Seabird bycatch in Spanish Mediterranean large pelagic longline fisheries, 2000-2008

Abstract

-Incidental catch or bycatch represents a significant threat for the conservation of seabird populations. The western Mediterranean is an important fishing area where the Spanish pelagic and semi-pelagic longline fleet targeting swordfish (Xiphias gladius), bluefin tuna (Thunnus thynnus) and albacore (Thunnus alalunga) operates. Bycatch of these fisheries includes several seabird species. Given the importance of conservation of the bycatch species (marine mammals, turtles, sharks and seabirds), an on-board observer program was implemented by the Spanish Oceanographic Institute (IEO); this included collecting data on effort and catch, as well as weight and number of individuals of the main bycatch species. The aim of the present study is to report data on seabird bycatch collected by the on-board observer program of the IEO in the Western Mediterranean. Data on seabird bycatch were collected for the period 2000-2008, throughout the year. Six longline gears targeting large pelagic fish were identified operating in the area of study, but only three had an effect on seabird species. Differences in catch per unit effort (CPUE, birds per 1000 hooks) for each gear, as well as their effect on particular seabird species, are reported in this study. A total of 4 786 466 hooks were monitored, which yielded 182 seabirds belonging to 7 different species. The average CPUE for the studied period was 0.038 birds per 1000 hooks. Cory's shearwater (Calonectris diomedea) and yellow-legged gull (Larus michahellis) were the species the most highly represented in the catch. In contrast, Balearic shearwater (Puffinus mauretanicus) was only present in the longline fishery targeting albacore (CPUE = 0.005 birds per 1000 hooks). Our results suggest that Cory's shearwater is the species the most affected by the longline fishery in the Western Mediterranean, probably due to its biological characteristics, and corroborate the well-established downward trend in its population.Key words: Bycatch / Seabird / CPUE / Western Mediterranean Sea / Pelagic longline Résumé -Les captures fortuites ou accessoires représentent une menace considérable pour la sauvegarde des populations d'oiseaux de mer. La partie occidentale de la Méditerranée est une zone importante de pêche où la flotte espagnole de palangriers pélagiques et semi-pélagiques opère et cible l'espadon (Xiphias gladius), le thon rouge (Thunnus thynnus) et le germon (Thunnus alalunga). Les captures accessoires de ces pêches incluent plusieurs espèces d'oiseaux de mer. Étant donnée l'importance de la protection des espèces capturées accidentellement (mammifères marins, tortues, requins et oiseaux de mer), un programme a été mis en place par l'Institut espagnol d'Océanographie (IEO) : des observateurs étant à bord collectent des données d'effort de pêche et de capture, aussi bien que le nombre d'individus et le poids des principales espèces des prises accessoires. L'objectif de cette étude est de rapporter les données de captures accessoires des oiseaux de mer, collectées par ce prog...

Global patterns of marine mammal, seabird, and sea turtle bycatch reveal taxa-specific and cumulative megafauna hotspots

“…This direct and comprehensive assessment differs from most previous studies that have focused on a proxy of bycatch (e.g., fisheries yield) rather than empirical bycatch data (19), a single species or taxon (20)(21)(22), or a single type of fishing gear in one region (23,24), often without consideration of the spatial distribution of bycatch. A direct, spatially explicit cross-taxa and cross-gear bycatch assessment is necessary to analyze the complex patterns of global bycatch.…”

Global seabird bycatch in longline fisheries

“…The only rigorous scientific investigations to date have come from Spanish waters in the western Mediterranean (e.g. García-Barcelona et al 2009). Elsewhere, there are thousands of vessels, mostly artisanal, fishing within the region, yet very little is known of their impacts on seabirds or other vulnerable species.…”

Assessing the influence of the atmospheric oscillations on pelagic and highly migratory sharks bycatches from Spanish Mediterranean Sea, a meta-analytic approach

“…Many studies indicate that the Spanish longline fleet is concentrated mainly around the Balearic Islands (Camiñas et al 2006, Báez et al 2007a, 2007b, García-Barcelona et al 2010, Báez et al 2013b. Thus, Alboran Sea was used by approximately 5% of the operative fleet; while Balearic Sea was used by approximately 80% of the operative fleet.…”

“…Vessel length range from 12 to 27 m and fishing trips are often of short duration (one day to six days). A major description of these gears and fisheries are available in Camiñas et al (2006), Báez et al (2007a, b), García-Barcelona et al (2010), and Báez et al (2013b).…”