Fishing is carried out on a large scale not only on the high seas, but also in the species-rich coral reefs. This has now led to two-thirds of all reefs being overfished, a new study reveals. On one in ten reefs fished, fish stocks have already collapsed. In order for the fan areas to be able to recover, a complete stop to fishing is not necessary. Instead, researchers recommend reducing fishing to 80 percent of the maximum possible yield.
Coral reefs are hotspots of biodiversity – and fishing. It is estimated that around six million people work in reef fisheries worldwide. In the Middle East and the Caribbean, it accounts for around 40 percent of all marine fisheries. Particularly sought-after catches from reef areas include snapper, grouper, wrasse and surgeonfish. However, until now only fragments were known about how badly their populations suffered from fishing.
census in the reef
Researchers led by Jessica Zamborain-Mason from Harvard University have now carried out a global inventory of reef fish for the first time. To do this, they first gained an overview of the current populations by counting the fish from over 2,000 coral reefs along defined areas and identifying their species. Because they carried out these counts both on fished reefs and on those far away from human influence, they were ultimately able to compare how much fishing had changed the natural state of a coral reef and whether overfishing had already occurred.
In addition, the researchers also used the collected data to determine so-called sustainability reference values for each individual reef. Specifically, these values can be used to answer two central questions: What would be the maximum yield of a reef if fishing were sustainable? And how big would the biomass of the fish stocks in the coral reef have to be to achieve this yield?
Many reefs are overfished
The large reef census revealed: “At almost two thirds of the locations, more is being fished than the biomass stocks can produce - so they are being overfished,” reports Zamborain-Mason’s colleague Sebastian Ferse from the Leibniz Center for Tropical Marine Research in Bremen. In every tenth fished reef, the fish stocks have already collapsed. There, the researchers found less than ten percent of the biomass that the reef would actually have if no fish were caught there. The proportion of overfished reefs was particularly high in Southeast Asia, the Persian Gulf and parts of the Caribbean, as Zamborain-Mason and her team report. One of the reasons for this is that an above-average number of people live from reef fishing in these regions.
The current figures may seem alarming at first glance, but according to the researchers there are various adjustments that can counteract overfishing. “The models show that improved fishery management and the reduction of fishing to 80 percent of the maximum possible yield lead to a significant relaxation of stocks and more biodiversity. It is not necessary to ban fisheries from the reef to save the ecosystem,” explains Ferse. For each location, compromises would now have to be found using the collected data that sufficiently take both the concerns of the population and environmental protection into account.
Source: Leibniz Center for Tropical Marine Research (ZMT); Specialist article: Nature Communications, doi: 10.1038/s41467-023-41040-z