The AFSC released the most recent estimates of seabirds caught as bycatch in commercial groundfish fisheries in Alaska operating in federal waters of the U.S. Exclusive Economic Zone for the years 2007–11. The report can be found in the 2012 Ecosystem Considerations report, available at http://access.afsc.noaa.gov/reem/ecoweb/index.php.
The gear types represented are demersal longline, pot, pelagic trawl, and non-pelagic trawl. The bycatch estimates do not apply to gill-net, seine, troll, or halibut longline fisheries. Seabird bycatch in pot fisheries is minimal. These estimates are based on two sources of information: 1) data provided by NMFS-certified fishery observers deployed to vessels and floating or shoreside processing plants, and 2) catch estimates provided by the NMFS Alaska Regional Office Catch Accounting System.
The 2007-11 bycatch estimates are produced from the NMFS Alaska Regional Office Catch Accounting System.
Total estimated seabird bycatch in all Alaskan groundfish fisheries is shown in Table 1. Northern fulmars (Fulmaris glacialis) are the most commonly caught seabird in each year. Gulls and shearwaters, both of which are combined species groups, were typically the second and third most commonly caught, although shearwater bycatch was much reduced in 2011. Albatross bycatch varied annually. The greatest numbers of albatross were caught in 2008. In 2011, 87.0% of albatross bycatch occurred in the GOA which accounts for only 18.5% of overall seabird bycatch. Of special interest is the endangered short-tailed albatross. Since 2003, bycatch estimates were above zero only in 2010 and 2011, when two birds and one bird were incidentally hooked respectively. This incidental take occurred in the Bering Sea area.
Figure 1. Estimated seabird bycatch by year in the Alaskan demersal groundfish longline fishery, 1993 through 2011, for all birds (left axis) and all albatross (right axis). The deployment of streamer lines as bird deterrents began in 2002.
In the longline fishery, the 2011 numbers are 30.5% above the 2007-10 average of 7,249 (Fig. 1). Bycatch in the longline fishery showed a marked decline beginning in 2002 due to the deployment of streamer lines as bird deterrents. Since then, annual bycatch has remained below 10,000 birds. The 2010 bycatch (3,704 birds) was the lowest estimated in this fishery overall, but the numbers increased to 8,914 in 2011, the second highest in the streamer line era. The increased numbers in 2011 are due to a doubling of the gull numbers (1,084 to 2,206) and a 3-fold increase in northern fulmar bycatch from 1,782 to 5,848.
There are many factors that may influence annual variation in bycatch rates, including seabird distribution, population trends, prey supply, and fisheries activities. The longline fleet has traditionally been responsible for about 91% of the overall seabird bycatch in Alaska, as determined from the data sources noted above. However, standard observer sampling methods on trawl vessels do not account for additional mortalities from net entanglements, cable strikes, and other sources. Thus, the trawl estimates are biased low. A project is underway that addresses this issue.
Seabird mitigation gear used on longline vessels can substantially reduce bycatch (Fig. 1). Individual vessel performance varies, and further reduction of overall fleet averages may depend on targeted improved performance for a handful of vessels within the fleet. Additional methods, such as integrated weight longline gear, have been researched and shown to be effective (Washington Sea Grant Program). Continued collaboration with the longline industry will be important. Albatross bycatch in the Gulf of Alaska is generally higher than in other regions. With observer program restructuring and the deployment plan recommended by NMFS and approved by the North Pacific Fisheries Management Council, we will have a better sense of albatross bycatch issues within GOA-fisheries.
Table 1. Total estimated seabird bycatch in Alaskan groundfish fisheries, all gear types and Fishery Management Plan areas combined, 2007 through 2011. Note: estimations extrapolate observed bycatch to unobserved portions of the fisheries fleets and thus are greater than actually observed bycatch.
