It has been widely acknowledged that fishery discard practices constitute a purposeless waste of valuable living resources, which plays an important role in the depletion of marine populations. Furthermore, discarding may have a number of adverse ecological impacts in marine ecosystems, provoking changes in the overall structure of trophic webs and habitats, which in turn could pose risks for the sustainability of current fisheries. The present review aims to describe the current state-of-the-art in discards research, with particular emphasis on the needs and challenges associated with the implementation of the Ecosystem Approach to Fisheries Management (EAFM) in European waters. We briefly review the international and European policy contexts of discarding, how discard data are collected and incorporated into stock assessments, selectivity in fishing and the main consequences of discarding for ecosystem dynamics. We then review implementation issues related to reducing discards under the EAFM and the associated scientific challenges, and conclude with some comments on lessons learned and future directions.
SUMMARY: Surface longline gears are used to fish different species, mainly albacore Thunnus alalunga (Bonnaterre, 1788), bluefin tuna Thunnus thynnus (Linnaeus, 1758), and swordfish Xiphias gladius Linnaeus, 1758, and are considered highly dangerous for threatened marine turtles. Loggerheads Caretta caretta (Linnaeus, 1758) can be incidentally captured by surface longlines. A number of captured individuals die during the fishing operation, which we consider direct mortality due to fishing. We analysed the relative loggerhead by-catch and direct mortality associated with each type of boat and gear from April to December during the period 1999-2004 in the Spanish surface longline fleet that fishes in the western Mediterranean Sea, an important fishing area for this fleet. We used different indices to compute the catch per unit effort (CPUE) according to the number of hooks and to the number of fishing operations for each type of boat and gear. Both bycatch and direct mortality differed significantly according to the type of boat and gear. With respect to the number of hooks, boats longer than 12 m not using a roller and targeting bluefin tuna captured the highest number of loggerheads, whereas boats longer than 12 m with a roller that targeted swordfish caused the highest direct mortality. With respect to the number of fishing operations, boats longer than 12 m without a roller that targeted albacore captured the highest number of loggerheads; the highest direct mortality was caused by this type of boat and by boats longer than 12 m using a roller and targeting swordfish.Keywords: Caretta caretta, drifting longline, fisheries, incidental capture, pre-release mortality, sea turtle. -El palangre de superficie es usado para la pesca de diferentes especies, fundamentalmente atún blanco Thunnus alalunga (Bonnaterre, 1788), atún rojo Thunnus thynnus (Linnaeus, 1758) y pez espada Xiphias gladius Linnaeus, 1758, y es considerado altamente peligroso para las tortugas marinas amenazadas. La tortuga boba Caretta caretta (Linnaeus, 1758) puede ser capturada incidentalmente por el palangre de superficie y un número considerable de ellas puede morir durante la operación de pesca, y son consideradas como muertas directamente en el palangre. En este trabajo se analizan la capturas incidentales y la mortalidad directa relativa asociada a cada tipo de barco y aparejo de pesca, desde abril a diciembre durante el periodo 1999-2004, en la flota palangrera española en el Mediterráneo occidental, una importante área de pesca para esta flota. Se usaron diferentes índices para calcular las capturas por unidad de esfuerzo (CPUE) de acuerdo al número de anzuelos y al número de operaciones de pesca para cada tipo de barco y aparejo. Tanto las capturas no dirigidas de la tortuga boba como la mortalidad directa presentan diferencias significativas en función del tipo de barco y aparejo. Con respecto al número de anzuelos, los barcos mayores de 12 m de eslora sin rulo y especie objetivo atún rojo presentaron el mayor número de capturas relativ...
Strandings of marine mammals on the north-western Spanish coast (Galicia) have been systematically recorded since 1990. A total of 1433 marine mammals belonging to 15 species was recorded from 1990 to 1999. The most frequently recorded species stranded were common dolphin (47%), bottlenose dolphin (11%) and harbour porpoise (7%). The number of strandings recorded increased annually over the study period, probably reflecting an increased observer effort. During 1996–1999, an average of 1·65 animals were stranded annually for each 10 km of coastline, the highest density of strandings recorded on the Atlantic coast of the Iberian Peninsula. More than 80% of the strandings were located on the western coast of Galicia, mainly in autumn and winter. During the study period, 42 proven incidental catches were recorded, although signs of by-catch were seen in a further 198 animals. The average size of stranded common dolphins and the proportion of males both increased towards the end of the calendar year.
Cetacean sightings are reported from opportunistic deployment of observers on ¢shing boats during 1998^1999 in Galician waters (north-west Spain), a region of high biodiversity, intensive ¢shing activity and an important cetacean habitat. During 111 trips, a total track length of 8128 km and estimated area of approximately 9840 km 2 was surveyed, including both inshore and o¡shore waters.The most frequently sighted species were common dolphins (Delphinus delphis) and bottlenose dolphins (Tursiops truncatus). Taking account of biases in the survey data, the former species was most commonly sighted in deeper o¡shore waters (4200 m depth) with the highest sightings rate in the second quarter of the year. Bottlenose dolphins were seen mainly in inshore waters to the south of Galicia but also in o¡shore waters further north. Sightings rates were higher when the observers' boats were engaged in ¢shing than when travelling. Published dietary data suggest that this may simply indicate that dolphins tend to congregate in ¢shing areas where their main prey occur.Several di¡erent treatments of the data were used to derive relative abundance indices (taking account of observation biases and of spatial variation in survey coverage). These calculations suggest that there may be around 7000^10,000 common dolphins and 600^1000 bottlenose dolphins in Galician waters, although dedicated surveys are needed to produce robust estimates.Other species seen during surveys included the long-¢nned pilot whale (Globicephala melas), harbour porpoise (Phocoena phocoena), Risso's dolphin (Grampus griseus) and ¢n whale (Balaenoptera physalus). Incidental observations from boats and land-based surveys supported the high relative abundance of common dolphins and, in inshore waters, of bottlenose dolphins, as well as providing additional records of porpoises and Risso's dolphins.
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