Age And Growth Of Atlantic Horse Mackerel (Trachurus Trachurus) In The Eastern Tunisian And Southern Italian Waters

Age and growth of the horse mackerel Trachurus trachurus, caught in the two sides of the Strait of Sicily, central Mediterranean Sea (Italy: GSA16 and Tunisia: GSA13), were estimated by length-frequency analysis using FISAT II software. The estimated Von Bertalanffy growth parameters, compared with likelihood ratio test showed significant differences in horse mackerel growth, caught from the two areas. Trachurus trachurus from Tunisia tended to be greater in size than those from Italy. Satellite sea surface temperature revealed a constant higher temperature regime in Tunisian waters, which resulted 1 degrees C warmer than Italian waters. Chlorophyll a concentration showed a higher primary production (+ 12%) in the Italian waters compared to Tunisian waters. Relationships between growth and geographical distribution denote the effect of environmental conditions on growth especially water temperature and primary production, although the role of other factors could not be excluded, among them genetic and/or epigenetic ones.