4. The Status of Spiny Dogfish in Puget Sound
Wayne A. Palsson
Abstract.—Spiny dogfish Squalus acanthias in Puget Sound have undergone two phases of high fishery harvests followed by rapid declines. Dogfish were heavily fished during WWII for their vitamin-rich livers, and annual catches approached 4,000 metric tons (mt) per year. This fishery declined from the early 1950s until new markets developed during the mid-1970s that led to increased commercial catches by trawl, set net (sinking gill nets), and setline (long lines) gear types. Annual harvests again approached 4,000 mt per year but declined to 1,000 mt after 1997 and have fallen to less than 300 mt in recent years. Dogfish caught by recreational fishers now account for the greatest catches of dogfish in Puget Sound.
Two population measures show that spiny dogfish populations have declined in Washington’s inland marine waters. Fishery-dependent measures of catch per unit of effort for the setline fishery dramatically decreased beginning in 1997; only since 2003 have these measures showed increases. Biomass indicators developed from a series of bottom trawl surveys decreased by 64% and 73% in northern and southern Puget Sound, respectively, based on surveys conducted during 1987–1991 and after 1995–1996. The causes of these biomass and fishery declines are unclear but may relate to oceanographic factors, such as El Niño or climatic shifts, or to excess fishery removals. The magnitude of the decline in biomass and the long-lived life-history parameters classify dogfish as vulnerable in southern portions of Puget Sound and near the point of vulnerability in northern portions.