Restoration of Lake Trout in Parry Sound, Lake Huron

Abstract

The purpose of this study was to explain how a series of management actions facilitated the restoration of lake trout Salvelinus namaycush in Parry Sound of Lake Huron. Since 1988, the relative abundance of wild spawning lake trout has increased in Parry Sound. Estimates of the spawning population (1994–1997) varied between 16,000 and 29,000 individuals. This increase in abundance was achieved by controlling sea lampreys Petromyzon marinus (1960), stocking yearling lake trout derived from the remnant stock (1981–1997), creating a refuge (1987), restricting harvest by reducing both angling seasons and possession limits (1981), and imposing a size limit for retention (1994). By 1997, the three criteria of successful restoration were achieved, that is, the average age of mature females was 1 year older than the age of first maturation, wild fish composed 50% of the spawners, and the abundance of wild lake trout had been stable or increased for three consecutive years. As a consequence, stocking of yearlings was discontinued after 1997. A stochastic simulation model was developed to assess the likelihood of realizing sustainable harvests over a range of total mortality rates. We concluded that lake trout restoration is possible if sea lampreys are controlled, the appropriate strain is stocked, and exploitation is restricted, although additional limiting factors could hinder rehabilitation success in some locations of the Great Lakes.