Untitled - CNR

Fishery and Sea Resources5 Analysis of demersal assemblagesIn the Mediterranean Sea, trawl catchesare composed of a highly diversified mixof fish, cephalopods, crustaceans and severalepifaunal macrobenthic species [20].Monitoring and management of Mediterraneantrawling requires a multispecies andecosystem-based approach. In this contextthe study of demersal assemblages is a fundamentaland priority aspect. This kind ofanalysis permits to collect some importantinformation which can be correlatedwith the “status” of the studied biotopesand that can be useful for the managementof the alieutic resources. The demersalassemblages off the Southern TyrrhenianSea have been analysed [21, 22]. Specifically,the structure of fish demersal assemblageshas been analysed on a temporal (10years) and spatial scale using a multivariateapproach; ecological indices (Shannon-Wiener and Pielou) for each group resultingfrom Multidimensional Scaling Ordinationwere calculated; areas supportinghigh values of diversity and evenness hasbeen identified by a Geographical InformationSystem (GIS) method.Multidimensional scaling ordinationshowed four groups distributed accordingto the depth gradient: a coastal group(< 100 m depth), a group in the lowerpart of the continental shelf (101 – 200m), an epibathyal group (201 - 500 m) andthe last one derived from hauls made inthe middleslope. All the study area wascharacterised by diversity values quite heterogeneous.The persistence index wasgenerally low. Results could be usefulfrom an ecological point of view and forthe management of fisheries activities [22].6 Parasitosis effects onichthyc populationsParasites are the main cause of pathologiesin fishery products. Parasites may be causeof zoonosis, may contain toxic substancesin their body fluids, can cause breathingdifficulties, severe anemia and emaciationin fish infested with consequent economicdamage, may reduce the reproductive performance,can cause changes in chemicaland nutritional profile of meat.Studies on evaluation of parasitosis effectson ichthyc populations have been carriedout in cooperation with the Department ofVeterinary Public Health - University ofMessina. Specifically, several species ofpandalid shrimps were examined for occurrenceof isopods. Pseudione affinis (Epicaridea:Bopyridae) parasitized Plesionikamartia, P. antigay and P. edwardii. Parasiticeffects on the hosts included carapacedilation and gill atrophy [23].The presence of Unitubulotestis sardae(Trematoda: Didymozoida) in the gills ofAtlantic bonito (Sarda sarda) populationscaught in the strait of Messina has been reported.The histopathological change wereneovascularisation and hyperplasia of thegill epithelium, leading to the formation ofa bistratified cystic wall; SEM investigationsand tissue damage due to Gnathia vorax(Isopoda Gnathiidae) larvae have beenreported [24]. Severe infestations affecteddifferent teleosts species. The amount ofblood sucked up by single parasite wasevaluate. Haematophagia may play an importantrole in the pathogenesis of such infestation[25].A research on Aggregata sp. infection inSepia officinalis and the influence of parasitosison biometrics was carried out. Parasiteswere found in the 100% of sam-2078