| Summary: | Depletion of Nelson River sturgeon through over-exploitation by the commercial fishery forced two closures of this fishery between 1921 and 1946. These failures prompted a program of biological research to determine rates of growth, reproduction and increments to stocks to provide a basis for the scientific management of this economically important species of fish. From 1953 to 1956 and 1959, 791 sturgeon were sampled from the commercial catch in the Sipiwesk Lake area of the Nelson River. Preliminary studies were conducted to determine the best method of age determination and back-calculation of growth. It was concluded that the best cross-sections of pectoral "spines", for purposes of age determination and back-calculation of growth, were located at the proximal end of the spine at the base of the swelling which forms the "knuckle"of the spine. The easiest and best measurement on this cross-section for back-calculation of growth was along the radius of the spine from the centre of ossification to the posterior edge of the spine, along the acute angles formed by the annuli in this area. The relationship between fork length (x) and the average radius of the pectoral spine (y) as determined by the method of least squares was: x = .14y + 2.2. In the calculation of size at any previous age, best results were obtained by back-calculating along a line which converged with the intercept. The best representation of growth in Nelson River sturgeon was obtained by cumulatively totalling the average annual calculated increments of growth for a number of specimens. It is readily apparent that female lake sturgeon of the Nelson River grows faster and lives much longer than the male. The average annual Depletion of Nelson River sturgeon through over-exploitation by the commercial fishery forced two closures of this fishery between 1921 and 1946. These failures prompted a program of biological research to determine rates of growth, reproduction and increments to stocks to provide a basis for the scientific management of this economically important species of fish. From 1953 to 1956 and 1959, 791 sturgeon were sampled from the commercial catch in the Sipiwesk Lake area of the Nelson River. Preliminary studies were conducted to determine the best method of age determination and back-calculation of growth. It was concluded that the best cross-sections of pectoral "spines", for purposes of age determination and back-calculation of growth, were located at the proximal end of the spine at the base of the swelling which forms the "knuckle"of the spine. The easiest and best measurement on this cross-section for back-calculation of growth was along the radius of the spine from the centre of ossification to the posterior edge of the spine, along the acute angles formed by the annuli in this area. The relationship between fork length (x) and the average radius of the pectoral spine (y) as determined by the method of least squares was: x = .14y + 2.2. In the calculation of size at any previous age, best results were obtained by back-calculating along a line which converged with the intercept. The best representation of growth in Nelson River sturgeon was obtained by cumulatively totalling the average annual calculated increments of growth for a number of specimens. It is readily apparent that female lake sturgeon of the Nelson River grows faster and lives much longer than the male. The average annual Recommendations for the management of future fisheries on the Nelson River and other areas are given. These pertain to production limits, fishing seasons and the minimum legal size of fish and fishing gear. Science, Faculty of Zoology, Department of Graduate
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