Geographical patterns of seabird attendance to a research trawler along the Iberian Mediterranean coast

Abstract

SUMMARY: The attendance of seabirds to a research trawler along the Mediterranean coast of the Iberian Peninsula was monitored during six demersal surveys (MEDITS project). Cruises were performed in late spring during the period 1994-1999. Twenty seabird species were recorded, including both breeders and migrants. The four most common species behind the boat were local breeders, namely the Balearic shearwater Puffinus mauretanicus, Cory's shearwater Calonectris diomedea, Audouin's gull Larus audouinii and the yellow-legged gull Larus cachinnans. Most seabirds made use of trawler discards to some extent, with the exception of the Puffin Fratercula arctica. Geographically consistent patterns were identified in the six years surveyed. Seabirds were most abundant along the eastern coast of Iberia, especially off the Ebro Delta and around the Columbretes Islands, coinciding with one of the major areas of primary productivity and one of the largest trawling fleets in the western Mediterranean. The location of the main seabird colonies also influenced the distribution of breeders.Key words: seabirds, distribution, trawl survey, western Mediterranean RESUMEN: PAUTAS GEOGRÁFICAS EN LA ASOCIACIÓN DE AVES MARINAS A UN ARRASTRERO DE INVESTIGACIÓN A LO LARGO DELAS COSTAS MEDITERRÁNEAS IBÉRICAS. -La atracción de aves marinas a un buque arrastrero de investigación fue estudiada durante seis campañas pesqueras demersales (proyecto MEDITS). Las campañas se realizaron a finales de primavera durante el periodo 1994-1999. Se registraron un total de veinte especies de aves marinas, incluyendo tanto especies reproductoras como migrantes. Las cuatro especies más comunes a popa del buque fueron especies reproductoras, concretamente la pardela balear Puffinus mauretanicus, la pardela cenicienta Calonectris diomedea, la gaviota de Audouin Larus audouinii y la gaviota patiamarilla Larus cachinnans. La mayor parte de las aves marinas usaron descartes pesqueros en mayor o menor grado, con la excepción del frailecillo Fratercula arctica. Se identificaron pautas geográficamente consistentes en los seis años muestreados. La mayor abundancia de aves marinas se registró a lo largo de las costas orientales de la península ibé-rica, especialmente en la zona del delta del Ebro y alrededor de las islas Columbretes, coincidiendo con una de las áreas más importantes de producción primaria y con una de las mayores flotas de arrastre en el Mediterráneo occidental. La localización de las principales colonias de cría también afectó a la distribución de las especies reproductoras en la zona.Palabras clave: aves marinas, distribución, campañas de arrastre, Mediterráneo occidental

Ecological Role of Submarine Canyons and Need for Canyon Conservation: A Review

“…Canyons have also been shown to provide habitat for spawning females of pelagic and benthic species of commercial interest (Farrugio, 2012). Other faunal components of marine ecosystems, including mammals and marine birds, also use canyons, for example, as feeding grounds (Abelló et al, 2003;Garcia and Thomsen, 2008;Roditi-Elasar et al, 2013;Moors-Murphy, 2014). Habitat diversity and specific abiotic characteristics enhance the occurrence of high levels of biodiversity in some canyons (Vetter and Dayton, 1998;McClain and Barry, 2010;Company et al, 2012;De Leo et al, 2014).…”

Exploiting the closest productive area: geographical segregation of foraging grounds in a critically endangered seabird

“…5, Millot 1999 Breeding Balearic shearwaters likely use the same foraging grounds year after year as the western Mediterranean is characterised by a relatively stable coastal circulation, and overall chl a values may not differ greatly between years (Gordoa et al 2008). In fact, the location of resources at large and intermediate scales appears reasonably predictable for pelagic seabirds over long time periods in the Mediterranean because they associate to the same mesoscale features along the Iberian continental shelf during different years (Arcos & Oro 2002, Abelló et al 2003, Louzao et al 2006a). The use of tracking devices may link foraging trip characteristics to fitness parameters such as breeding performance.…”

Activity patterns and foraging behaviour of Audouin' s gulls in the Ebro Delta, NW Mediterranean

“…Some other studies in the same area, however, have shown that gulls still forage at sea even when trawlers do not operate (Oro, 1995b;Abelló and Oro, 1998a;Abelló et al, 2003), probably taking advantage of the relatively high natural production of the continental shelf (Estrada, 1996), or in association with purse seiners (Arcos et al, 2001). Our results, then, are probably the consequence of birds leaving the colony after reproductive failure (Oro and Martínez-Vilalta, 1994), rather than a change in foraging behaviour associated with the trawling moratoria.…”

“…As a result, the foraging ranges were probably smaller here than in other colonies (Burger and Gochfeld, 1996;Oro, 1998a, Baccetti et al, 2000. Maximum foraging activity (as number of birds outside the colony) took place every day in mid-morning and mid-afternoon, whereas minimum activity occurred at midnight, suggesting that gulls may adjust their timetable to that of trawlers (Castilla and Jiménez, 1995;Oro, 1995a;González-Solís et al, 1999;Abelló et al, 2003), but also to that of purse-seiners or diel (vertical) migrations of cupleids (with one peak at dawn and another at dusk), which would explain why some birds leave the colony at or just before dawn, or arrive just before midnight. In the study area, Audouin's gulls probably exhibited a more marked pattern of diurnal activity than in other areas where fishing activity is not relevant for gulls (Gonzalez-Solis et al, 1999).…”