Climate change could be affecting some sharks, a new study suggests. The study found that spotted catshark eggs are much less likely to survive in a worst-case climate scenario by 2100. Still, the findings suggest that these sharks can continue to thrive in less dire climate conditions.
The research was conducted by scientists from the Laboratory of Biology of Aquatic Organisms and Ecosystems (BOREA, for short) in France. published earlier in April in the newspaper Marine environmental research and the scientists are expected to present their findings Wednesday at the annual conference of the Society for Experimental Biology.
THE small spotted catshark (Scyliorhinus canicula), also known as the sandy flying fox or spotted flying fox, is currently doing well overall, with many specimens along the northeastern Atlantic Ocean surrounding Europe. But according to the scientists behind the new study, the species has shown signs of increased vulnerability amid increasing global warming.
“The spotted catshark is already experiencing habitat loss in coastal areas, particularly during the summer months when egg laying is at its peak,” Noémie Coulon, principal investigator and doctoral student at BOREA, said in a statement. statement of the Society of Experimental Biology.
To better understand how these sharks will behave in the future, Coulon and his team raised and monitored batches of their eggs in three different scenarios. These scenarios were distinguished by the temperature and pH of the water in which the eggs were kept. This last variable is particularly important because increasing ocean acidification is a leading cause of shark mortality. major complications increasing carbon dioxide emissions. The team checked these eggs every week for four months (baby catsharks usually hatch after 5 to 11 months), then followed the newborns’ progress for an additional six months.
The first scenario was a control, with eggs kept in temperature and pH conditions roughly the same as today (based on data collected between 1995 and 2014). In the other scenarios, the team modified the water to match what would happen under two sets of climate projections developed by the United Nations, known as shared socioeconomic pathways (SSPs): SSP2 and SSP5.
Under SSP2, considered the intermediate scenario, the global average temperature would rise by about 4.9 degrees Fahrenheit (2.7 degrees Celsius), while water pH would drop by 0.2 by 2100. Under SSP5, the most extreme scenario, the temperature would rise by nearly 8 degrees Fahrenheit (4.4 degrees Celsius) and water pH would drop by 0.4.
In the worst case, only 11% of spotted shark eggs hatched, compared with 81% and 83% survival rates observed in the control and SSP2 conditions, respectively. The embryos inside these eggs consumed less yolk, developed at a slower rate, and were less able to successfully form their internal gills. There was no difference in survival between the groups once the sharks hatched from their eggs, which is likely due to the drop in water temperatures over the year, the authors explain.
This is just one study by one team, so more research is needed to verify their findings. But if the team’s projections prove correct, an SSP5 world could certainly spell disaster for these fish and others like them, including rays, which are close cousins of sharks.
“Embryo hatching success is a crucial factor in population dynamics. In the case of rays and sharks, which have slow life cycles, low hatching rates could be essential for population renewal,” Coulon said.
That said, many experts say that an SSP5 scenario is unlikely to happen (although some still believe that there remains highly plausible). The team’s overall results can therefore be seen as somewhat reassuring, the researchers say. If humans can prevent the worst possible climate future, then these fish will still be around and kicking swimming.
“First, it warns us about the responses of other species that may be even more sensitive to environmental changes,” Coulon said. “Second, our results demonstrate that the more moderate SSP2 scenario can limit the harm to species like the spotted catshark, which provides an incentive to reduce our greenhouse gas emissions.”
