Seabirds are protected under the Migratory Bird Treaty Act (MBTA) and Washington state law, but are inadvertently entangled and killed in Puget Sound commercial drift gillnet fisheries. Observer programs have documented seabird entanglement rates in these fisheries. The two species most frequently entangled are alcids, rhinoceros auklets (Cerorhinca monocerata) and common murres (Uria aalge). The Washington Department of Fish and Wildlife (WDFW) estimated that 3,569 seabirds were entangled in the 1994 non-treaty sockeye gillnet fishery in North Puget Sound and 90% of these seabirds were entangled in Management Area 7. Seabird mortalities in these fisheries are a violation of MBTA, a misdemeanor offense, and may contribute to declines in local seabird colony attendance.
Under MBTA, the U.S. Attorney for the Western District of Washington has declined to prosecute non-treaty gillnet associated violations provided that the commercial net sector (1) develops and implements a conservation action plan to identify impacts to migratory birds, and (2) develops and implements methods to eliminate or significantly reduce seabird mortality. In response to this mandate, the non-treaty commercial fishing industry prepared a five-year action plan in 1994. Its objectives were to:
In 1995, the WDFW and U.S. Fish and Wildlife Service required the continuation of gear modification research begun in 1994 as a condition for opening Management Area 7 (San Juan Islands) to the non-treaty sockeye fishery and restricted gillnet openings to primarily daylight hours. It was agreed that fishers could better avoid seabirds and seabirds might better see and avoid gillnets during the day. These primarily daylight openings avoided early change-of-light hours when seabird feeding activity and therefore vulnerability to the nets was thought to be greatest. In addition, several sub-areas within Management Area 7 were closed to commercial salmon fisheries to protect marbled murrelets (Brachyramphus marmoratus), a threatened species under the Endangered Species Act.
This study compared seabird and marine mammal entanglement rates and fish catch among two gear treatments (modifications) and a control throughout the day-night cycle during the 1995 Puget Sound sockeye and pink salmon fishery in Area 7. The goal was to test methods to eliminate or significantly reduce the incidental capture of seabirds in gillnet salmon fisheries without significantly reducing fishing efficiency. The two gear modifications tested incorporate 10-inch mesh opaque netting at two depths in the upper quarter (50 Mesh) or upper eighth (20 Mesh) of a monofilament net and were compared to an unmodified monofilament control. The experimental nets were fished over a 24-hour period in a WDFW Test Fishery to determine if seabird entanglement and sockeye catch rates vary by time of day.
In 12 fishing trips completed between July 15Aug. 24, 1995, 5,866 salmon were caught in 383 sets or 1,149 shackle sets (1/3 full net). Seabirds were observed in the sighting zone (between 10 and 100 meters of the corkline) in 29% of the sets, the encounter zone (within 10 meters of the net) in 14% of the sets, and were entangled in only 1.9% of the sets. Twenty-three seabirds were entangled: eight common murres and 15 rhinoceros auklets. All rhinoceros auklets were hatch-of-the-year birds (one to two months old) and, of the common murres half were adults and half were hatch-of-the-year birds. (Seabird entanglement rates in Puget Sound gillnet fisheries probably vary dramatically with the relative abundance of common murres and rhinoceros auklets from year to year.)
Marine mammals, almost all harbor seals, were observed in the sighting zone in 23.3% of the sets, in the encounter zone in 30% of the sets, and were entangled in only 0.4% of the sets. Four juvenile harbor seals were entangled; three were released alive with no apparent injury.
In experimental nets both fishing efficiency and seabird entanglements decreased with increasing depth of opaque netting from the surface. Sockeye catch and seabird entanglement rates were significantly different (P<0.05) among experimental gear treatments and the monofilament control. Although experimental gillnets with visual barriers reduced seabird bycatch by 43% (20 Mesh) to 93% (50 Mesh), our goal of reducing seabird bycatch without any reduction in fishing efficiency was not achieved. Fishing efficiency was reduced by 7.6% and 35.8% in the 20 and 50 Mesh nets, respectively.
This research was carried out in cooperation with the Puget Sound Gillnetters' Association (PSGA) and the Washington Department of Fish and Wildlife (WDFW) with funding from the U.S. Fish and Wildlife Service, Nestucca Oil Spill Restoration Program, and with partial support from Washington Sea Grant Program, University of Washington.
Lanny Pillatos, PSGA president, arranged contracts and organized logistics with individual vessel owners to fish the experimental nets as a test fishery. Dan Crawford, F/V Michelle Evonne; Steve Kuchin, F/V Silver Fox; Lanny Pillatos, F/V Lady Laura; and Frank Fletcher, F/V Ever Ready fished experimental nets. Stew Ellison and Terry Crum of LFS, Inc., Bellingham, contributed to the design of the experimental nets and expedited their construction.
Debbie Holtz, Dan Cunningham, Natalie Herner and Helen Read were observers. Keith Matteson coordinated observer activities, entered data and helped develop data sheets and train observers. Monique Wilson, WDFW and later WSGP, did necropsies, helped hire, train and equip observers, developed data sheets and summarized data. John Pierce, WDFW, administered contracts between WDFW and PSGA and observer hirings. Taina Honkalehto and John Grettenberger reviewed the manuscript and provided helpful suggestions.
[Summarized from the 1996 Washington Sea Grant publication, Reduction of Seabird Bycatch in Salmon Drift Gillnet Fisheries: 1995 Sockeye/Pink Salmon Fishery Final Report (WSG AS 96-01)]
For more information on this subject, contact Ed Melvin by email at emelvin@u.washington.edu. Or write to him in care of Washington Sea Grant Program, 3716 Brooklyn Ave NE, Seattle, WA 98105, or call (206) 543-9968.
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