Climate change threatens Caribbean reef fish conservation

More than two decades of conservation efforts to protect the endangered Nassau grouper have proven to be successful, as some populations of the species have strengthened across the Caribbean. However, research from the University of Texas at Austin has revealed that this restorative success may be substantially hindered due to climate change.

A team of marine scientists has found that the breeding habitats of the Nassau grouper are projected to decline by 82 percent during this century if climate change is not mitigated.

Acceptable spawning habitats are critical to the survival of these and other reef fish. Nassau groupers, for example, have a narrow temperature range that they can tolerate while spawning.

The experts also found that suitable habitats for non-spawning fish are projected to decline by 46 percent by 2100.

“The effects of climate change could override some of the successes of conservation efforts at local and regional scales,” said study co-author Brad Erisman. “That is, if Nassau grouper no longer migrate to spawn in a particular region because the water is too warm, then protecting spawning sites in that region will be ineffective.”

“Likewise, if the months when spawning occurs in certain regions shifts in response to climate change, then seasonal protection measures in those regions will need to shift accordingly to ensure that spawning is still protected.”

The reproduction success of the Nassau grouper depends on large breeding events, called spawning aggregations, where hundreds to thousands of fish gather in the same region for a few days to mate. These events make the fish easy targets for commercial fishing, and overfishing is what caused the species to become endangered in the first place.

Many countries like the United States have banned the fishing of Nassau grouper, while other nations such as Cuba and the Dominican Republic have restricted fishing during spawning season.

Study co-author Rebecca G. Asch is an assistant professor of Fisheries Biology at East Carolina University.

“To truly understand how climate will impact fishes, we need to know how it will impact the most vulnerable life history stage, spawning,” said Professor Asch. “If this link in the life cycle is jeopardized, the species as a whole will be in jeopardy.”

Grouper are preyed upon by large predators such as sharks, and the health of the marine ecosystem depends on such important components of the food chain.

“The loss of these important, energy-rich events has negative impacts that span entire food webs and ecosystems,” said Erisman.

According to the scientists, the breeding habitat for the Nassau grouper may only be reduced by 30 percent if major steps are taken to slow climate change.

The study is published in the journal Diversity and Distributions.

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By Chrissy Sexton, Earth.com Staff Writer

Image Credit: Alfredo Barroso