The Change of Catch of Tuna Longline Depends on Soaking Time and Soaking Time Zone of Gear

Abstract

This paper deals with the problem of decrease in the fishing efficiency as soaking time of gear increased over a certain limit, and with the fishing effect where the soaking time zone of gear shifted.
The results are as follows:
1. It was estimated from the results of various examinations of factors in tuna longline fishing that decrease in the fishing efficiency as soaking time of gear increased over a certain limit, was caused by change of the original setting form when the tuna longline settled under the sea.
2. No clear differeuce of fishing effect of Bigeye tuna and Yellow-fin tuna was recognized by X₂ test (5% level of significance) when soaking time zone of gear shifted.