Long-term changes in the shark and ray communities of the Adriatic Sea are assessed in a study published in Scientific Reports this week. The study shows that these communities have been highly depleted in recent years and that fishing has been a key driver of these changes.
The abundance of elasmobranchs, a group of cartilaginous fish that includes sharks and rays, can decline considerably with fishing, but assessing the drivers of community changes can be complicated by interactions between species and variations in vulnerability and exposure to fishing. The Adriatic Sea is a heavily exploited Mediterranean basin, but fisheries have developed unevenly between its eastern (Croatian) and western (Italian) sides.
Francesco Ferretti and colleagues combined and standardized catch data from five trawl surveys conducted between 1948 and 2005 to evaluate long-term trends in elasmobranch populations of the Adriatic Sea. Communities were already depleted in 1948, and since then catch rates have declined by more than 94%, with 11 species ceasing to be detected, the authors found. They report a greater abundance and diversity of elasmobranchs in the eastern Adriatic, reflecting the less intense historical and recent fishing pressure in Croatian compared to Italian waters. The exploitation history and changes in fishing pressures could explain most of the observed patterns of abundance and diversity, including the absence of strong compensatory increases, the results show.
The study suggests that careful planning and international management of developing fisheries in the Adriatic and the creation of ecological corridors and large-scale protected areas could help to promote recovery among shark and ray communities throughout this sea.