Comparing life-history traits in two contiguous stocks of the deep-water rose shrimp Parapenaeus longirostris (H. Lucas, 1846) (Crustacea: Decapoda) in the Southern Tyrrhenian Sea (Central Mediterranean Sea)

Abstract

Most Mediterranean fish and crustaceans’ stocks are overexploited, but they could increase if fishing intensity would be reduced for only a few years. Today exploited stocks are constituted of young and small fish that are mostly caught before they can reproduce. This paper, which is based on long-term data (1994–2010) obtained from experimental bottom trawl surveys, contributes to the Parapenaeus longirostris exploitation control in South Tyrrhenian Sea (SW Mediterranean; GSA 10). Stock dynamics parameters of rose shrimp were investigated and compared in two different locations along the North coasts of Sicily (South of GSA 10) characterized by different fishing patterns. A huge inter-annual biomass and density fluctuations of the investigated rose shrimp were recorded, although no significant trends over time were observed, in both sectors. It is worth highlighting that the mean year fishing indices (mean KW of the trawl fleet, as capacity index, and number of days at sea per month, as activity index), contrary to what is reported in literature, were significantly higher in the western part of the area, where the stock is surprisingly mainly composed of young specimens. The fishing / total mortality ratio F/Z showed an overfishing status of rose shrimp in the two sectors, but at a lower degree than the rose shrimp of the whole GSA 10. The present paper support two stocks conjecture for the rose shrimp. The different biological structures in the two studied sectors are mainly influenced by interactions among the typical high plasticity of the life history species in the Mediterranean Sea and several typologies and activities (including the illegal aspects) of fishing fleets harbored in the E and W sectors.