Piscivorous birds have received much attention with respect to competition with fisheries for resources. The majority of studies have been focused on cormorants Phalacrocoracidae, while predation by other piscivorous bird species has often been overlooked. This study was designed to supplement sociological research (Bell, 2004), which revealed that the fishermen community at the Lithuanian section of the Curonian Lagoon considers great cormorants Phalacrocorax carbo, but not other fish-eating birds, to be significant competitors of fish resources. In this paper, we estimate fish consumption by cormorants and other abundant piscivorous birds, and attempt to interpret this level of predation in relation to fish resources and commercial fishery landings. We estimate that four piscivorous bird species consumed nearly 700 tonnes of fish during the breeding season of 2001 and winter 2001/2002, which corresponds to *9% of the total fish resources in our study area. Bird consumption equalled two-thirds of the amount of fish landed by commercial fishermen. However, we argue that direct competition between birds and humans for fish resources is low, because there is a size segregation of exploited fish stock segments and abundant fish species that dominate the diet of birds. Fish monitoring and commercial fish landings indicated no apparent changes in fish stock size and composition, which could be attributed to a recent increase in piscivorous birds. Great cormorants consumed the largest biomass of fish compared to other piscivorous bird species. However, total fish intake by grey herons Ardea cinerea, great-crested grebes Podiceps cristatus, and goosanders Mergus merganser combined, equalled that of cormorants. Our results do not support the common public perception that cormorant predation greatly exceeds that of other piscivorous birds, and is detrimental to commercial fisheries.

The genetic diversity and differentiation of sea trout were studied in three river basins in Lithuania: Akmena-Dane, Bartuva, and Nemunas. A total of 282 individuals were genotyped at eight microsatellite loci. A similar level of genetic diversity was found in all of the populations studied: mean allelic richness ranged from 3.64 to 5.03, and average expected heterozygosity ranged from 0.588 to 0.721. Significant genetic divergence was observed among the different river basins as well as between populations within the drainages. All pairwise F (ST) values were highly significant, ranging from 0.027 to 0.197. The analysis of molecular variance showed rather weak hierarchical population structuring within the Nemunas basin, which may be explained by extensive gene flow among different river basins or, alternatively, reflect the influence of artificial breeding. Information on genetic diversity and differentiation of the Lithuanian sea trout populations will be useful for future management decisions.

To date, no characterization of spawning habitats on scientific basis was made for the eastern Baltic salmonid populations. The aim of the present study was to characterize spawning habitat preferences and redd gravel structure of sea trout in lowland streams of western Lithuania. The redd position at the habitat-unit scale, microhabitat hydrological characteristics and the redd gravel structure have been analyzed. The spawning site selection by sea trout was related to the in-stream characteristics, but not to the riparian features. Redds were positioned mainly in the transitional pool-riffle zones, associated with close proximity to potential cover for spawners. At the microhabitat scale, sites with relatively consistent hydrological parameters (mode of water depth 0.25–0.40 m, flow velocity 0.4–0.7 m s−1 and Froude number 0.2–0.4) were selected from a wide range of available sites. Egg incubation conditions, in terms of the redd gravel structure in the spring, were of intermediate quality, while varied widely within particular reaches. According to the results of the present study, it is apparent that sea trout have particular preferences for spawning sites, which should be considered in emerging river-restoration projects.

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