Results From The 2000 Transboundary Trawl Survey of the Eastern Strait of Juan De Fuca and Discovery Bay

During May 2000, a synoptic survey of the eastern Strait of Juan de Fuca and Discovery Bay was conducted in the transboundary waters of Washington and British Columbia. The survey was designed to estimate the abundances and biomass of key benthic species, identify population trends, and quantify the impact of fisheries. The 2000 survey was also designed to describe the distribution of key commercial fishes that inhabit the Strait of Juan de Fuca and determine which are likely to move between both sides of the international boundary and which species are vulnerable to fisheries on either side of the border.

Standard trawl survey methodology was used to design the stratified systematic survey. A 400 mesh Eastern Trawl was towed by a chartered fishing vessel. The bottom trawl was fitted with a codend net liner with a 3 cm mesh opening, and the trawl was towed at predetermined stations for approximately ten minutes. The survey was stratified by country and by four depth strata: 5- 20 fathoms, 21-40 fm, 41-60 fm, and >60 fm stratum. There were 40 trawl samples collected in the 1,400 km2 of the Washington Strait of Juan de Fuca, and 25 samples collected in the 463 km2 of the B.C. Strait of Juan de Fuca. A special survey of Discovery Bay included 12 trawl samples within the 31 km2 study area.

Seventy-two identifiable species of fish were collected during trawling exclusive of the Discovery Bay survey. Sixty-seven species of fish were collected in Washington, and 48 fishes were collected in B.C. An estimated 35,600 individual fish were caught during the trawl survey, and they weighed 7.9 mt. Thirty-three species of fish were collected during the twelve trawls conducted in Discovery Bay.

There was an estimated population of 132.2 million fish weighing 27,000 mt living in the eastern Strait of Juan de Fuca. Washington contained 112 million bottomfish while B.C. had 20 million. The B.C. bottomfish resource constituted an estimated 8,500 mt while the Washington resource weighed an estimated 19,000 mt. As expected, Discovery Bay had far fewer fish than either of the two larger survey areas. There was a fish population of 2.9 million fish weighing and estimated 90 mt in Discovery Bay.

Spotted ratfish comprised more than 75% of the fish populations in Washington and B.C. Flatfish as a group was the second most dominant species group in Washington while other species contributed together to form the second greatest proportion of any species group in B.C. Biomass and numerical abundance estimates and occurrence patterns were presented for key species including spiny dogfish, spotted ratfish, Pacific cod, walleye pollock, lingcod, English sole, rock sole, starry flounder, sand sole, Dover sole, Dungeness crab, and spotted prawn.

Overall, most populations were in less abundance than estimated during previous surveys of the Washington Strait of Juan de Fuca. Depressed species such Pacific cod and lingcod appear to be in continued low abundance despite fisheries that have been substantially reduced in recent years. Discovery Bay contains almost exclusively juvenile and small individuals of key species once harvested in commercial bottom trawl fisheries.

The geographic distribution and depth preferences of key species and invertebrates resulted in a complex pattern for transboundary management. The shallow banks and deep basins in the central Strait provides habitat for both deep and some shallow waters species resulting in a wide and continuous distribution spanning the international boundary. These continuous distributions require coordination between Washington and Canada if substantial fisheries re-develop in the area.