Relationship between temperature and fluctuations in sandfish catch (Arctoscopus japonicus) in the coastal waters off Akita Prefecture

Abstract

The sandfish (Arctoscopus japonicus) catch in the coastal water off Akita Prefecture have fluctuated greatly over the period 1962-1990. The difference between the maximum and minimum catches over those years is more than 200 times. The aim of this paper was to investigate the relationships between water temperature and the fluctuations of the catch. Using the fuzzy logic approach, the water temperatures measured in the different points off the Prefecture were summarized as an index which would indicate the variation of water temperatures. In this study, the sensitivity tests showed that the index inferred using the water temperatures observed in 100-150 and 200-300 m depth at 9 and 65 km off the coast with time lags 1, 2, 3 and 4 years could explain the fluctuation of sandfish catch. That is, large changes in catch can be simply explained by the fluctuation of water temperatures.