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Considerations on the 1990 and 1991 bivalve repopulations in the northern Adriatic Sea (Croatia)

Background and purpose: The recovery process of bivalve populations after the 1989 benthic mass mortality in the northern Adriatic Sea was studied because of its structural importance in benthic communities. The repopulation pattern with very high larval settlements in the spring and summer of 1990 and negligible ones until the end of 1991was established. This paper is an attempt to consider selected environmental factors which could be engaged in the bivalve repopulation pattern during a two year period. Material and methods: Bivalve settlements, abiotic and biotic literature relating to the p! eriod between 1989 and 1991, divers and information from fishermen were used in this review. Results and conclusions: Differences in the bivalve repopulation pattern during two years resulted from a complex interaction of various environmental factors. Originally established short-term bivalve assemblage in the spring and summer of 1990 soon changed into a new adult-juvenile relationship after summer months. Contrary to the first assemblage this new one seems to have resulted from a diminished spawning stock, feasible larval immigration, appearance of new recruits from bivalves with autumn and winter spawning seasons, increasing number of juvenile enemies, natural mortalities of short lifespan species that successfully survived the 1989 oxygen crisis, and others.

bivalve; repopulation; environmental conditions; Adriatic Sea

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