Some aspects of the relation between Antarctic krill abundance and CPUE measures in the Japanese krill fishery
The history of the Japanese krill fishery is reviewed briefly. Important aspects of the fishing operation are the constraints imposed by processing rate limitations on the vessels, and product quality considerations - in particular the increasing tendency to avoid catching “green” krill. These factors result in Catch-per-Day and Catch-per-Haul measures being unlikely to index krill abundance. During the high season, Catch-per-Towing-Time seems likely to index only within-swarm density. Search time data may be needed to assess the density of swarms in a concentration, but may be difficult to record in practice, and a number of other factors may complicate any analysis. The possibility of indexing the extent of the krill distribution through routine oceanographic monitoring merits attention. A data sample from the Japanese krill fishery statistics data-base has been selected for further studies.