MORTALITY OF SEABIRDS IN THE JAPANESE LAND-BASED GILLNET FISHERY FOR SALMON

Mortality rates of seabirds in the Japanese land-based drift gillnet fishery for salmon were assessed from 413 gillnet sets made by Japanese research vessels in offshore areas used by the commercial fleet. Sixteen species of seabirds were recorded in nets. Shearwaters, primarily Short-tailed Shearwaters (Puffinus tenuirostris), and to a lesser extent Sooty Shearwaters (P. griseus), predominated in the catches, followed by lesser numbers of Tufted Puffins (Fratercula cirrhata) and Thick-billed Murres (Uria lomvia). Catch-rates of seabirds varied by oceanographic zone, with most being caught in oceanic waters north of the Subarctic Front. Approximately 151,000 seabirds were killed in the offshore component of the land-based fishery in 1977. Mortality was reduced to about 57,000 seabirds in 1987 because of a reduction in fishing effort. No estimates are available of seabird mortality in the nearshore component of the fishery. Mortality of seabirds in the land-based fishery is discussed with respect to other major drift gillnet fisheries in the North Pacific.