Abstract
Our knowledge for the distribution of Atlantic mackerel (Scomber scombrus) in the Mediterranean Sea is very limited and fragmented. In the current work habitat suitability modelling was applied to summer acoustic surveys data of Atlantic mackerel juveniles derived from the north part of the Mediterranean (i.e. acoustic data from the Gulf of Lions, pelagic trawls held during acoustic surveys in Spanish Mediterranean waters, south Adriatic Sea, Strait of Sicily and North Aegean Sea) using generalized additive models along with satellite environmental and bathymetry data. Bathymetry along with sea surface temperature and circulation patterns, expressed through sea level anomaly and the zonal component of the absolute geostrophic velocity, were the variables found important. The selected model was used to produce maps presenting the potential nursery grounds of Atlantic mackerel throughout the Mediterranean Sea as a measure of habitat adequacy. However, the assessed potential nursery grounds were generally marked as “occasional”, implying that although there are areas presenting high probability to encounter Atlantic mackerel, this picture can largely vary from year to year stressing the high susceptibility of the species to environmental conditions. In a further step and towards a spatial management perspective, we have estimated and visualized the overlap between Atlantic mackerel and anchovy/ sardine juvenile grounds throughout the basin. Results showed that although the degree of overlapping was generally low, not exceeding 15 % in general, this varied at a regional level going up to 30%. The potential of the output of this work for management purposes like the implementation of spatially-explicit management tools is discussed.
Highlights
It is well-known that the most landed small pelagic species in the Mediterranean Sea are anchovy Engraulis encrasicolus, and sardine, Sardina pilchardus (FAO, 2016)
The final generalized additive models (GAMs) for pooled data included as main effects: SST, UADT and the interaction of Depth with SLA (Deviance explained = 30.7%, Akaike’s information criterion (AIC) = 1098.73, p
We need to note that previous info on the spatial distribution of the juvenile grounds of the species was largely missing being available only on limited local scales such as the north-eastern part of the Adriatic Sea
Summary
It is well-known that the most landed small pelagic species in the Mediterranean Sea are anchovy Engraulis encrasicolus, and sardine, Sardina pilchardus (FAO, 2016). As a consequence the majority of pelagic surveys in the Mediterranean used mainly for stock assessment purposes target these two species. The ecosystem approach to fisheries entails the need to update our knowledge for species that might contribute less in the total landings or have lower economic value but play an important ecological role in the ecosystem. This is the case of Atlantic mackerel (Scomber scombrus) in the Mediterranean Sea. Purse seiners is the main gear targeting Atlantic mackerel in the basin with midwater pelagic trawls operating in the Adriatic Sea, the Strait of Sicily and the French coastal waters. The high importance of these stocks in the Mediterranean and the need for stock assessment was recently highlighted (STECF, 2016)
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