A Study of Populations of Fish Based on Catch-Effort Statistics

Abstract

The Department of Lands and Forests of the Province of Ontario conducts an annual program of netting small-mouth black bass (Micropterus dolomieu) from waters in the Province where these fish are abundant, but small. The fish are transported to waters where angling is reported to be poor. In the course of this work many non-game fish are taken in the nets. These are destroyed, since it is believed to be desirable to exert the same fishing pressure on all species present in order that the relative population levels in the waters will not be seriously influenced. The present paper is an attempt to use the catcheffort data of three such fisheries to assess the populations of the lakes. O'Reilly Lake, Davern Lake and Little Silver Lake, in Eastern Ontario, north of the Kingston-Gananoque area are dealt with here. In accordance with our usual method, trap nets were set in each lake, and catches recorded from day to day. It was found that a net set in a likely looking spot would fish well for a few days, when catches would drop off sharply. The net was then moved, in some cases only about 200 yards, and high catches would again be reported. The entire impression was one of exploitation of a series of local populations, usually in sheltered bays. The setting of the trap net is limited to rather shallow water (up to ten feet) and no effort at exploitation of those areas where shore water was over this