Incidental Catch of Marine Birds in the North Pacific High Seas Driftnet Fisheries in 1990.

The incidental take of marine birds was estimated for the following North
Pacific driftnet fisheries in 1990: Japanese squid, Japanese large-mesh, Korean
squid, and Taiwanese squid and large-mesh combined. The take was estimated by
assuming that the data represented a random sample from an unstratified
population of all driftnet fisheries in the North Pacific. Estimates for 13
species or species groups are presented, along with some discussion of
inadequacies of the design. About 416,000 marine birds were estimated to be
taken incidentally during the 1990 season; 80 % of these were in the Japanese
squid fishery. Sooty Shearwaters, Short-tailed Shearwaters, and Laysan
Albatrosses were the most common species in the bycatch.

Regression models were also developed to explore the relations between bycatch
rate of three groups Black-footed Albatross, Laysan Albatross, and "dark"
shearwatersand various explanatory variables, such as latitude, longitude,
month, vessel, sea surface temperature, and net soak time (length of time nets
were in the water). This was done for only the Japanese squid fishery, for
which the most complete information was available. For modeling purposes,
fishing operations for each vessel were grouped into 5-degree blocks of
latitude and longitude.

Results of model building indicated that vessel had a significant influence on
bycatch rates of all three groups. This finding emphasizes the importance of
the sample of vessels being representative of the entire fleet. In addition,
bycatch rates of all three groups varied spatially and temporally. Bycatch
rates for Laysan Albatrosses tended to decline during the fishing season,
whereas those for Black-footed Albatrosses and dark shearwaters tended to
increase as the season progressed. Bycatch rates were positively related to net
soak time for Laysan Albatrosses and dark shearwaters. Bycatch rates of dark
shearwaters were lower for higher sea surface temperatures.