Abstract
This paper proposes a simulation model of the gear efficiencies of trawlers for flatfish in order to predict the effectiveness on the limitations of horsepower of engines and gear scales. Gear efficiency of each boat is defined as (catching efficiency)×(swept area per tow)⁄(size of fishing areas). The catching efficiency is presented by a function of the gear scales, the depth of fishing area and the horsepower of engines, with the probabilities of a fish reacting at contact to ground gears and with distance of jump of fish. The swept area per haul is defined as (distance between two otter boards)×(towing speed)×(towing time), and is expressed by a function of the variables and the towing time. The parameters of the probabilities are estimated by the method of least squares from data of the above variables of boats, CPUE in the same month and fishing area and the distance of jump of fish. From the estimations from the data of five trawlers mean catching efficiencies for bastard halibut Paralichthys olivaceus are 0.031-0.125 haul-1 for (distance of jump)=1-5m. The problems in the model and estimation method, the results of the estimations, and the limitation for applications are discussed.
