The 2005 through 2008 die off of muskellunge on the 1000 Island section of the St Lawrence River was the subject of a recent paper by Dr John Casselman of Queens University. Examination of the results of the die off indicate a greater need for the biologically based minimum length limit to be raised from the current 48 inches to 54 inches.
Abstract - From 2005 to 2008, a catastrophic die-off occurred in the prized muskellunge population of the 1,000 Islands section of the upper St. Lawrence River. Approximately half of the mature population succumbed to viral hemorrhagic septicemia (VHS), and recruitment has declined dramatically. Mortality was greater in older, slower-growing individuals. Anglers reported increased handling stress. There has been increased concern that management actions are needed to restore this high-quality population and fishery. From 2004 to 2010, anglers provided the carcasses of 12 large females and 4 males that made it possible to examine individuals that were surviving before and after the mortality but succumbed to angling stress. A study of changes in growth rate, growth potential, and mean and maximum ultimate size indicated (from sequential sampling and annual growth increments) that mortality and impact were inversely related to growth rate, leaving a population that is considerably faster growing than before the die-off. In females, the relative difference was greater in the slowest-growing fish (+10.0%, lower limit) than average (+5.3%) and least for the fastest-growing fish (+0.4%, upper limit). Results were similar for males, although data were fewer. Although there may be a number of ways to try to manage and mitigate this problem, one of the simplest ways could be to regulate an increase in size limit, thus increasing reproductive potential. Following the standard procedure used in Ontario of using biologically based growth potential, the female size limit would increase from 49 inches (in the late 1990s 48 in. was chosen to fit a standard Ontario size-limit category) to a new minimum ultimate size limit of 54 inches (139 cm). There is some evidence that this change would regulate the protection of almost 50% of the reproductive capacity of the existing spawning population. It appears that the surviving muskellunge population in the upper St. Lawrence River is now the fastest-growing population in Ontario and has the potential to reach an extreme ultimate size. Mitigative management is encouraged, but anglers should minimize handling stress in this population and ensure complete recovery before release. All angled fish that succumb or are harvested should be necropsied for biological and growth data to monitor these record changes in growth rate.