A method for estimating mortality coefficients of chum salmon Oncorhynchus keta from tagging experiments.

Abstract

Mature chum salmon are caught by coastal and river fisheries during their spawning migra-tion. In the tagging experiments of chum salmon in coastal waters of Japan, most early recaptures occurred in coastal fisheries, and the number of recaptures in the river fisheries gradually increased later. Therefore both fishing intensities are time dependent. In this paper, we consider a method for estimating the non-fishing mortality coefficient (M, day-1) and the time dependent mortality coefficients by coastal fisheries (F, day-1) and by river fisheries (R, day-1) from the tag recoveries using a method by Hearn et al. and the well known catch equation. We also apply this method to an example of actual recapture data. In this example, M was estimated to be 0.141, F varied from 0.000 to 0.100 and R fluctuated between 0.000 and 0.545.