Beached bird surveys in lithuania reflect marine oil pollution and bird mortality in fishing nets

摘要

We report the results of beached bird surveys on the Lithuanian coast of the Baltic Sea during the winters 1992/93 through 2002/03. The purpose of the present study was to establish baseline oiling levels for beached birds in the eastern Baltic. We also attempted to evaluate the influence of bird mortality in gillnets on the results of beached bird surveys. The coastal gillnet fishery, which was initiated and expanded along the Lithuanian coast over the course of our study period, caused an increase in waterbird mortality. The presence of mostly unoiled, gillnet-drowned birds among beached birds may have lowered the observed oiling rates and considerably affected beached bird species composition by increasing the proportion of diving birds. Nevertheless, we conclude that minimum oiling rates were high (27%) on the Lithuanian coast during our study, and this finding indicates the presence of chronic oil pollution in the area. We also concluded that beached bird surveys have limited value in studying bird bycatch issues. Beached bird surveys help to identify the existence of bird bycatch, the geographic scope of the problem and the bird species involved, but they do not allow for determining bycatch rates, fishing gear involved or the precise locations and circumstances of birds drowning--that is, the basic questions to be answered when analyzing fisheries bycatch.