The 2006 Spring International Cooperative Salmon Research Cruise of the R/V Kaiyo maru

A spring high-seas research cruise to investigate the stock condition of Pacific salmon was conducted in the North Pacific Ocean and the Bering Sea from 22 April to 20 May (first leg) and from 24 May to 22 June (second leg) onboard the Japanese research vessel Kaiyo maru. Research cruise activities included the collection of data on oceanography, primary production, zooplankton, micronekton, salmonid fishes, and other organisms. A total of 7,197 salmonids were caught by midwater trawl and angling: 4,487 fishes in the first leg and 2,627 fishes in the second leg. In the first leg, chum salmon was the most abundant species (42.3%), followed by pink (34.4%), sockeye (22.5%), chinook (0.45%), and coho salmon (0.33%). In the second leg, chum salmon was the most abundant species (50.3%), followed by sockeye (21.1%), pink (21.0%), chinook (7.45%), and coho salmon (0.11%). A total of 5,109 salmonids were measured for fork length, body and gonad weight, lipid content by fat meter, sexed, and removed scales for age determination. Isotope (n = 210), genetic (n = 2,278), otolith (n = 2,798), stomach contents (n = 4,319), lipid (n = 1,160), muscle (n = 113), parasite (n = 60) samples were obtained for future studies. There were 122 salmon (47 sockeye, 46 chum, 24 pink, 1 coho, and 4 chinook salmon) tagged and released in the North Pacific Ocean and the Bering Sea. From among fish released, 15 sockeye, 5 chum, and 4 chinook salmon were released carrying archival tags.