Population Dynamics and Stock Assessment of European Pilchard (Sardina pilchardus) in the North coast of Tunisia

Abstract

Population dynamics and stock assessment of the European pilchard (Sardina pilchardus) was carried out in the north coast of Tunisia. Growth parameters, mortalities, yield-per-recruit (YPR), spawning biomass-per-recruit (SBPR) and maximum sustainable yield (MSY) were estimated. Asymptotic length (L∞) and growth co-efficient (K) was estimated at 26.25 cm and 0.65 yr-1, respectively. Total mortality (Z), natural mortality (M) and fishing mortality (F) was calculated at 1.71 yr-1, 0.54 yr-1 and 1.17 yr-1, respectively. The F0.1, the level of fishing mortality at which the marginal increase in relative yield per recruit is 10% was calculated at 1.02 yr-1 and found to be lower than the current fishing mortality (F) revealing over capacity of fishing intensity. The current length at first capture (Lc) was 15.27 cm lower than the optimum length at first capture (Lcopt) 18 cm, indicating growth-overfishing. Moreover, the estimated SBPR revealed recruitment overfishing as the spawning biomass of the current stock represents 13% of the virgin stock. The current fishing effort and the fishing effort that would give the maximum sustainable yield (fmsy) were 361 and 220 vessels, respectively. Therefore, it could be concluded that the stock of S. pilchardus shows 38% overfishing in the investigated areas.