3 research outputs found
Analisi morfologica e variabilitĂ intraspecifica della colonna vertebrale in Mullus surmuletus (Teleostei, Perciformes)
Temporal trend in biodiversity of the middle-slope assemblage in Sardinian seas (Central Western Mediterranean)
It has been amply demonstrated that trawl fishing affects overall biomass, size and species structure of demersal fish communities,
and an increasing number of studies are proving that this could have even greater unexpected effects on biological
diversity. The aims of this study are: (1) to examine the temporal trends of several ecological diversity indices for middle-slope
communities in specific locations within the Sardinian seas, which have been recently subject to increasing fishing capacity;
and (2) to simulate the Shannon’s entropy (H′) temporal trend, using a multiple linear regression, in order to investigate
about the relationships between fishing effort and species diversity. The data come from 11 MEDITS trawl surveys (1994
to 2004). Temporal trends in fishing effort were analysed and ecological diversity indices were measured. Analysis was conducted
for four areas (NW, NE, SE, SSW). Significant variations over time in both fishing pressure and ecological diversity
indices were found for the southern zones. More precisely, the SE zone showed an increase in fishing effort (+120% in 2004),
and a decrease of Shannon–Weiner’s diversity. The SSW zone exhibited a 22.6% increase of fishing effort and a decrease of
species richness. The best model of H′ incorporates species richness and fishing effort expressed as number of boats per trawling
area. Our results seem to indicate that fishing pressure affected the species richness and the abundance of middle-slope species
and that variation in ecological diversity indices differed with different levels of fishing effort