Protecting fish populations seen as key to coral reef conservation

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Coral reefs need abundant and diverse fish populations to survive. Photo via NOAA.

Fishing regulations around coral reef hotspots must be enforced

Staff Report

FRISCO β€” Protecting fish populations around coral reefs may be the key to helping sustain coral ecosystems, according to a new study by the Wildlife Conservation Society that has major implications for coral reef management.

The study focused on coral reef diversity ‘hotspots’ in the southwestern Indian Ocean, finding that they rely more on the biomass of fish than where they are located.

The conclusions are based on data gathered during a 12-year period at about 270 coral reefs across the southwestern Indian Ocean. The highest conservation priorities in the region should be reef systems where fish biomass exceeds 600 kilograms per hectare.

This finding conflicts with a common conservation and management policy that emphasizes the geographical location and physical factors that are often associated with reef diversity.

“While geography has often been the main factor that conservation policy has used to establish protected areas, this study shows that protecting fish biomass should be the priority and this can be done with improved fisheries management,” said Dr. Tim McClanahan, a senior conservationist for WCS. “A hotspot is not a permanent feature and can be lost if the fish and the habitat are not protected.”

Experts agree that fishing is a primary cause in the degradation of coral reefs, and needs to be better managed. But there’s not always agreement on how to do that. McClanahan found that the hotspot in the Indian Ocean is a real feature but is maintained more by fish biomass and habitat than by the geographic location. This means that fish biomass and habitat are the most influential factors and should be used to guide management decisions rather than location.

McClanahan’s study of 266 sites in seven countries of the southwestern Indian Ocean measured numbers of fish species while simultaneously collecting information on the abundance of corals and algae, depth, geographical location, and the types of fisheries management. This allowed him to compare the importance of each of these factors.

The results support previous studies identifying the Mozambique Channel as a center of species richness in the southwestern Indian Ocean. However, sites in this region with low fish biomass also lacked full diversity, and being in this hotspot center alone did not ensure high diversity.

Stronger correlations were found between biomass and local factors such as restrictions on fishing along with coral cover and water depth. The latitude and longitude were significant but found to contribute the least to the variation in numbers of species – a finding that challenges common conservation wisdom.

The study also reveals that protected areas that lacked regular and strong enforcement of fishing bans – classified as ‘low compliance’ fisheries closures – had nearly as low numbers of fish species as reefs that were regularly fished.

“Having fishing restrictions is better than closing reefs to fishing if the closure rules are not followed, which was common and found for nearly half of the studied closures,” McClanahan said.

“The Southwest Indian Ocean is a globally important marine biodiversity hotspot. Unfortunately, this study shows that many protected areas are not doing a good job at protecting fish diversity, a shortcoming that threatens some of the world’s most important coral reefs,” said Dr. Caleb McClennen, executive director of the WCS marine program.

“While these ecosystems are complex, it is clear we need to do at a minimum two things very well to save the world’s coral reefs: strictly enforce established marine protected areas, and; outside these areas, increase the sustainability of fishing practices to increase biomass.”

The study–authored by Dr. Tim McClanahan of WCS (Wildlife Conservation Society)–appears in the latest edition of the Journal of Biogeography. Click here for a link to the study: http://onlinelibrary.wiley.com/doi/10.1111/jbi.12604/abstract.

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