Mortality from parasitosis in eggs of Engraulis encrasicolus e Sardinella aurita in the Sicilian channel's continental shelf and in the waters offshore the island of Malta

The two pelagic species of Engraulis encrasicolus and Sardinella aurita show the same reproductive trend (Whitehead, 1994, 1985), they fill the same trophic niche (Armstrong et al., 1991, Bowman et al., 2000), they have similar areal of distribution and an overlapping area of reproduction (Cuttitta et al., 2003, 2007). However, their commercial value is different. The main areas of spawning of the two species are found either in the Sicilian shelf, in front of the Egadi Islands and along the Southern Sicilian coast, with an higher density of eggs near Capo Passero (SR), or in the Maltese continental shelf along the South-Eastern coast of Malta. The aim of this work is to assess the incidence of mortality in both species, within the two different areas of study, namely the Maltese continental shelf and the waters offshore the Island of Malta. This mortality can be attributed to endo-parasites, under study. There are precedent studies addressing parasites-affected eggs belonging to pelagic species (Stratoudakis et al., 2000; Meneses and Rè, 1991; Borges, 1993; Borges et al., 1996; Barbosa, 1999): these parasites inhibit eggs'embryonic development (Yan et al., 2000). From an hydrographic point of view, in the period of sampling (June/July), the MAW skims along the Sicilian coasts only in the neighbours of Egadi Islands and at Capo Passero, while there is a shift of the tide in the central part of the South-Western coast. The study also aims at assessing the relation between the MAW's distribution, the areas of spawning and the presence of parasitosis.