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We documented krill distribution in the Spanish Mediterranean Sea for the first time using acoustic methods, highlighting the method's suitability to study marine communities restricted to specific areas with patchy aggregation behavior. The 2009–2017 acoustic time series analysis revealed that krill distribution, mainly located on the continental shelf edge, was driven by the presence of fronts and submarine canyons. On the other hand, areas of persistent krill distribution included from Cape La Nao to the eastern part of Almeria Bay, although an interannual northwards increase of krill presence had been detected in 2015–2017 likely related to the position of the Balearic front. We provide information on the aggregation characteristics and biological parameters of three krill species, Nyctiphanes couchii , Nematoscelis megalops and Meganyctiphanes norvegica. N. couchii and N. megalops formed patchy pelagic aggregations in the neritic and oceanic zone, respectively, and they were the most common species in the net tows. By contrast, M. norvegica formed a large demersal aggregation on the continental shelf edge and was only found in 2017; nevertheless, its 861-kg catch represented a unique milestone in the Mediterranean. Finally, krill species shared distribution area with Maurolicus muelleri ; thus, coexistence between them are also described. [ABSTRACT FROM AUTHOR]

López-López, L., Preciado, I., Villamor, B., Velasco, F., Iglesias, M., Nogueira, E. Gutierrez-Zabala, J. L., and Olaso, I. 2012. Is juvenile anchovy a feeding resource for the demersal community in the Bay of Biscay? On the availability of pelagic prey to demersal predators. – ICES Journal of Marine Science, 69: .The role that juvenile anchovy (Engraulis encrasicolus) play as a food resource for the demersal community in the southern Bay of Biscay is assessed using 21 years of anchovy abundance data and demersal predator diets. During the study period, a total of 26 fish and elasmobranch species preyed on anchovy either frequently or occasionally. Predators with a crustacean-based diet targeted the smaller anchovy individuals. The size range of anchovy juveniles (centred at 7.5–8.9 cm) was comparable to that of the largest nektonic–benthic crustaceans, but generally smaller than other demersal and pelagic fish prey. Hake (Merluccius merluccius) and megrim (Lepidorhombus whiffiagonis) were the predators that consumed the highest number of anchovy, one of the main prey items driving the variability of their diets. Anchovy consumption conformed only partially to the abundance of anchovy in the southern Bay of Biscay, suggesting that factors other than abundance might condition its availability to demersal predators. Prey size could be one of them, as the size of the anchovy preyed on proved to be significantly smaller than the individuals collected with bottom trawls. However, other factors, such as the vertical position of the shoals of anchovy juveniles, could also constrain anchovy availability to demersal predators. [ABSTRACT FROM PUBLISHER]

Tugores, M. P., Iglesias, M., Díaz, N., Oñate, D., Miquel, J., and Giráldez, A. 2010. Latitudinal and interannual distribution of the European anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) in the western Mediterranean, and sampling uncertainty in abundance estimates. – ICES Journal of Marine Science, 67: 1574–1586.On the Spanish Mediterranean continental shelf, late-autumn echo-integration acoustic surveys have been performed annually since the 1990s. The surveys coincide with the recruitment season of anchovy (Engraulis encrasicolus) and the start of the spawning season of sardine (Sardina pilchardus), and they provide estimates of stock size for the main fisheries in the area. Latitudinal distribution of the abundance of the two species from 2003 till 2006 is evaluated, and transitive geostatistical techniques applied to estimate the sampling uncertainty of the overall abundance estimate. The anchovy stock was found mainly in areas influenced by river run-off, in well-known anchovy spawning areas, suggesting that anchovy remained on their spawning grounds until late autumn or that survival was higher in these regions of enhanced productivity. By the time of the surveys, sardine were already occupying their spawning grounds over the continental shelf. The precision of the abundance estimates was generally high. The few cases of low precision were re-examined and found to stem most probably from processing errors, so the re-examination has contributed to an improvement in the accuracy of the estimates. The greater precision obtained in the southern subarea suggested a greater homogeneity in the spatial distribution of both species. [ABSTRACT FROM PUBLISHER]

This paper describes the main characteristics of sardine schools detected in the Spanish-Atlantic surveys carried out from 1992 to 1997 (except 1994). A series of parameters were obtained for each school (morphological, positional and energetic) as well as environmental factors (temperature and salinity). The relationships between the school parameters were analyzed by a PCA and then the school parameters per se were described using both univariate and multivariate analyses (Box-plots, ANOVAs, MANOVA, and discriminant analysis). The results show that significant differences exist between years and geographic areas in that the Rı´as Baixas schools were smaller in size and of higher density than those from the Cantabric area. These differences could be related to the facts that the Rı´as Baixas is a nursery zone and sardine length and age are smaller than in the Cantabric Sea. It would seem that the differences in school morphology and energetic characteristics related to length and age of individuals allow us to distinguish between the sardine echo traces in this area. There is a high annual variability in the number of schools and this is not a function of either survey design or strategy and it is not related to the abundance estimates of sardine. These results are important for both future species identification and the improvement of survey design and strategy. [Copyright &y& Elsevier]