Flexible Turtle Excluder Device (TED): an effective tool for Mediterranean coastal multispecies bottom trawl fisheries

Petetta

et al. 2019

Preprint

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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 ...

Section: Discussionsupporting

confidence: 93%

Section: Discussionsupporting

confidence: 59%

Section: Discussionmentioning

confidence: 99%

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

Petetta

et al. 2019

Preprint

Self Cite

“…The area is characterized by shallow waters (<100 m) and rich benthic communities, and is considered as a key-feeding habitat in the whole Mediterranean, where turtles in the demersal stage spend the winter (Lazar & Tvrtkovic, 1995; Casale, Laurent & De Metrio, 2004; Lazar, Ziza & Tvrtkovic, 2006; Lucchetti & Sala, 2010). However, the Northern and Central Adriatic are also characterized by a wide continental shelf, low depth, and a flat seabed, which is ideal for trawling (Lucchetti, Punzo & Virgili, 2016). The high density of turtles and trawlers in autumn and winter in this area give rise to a bycatch hotspot, also supported by the ZINB analysis that highlighted how trawl net was perhaps the most dangerous gear in terms of predicted catches per boat.…”

Section: Discussionmentioning

confidence: 99%

An interview-based approach to assess sea turtle bycatch in Italian waters

Lucchetti

2017

PeerJ

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The loggerhead sea turtle (Caretta caretta, Linnaeus, 1758) is the most abundant sea turtle species in the Mediterranean Sea, where commercial fishing appears to be the main driver of mortality. So far, information on sea turtle bycatch in Italy is limited both in space and time due to logistical problems in data collected through onboard observations and on a limited number of vessels involved. In the present study, sea turtle bycatch in Italian waters was examined by collecting fishermen’s information on turtle bycatch through an interview-based approach. Their replies enabled the identification of bycatch hotspots in relation to area, season and to the main gear types. The most harmful fishing gears resulted to be trawl nets, showing the highest probabilities of turtle bycatch with a hotspot in the Adriatic Sea, followed by longlines in the Ionian Sea and in the Sicily Channel. Estimates obtained by the present results showed that more than 52,000 capture events and 10,000 deaths occurred in Italian waters in 2014, highlighting a more alarming scenario than earlier studies. The work shows that in case of poor data from other sources, direct questioning of fishermen and stakeholders could represent a useful and cost-effective approach capable of providing sufficient data to estimate annual bycatch rates and identify high-risk gear/location/season combinations.

“…Considering the high diversification of the Mediterranean fishing fleet, all three life‐cycle phases can be affected, by different types of fishing gear (Camiñas, ; Casale, ; Lucchetti & Sala, ). Vessels from large‐scale and small‐scale fisheries (SSFs) using trawls (Casale, Laurent, & De Metrio, ; Jribi, Bradai, & Bouain, ; Lucchetti, Punzo, & Virgili, ; Lucchetti & Sala, ), longlines (Deflorio, Aprea, Corriero, Santamaria, & De Metrio, ; Piovano, Celona, Basciano, Di Marco, & Giacoma, ; Piovano, Swimmer, & Giacoma, ; Piovano et al, , ), gillnets (Casale, Freggi, Basso, & Argano, ; Echwikhi, Jribi, Bradai, & Bouain, , ), encircling nets (Casale, ), and other gears all result in sea turtle bycatch. According to recent estimates (Casale, ), fishing activities in the Mediterranean are responsible each year for the incidental catch of some 130 000 marine turtles, caught by longlines (70 000 individuals), bottom trawls (40 000), and fixed nets (23 000), leading to more than 40 000 deaths.…”

Section: Introductionmentioning

confidence: 99%

Sea turtles bycatch in the Adriatic Sea set net fisheries and possible hot‐spot identification

Lucchetti

2017

Aquatic Conservation

Self Cite

Bycatch resulting from fishing activities is the main threat for the conservation of sea turtles in the Mediterranean Sea. Fixed nets are a matter of concern for sea turtles mainly in coastal areas during the neritic stage when both juvenile and adult life stages are affected. Mortality caused by entanglement in set nets is related to forced apnoea due to the high soak time of the nets and consequent drowning. This study investigated the loggerhead turtle bycatch in set net coastal fisheries in the northern Adriatic Sea (General Fisheries Commission for the Mediterranean Geographical Sub‐Area 17, [GSA 17]) through an interview‐based approach, to understand the potential contribution of these fisheries to the general decline of the sea turtle population. A second goal was to identify a possible hot‐spot turtle bycatch area through on‐board observations. The study estimates that more than 5400 turtles are caught in the west GSA 17 each year with the largest number in the summer. A hot‐spot for entanglement was also identified in an area located south of the River Po delta (41.5–69 m depth) during the summer. Sixty‐four turtles were caught over a period of 30 fishing days by either trammel nets and gillnets (0.7 and 0.5 turtle per km of net respectively) and was the greatest number that has been observed anywhere in the Mediterranean. Possible management strategies to reduce bycatch include technical modification to gear setting (such as reducing netting slack and using small meshes), bycatch reducer devices (such as LED UV), and area and seasonal gear restrictions to small‐scale fisheries in areas of greatest concern in the northern Adriatic Sea.