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Resource Ecology & Ecosystem Modeling Program

Seabird Bycatch Estimates for Alaskan Groundfish Fisheries, 1993-2012

Research Reports
Oct-Nov-Dec 2013
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Seabirds are caught as bycatch in Alaskan commercial groundfish fisheries operating in federal waters of the U.S. Exclusive Economic Zone. Fisheries observers record seabird bycatch from their sample and other sources while on board these demersal longline, pot, pelagic trawl, and non-pelagic trawl vessels. The AFSC produces annual estimates of total seabird bycatch from these fisheries each year.  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) industry reports of catch and production. The 2007-12 seabird bycatch estimates presented here (Table 1) are produced from the NMFS Alaska Regional Office Catch Accounting System (CAS).  

These estimates update those previously reported from 1993 to 2006. These numbers do not apply to gillnet, seine, troll, or halibut longline fisheries. Data collection on the Pacific halibut longline fishery began in 2013 and will be summarized in future documents. Figure 1 provides seabird bycatch in the groundfish fisheries for 1993 through 2012, using results from two analytical methods employed.  The AFSC produced estimates from 1993 through 2006 and the CAS from 2007 through 2012.

Table 1.  Total estimated seabird bycatch in Alaskan federal groundfish fisheries, all gear types and Fishery Management Plan areas combined, 2007 through 2012.
Species/ Species Group Year
2007 2008 2009 2010 2011 2012
Unidentified Albatross 16 0 0 0 0 0
Short-tailed Albatross 0 0 0 15 5 0
Laysan Albatross 17 420 114 267 189 128
Black-footed Albatross 176 290 52 44 206 136
Northern Fulmar 4,581 3,426 7,921 2,357 6,214 3,016
Shearwater 3,602 1,214 622 647 199 510
Storm Petrel 1 44 0 0 0 0
Gull 1,309 1,472 1,296 1,141 2,208 885
Kittiwake 10 0 16 0 6 5
Murre 7 5 13 102 14 6
Puffin 0 0 0 5 0 0
Auklet 0 3 0 0 0 7
Other Alcid 0 0 105 0 0 0
Other Bird 0 0 136 0 0 0
Unidentified 509 40 166 18 259 284
Total 10,228 6,914 10,441 4,596 9,298 4,977
 

The 2012 numbers for the combined groundfish fisheries (Table 1) are 40% below the rolling 5-year average of 8,295 for 2007-11. Albatross bycatch was reduced in 2012 by 27% compared to the previous 5 years, with the greatest decrease in Laysan (Phoebastria immutabilis) versus Black-footed (P. nigripes) Albatross (36% and 11% declines, respectively). Northern fulmar (Fulmaris glacialis) bycatch, down by 39% compared to the 5-year average and 52% from the year before, remained the highest proportion in the catch at 61%.  Fulmar bycatch has ranged between 45% and 76% of the total seabird bycatch since 2007. Average annual mortality for fulmars since 2007 has been 4,586. However, when compared to estimates of total population size in Alaska of 1.4 million, this represents an annual 0.33% mortality due to fisheries. There is some concern that the mortality could be colony-specific, possibly leading to local depletions.

The demersal longline fishery in Alaska typically drives the overall estimated bycatch numbers and constitutes about 91% of seabird bycatch annually (but see comment regarding trawl estimates below).  Bycatch in the longline fishery showed a marked decline beginning in 2002 (Fig. 1) due to the deployment of streamer lines as bird deterrents. Since then, annual bycatch has remained below 10,000 birds, dropping as low as 3,704 in 2010. Numbers increased to 8,914 in 2011, the second highest in the streamer line era, but fell back to 4,544 in 2012. The increased numbers in 2011 were due to a doubling of the gull (Larus spp.) numbers (1,084 to 2,206) and a 3-fold increase in fulmars, from 1,782 to 5,848. These species group numbers have decreased in 2012 as well, to 885 and 3,016 respectively. There are many factors that may influence annual variation in bycatch rates, including seabird distribution, population trends, prey supply, and fisheries activities. Work has continued on developing new and refining existing mitigation gear.

  refer to caption
  Figure 1. Seabird bycatch in Alaskan groundfish fisheries, all gear types combined, 1993 to 2012.  Total estimated bird numbers are shown in the left-hand axis while estimated albatross numbers are shown in the right-hand axis. 

Albatross bycatch varied annually. The greatest numbers of albatross were caught in 2008. In 2012, 57.0% of albatross bycatch occurred in the Gulf of Alaska (GOA) (down from 87% in 2011).  The GOA typically accounts for 10% to 20% of overall seabird bycatch.  Only Laysan Albatross were taken in the Bering Sea-Aleutian Islands (BSAI), and all Black-footed Albatross were taken in the GOA (along with about 14 Laysan).  While the estimated bycatch of Black-footed Albatross underwent a 4-fold increase in bycatch (44 to 206) between 2010 and 2011, the 2012 numbers are about 11% under the long-term average of 153 birds per year. Although the Black-footed Albatross is not endangered (like its relative, the Short-tailed Albatross), it was considered for listing as threatened and is currently a Bird of Conservation Concern by the U.S. Fish & Wildlife Service. (continued)

 

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