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

Abstract

16The Mediterranean Sea is a hotspot of biodiversity, but the high fishing pressure results in high 17 bycatch rates of protected (sea turtles and cetaceans) and top predator species (sharks). The 18 reduction of bycatch is challenging for fishery scientists, as conservation of these species has 19 become a priority. Among the animals threatened by fishing activities, the loggerhead (Caretta 20 caretta) represents a charismatic species considered as "vulnerable" at the global scale by IUCN. 21 In the Mediterranean Sea, trawl nets show the highest probabilities of bycatch of protected species, 22 with high rates of mortality. A new flexible Turtle Excluder Device (TED) has been tested for the 23 first time on a commercial scale in the Mediterranean Sea to assess its effectiveness in reducing 24 bycatch. The results did not show any significant (α = 0.05) loss in terms of commercial weight, but 25 a significant reduction of debris in the codend of the nets mounting the TED respect to traditional 26 nets. The catch comparison of the main commercial species showed similar rates without any 27 significant loss of sizes, with the only exception of anglerfishes (Lophius spp.) that showed a loss of 28 the largest individuals by TED. In terms of bycatch, the traditional nets captured mostly rays and 29 sharks, while no turtles were captured, at all. In this regard, the authors were informed by other 30 vessels operating in the same areas at the time of the trials about some accidental catches of 31 loggerhead turtles. Our results demonstrated that the flexible TED represents a practical and 32 effective solution to reduce the bycatch of endangered species in coastal Mediterranean demersal 33 multispecies fisheries, as demonstrated experimentally also in other areas of the world. The 34 measures involving technical modifications of fishing gears require significant investments but are 35 technically feasible and could guarantee the success of the conservation.36 37 3 38 Introduction 39The Mediterranean fishing fleet is highly diversified and targeting several species. The 40Mediterranean basin is also considered as a hot spot of biodiversity [1]. Nevertheless, the high 41 fishing effort has resulted in overexploitation of fish resources [2] and in the deterioration of marine 42 ecosystem services [3,4]. The bycatch of protected species, such as cetaceans [5] and sea turtles [6] 43 and top predator species, such as sharks without any economic importance [7] is a consequence of 44 the intense fishing pressure. The solution to reduce the bycatch has become a challenge for fishery 45 scientists as the conservation of species has become a priority for large international organizations. 46 The Habitats Directive [8], for examples, imposed, among others, a conservation policy aimed at 47 reducing the bycatch of species present in the list animals of Annex IV. FAO's International 48 Guidelines on Bycatch Management and Reduction of Discards [9] identified management 49 measures necessary to ensure the conservation of ...

Testing experimental devices in the extension piece to increase the selectivity of bottom trawl in the Nw Mediterranean

“…Selection grids aimed at reducing bycatch of undersized individuals have been tested in some areas of the Mediterranean (Sardà et al, 2005;Massuti et al, 2009;Özvarol, 2016). Although this device was proposed in the early 1980s to reduce the capture of large sized animals, such as sea turtles (Epperly, 2003;Lucchetti et al, 2016;Lucchetti et al, 2019;Vasapollo et al, 2019), experiments have shown that grids can be used to reduce the catch of juveniles, without affecting the catch of large sized fish Aydın and Tosunoglu, 2011). Therefore, according to the characteristics of the fishery and the target species, different typologies of grids can be used.…”