Climate change may be coming for some sharks, a new study suggests. The study found that eggs belonging to the small spotted shark are much less likely to survive under the worst-case climate scenario until the year 2100. The findings still indicate that these sharks may continue to thrive under less catastrophic climate conditions.
The research was led by scientists from the Laboratory of Biology of Aquatic Organisms and Ecosystems (BOREA, for short) in France. it Was published earlier this April in the magazine Marine Environmental Research and the scientists will present their findings Wednesday at the Society for Experimental Biology’s annual conference.
of small spotted shark (Scyliorhinus canicula), also confusingly known as the sand dogfish or less spotted dogfish, is currently doing well for the most part, with fair numbers along the northeastern Atlantic Ocean surrounding Europe. But according to the scientists behind the new research, the species has shown some signs of becoming more vulnerable in an increasingly warming Earth.
“The small-spotted catfish is already experiencing habitat loss in coastal areas, especially during the summer months when spawning is at its peak,” lead researcher Noémie Coulon, a PhD student at BOREA, said in a statement. STATEMENT from the Society for Experimental Biology.
To better find out how these sharks will fare in the future, Coulon and her team raised and monitored shoals of their eggs under three different scenarios. These scenarios were distinguished 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 of increasing carbon dioxide emissions. The team checked these eggs every week for four months (shark pups usually hatch after 5 to 11 months), then tracked how the newborns fared for another six months.
The first scenario was a control, with eggs kept in roughly the same basic temperature and pH conditions as today (based on data collected between 1995 and 2014). In others, the team changed the water to match what would happen under two sets of climate projections developed by the United Nations known as common socio-economic pathways (SSPs): SSP2 and SSP5.
Under SSP2, considered the middle-of-the-road scenario, 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 will rise by nearly 8 degrees Fahrenheit (4.4 degrees Celsius) and the pH of the water will drop by 0.4.
In the worst-case scenario, only 11% of small spotted shark eggs hatch, compared to the 81% and 83% survival rate seen under the control and SSP2 condition, respectively. Embryos inside these eggs consumed less yolk, grew at a slower rate, and were less able to successfully form their internal gills. There was no difference in survival between the groups after the sharks hatched, which is likely due to declining water temperatures over the year, the authors say.
This is just one study from a single team, so more research is needed to verify their findings. But if the team’s predictions bear fruit, an SSP5 world could certainly be disastrous for these fish and others like them, including skates, close cousins of sharks.
“The success of hatching 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 can be critical for population renewal,” Coulon said.
That said, many experts say that an SSP5 scenario is unlikely to happen (although some still believe it remains very reliable). So the team’s overall results can be taken as somewhat reassuring, the researchers say. If humans can prevent the worst possible climate future, then these fish will still be around and kicking Swiming.
“First, it serves as a warning about the responses of other species that may be even more sensitive to environmental changes,” Coulon said. “Second, our findings show that the more moderate SSP2 scenario can limit the damage caused to species like the small spotted shark, which gives us a positive incentive to reduce our greenhouse gas emissions.”