually conducted, such as the depth, duration, and time-of-day that the longlines are fished can be a major driver of shark survival, depending on the species,” said UM Rosenstiel School Ph.D student and lead author Austin Gallagher. “At-vessel mortality is a crucial piece of the puzzle in terms of assessing the vulnerability of these open-ocean populations, some of which are highly threatened.”

The researchers also generated overall vulnerability rankings of species taking into account not only their survival, but also reproductive potential. They found that species most at risk were those with both very slow reproductive potential and unusual body features, such as hammerheads and thresher sharks. The paper’s authors suggest that bycatch likely played an important role in the decline of scalloped hammerhead species in the Northwest Atlantic, which has been considered for increased international and national protections, such as the U.S. Endangered Species List.

The researchers suggest that high at-vessel mortality, slow maturity, and specialized body structures combine for the perfect mixture to become extinction-prone.

“Our results suggest that some shark species are being fished beyond their ability to replace themselves,” said UM Research Assistant Professor Neil Hammerschlag. “Certain sharks, such as big eye threshers and scalloped hammerheads, are prone to rapidly dying on the line once caught and techniques that reduce their interactions with fishing gear in the first place may be the best strategy for conserving these species.”

The study, titled “Vulnerability of oceanic sharks as pelagic longline bycatch” was published online in the open-access journal Global Ecology and Conservation.

The study’s co-authors include Austin Gallagher, Neil Hammerschlag from the UM RJ Dunlap Marine Conservation Program, and Joseph Serafy and Eric Orbesen from the NOAA’s Southeast Fisheries Science Center.

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10 comments

  1. This “data” connects back to Sun Oil thru Wiki in 15 minutes flat. These stories are paid to be run in the media to alter the perception people have of sharks. Why? Purely to grab the donation money and territory ie ocean for the future.

    Big oil is paying for nearly every “shark endangered” story that you read. When you are dead they move the rigs in. So simple..they are planning for the future using the shark and various “institutes” to alter the publics perception. Happy swimming everyone..

  2. You are so right about (Big Oil) footing the bill for every endangered shark story. All of the charter and commercial fisherman I know are having a hard time making a living because the sharks eat over 40 percent of what they catch.
    When there was a shark fishery , the percentage was around 8 percent. There is no doubt that sharks have made a drastic comeback from whatever state they might have been in.
    You are one of the few people that seem to know and acknowledge the truth.

  3. And this shocking article…people are dying from this misinformation my fellow humans. Neff here in Australia is the devil incarnate, this boy with a chip on his shoulder is directly contributing to the deaths of us Australians by misinformation and word games. Paid to by Pew who is owned by Sun Oil and Texaco…shark .orgs are a cover for big oil to much later sneak into that ‘marine reserve’ they ‘helped’ create by donations to so many people we cant keep track of it. Im watching their every move though. 

    Burgess and Neff are committing an almost perfect crime and making millions from it. Both ‘donated’ to by the many shark .orgs that Pew ‘assist’ Neff and Burgess are Pew ‘fellows’. Neff is political lobbyist and we all know politicians and oil are in bed together…join the jots. Copy and paste please…and forward it to people in the ocean as they are being lied to. This is it all in a loose nutshell…shark .orgs shame on you all. Your credibility is in the toilet im afraid.

    http://www.hesawyer.com/Pew-And-Response.html

  4. Dafen72 I have stacks of evidence also Dafen72. Reunion Island have a massive problem with Pew. Palau has started oil exploring now..I guess their tiny govt was paid of by SunOil and Texaco via Pew. There is no such thing as peak oil ok. We have a deep global layer of plant matter, oh I mean oil sorry. This is all under the ocean. Just like us humans will be a layer one day that layer is oil..simple. 

    Some shark attack survivor people I know have been tricked into the Pew circle under the guise of saving sharks that dont need saving. Our last fatal here was totally consumed, the seagulls finished her off. She was someones daughter, a Nana…a person. No body for the family eh. I have an accurate shark attack graph here that is spiking off the page now. Solid accurate data with no silly ‘provoked’ word games or dodgy categories…all word trickery.

    I am one of the few people that do know this Dafen, maybe 10 around the world know the full picture. But many many more are being told. My friends in the media since my attack know all of this and have all the files I have..just in case..I cant be bought, money doesn’t float my boat. This is partly out of respect for all the fatals we have had in the last few years..good young people torn to shreds while they gurgle blood in shock. I know I did it. But by a slim chance I lived..they didnt.

    Big Oil are using .orgs that prey on human empathy for animals of any kind. Very clever…

    Glen Folkard.

  5. The blue blurry graph is from the ISAF website…interesting that it follows my graph.

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