Bottom trawl catch comparison in the Mediterranean Sea: Flexible Turtle Excluder Device (TED)vstraditional gear

Abstract

AbstractThe Mediterranean Sea is a hotspot of biodiversity, but the high fishing pressure results in high bycatch rates of protected (sea turtles and cetaceans) and top predator species (sharks). The reduction of bycatch is challenging for fishery scientists, as conservation of these species has become a priority. Among the animals threatened by fishing activities, the loggerhead (Caretta caretta) represents a charismatic species considered as “vulnerable” at the global scale by IUCN.In the Mediterranean Sea, trawl nets show the highest probabilities of bycatch of protected species, with high rates of mortality. A new flexible Turtle Excluder Device (TED) has been tested for the first time on a commercial scale in the Mediterranean Sea to assess its effectiveness in reducing bycatch. The results did not show any significant (α = 0.05) loss in terms of commercial weight, but a significant reduction of debris in the codend of the nets mounting the TED respect to traditional nets. The catch comparison of the main commercial species showed similar rates without any significant loss of sizes, with the only exception of anglerfishes (Lophiusspp.) that showed a loss of the largest individuals by TED. In terms of bycatch, the traditional nets captured mostly rays and sharks, while no turtles were captured, at all. In this regard, the authors were informed by other vessels operating in the same areas at the time of the trials about some accidental catches of loggerhead turtles. Our results demonstrated that the flexible TED represents a practical and effective solution to reduce the bycatch of endangered species in coastal Mediterranean demersal multispecies fisheries, as demonstrated experimentally also in other areas of the world. The measures involving technical modifications of fishing gears require significant investments but are technically feasible and could guarantee the success of the conservation.