Components Analysis of a Density-Dependent Catchability Coefficient in a Salmon Hook and Line Fishery

Abstract

The relationship between the catch per unit of effort (C/E) of salmon anglers and salmon abundance was determined by using simultaneous estimates of both C/E and salmon density (n). Salmon in their natural marine environment were observed as they approached fishing gear. The components of catch, such as the number of fish approaching, attacking, and biting the lure per unit of fishing effort, were recorded. C/E was not linearly related to density because the estimate of the catchability coefficient q increased with abundance. This result contrasts with previous empirical studies of catchability in which q declined with fish abundance. However, because only historical catch records had been used to estimate catchability, the interactions between the fishing gear and fish were not available in past research. This study suggests that feeding facilitation among salmon may be the mechanism underlying increased catchability with abundance.