Estimated distribution and movement of hairtail Trichiurus lepturus in the Aru Sea, based on the logbook records of trawlers

The distribution and movement of the hairtail Trichiurus lepturus stock in the Aru Sea were investigated using logbook data from four Taiwanese commercial otter trawlers. Fluctuations in population size, population density index and the distribution of catch per unit effort (CPUE) and fishing effort are discussed. The CPUE data were standardized by using the generalized linear model (GLM) in which fishing month, fishing area and size category of the hairtail were taken into account. The fishing season could be divided into three episodes: aggregation between March and April, dispersion between May and June, and aggregation again between July and December. A seasonal two-peak distribution of the population size of hairtail reflects the aggregation-dispersion pattern. The first peak in May-June can be explained in terms of the hairtails' overwintering migration. The second peak in October-December is likely to be the result of spawning aggregation.