Anchovy (Engraulis encrasicolus) otoliths reveal growth differences between two areas of the Spanish Mediterranean Sea

In the Mediterranean, small pelagic provide the larger catches, based mainly on 2 species: anchovy and sardine (Sardina pilchardus). Although the Mediterranean Sea is considered oligotrophic, there are areas with increased production due to their unique conditions related to the bathymetry, hydrography and meteorology. In the Spanish Mediterranean Sea, there are two areas with increased production due to their environmental characteristics: the Ebro Delta continental shelf, due to the discharge of the Ebro River and the Alborán Sea that receives Atlantic water, rich in nutrients, through the Strait of Gibraltar. The amount of growth in the first year can be measured from the otolith (R1) and some cases may be suitable to use it as a tool for stocks separation. This study presents and analyses anchovy otolith R1 distributions from these two different areas, from samples collected during acoustic surveys in the Spanish Mediterranean in 2012 and 2013 during the months of June and July. In addition, the condition factor was estimated for the total number of individuals and for the sexes separately. Regression analysis, similarity analysis, principal components analysis (PCA) and the Wilcoxon-Mann Whitney test were undertaken in order to identify any different growth patterns. The results suggested that the differences may be characteristic of the existence of population groups, and these could be used as a tool for differentiating stocks