Muskellunge Management: Fifty Years of Cooperation Among Anglers, Scientists, and Fisheries Biologists

<em>Abstract</em>.—Sustainability of trophy Muskellunge <em>Esox masquinongy </em>populations and fisheries was examined from Muskies, Inc. catch data (335,954) from 43 years (1971–2013), along with more than 35 years (late 1970s–2013) of trophy Muskellunge data and cleithra (2,633) submitted to the Cleithrum Project. Catch has increased substantially over the past five decades, but harvest has been greatly reduced because of increased size limits (e.g., in Ontario, set by using growth potential) and voluntary catch and release of legal-sized fish promoted by organized Muskellunge anglers. The Cleithrum Project exemplifies cooperative interaction; although fewer samples have been submitted in recent years, length, weight, and age have increased significantly. Pivotal change occurred in the mid-1990s (means for late 1970s–1994, total length 108.7 cm, total weight 9.7 kg, age 11.6 years; 1995–2013, 121.0 cm, 13.4 kg, 15.1 years). A predictive mortality rate–longevity relationship was used on the Cleithrum Project age data to estimate mortality rate of trophy Muskellunge. Annual mortality rate (<EM>A</EM>) of trophy Muskellunge usually ranged from 16% to 26% and corresponded to maximum ages of 24 to 14 years. Estimated annual mortality of the oldest Muskellunge increased slightly over the past 35 years—13.0% to 14.3%, with a decrease in maximum age from 30 to 27 years. Mortality was high to the mid-1990s but has decreased subsequently, even though angling pressure has increased. Size and mean age of trophy Muskellunge have increased substantially (10.2 to 15.8 years) with associated decreases in annual mortality (<EM>A</EM>, 31.0% to 21.9%), indicating an increase in the mature population and reproductive potential. To ensure sustainable trophy Muskellunge populations, fish younger than 15 years should not be exposed to fishing mortality and older fish should not have a fishing mortality rate that exceeds the rate of natural mortality (<EM>F ≯</EM> <EM>M</EM>). Management for large size (older age) by using excessive size limits, in combination with catch and release, can have unexpected outcomes because older fish are increasingly sensitive to stress (e.g., viral hemorrhagic septicemia [VHS] mortalities). If Muskellunge populations are managed for high reproductive capacity (protecting fish to larger size and older age), they will be more reproductively resilient, producing larger year-classes, better sustaining trophy populations and fisheries.

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