(English) Changes in the muskellunge fishery and population of Lake St. Clair after an increase in the minimum size limit

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In response to high harvests and indications of stock declines in the late 1970s and early 1980s the minimum size limit for muskellunge (Esox masquinongy) for Lake St. Clair was elevated from 76 to 102 cm (30 to 40 inches) in 1987. This regulation change was implemented to protect female muskellunge through two repeat spawnings and to support a muskellunge management objective for a high quality trophy fishery based on natural reproduction. Changes in the muskellunge stock and fishery of Lake St. Clair were demonstrated by calculating length group specific indices of relative abundance. This analysis indicated that an immediate and dramatic increase had occurred in the newly protected 76 to 102 cm length group (an average annual increase of 15% with a doubling of the stock in seven years). Elevation of the minimum size limit afforded important protection to this segment of the stock which represents the prime breeding muskellunge. It also enabled a buildup of the spawning stock over the next four year period (1987-1990), with subsequent enhancements to recruitment based on strong year-classes occurring in 1991 and 1994. The dramatic turn-around in the Lake St. Clair muskellunge fishery emphasizes the need for, and benefit of, appropriate size-based regulations and effective angler catch-and-release initiatives. An angler diary program can make an extremely valuable contribution to management of muskellunge through the provision of comprehensive and cost-effective stock monitoring data. Favourable changes to musky habitat occurred during the same period but the habitat contribution to musky production and abundance, relative to changes in angling regulations and angler attitudes is unknown.