engleski

Application of Visual Census for the Study of Bivalve Distribution in Saltwater lake Malo jezero (Mljet National Park, South Adriatic Sea)

Visual census of easily visible bivalve species and collection of surface sediment was preformed by SCUBA diving along four transect lines in saltwater lake Malo jezero, Mljet National Park during summer of 1998. Statistically significant difference in distribution of Pinna nobilis (Kruskal-Wallis = 13.363, P = 0.004), Arca noae (Kruskal-Wallis = 12.929, P = 0.005) and Chlamys glabra (Kruskal-Wallis = 16.667, P = 0.001) was found with respect to depth. No Pinna nobilis was found at depths greater than 15 m (maximum depth of a lake is 29 m). For species Chlamys varia, Ostrea edulis, Modiolus barbatus, and Gastrochaena dubia only presence/absence data were collected. For all species observed it was found that as depth increases, number of bivalves decreases. Sediment analyses showed that at depths between 15 and 20 m percentage of sand in the sediment sharply decreases while the percentage of mud increases. Observed change in sediment composition correlate with changes in bivalve distribution. Survey method used in this study is non-destructive and relatively simple to perform and as such can be used for monitoring long term changes in bivalve distribution.

bivalves; visual census; Mljet National Park

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