Fluctuation of the South Pacific Albacore Stocks (Thynnus alalunga) Relative to the Sea Surface Temperature

Abstract

Both biomass and production of the south Pacific albacore stocks were estimated by the improved surplus production model. Estimations were based on the catch and effort data of the south Pacific albacore tuna longline fisheries.

Indices of the area and perimeter of the isotherms of the albacore preferred sea surface temperature and the highersea surface temperature (over 28°C) were measured. They were then used as indices of the sea surface temperature of the south Pacific albacore tuna longline fishing grounds.

The relations between the albacore stocks and the index of the sea surface temperature were examined. The results are as follows:

(1) Fluctuations of the south Pacific albacore stocks can not be explained by the distributions of the preferred sea surface temperature alone.

(2) Fluctuations of the south Pacific albacore stocks depend mainly on the distributions of over 28°C sea surface temperature.

(3)The heavier El Nino events in 1982/83 and the particular development of the gill netters in 1989 to 1991 clearly influenced the south Pacific albacore stocks.

(4)After adjusting for the effects of the heavier EI Nifioevents and the rapid development of the gill netters, albacore stocks show a significant correlation with the index of over 28°C sea surface temperature.

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