Dynamics of individual growth in a recovering population of lake trout (Salvelinus namaycush)

• Published in: Canadian journal of fisheries and aquatic sciences Vol. 58; no. 2; pp. 262 - 272
• Main Authors: Fabrizio, Mary C, Dorazio, Robert M, Schram, Stephen T
• Format: Journal Article
• Language: English
• Published: Ottawa, Canada NRC Research Press 01.02.2001; National Research Council of Canada; Canadian Science Publishing NRC Research Press
• Subjects: Animal populations; Animal, plant and microbial ecology; Applied ecology; Aquaculture; Biological and medical sciences; Exploitation and management of natural biological resources (hunting, fishing and exploited populations survey, etc.); Fish; Freshwater; Fundamental and applied biological sciences. Psychology; Lakes; Natural resources; Salvelinus namaycush; Trout; USA, Wisconsin, Superior L; Wildlife conservation; Lake Superior; Great Lakes of America; North America; America; North America, Superior L., Gull Island Shoal; USA, Michigan; Salmonidae; Salvelinus namaycush; Population management; Overexploitation; Growth rate; Population structure; Spatial variation; Refuge; Protected area; Freshwater environment; Conservation area; Population survey; Vertebrata; Pisces; Body size; Models; Intraspecific comparison; Population recovery; Stock; Protected species
• ISSN: 0706-652X; 1205-7533
• DOI: 10.1139/f00-232

In 1976, the Wisconsin Department of Natural Resources established a refuge for a nearly depleted population of lake trout (Salvelinus namaycush) at Gull Island Shoal, Lake Superior. The refuge was intended to reduce fishing mortality by protecting adult lake trout. We examined the growth dynamics of these lake trout during the period of recovery by comparing estimates of individual growth before and after the refuge was established. Our estimates are based on an annual mark-recapture survey conducted at the spawning area since 1969. We developed a model that allowed mean growth rates to differ among individuals of different sizes and that accommodated variation in growth rates of individuals of the same size. Likelihood ratio tests were used to determine if the mean growth increments of lake trout changed after the refuge was established. Our results suggest that growth of mature lake trout (particularly wild fish) decreased significantly in the postrefuge period. This decreased growth may have been associated with a reduction in food availability. We also observed reductions in growth as wild fish grew older and larger, which suggests that the growth of these fish may be adequately approximated by a von Bertalanffy growth model if it becomes possible to obtain accurate ages.