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This study describes fisheries, stock status, ICES advice and management measures for the Northern and Southern sardine stocks in EU Atlantic waters. Information on sardine biology and ecology is provided for a better understanding of stock development. Social and economic dimensions are addressed for sardine fisheries in France, Spain and Portugal. The study provides recommendations to improve knowledge on the species and indicates management measures which might be considered for the sustainability of the fisheries. Versión del editor

The Spanish acoustic-trawl times PELACUS 0314 was carried out on board R/V Miguel Oliver from 9th March to 8th 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 1903 nautical miles were steamed, 1075 corresponding to the survey track. Besides 52 fishing stations were performed (Figure 2). PELCACUS 0314 was characterised by relative stable weather conditions along the surveyed area. Besides, there was an important increase in backscattering energy as compared with the previous year. This resulted in an increase of the biomass estimated for the majority of the fish species, but still sardine is at lowest productivity ever recorded. Good recruitment would be observed in horse mackerel, but for the rest of the fish species, no strong signals for age group 1 have been detected. The reasons for this increase would be related to the weather stability which could have increased the fish availability either for a change in the behaviour (i.e. spatial pattern distribution) or for an increase in the food availability. This is relevant accounting the increase of the occurrence of mackerel subsurface layers observed this year. As PELACUS is a multidisciplinary survey series (we collect environmental and biological ancillary information, stomach contents, including CTD cats, plankton tows or continuous records of plankton, eggs, S, T and flourometry), we will try to explain this change of behaviour. Our main hypothesis is that these species could follow mackerel when is undertaking vertical migration, probably related with the spawning activity, just for feeding eggs and, therefore, changing the expected schooling behaviour by the dispersed one, used during the feeding activity.

The Iberian sardine ( Sardine pilchardus ) is a good example of the typical life strategy of small pelagic fish species around the world: short life span, fast growth and long spawning season, which in the case of the Iberian stock presents two peaks (in winter and spring). This life strategy makes new year classes ve ry dependent on the right environmental conditions to survive the early life stages. Egg and larval survival relies on the right oceanographic mechanisms, to ensure retention in favourable areas, and availability of food. Dispersal of eggs and larvae serio usly reduces their survival and decreases the chances of a good new year class. Because of this dependency on environmental conditions in early life, there is no relationship between the stock size (measured as SSB) and recruitment. Previous studies have e xplored the relationship between environmental variables, at large and local spatial scales, and sardine recruitment in the Galician and Portuguese sardine fishery but have faced two main analytical challenges: short time series and autocorrelated data. We carry out new analysis using statistical methods designed to cope with these challenges, including Dynamic factor Analysis and mixed modelling, to identify and characterise relationships between sardine populations (recruitment, spawning stock biomass, an d (to extend the time series) fishery landings in the area) and a series of global, regional and local environmental variables.

The natural abundance of stable nitrogen isotopes (δ15N) in sardine (Sardina pilchardus) and plankton was determined from samples collected between 1998 and 2003 in the northwestern shelf of the Iberian Peninsula with the purpose of studying the variability in the trophic position of sardine. Sardines were grouped in three size-length classes (small: < 16 cm; medium: 16-20 cm; large: > 20 cm). Plankton samples were size-fractionated between ca. 0.7 and 2000 μm of individual length. The plankton at the base of the pelagic food web in the western shelf region (Galicia) was more enriched in δ15N than plankton in the northern and eastern region (Mar Cantábrico), likely because of upwelling. Variability in δ15N in sardine was related both to changes in feeding strategies during growth and to the mobility of size classes between adjacent shelf regions. Large sardines showed regional differences in δ15N similar to those of small plankton, suggesting that old specimens remained for long periods in the same region. In contrast, small and medium-sized sardines have similar δ15N values in all regions. We hypothesize that interannual differences in δ15N of sardine are caused mainly by variations in the mobility of large size classes, as the isotopic signature of the small sardines was relatively less variable and suggests low variability in the plankton food web. In turn, such variations would be related to changes in the size of the sardine population in the north Iberian shelf.