Abstract

The Japanese squid driftnet fishery began in 1978 in the northwestern Pacific, targeting the flying squid, Ommastrephes bartrami, and was effectively closed in 1992. In response to the rapid growth of the fishery, the Japanese Government adopted a limited-entry licensing system in 1981, under which various regulations were implemented. The regulations established a seven month fishing period from 1 June to 31 December, and a fishing area between 20°N and 46°N and between 170°E and 145°W; the northern boundary changed monthly to minimise the bycatch of salmonids while maintaining the squid catch. Fishing effort was mostly confined to the north of 38°N. Most squid driftnet vessels were also engaged in other fisheries during the year. They were usually converted from salmon driftnet, long-line, jig and trawl vessels. Their gross tonnages ranged from about 60 to 500 CRT. A typical vessel deployed about 1,000 tans of net per operation. A tan is a unit of gillnet with a length and depth of 30-50m and 7-10m respectively. The net material was nylon monofilament and the mesh size ranged from 110-135mm, but mostly 110-120mm. The number of licensed vessels gradually decreased from 534 in 1981 to 231 (actually operated) in 1992, while the number of operations (fishing days) per year fluctuated between 13,775 and 35,549 during 1983-92. The total number of tans (not standardised) deployed per year gradually increased from 21 million (1982) to 36 million (1986) and then became stable at 32-36 million (1987-89). The total number decreased to 16 million tans in 1992. The annual flying squid catch also fluctuated between 123,719 and 215,778 tonnes, resulting in annual average catch rates of 3.8-7.9 t/day or 7.2-8.6 kg/tan. The estimated total cetacean bycatches for the 1989, 1990 and 1991 fishing seasons respectively are: 3,065, 3,093 and 3,204 (Dall’s porpoises), 12,449, 7,909 and 9,320 (northern right-whale dolphins), 6,154,4,447 and 3,784 (Pacific white-sided dolphins), 286, 562 and 1,035 (common dolphins), and 1,079, 624 and 664 (other and unidentified cetaceans). Possibilities for mitigating the bycatch of the cetaceans are discussed with respect to (1) the modification of driftnets including subsurface nets and smaller mesh size, (2) time-area regulation and (3) squid jigging.