A CATCHING MODEL OF FISH TRAP FOR PUFFER

A study was conducted to clarify the fish catching mechanism of a fish trap for the puffer fish. The authors have proposed a catching model for puffer trap fishery, taking into account the mutual relation betwe en the entrance shape of the pot and fish behavior. The probability of fish being entrappead and relative catch efficiency were theoreticall y calculated from a model based on four main assumptions. The theoreti cal results were examined by comparing the measured values of turning diameter of puffer in a narrow water channel and the size of the entra nce of traps presently used, through tank and field experiments. From the turning motion analysis, two major ratios were introduced in the m odel to clarify the catch efficiency in terms of trap selectivity and escape. One is the ratio of width of water channel to total length of fish body and the other is the ratio of turning diameter of a given fi sh to total length of fish body. The catch efficiency was expressed by Eq. 7. The lower and upper selection limits were 1.24 and 1.38 times the width of trap entrance. These limits approximately agreed with the experimental values obtained from field research.