Seabird mortality on longline fisheries in the western Mediterranean: factors affecting bycatch and proposed mitigating measures

Belda, Eduardo J.; Sánchez, Antonio

doi:10.1016/s0006-3207(00)00178-6

Cited by 92 publications

(109 citation statements)

References 9 publications

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“…No mitigation measures to reduce seabird mortality were used in the study fishery. Data from Belda and Sánchez (2001) on seabird mortality on longlines around the Columbretes Islands (Spain) suggests that bycatch rates could be very variable at the local level, due to seabird distribution and also to the dynamics of the drifting longline fishing fleet. Owing to the existence of several large breeding colonies of seabirds in the western Mediterranean, seabird bycatch could be a cause for concern.…”

Section: Discussionmentioning

confidence: 99%

The incidental capture of seabirds by Spanish drifting longline fisheries in the western Mediterranean Sea

Valeiras¹,

Camiñas²

2003

Sci. Mar.

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SUMMARY: The western Mediterranean Sea is an important fishing area for the Spanish drifting longline fleet, targeting swordfish (Xiphias gladius), bluefin tuna (Thunnus thynnus) and albacore (T. alalunga). Some seabird species can be captured incidentally as bycatch marine fauna. From July 1999 to August 2000 information on 554 surface longline sets was collected by onboard observers of the Spanish Oceanographic Institute (IEO) on 18 longline fishing boats working within the Spanish Mediterranean fishing area. Eleven yellow-legged gulls (Larus cachinnans), 9 Cory's shearwaters (Calonectris diomedea) and 1 Northern gannet (Morus bassanus) were captured incidentally. Bycatch rates ranged from 0.002 to 0.023 birds/1000 hooks.

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Section: Discussionmentioning

confidence: 99%

The incidental capture of seabirds by Spanish drifting longline fisheries in the western Mediterranean Sea

Valeiras¹,

Camiñas²

2003

Sci. Mar.

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“…There is evidence for occasional accidental catch by line fishers (Thébault 2011), but there is currently no evidence to suggest that fisheries bycatch has been a significant threat to the species within the study area in recent years. This contrasts with the situation in Portuguese and Mediterranean waters, where commercial longline and seine net fishing are considered threats (Belda & Sanchez 2001, ICES 2008b, Laneri et al 2010, Boué et al 2013. Further monitoring of interactions with commercial fishing boats in the northern parts of the species' range will be required to assess whether bycatch is an issue on a larger scale.…”

Section: Conservation Implicationsmentioning

confidence: 92%

Using integrated land- and boat-based surveys to inform conservation of the Critically Endangered Balearic shearwater

Jones¹,

Wynn²,

Yésou³

et al. 2014

Endang. Species. Res.

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We investigated spatio-temporal distribution patterns of the Critically Endangered Balearic shearwater Puffinus mauretanicus in the northern part of its migratory range, using a combination of effort-corrected land-and boat-based survey data (2007−2010). The species was recorded regularly along the western English Channel (Western Channel) coasts of northwest France and the southwest UK, with peak counts occurring during the summer and autumn months. Foraging aggregations comprising hundreds to thousands of birds (~1 to 20% of the global population) were recorded in the large shallow embayments of northern Brittany in all survey years. Elsewhere, most birds were recorded on passage, with maximum birds-per-hour (BPH) of 169 off northwest France and 36 off the southwest UK. Few birds were recorded offshore, beyond sight of land. A distance-from-shore analysis revealed that the species passed closer to shore than other pelagic seabirds such as sooty shearwater Puffinus griseus. A constant-effort seasonal survey from the southwest tip of the UK mainland recorded the species on 93% of survey days, with BPH rates peaking in the morning between 08:00 and 11:00 h. These results have important monitoring and conservation implications for this Critically Endangered species. In particular, the records of large aggregations in spatially restricted areas of the Western Channel during the inter-breeding period suggests the species could be vulnerable to impacts such as oil spills, or disturbance from offshore construction projects. We also provide evidence that some birds remain in the survey area during the breeding season, suggesting it may be an important site for non-breeding birds.

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“…Population sizes and trends for albatrosses are generally well documented and vary from a few tens of breeding pairs in some species to hundreds of thousands of pairs in others; for a few populations detailed demographic data exist showing which particular component of the population is subject to elevated mortality rates due to long-line fishery bycatch. Several albatross and petrel species are already listed as 'Critically Endangered', 'Endangered' or 'Vulnerable' by the World Conservation Union, and long-line fisheries are contributing to population declines in several of these species, with a clear risk of species extinctions if current trends are allowed to persist, since drowning of only one or two adults per year from a breeding population of only a few tens of breeding pairs will cause population decline (Croxall and Gales, 1997;Belda and Sánchez, 2001). Mitigation measures are legally required in a number of regions and fisheries, but not all fisheries adopt these, and the efficacy of the many possible mitigation measures requires further study (Brothers et al, 1999;Weimerskirch et al, 1999), although there is no doubt that they can greatly reduce bycatch rates (Murray et al, 1993;Melvin and Parrish, 2001).…”

Section: Long-line Bycatchmentioning

confidence: 99%

Impacts of fisheries on seabird communities

Furness¹

2003

Sci. Mar.

192

156

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SUMMARY: Long-line by-catch of albatrosses and petrels may soon lead to species extinctions. Set-net bycatch has caused major reductions in certain seabird populations. Some fisheries may decrease numbers of seabirds by reducing abundance of prey-fish. Other fisheries may increase seabird numbers, by increasing prey-fish abundance through depletion of predatory fish stocks, or by provision of offal and discards. These latter impacts of fisheries on seabirds are often difficult to measure against a background of many and varied environmental and human influences. Depletion of stocks of small lipid-rich fish have reduced numbers of seabirds, in Peru, the Norwegian Sea, and the Barents Sea. However, reductions of predatory fish stocks in the North Sea have more than compensated for quantities of sandeels removed by the sandeel fishery. While piscivorous fish stocks remain low, sandeel fishery and seabirds appear to be able to coexist. However, if piscivorous fish stocks recover in the North Sea, reduced availability of sandeels to seabirds may affect certain species. Provision of discards and offal can stimulate large increases in scavenging seabird numbers. Desirable reductions in discard rates may have an unfortunate side-effect of forcing some scavenging seabirds to turn to killing smaller seabirds, with drastic consequences for community structure.Key words: conservation, discards, ecosystem, fisheries management, industrial fisheries, predator-prey, sandeel. RESUMEN: EL IMPACTO DE LAS PESQUERIAS EN LAS COMUNIDADES DE AVESMARINAS. -Las capturas accidentales de los albatros y petreles en palangres pueden llevar pronto a algunas especies a la extinción. La captura en redes de trasmallo ha causado también grandes reducciones en ciertas poblaciones de aves marinas. Ciertas pesquerías pueden provocar la disminución en el número de aves marinas al reducir la abundancia de los peces presa. Otras pesquerías pueden hacer crecer el número de aves marinas, al incrementar la abundancia de los peces presa mediante la disminución de las efectivos de los peces depredadores, o mediante el suministro de despojos y descartes. Estos últimos impactos de las pesquerías en las aves marinas son con frecuencia difíciles de medir por el efecto de numerosas y variadas influencias ambientales y humanas. La disminución de efectivos de pescado azul de pequeño tamaño ha reducido el número de aves marinas en Perú, el Mar de Noruega y el Mar de Barents. Sin embargo, en el Mar del Norte, la reducción del lanzón (A. marinus) como consecuencia de su pesca específica se ha visto ampliamente compensada por una reducción en los efectivos de peces predadores. Mientras los efectivos de peces piscívoros se mantengan bajos, la pesca del lanzón y las aves marinas parecen ser capaces de coexistir. No obstante, si los efectivos de peces piscívoros se recuperan en el Mar del Norte, reduciendo la disponibilidad de lanzones para las aves marinas, esto afectaría a ciertas especies. El aprovisionamiento de descartes y despojos pudiera estimular grandes increme...

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Seabird mortality on longline fisheries in the western Mediterranean: factors affecting bycatch and proposed mitigating measures

Cited by 92 publications

References 9 publications

The incidental capture of seabirds by Spanish drifting longline fisheries in the western Mediterranean Sea

The incidental capture of seabirds by Spanish drifting longline fisheries in the western Mediterranean Sea

Using integrated land- and boat-based surveys to inform conservation of the Critically Endangered Balearic shearwater

Impacts of fisheries on seabird communities

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