Most anthropogenic influences on marine ecosystems, except for river- or terrestrial-borne pollution, involve some sort of vessel activity. Increasing anthropogenic activities mean that many countries are being forced to develop spatial planning schemes, while at the same time implementing conservation sites for sensitive species at sea. The effects of ship traffic on seabirds sensitive to human disturbance are currently too poorly understood to allow for the development of proper planning and conservation guidelines. We therefore used aerial surveys and experimental disturbance to elucidate the effects of passing ships on the distribution patterns, habitat loss, and species-specific flight reactions of birds, as well as the potential for habituation. Loons (Gavia spp.) showed clear avoidance of areas with high shipping intensity. Flush distances of four sea duck species differed significantly, with the longest distances recorded for Common Scoters (Melanitta nigra) and the shortest for Common Eiders (Somateria mollissima). Flush distance was positively related to flock size. Among all the sea duck species studied, the duration of temporary habitat loss was longest for Common Scoters. We found indications of habituation in sea ducks within areas of channeled traffic. However, it is questionable if habituation to free-ranging ships is likely to occur, because of their unpredictable nature. We therefore recommend that spatial planning should aim to channel ship traffic wherever possible to avoid further habitat fragmentation and to allow for habituation, at least in some species. Information on the effects of shipping on other seabird species and during different periods of the year is urgently needed, together with information on the effects of different types of boats, including recreational and fishing vessels.

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.

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