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The goal of this paper is to investigate the relationship between environmental variables and the occurrence of anchovy (Engraulis encrasicolus) spawning over a year, in order to enable the timing and strength of high spawning activity to be predicted. Biological sampling of anchovy was conducted on the fishing grounds of the eastern Adriatic (the northernmost semi‐enclosed basin in the Mediterranean) on a monthly basis from January 1999 to December 2010, while data on environmental parameters were taken from in situ measurements at the most representative and best surveyed eastern Adriatic hydrographic station and from I‐COADS monthly surface fields. Anchovy spawning seasonality was defined by monthly changes of the maturity stages and the gonadosomatic index. Fluctuations of the gonadosomatic index revealed that spawning begins in March and lasts until September, with reproductive activity peaking from April to July. A significant correlation was found between the gonadosomatic index and upper layer salinity in the two preceding months, while the lagged wind‐mixing index and surface temperature are barely correlated to the gonadosomatic index. An enhanced input of nutrient‐rich freshwater of river origin, which reduces upper layer salinity and enhances primary production up to 2 months before anchovy spawning, seems to be correlated with the anchovy fertility, especially for a late spawning maximum (in July).

Papetti, C., Di Franco, A., Zane, L., Guidetti, P., De Simone, V., Spizzotin, M., Zorica, B., Čikeš Keč, V. and Mazzoldi, C. 2013. Single population and common natal origin for Adriatic Scomber scombrus stocks: evidence from an integrated approach – ICES Journal of Marine Science, 70: 387–398. In order to implement proper fishery management strategies aimed at avoiding stock declines, information about connectivity among stocks and populations is critically required. In this perspective, the present study investigated population structure of the Atlantic mackerel Scomber scombrus in the northern–central Adriatic Sea by integrating multiple approaches (analysis of fisheries data, population genetics, and otolith chemistry). Monthly data of fishery landings indicate a latitudinal trend along the western Adriatic coast, with Atlantic mackerel disappearing from the northern waters in winter, corresponding to the reproductive season. Population genetic analyses by genotyping of eight microsatellites clearly point to the presence of a single panmictic population in the northern–central Adriatic Sea. Otolith cores of samples from the northern–central Adriatic were chemically homogeneous, suggesting a common spawning ground. These results strongly suggest that Atlantic mackerel perform an autumn–winter migration in the northern–central Adriatic Sea, from the northern to the central sector, to reach a single spawning ground, and that a single population is present in this area. Considering that S. scombrus has shown a marked decline in the last 40 years in the Adriatic, this study highlights a potential high vulnerability to collapse by overfishing for the Atlantic mackerel stocks in this geographic area.

We examined the stomach contents of two of the most economically and ecologically important small pelagic fish species, the sardine, Sardina pilchardus and the anchovy, Engraulis encrasicolus, obtained monthly from commercial purse-seine catches operating on Croatian fishing grounds during a one-year period (January–December, 2011). Both species generally showed a similar diet, with copepod and decapod larvae as dominant prey groups. The composition of anchovy and sardine stomach contents was not size- or sex-related, but throughout the year, a significant difference in diet composition was observed for each species as well as between species. Two gastrointerstinal helminths; the digenean Parahemiurus merus and nematode Hysterothylacium aduncum, were recorded during the stomach content analysis. Differences in population dynamics between the two parasites are congruent with differences in the prey composition of sardine and anchovy, reflecting fine-tuned interactions in the trophic web between parasites and intermediate or paratenic hosts included in the sardine and anchovy diet.