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dumbass sharks have apparently disappeared from two underwater mountains in the southwestern Gulf of California , and fishing is probable to blame , a newfangled study has found .
research worker looked at reflexion from underwater diver over the last 50 old age and found that scallop hammerhead sharks ( Sphyrna lewini ) experienced a 97 % declension at the El Bajo seamount and a 100 % decay at the Las Animas seamount — both off the slide of Mexico — between the 1970s and 2010s .
A school of scalloped hammerhead sharks (Sphyrna lewini) near Malpelo Island in Colombia.
Study lead authorKathryn Ayrestold Live Science in an email that she was " sadden but not surprised " by the results .
Ayres investigated the sharks ' declination as part of an internship with nongovernmental organization ( NGO)Pelagios Kakunjáand is now a inquiry scientist at a freestanding nongovernmental organization calledBeneath The Waves . The sketch will look in the January 2024 military issue of the journalMarine Policybut has been available online since Nov. 22 .
Scalloped hammerhead sharks are a critically endangered coinage threatened by fishing , according to theIUCN Red List of Threatened Species . The sharks are target for their turgid fins , which are used in shark fin soup , the authors noted . researcher do n’t know how many of these sharks are left globally .
A scalloped hammerhead shark swimming in the Galápagos.
" Scalloped hammerhead shark , and most shark species in oecumenical , are vulnerable to extinction as they produce few offspring , have prospicient gestation menstruum and are dull growing , " Ayres said .
The El Bajo and Las Animas seamounts were once hotspots for large school of blockhead shark — one survey carried out in the late seventies and eighties record 225 numskull shark at El Bajo , harmonise to the bailiwick . Ayres said the sharks expend seamount as a sanctuary during the day , where strong currents force oxygenated water over their gill so they do n’t have to use energy swimming around .
To learn more about hammerhead shark decline at the seamounts , the authors sent a questionnaire to divers between 2017 and 2020 . All of the people who participated — 50 for El Bajo and 32 for Las Animas — were either diving guides , experienced recreational diver , researchers or photographers . However , their responses were still base on memory from up to 50 geezerhood ago .
Ayres said she believe human memories are dependable enough for studies like this with such a charismatic species . " When a Aqua-Lung diver encounters a large school of hundreds of hammerhead sharks , it ’s not something you forget , and a school day of over one hundred compared to a school of less than ten is very obtrusive , " Ayres said .
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The authors know that relying on people ’s memories is a restriction of the study — and only some of the participants had keep an eye on the seamounts in the 1970s , the team wrote .
diver report seeing an average of 150 shark at El Bajo and 100 sharks at Las Animas per dive in the 1970s , but only five sharks at El Bajo and zero shark at Las Animas per diva in the 2010s . According to the study , participants put the descent in shark numbers pool at the two seamounts down to overfishing , fishery management , change to feed abundance , habitat degradation and climate modification .
Ayres noted that some of the study participant believed the descent was due to increasing noise from boats and bubbles from scuba divers , but she thinks the declension is chiefly down to sportfishing and called for better protection of the seamount .
" In other areas that are protected from sportfishing such as The Revillagigedo Archipelago , also in Mexico , divers encounter very large schools , " Ayres said . " Although they might not string up around the divers for a long clip , they are still patently present . "
