Preliminary study of age, growth and birthdates of juvenile sardine Sardina pilchardus (Walbaum, 1792) and European anchovy Engraulis encrasicolus (Linnaeus, 1758) in the east coast of Tunisia

Abstract

The microstructures of the otoliths of juvenile sardines (Sardina pilchardus) and anchovies (Engraulis encrasicolus), collected in the East coast of Tunisia, were analyzed in order to estimate age, daily growth and hatch date. The fork length of sardines varied from 48 to 103 mm and estimated age ranged from 105 to 297 days. For the anchovies, the estimated age ranged from 79 to 300 days and the fork length from 42 to 86 mm. The length-age data of both species were fitted to the laird-Gompertz model. The corresponding growth equations were [l sub(t)=10.8 exp(2.74(1-exp(-0.006t)))] for sardines and [l sub(t)=3.1 exp(3.2(1-exp(-0.02t)))] for anchovies. The instantaneous growth rates of the juvenile of both species in the East of Tunisia were in agreement with the data reported for other areas of the Western Mediterranean Sea. However, the juvenile of sardines had an instantaneous growth rate lower than the juvenile anchovies. The distribution of the back calculated hatch dates indicated that hatching dates of anchovies occurred from April to October with a peak in June while the hatching dates of sardines occurred from October to February with a peak in December-January