1Wakkanai Fisheries Research Institute, Hokkaido Research Organization, Wakkanai, Hokkaido 097-0001, 2Central Fisheries Research Institute, Hokkaido Research Organization, Yoichi, Hokkaido 046-8555, 3Future University Hakodate, Hakodate, Hokkaido 041-8655, 4Tokyo University of Agriculture, Setagaya, Tokyo 156-8502, 5Wakkanai Fisheries Extension Office, Wakkanai, Hokkaido 097-0001, 6Rumoi-Nanbu Fisheries Extension Office, Rumoi, Hokkaido 077-8585, 7Field Science Center for Northern Biosphere, Hokkaido University, Hakodate, Hokkaido 041-8611, Japan
The populations of sea cucumber Apostichopus armata in four coastal areas of northern Hokkaido, Japan were estimated based on data collected between June and September 2008 using two methods: the initial population was calculated from CPUE (catch per dredge-net) against cumulative catch (DeLury method), and from the catch against dredged area (swept-area method). The estimation obtained using the DeLury method did not reflect the actual population size in the two areas as the data requirements were insufficient; the slope of linear regression of CPUE on cumulative catch was gentle or the coefficient of determination was low. The estimates using the swept-area method seemed to be lower than the actual population size for all the areas because the catch efficiency was assumed as 1; however, sampling errors were low, as the estimates were based on a large number of sampling data collected directly from a wide area. We conclude that the swept-area method provides a more accurate assessment of sea cucumber stock in the coastal areas of northern Hokkaido than the DeLury method.