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

Abstract

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.

Reducing Sea Turtle Bycatch in the Mediterranean Mixed Demersal Fisheries

“…The size of dots refer to the sum (LED + CTRL) of specimens for each length class. the first time this BRDs applied to gillnets targeting rays in the Adriatic Sea (offshore waters), in an area that has been proven to be a hotspot of sea turtle occurrence (Lucchetti et al, 2017b). The net was illuminated with the same UV-LED lamps used in the present study, which have a longer life and provide greater light intensity than ordinary light-sticks.…”

Sea turtle strandings, sightings and accidental catch along the Croatian Adriatic coast

“…However, even though the data on stranded turtles were collected along the entire Croatian Adriatic coast, reliable comparative data regarding the potential causative factors are missing. Thus, to clarify the reasons behind the seasonal stranding dynamics, future monitoring activities in the Croatian Adriatic should take into consideration acquiring comparative seasonal and spatial data on two major anthropogenic threats for sea turtles recognized in the Mediterranean and Adriatic: fishing bycatch (by different fishing equipment) and marine traffic (Caminas, 2004;Lazar et al, 2006;Casale et al, 2007;Lewison & Crowder, 2007;Lucchetti & Sala, 2010;Casale, 2011;Levy et al, 2015;Lucchetti et al, 2017aLucchetti et al, , 2017b. Nevertheless, the records confirm the existence of bycatch by trawlers, gillnets and longlines within the entire Croatian Adriatic Sea.…”

“…In addition to fishery bycatch in the Adriatic, boat col-lisions seem to be the second major threat for frequently occurring C. caretta species (Lazar & Tvrtković, 1995;Lucchetti et al, 2017aLucchetti et al, , 2017bLucchetti et al, , 2018. Despite a generally low number of recorded injuries, the data presented in this study revealed the presence of severe mechanical injuries caused by marine vessels.…”

“…Also, this region is one of the key neritic feeding habitats for C. caretta individuals in the Mediterranean Casale et al, 2018). Intensive fishing activity in the Mediterranean and subsequently the Adriatic Sea is the main cause of sea turtle (C. caretta) mortality, followed by boat collisions (Lazar & Tvrtković, 1995;Gerosa & Casale, 1999;Lucchetti & Sala, 2010;Turkozan et al, 2013;Wallace et al, 2013b;Lucchetti et al, 2017aLucchetti et al, , 2017bVirgili et al, 2018;. Thus far, such events were quantified along the north and western part of the Adriatic, whereas similar cases were only mentioned to have occurred along the Croatian coast (Casale et al, , 2018.…”

Rapid Assessments of Leatherback Small-Scale Fishery Bycatch in Internesting Areas in the Eastern Pacific Ocean

“…The use of fishers' knowledge, gathered through rapid bycatch assessments (i.e., direct interviews of fishers), to obtain information about fisheries interactions with threatened species (e.g., marine turtles) has been implemented in various locations (Moore et al, 2010;Lucchetti et al, 2017a;Alfaro-Shigueto et al, 2018). Rapid assessments represent a standardized, lowcost, and relatively fast methodology when compared to the implementation of on-board monitoring programs (Lucchetti et al, 2017b). Rapid assessments are also particularly affordable considering the large geographic areas where fishing activities operate and when funds are limited.…”