Amphiura chiajei Forbes, comensal de Maldane glebifex Grube, en la Ría de Muros (Galicia)

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Contribution of infauna and mussel-raft epifauna to demersal fish diets

The contribution of infauna and mussel-raft epifauna to the diet of 3 dominant species in the demersal fish community of the Ria de Arosa, N. W. Spain - Lesueurigobius friesii (Gobiidae), Callionymus lyra (Callionymidae) and Trisopterus luscus (Gadidae) - was determined. Intense raft mussel culture in the Ria de Arosa supports a rich epifauna which constitutes the main food resource for the fishes studied. In contrast, infauna density is low and contributes only a small proportion to fish diets. Prey consumed was similar in the 3 fish species. Gut contents consisted mainly of the small crab Pisidia longicornis. This decapod is a dominant component of the raft epifauna, and electivity indices indicate that it is selected by the fishes. In the Ria de Pontevedra, which contains fewer mussel rafts, these fish fed on infauna. Thus, one effect of intense mussel aquaculture has been to change the food habits of these 3 fishes from predominantly infauna to raft epifauna diet.versión del edito

Upwelling and outwelling effects on the benthic regime of the continental shelf off Galicia, NW Spain

The benthic regime off the Galician coast of NW Spain was surveyed to assess biogenic enrichment from coastal upwelling and detritus outwelling from the rías, large coastal embayments: the Rías Altas along the northern and the Rías Bajas along the western coast, which have intense mussel aquaculture. Sediment samples were collected from 1984 to 1986 and used for geological, microbiological, and macrofaunal studies. Sub-bottom acoustic profiler records and grab and core samples identified two main mud deposits on the western shelf that were aligned north to south and parallel with the coastline. The major axis of the mud deposit, which extended south to the Portuguese border, is associated with the three most southern rías (Arosa, Pontevedra and Vigo) along the western shelf. Sediment particle size analysis showed that sediments on the western shelf were heterogeneous, and grain size increased from the inner shelf to the shelf break. On the northern shelf, sediments exhibited a more homogeneous textural distribution. Sediment organic matter followed a similar pattern with that of particle size. The highest organic matter values, 10%, occurred on the western shelf nearest the Rías Bajas, but these values decreased offshore to between 2 and 4%. On the northern shelf organic matter content was generally less than 4% but with patches of higher organic content. The composition and structure of macroinfauna on the northern shelf, where seasonal coastal upwelling results in benthic enrichment, showed mainly small, surface feeding, and fast growing polychaetes. In contrast, macroinfauna on the western shelf showed more subsurface, deposit-feeding polychaetes. A main difference between the two shelves is that off the rías Bajas, besides coastal upwelling, outwelling from the highly productive rías Bajas, with their intense mussel aquaculture, also enriches the coastal sediment regime with a steady source of organic matter. Although seasonal and interannual variations occurred in the benthic bacteria, their general density distribution followed the pattern of organic matter content and particle grain size seasonally and interannually. The highest numbers of bacteria occurred in the upwelling region off the northern shelf and nearest the Rías Bajas on the western shelf. Both coastal upwelling and organic outwelling from the rías Bajas support benthic production alongthe western Galician shelf. The main commercialdemersal finfishalongthis coast is hake, Merluccius merluccius and blue-whiting, Micomesistius poutassou. The norwegian lobster, Nephrops norvegicus is also an important crop, and is more abundant off the rías Bajas in the finer and organic-richsediments where there are abundant prey resources of benthic infauna

Coastal upwelling off the Rías Bajas, Galicia, Northwest Spain. II. Benthic studies

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Sublittoral soft bottom communities and diversity of Mejillones Bay in northern Chile (Humboldt Current upwelling system)

The macrozoobenthos of Mejillones Bay (23°S; Humboldt Current) was quantitatively investigated over a 7-year period from austral summer 1995/1996 to winter 2002. About 78 van Veen grab samples taken at six stations (5, 10, 20 m depth) provided the basis for the analysis of the distribution of 60 species and 28 families of benthic invertebrates, as well as of their abundance and biomass. Mean abundance (2,119 individuals m-2) was in the same order compared to a previous investigation; mean biomass (966 g formalin wet mass m-2), however, exceeded prior estimations mainly due to the dominance of the bivalve Aulacomya ater. About 43% of the taxa inhabited the complete depth range. Mean taxonomic Shannon diversity (H', Log e) was 1.54 ± 0.58 with a maximum at 20 m (1.95 ± 0.33); evenness increased with depth. The fauna was numerically dominated by carnivorous gastropods, polychaetes and crustaceans (48%). About 15% of the species were suspensivorous, 13% sedimentivorous, 11% detritivorous, 7% omnivorous and 6% herbivorous. Cluster analyses showed a significant difference between the shallow and the deeper stations. Gammarid amphipods and the polychaete family Nephtyidae characterized the 5-mzone, the molluscs Aulacomya ater, Mitrella unifasciata and gammarids the intermediate zone, while the gastropod Nassarius gayi and the polychaete family Nereidae were most prominent at the deeper stations. The communities of the three depth zones did not appear to be limited by hypoxia during non-El Niño conditions. Therefore, no typical change in community structure occurred during El Niño 1997–1998, in contrast to what was observed for deeper faunal assemblages and hypoxic bays elsewhere in the coastal Humboldt Current system

Coastal upwelling in the Rías Bajas, NW Spain: Contrasting the benthic regimes of Rías de Arosa and de Muros

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Factors driving patterns and trends in strandings of small cetaceans

The incidence of cetacean strandings is expected to depend on a combination of factors, including the dis- tribution and abundance of the cetaceans, their prey, and causes of mortality (e.g. natural, fishery bycatch), as well as currents and winds which affect whether carcasses reach the shore. We investigated spatiotemporal patterns and trends in the numbers of strandings of three species of small cetacean in Galicia (NW Spain) and their relationships with meteoro- logical, oceanographic, prey abundance and fishing-related variables, aiming to disentangle the relationship that may exist between these factors, cetacean abundance and mor- tality off the coast. Strandings of 1166 common dolphins (Delphinus delphis), 118 bottlenose dolphins (Tursiops truncatus) and 90 harbour porpoises (Phocoena phocoena) during 2000–2013 were analysed. Generalised additive and generalised additive-mixed model results showed that the variables which best explained the pattern of strandings of the three cetacean species were those related with local ocean meteorology (strength and direction of the North– South component of the winds and the number of days with South-West winds) and the winter North Atlantic Oscil- lation Index. There were no significant relationships with indices of fishing effort or landings. Only bottlenose dolphin showed possible fluctuations in local abundance over the study period. There was no evidence of long-term trends in number of strandings in any of the species and their abun- dances were, therefore, considered to have been relatively stable during the study period.Versión del editor2,01

Primeros datos sobre la biomasa y la composición del bentos infaunal de la Ría de Pontevedra, en relación con el contenido en materia orgánica del sedimento

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Distribución espacial de las comunidades bentónicas infaunales de la Ría de Arosa

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