PELACUS 0316-Cruise Report

Archivo actualizado diciembre 2016The Spanish acoustic-trawl time series PELACUS 0316 was carried out on board R/V Miguel Oliver from 13th March to 16th April, covering the north Spanish waters (Atlantic and Bay of Biscay) from the coast to the 1000 m isobath on a systematic grid with tracks 8 nmi apart and equally spaced. Acoustic , fishing stations, fish egg counting, microplastic, and apical predators observations were done during daytime whilst the oceanographic characterisation was done during night time. A total of 3650 nautical miles were steamed, 1248 corresponding to the survey track. Besides 49 fishing stations were performed . Unexpectedly, weather and oceanographic conditions found during PELACUS 0316 were those of the winter time rather than the incipient spring ones. Together with dominant N-NE at the beginning of the survey, which produced a coastal upwelling in the Galician waters, then consecutive deep W/NW storm fronts have affected the survey plan; five days were lost due to the bad weather conditions. And during the last part of thesuvey either strong south wind (up to 45 knots) or a persistent swell of about 2-4 m height have also made problems to achieve clean echograms (i.e. without bubbles) and good performance at the fishing station. These conditions might have been also affected the availability of the fish. This seems clearer in the southern part (IXaN), where a stronger winter poleward current led the continental self almost empty of plankton and with a very scarce concentration of fish. Abundance of the main pelagic fish species was lower than that of the previous year. For sardine the abundance was very low, practically below of an acceptable threshold for an acoustic assessment. Moreover, the 75% of the estimated biomass was concentrated in a single large and thick school. Although this school was not caught (i.e. no ground truth) the acoustic and morphological characteristics were similar to those found in other ground-truthed sardine schools. In total the assessed biomass was very low, and excluding this school only 3 thousand tons were estimated, the lowest record in the time series (13 thousand tons including this school but still at a very low level) Horse mackerel showed also an important decrease while anchovy has been mainly detected at the inner part of the Bay of Biscay, although as it was observed for sardine, the presence of thick schools in the western part, presumably being anchovy, had an important impact in the final assessment. Concerning mackerel, it seems the southwards migrations was delayed, and contrary to that found in previous years, adult fish were almost not available in the Cantabrian sea until the end of March. The lack of both eggs and adults observed during the ichthyoplankton-trawl survey CAREVA corroborated this finding. Moreover, fish rather occurred in isolate dense patches than in a continuous way as observed in previous yearsEU-DC