A team from the Cavanilles Institute of Biodiversity and Evolutionary Biology (ICBiBE), located in the scientific-academic area of the University of Valencia Science Park (PCUV), has identified the main factors that explain the mortality of sharks caught accidentally in Western Mediterranean trawl fisheries. Carried out in collaboration with the Catsharks association for the study and conservation of elasmobranchs and their ecosystems, the study has analysed 2,445 specimens of two species of small sharks very common in the Mediterranean: Scyliorhinus canicula and Galeus melastomus.
The results show that mortality increases dramatically when the atmospheric temperature exceeds 20 °C for the shallow-water shark and 16 °C for the deep-water shark. The risk is also increased when individuals remain on deck for more than 15 minutes, sufficient time because exhaustion and lack of oxygen compromise their recovery. To this is added the body size, since, according to the article, the smallest specimens show a greater vulnerability to physiological stress generated during capture.
"Investing in practices that make fishing activity compatible with conservation is to invest in more resilient seas and a sustainable future for both biodiversity and those who depend on the sea," explains David Ruiz-García, ICBiBE researcher and lead author of this study. "Knowing these thresholds allows us to propose specific measures to improve the survival of accidentally caught sharks," says David March (ICBiBE), co-author of the study.
"Investing in practices that make fishing activity compatible with conservation is to invest in more resilient seas and a sustainable future for both biodiversity and those who depend on the sea", David Ruiz-García, ICBiBE researcher and lead author of this study
The team proposes a combination of preventive measures, such as the protection of key areas for juveniles through spatio-temporal closures adapted to the periods of greatest risk, modification of fishing gears to increase their selectivity, or certain improvements in handling on board, such as the rapid release of specimens or the reduction of their exposure to high temperatures. "Working together with the fisheries sector is essential because these measures are effectively integrated and generate benefits for both shark conservation and fishing activity," adds Claudio Barría, from the Department of Functional Biology at the University of Oviedo, Co-author of the paper.
The research, recently published in the journal Conservation Biology, is carried out within the framework of the ECEME project with the support of the Biodiversity Foundation of the Ministry for Ecological Transition and the Demographic Challenge (MITECO).
Source: UV News