Muskellunge Growth

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Muskies like most fish never stop growing. However, rates of growth are dependant on sex, age, and population. Generally females are larger than males, younger fish grow the fastest, and large bodies of water produce the biggest fish.

However, individual variability within a population can be very large. For example, 5 year old muskies in Ontario will be, on average, 80cm (32 in) long and weigh approximately 3 Kg (8 lb), but the 95% confidence interval about that mean is approximately 15 cm and 1.5 Kg.1 In other words a 5 year old fish could be as long as 95 cm or as small as 65 cm and range in weight from 1.5 to 4.5 Kg. After age 10 growth slows to about 2.5 cm (1in) per year. Northern U.S. fish show similar trends. A study by Casselman and Crossman (2) showed no significant difference in size between Canadian and U.S. fish.

Note also that the weight at a given length will vary with season and among individuals. Consider the ranges in weight for muskellunge netted from Stony Lake (Peterborough Co., Ontario) plotted below (Fig 1.). For 42 inch fish, weight varied between 13 and 20 lbs. In this case, the thinner fish was a male and the heavier fish was a ripe female. Quick measurements of the length and girth of a fish enable very accurate weight estimates (side-bar). By taking this measurements while the fish is in the water, an angler can significantly reduce stress and improve the likelihood of a successful release.

Weights and lengths top out at about 16 Kg (35 lbs) and 135 cm (53 in) respectively. A fish of that size is approximately 21 years old. The world record however, is 65lbs therefore, much bigger fish do exist.

Not every large body of water produces fish of potential world record size. The analysis of growth data from the Cleithrum Project indicates that only a few populations have a combination of factors - genetics, longevity, forage base, density - for muskellunge to attain weights in excess of 60 lbs (Fig. 2, below). On lakes and rivers where the harvest of all fish over 40 lbs (for most anglers, a fish of a lifetime) is the norm, the odds of a fish reaching record size is reduced.

In Ontario, the record-class potential of a number of lakes and rivers has been recognized. In compliance with the new Provincial Management Strategy a minimum size limit of 54 inches was implemented for Georgian Bay and the North Channel and several waters in northwest Ontario (including Lake of the Woods, Eagle Lake, Wabigoon Lake and Longlegged Lake).

To learn more about fish growth in general "The Biology of Fish Growth"(4) edited by Weatherley and Gill published in 1987 is a good place to start. It is full of information on fish growth and is well referenced.

by Dr. Geoff Veinott

Stony length width.jpg

Figure 1. Length vs weight for Stony Lake (Peterborough County, Ontario) muskellunge. Graphic by Michael Butler.

Did you know that...

  • Both male and female muskellunge can live to be over 30 years of age?
  • Female muskellunge usually reach maturity at age 5, males typically one year earlier?
  • Female muskellunge can add 30% to their body mass in eggs prior to spawning?
  • Females grow much larger and faster than males?
  • Muskellunge populations can have a broad range of growth rates and ultimate sizes?
  • Theoretically female muskellunge can grow to 68 inches and 73.5 pounds?
  • Source: Casselman and Crossman. 1999 Cleithrum Project Booklet


Figure 2. Length at age for muskellunge from three lakes in northwestern Ontario (after Casselman and Robinson, 2000). Note the remarkable differences in growth rates and ultimate sizes.


  • Casselman, J.M. and C.J. Robinson. 2000. Muskellunge age and growth analysis for northwestern Ontario. Manuscript. Ministry of Natural Resources. Research, Science, and Technology Branch, Glenora Fisheries Station, Picton, Ontario. 24 pp.
  • 1). Casselman, J.M. and C.J. Robinson. 1995. Age and growth of trophy muskellunge from selected southeastern Ontario water bodies, 1979-1994. Ontario Ministry of Natural Resources. Research, Science, and Technology Branch, Glenora Fisheries Station, Picton, Ontario.
  • 2). Casselman, J.M. and E.J. Crossman. 1986. Size, age, and growth of trophy muskellunge and muskellunge-northern pike hybrids-- the cleithrum project, 1979-1983. American Fisheries Society Special Publication 15: 93-110.
  • 3). Porter, L.R. 1977. Review of selected literature on muskellunge life history, ecology and management. Minnesota Department of Natural Resources, Division of Fish and Wildlife, Section of Fisheries. Special Publication No. 119.
  • 4). Weatherley, A.H. and H.S. Gill. 1987. The biology of fish growth. Academic Press, New York.
  • Muskellunge Bibliography

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