Sharks could be killed off by climate change, new research has warned.
Projected global warming scenarios predict a “catastrophic decrease” in successful hatchings from 82% to 11% by the year 2100.
The experimental research analysing the combined effects of ocean warming and acidification on shark survival is also the first to show that monthly temperature variation plays a prominent role in shark embryo mortality.
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Scientists say that ocean warming and acidification are caused by greater concentrations of carbon dioxide (CO2) dissolving into marine environments, resulting in rising water temperatures and falling pH levels.
(Image: Barcroft Media via Getty Images)
Lead researcher Noemie Coulon said: “The embryos of egg-laying species are especially sensitive to environmental conditions.
“The hatching success of embryos is a crucial factor for population dynamics.
“In the case of skates and sharks, which have a slow pace of life, low hatching rates could be critical for population renewal.”
She says small-spotted catsharks (Scyliorhinus canicula) – one of the most common shark species in Europe – are already feeling the pressure.
“The small-spotted catshark is already experiencing habitat loss in coastal areas, particularly during the summer months when egg-laying is at its peak.”
(Image: Getty Images)
Noemie and her colleagues at the Laboratoire de Biologie des Organismes et des cosyst mes Aquatiques, France, compared small-spotted catshark embryo survival in three environmental scenarios.
The researchers say that the mortality was linked with lower yolk consumption rates, lower growth rates and failure to transition to internal gills.
The study also highlighted the importance of seasonal temperature variation, which can “significantly” increase mortality during critical egg laying periods.
Noemie said: “This mortality was most pronounced in August, coinciding with the highest temperatures, and during a stage of development where embryos undergo gill reabsorption.”
The researchers noticed that the surviving 11% did not exhibit the typical growth pattern of the other sharks, which may have contributed to their resistance to environmental change.
“What makes these individuals special remains unclear, but by acknowledging the inter-individual variation among young marine organisms, we could better evaluate the future ecological success of species.”
She said the findings offer both a serious caution and a beacon of hope for marine species.
Ms Coulon added: “Firstly, it serves as a warning about the responses of other species that may be even more sensitive to environmental change.
“Secondly, our findings demonstrate that the more moderate… scenario can limit the damage inflicted on species like the small-spotted catshark, which gives us a positive incentive to reduce our greenhouse gas emissions.”
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