Review and assessment of mitigation measures to reduce incidental catch of seabirds in longline, trawl and gillnet fisheries

Growing concerns have been raised about incide ntal capture of seabirds in various types of fisheries. Most attention has been given to
bycatches of albatrosses in the longline fisheries of the southern Ocean. This report describes technical and management mitigation measures that have been tested in longline, trawl and gillnet fisheries, and critically reviews their fishery suitability in terms of efficiency and practical applicability. It is emphasized that studies based on observer data must be interpreted with caution, and the only way to determine the effectiveness of a mitigation measure is to apply an experimental approach including a control treatment without any mitigation device.
There is no single solution to mitigate incidental seabird mortality in longline fisheries, and this review gives strong evidence that the efficiency of a mitigation measure is specific to each fishery. However, there is potential for considerable reductions in seabird mortality rates in all longline fisheries by employing appropriate and effective mitigation measures. In the Northern Hemisphere, where northern fulmar is the dominant seabird captured, streamer lines have proved to be very efficient in demersal fisheries. In the Southern Hemisphere, night setting has shown to be an efficient mitigation measure, and this measure should be used in combination with other measures such as streamer lines and longlines with integrated weight when fishing in areas inhabited by nocturnal and diving seabirds.
Although few studies have been conducted in trawl fisheries, results indicate rare interactions between seabirds and trawl gear at times of no offal discharge. Studies reported to date suggest that no-discharge policy and ban of netsonde cables would virtually eliminate seabird mortality. During trawling carried out under offal discharge, streamer lines proved to be an efficient mitigation measure. Studies in gillnet fisheries are very scarce, and development of seabird mitigation measures for this gear type is in its infancy.
Future research on seabird mitigation measures in longlining should apply an experimental approach to fine-tune the most promising mitigation measures for each specific fishery. Mitigation measures have been tested in only a few trawl and gillnet fisheries, and this work needs to be expanded to other areas where interactions with seabirds occur. Promising measures have been identified for trawls but not for gillnet fisheries.