A rational sampling method for estimation of demersal fish abundance

Abstract

Two contradictory requirements are anticipated in trawling experimentally a wide unexploited area with the purpose of estimating fish abundance. The one is to take large enough sample to analyse quantitatively in a locality, and the other is to collect data covering as wide an area as possible in each cruise. This difficulty could be settled by compromising between statistical accuracy and available facilities. Therefore, the present problem is reduced to finding the least necessary number of hauls for each locality by which the estimates of fish abundance in the respective localities are assured with the same degree of accuracy. When the observed frequency distribution of catch per haul in an area is fitted with the expected one from the Polya-Eggenberger model, the least necessary number of hauls therein can be expressed as a simple equation. Here, a relatively wide area along the east coast of the Malay Peninsula was divided into three subareas and the optimum number of hauls was calculated for the respective subareas.