Climate change may be coming for some sharks, new research suggests. The study found that eggs belonging to small-spotted sharks are significantly less likely to survive under a worst-case climate scenario until 2100. The findings still suggest that these sharks may continue to thrive under less catastrophic climate conditions.
The research was conducted by scientists from the Biology of Aquatic Organisms and Ecosystems (abbreviated as BOREA) laboratory in France. It was published in the newspaper at the beginning of April Marine environment research and the scientists are set to present their findings Wednesday at the Society for Experimental Biology’s annual conference.
The small shark (Scyliorhinus canicula), also confusingly known as the sand or lesser spotted dogfish, is currently largely doing well, with sufficient numbers along the northeastern Atlantic Ocean surrounding Europe. But according to the scientists behind the new research, the species is showing some signs of becoming more vulnerable in an increasingly warming country.
“The little catfish is already experiencing habitat loss in coastal areas, especially during the summer months when the clutch is at its peak,” said lead researcher Noémie Coulon, a PhD student at BOREA. declaration from the Society for Experimental Biology.
To better determine how these sharks will fare in the future, Coulon and her team raised and monitored their egg batches in three different scenarios. These scenarios were characterized by the temperature and pH of the water in which the eggs were kept. The last variable is particularly important because increasing ocean acidification is one of the major complications increasing emissions of carbon dioxide. The team checked these eggs every week for four months (cat shark pups they usually hatch after 5 to 11 months), then for another six months he watched how the newborns were doing.
The first scenario was a control, with eggs raised under roughly the same baseline conditions of temperature and pH as today (based on data collected between 1995 and 2014). In others, the team altered 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 the SSP2 scenario, which is considered a medium scenario, the average global temperature would rise by about 4.9 degrees Fahrenheit (2.7 degrees Celsius), while water pH would drop by 0.2 by 2100. Under the SSP5 scenario, the most extreme scenario, the temperature would rise by nearly 8 degrees Fahrenheit (4.4 degrees Celsius) and the water’s pH would drop by 0.4.
In the worst case scenario, only 11% of small spotted shark eggs hatched, compared to 81% and 83% survival rates observed under control and SSP2, respectively. The embryos inside these eggs consumed less yolk, grew more slowly, and were less able to successfully form their internal gills. The authors say there was no difference in survival between the groups once the sharks hatched from their eggs, which was likely due to the drop in water temperature over the year.
This is only one study from one team, so more research is needed to verify their findings. But if the team’s projections bear fruit, the world of SSP5 could certainly be disastrous for these fish and others like them, including skate fish, close cousins ​​of sharks.
“Embryo hatching success is a critical factor in population dynamics. In the case of skates and sharks, which have a slow pace of life, low hatching rates can be critical to population recovery,” Coulon said.
That said, many experts claim that the SSP5 scenario is probably won’t happen (although some still believe it remains highly credible). So the team’s overall results could be considered somewhat reassuring, the researchers say. If humans can prevent the worst possible climate future, then these fish will still be around and digging swimming.
“First, it serves as a warning against the responses of other species that may be even more sensitive to environmental changes,” Coulon said. “Secondly, our findings show that a more moderate SSP2 scenario can limit damage to species such as the basking shark, giving us a positive incentive to reduce our greenhouse gas emissions.”