知内におけるヒメエゾボラ籠の漁獲選択性と籠性能

抄録

In an attempt to find suitable fishing gear solely to trap whelks Neptunea arthritica, three different trap designs were used to carry out a preliminary survey. Trap A had two entrances from the side, while traps B and C had one entrance on the top. A string of thirty traps set in order of trap A, trap B, and trap C and baited with about 900g of sardine were set at depths between 21 to 23m.
In the four samplings conducted between July to December 1991, the soak time varied from 19h to 23h. The catch number differed significantly between the traps. The average catch number per trap/day in trap A was 43.9, in trap B 62.0, and in trap C 37.1. Mean catch rates in terms of weight varied from 1.40kg/trap in A, 2.22kg/trap in B, and 1.18kg/trap in C. The mean shell length taken by traps A, B, and C was between 61mm and 63mm. The overall results obtained from traps A, B, and C revealed that trap B was the most efficient for catching whelks. The present traps used in our survey were non-selective in catching whelks.