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 inf ormation on the changes that occurred in the composition and distribution o f 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 fact ors, since small sized species such as the smallspotted catshark (S. canicu la) or the brown ray (R. miraletus) were frequently collected in both surve ys, while bigger shark species and most other rays disappeared or were rare ly 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 scabb ardfish) have increased values, and some (mainly small sized species such a s 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) 200 1 Elsevier Science B.V. All rights reserved.