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1. The magnitude and temporal trends of seabird bycatch in coastal set net fisheries in the eastern part of the German Baltic Sea were studied, based on (i) a survey of 4% of the total fishery in the period 2006-2009, and (ii) results from bycatch monitoring in a part of this region covering a period of 20 years. Bird carcasses were collected and information on fishing effort obtained from fishermen using interviews and on-board observations on selected trips.2. Bycatch of seabirds occurred with all types of fishing gear and métiers studied, with highest bycatch rates in coastal lagoons. The minimum estimate of total bycatch in nets set by 440 commercial fishermen was found to be 17 551 (range 14 905-20 533) birds annually between November and May. Bycatch in set nets and on longlines in summer was much lower.3. Bycatch rates were found to depend either directly on bird abundance as shown for the long-tailed duck (Clangula hyemalis) or on predictors of abundance such as water depth and location. Bycatch in the Pomeranian Bay has decreased over 20 years due to the severe decline of seaducks, particularly of long-tailed ducks, which were most frequently bycaught. The estimated individual bycatch risk has also decreased in long-tailed ducks but the current monthly losses of 0.81% may still indicate a potential threat for this species.4. Bycatch monitoring based on carcass collections and interviews proved to be feasible over a 20-year period although the results contain some underreporting. Based on the results specific measures are recommended to reduce bycatch risk in the German coastal fisheries using targeted effort reductions and replacement of set nets with alternative gear.

AbstractSonntag, N., Schwemmer, H., Fock, H.O., Bellebaum, J., and Garthe, S. 2012. Seabirds, set-nets, and conservation management: assessment of conflict potential and vulnerability of birds to bycatch in gillnets. – ICES Journal of Marine Science, 69: 578–589. We addressed the issue of bird bycatch in set-nets in the southern Baltic Sea by (i) assessing the vulnerability of diving birds to drowning by developing a vulnerability index based on weighted bird abundance, (ii) providing information on set-net fishing activities, and (iii) using a spatial overlap approach to indicate the potential conflicts between diving birds and fishing activities. Birds and fisheries concentrated in the same areas. Vulnerability and potential conflict were highest during winter and spring in coastal waters and around shallow offshore grounds. Local bycatch studies validated the usefulness of our approach, which can provide a valuable tool for conservation purposes. Although the conflict analysis outlined the current extent of overlap between birds and fisheries, the vulnerability index indicated important areas and periods in terms of diving bird abundance, irrespective of fisheries, and enabled the development of appropriate conservation and management options. A suite of measures including temporal or spatial restrictions can be derived, despite a scarcity of real data for bycatch rates. This approach is particularly useful for assessing impacts that are difficult to monitor and where mortality cannot be properly addressed, as in artisanal gillnet fisheries. It is also generally applicable to any marine area or species worldwide.

In the last German breeding area of the rapidly declining ''Pomeranian'' population of the Aquatic Warbler (Acrocephalus paludicola), the Lower Oder Valley National Park, we investigated changes in habitat suitability between 1993 and 2006 by combining monitoring results with repeated assessments of vegetation structure and composition, site conditions, and land use. Sites with recent Aquatic Warbler records showed shorter and sparser vegetation, a thinner litter layer, and a higher total plant species richness and cover of small and least competitive (CSR) species than abandoned or unoccupied sites. On a long-term study plot, during a period of late mowing and subsequent cessation of land use, vegetation height increased, the cover of CSR species decreased, and the site became abandoned by Aquatic Warblers. The probability of Aquatic Warbler occurrence was dependent on elevation and increased with the proportion of early mown or grazed area in the preceding year, with early use being most important on slightly higher elevated sites. This rapid deterioration of eutrophic habitats by delayed or discontinued land use is atypical for the majority of Aquatic Warbler breeding habitats. We conclude that both late or no land use and land use during the breeding season negatively affect the Pomeranian breeding sites and that a more sophisticated and flexible land management is urgently needed.