Catch-per-unit-effort and Biological Data of Nephrops norvegicus from the SW Ireland Spanish Trawl Fishery

Norway lobster Nephrops norvegicus is a burrowing species inhabiting soft bottoms in the NE Atlantic and Mediterranean. In European western waters (SW Ireland) Nephrops is a comercial species of the bottom mixed fishery prosecuted by fletes from Ireland, France, UK and Spain. A comprehensive collection (1980-2000) of Spanish trawl fishery data and sampling of landings is available. Although Nephrops is a by-catch spcies for the Spanish trawl fleet, some vessels target it mainly during the spring and summer seasoon. This study presents a summarized description of that fishery and catch per unit effort trends. Annual Nephrops length composition by sex, length-weight relationship, sex-ratio and proportion of ovigerous females are given for the referenced period.IEO FPI grant (BOE 06.10.2000, No9). DEMICES project

Megabenthic decapod crustacean assemblages on the Galician continental shelf and upper slope (north-west Spain)

The original publication is avaliable at www.springerlink.comThe structure of megabenthic decapod crustacean assemblages on the Galician (north-west Spain) continental shelf (100 to 200 depth) and upper slope (200 to 500 m) was analyzed based on surveys carried out in autumn and spring, from 1980 to 1987. Forty species belonging to 19 families were caught. The portunid crab "Polybius henslowii", a species with pelagic phases, was the most abundant species, but displayed strong spatial and temporal fluctuations. Other dominant species were the Norway lobster "Nephrops norvegicus", the portunid "Liocarcinus depurator", the galatheids "Munida intermedia" and "M. sarsi", and the shrimps "Solenocera membranacea", "Plesionika heterocarpus", "Pasiphaea sivado" and "Dichelopandalus bonnieri". Total abundance and biomass (average values excluding Polybius henslowii = 255 individuals and 2.06 kg/30 min tow) and species richness and diversity, Ht (6.85 species and Ht = 1.45 per tow) displayed a significant positive correlation with depth, and strong interannual fluctuations. The factors determining community organization were depth and, to a lesser extent, spatial structure. There was clear evidence of bathymetric zonation, differentiating between species characteristic of the slope ("D. bonnieri" and "Pasiphaea sivado"), shelf-slope edge ("Macropipus tuberculatus", "Pontophilus spinosus", "Munida sarsi", "S. membranacea", "Processa spp.") and shelf ("L. depurator", "Macropodia tenuirostris", "Paguridae" and "Chlorotocus crassicornis"). The spatial zonation was related to changes in oceanography and sediment along the continental margin. "Goneplax rhomboides", "N. norvegicus", "C. crassicornis" and "Alpheus glaber" are benthic species which generally exhibit burrowing behaviour, and they were found mainly in the southern area where there are fine sediments due to the outwelling from the Rías Baixas. Different benthopelagic shrimps ("Pontophilus spinosus", "Plesionika heterocarpus", "Processa spp." and "Pasiphaea sivado") were typical of the zone just north of Fisterra, characterized by a convergence of water masses bringing about an increase in productivity due to upwelling. The benthic anomuran and brachyuran crabs "Munida intermedia", "M. sarsi", "L. depurator" and "Macropipus tuberculatus" were characteristic of the northwestern zone between Fisterra and Estaca, where the infauna reaches high biomass despite coarser sediments with a lower concentration of organic material than in the southern area. Lastly, both the "Paguridae" and "Macropodia tenuirostris" were species typically found in the waters in the northern shelf. Based on interannual changes in assemblage structure, two periods could be distinguished: between 1980 and 1984, when "Polybius henslowii", "D. bonnieri" and "Pasiphaea sivado" had abundance peaks; and another period from 1985 to 1987 when "L. depurator", "Munida intermedia", "M. sarsi" and "Macropipus tuberculatus" increased in abundanc

Distribution and abundance of molluscs and decapod crustaceans in trawl samples from the Galician Shelf (NW Spain)

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Morphometry of Norway lobster Nephrops norvegicus (Linnaeus, 1758) from Galicia (northwest Spain)

Se ha estudiado el crecimiento relativo o alométrico de la cigala Nephrops norvegicus (L., 1758) de Galicia (noroeste de España). Las variables analizadas en relación con la longitud del caparazón fueron la longitud total, la anchura y la longitud de los quelípedos, la longitud del primer par de pleópodos de los machos, la anchura abdominal de las hembras y el peso húmedo. En hembras, la longitud total, la longitud y anchura de los quelípedos y la anchura del abdomen presentaron un crecimiento alométrico positivo. En machos, la longitud y anchura de los quelípedos mostraron alometría positiva, mientras que la longitud total y la longitud del primer par de pleópodos presentaron alometría negativa. Se encontraron diferencias entre sexos en las ecuaciones alométricas que relacionan la longitud del caparazón y el peso húmedo. La mayor parte de los individuos de cigala examinados (96 %) mostró heteroquelia, con la quela fina (cortadora) o la gruesa (trituradora) situada indistintamente en el lado izquierdo o el derecho[Abstract] The present study focused on the relative or allometric growth of Norway lobster Nephrops norvegicus (L., 1758) from Galicia (northwest Spain). The variables analysed in relation to the carapace length included total size, length and width of chelipeds, length of first pair of male pleopods, width of female abdomen, and live weight. In females, total length, length and width of chelipeds, and abdominal width showed positive allometry. In males, the length and width of chelipeds also showed positive allometry, whereas the total length and first pair of pleopods’ length showed negative allometry. Differences were found between males and females regarding the relationship of carapace length to live weight. Most of the individuals sampled (96 %) showed handedness, with the cutter or the crusher claw indistinctly placed on the left or right sideInstituto Español de Oceanografí

Exploring long-term variability of Nephrops norvegicus population in the Porcupine Bank (SW Ireland)

PresentationNephrops norvegicus is a commercial species of the bottom fisheries in European western waters which yield has long-term variability. Their distribution is linked to suitable habitats of muddy sediment in which adults construct burrows but the influence of environmental factors on the populations was poorly investigated. Variability in the catch per unit effort (CPUE) of Nephrops norvegicus from Porcupine Bank (Southwest of Ireland) was explored using a time series approach. The CPUE time series (1979-2005) exhibited a seasonal pattern. The seasonal decomposition of the CPUE shows a declining trend in the trend and cycle component from 1982 onwards. ARMA univariate and dynamic regression models were fitted to the CPUE time series. Population (proportion of males, proportion of ovigerous females and recruits) and North Atlantic Oscillation index were tested at different lags to investigate possible factors related to the yield fluctuations