Long-term changes in demersal resources of the Adriatic Sea: comparison between trawl surveys carried out in 1948 and 1998

Trawl surveys carried out in the Adriatic Sea in 1948 and 1998 provided information on the changes that occurred in the composition and distribution of demersal fish resources over the 50 years period. The main change was the decrease of elasmobranchs diversity and frequency, mostly referring to the Hypotremata group. Life history parameters appeared to be determining factors, since small sized species such as the smallspotted catshark (S. canicula) or the brown ray (R. miraletus) were frequently collected in both surveys, while bigger shark species and most other rays disappeared or were rarely found during the 1998 survey. Regarding bony fishes, common species were collected with similar frequency in both surveys; some fishery target species (e.g. the hake) have similar percentage values (biomass) in both surveys, while others (the silver scabbardfish) have increased values, and some (mainly small sized species such as red mullet) replace elasmobranchs at the top of the catches. Despite the low number of observations (two surveys only) and some sampling differences, the data provide an interesting long-term comparison. (C) 2001 Elsevier Science B.V. All rights reserved.