Global warming puts Cocos Island’s sharks and rays at risk

According to experts from the University of Costa Rica (UCR), sharks and rays in Cocos Island National Park could be severely affected by climate change. Changes in temperature and weather patterns will affect these marine species. This is revealed in a recent study conducted by the Center for Marine Sciences and Limnology Research (CIMAR-UCR).

“Increasing sea surface temperatures due to global warming are forcing rays and sharks to migrate to deeper waters. But there is a limit to how deep these species can dive, because the deeper they go, the less oxygen there is, and rays and sharks need a certain amount of oxygen to survive,” CIMAR explains.

Experts also say global warming is causing a drop in ocean oxygen levels, leaving rays and sharks with a narrower zone of water where they can survive – between the so-called oxygen minimum zone and surface waters that are warming due to climate change.

“It is very likely that this phenomenon also occurs in other parts of the Pacific Ocean and affects other marine species,” said lead researcher Mario Espinosa.

Regarding the number of samples of certain species, Dr. Espinosa explained that the study found a decrease in the number of silky sharks, which he confirmed is one of the most important species in the Costa Rican fishery.

Dr Tyler Clark, co-author of the study, warned that the results have serious implications for the conservation of sharks and rays.

“Since they take up less space in the water column, they are easier to catch. Without proper fisheries management, they are more vulnerable to overexploitation,” she stressed.

Experts say there are a number of measures that can be taken to avoid overfishing. These include expanding existing marine protected areas, establishing new ones, implementing tighter restrictions and controls on fisheries, and delineating where, when and how deep fish can be fished.

The Cocos Island study suggests this could also happen in other parts of the Pacific and around the world. This is very worrying because it suggests climate change could increase vulnerability in these regions.

To carry out this vital research, CIMAR scientists monitored the animals’ behavior over a 10-year period, from 2010 to 2019. These dives collected a wealth of data and information, which was then analyzed by CIMAR’s scientific team.