Stock assessment of sea cucumber Apostichopus armata in coastal areas of northern Hokkaido estimated from dredge-net catch data

Abstract

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 insuffcient; the slope of linear regression of CPUE on cumulative catch was gentle or the coeffcient 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 effciency 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.