Evaluation of the effects of Fry and Fingerling Plants on walleye, Stizostedion vitreum vitreum (Mitchill), production in West Blue Lake, Manitoba via isozymes of Malate dehydrogenase

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Schweigert, J. F.
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The axiom that fish stocking is an effective and beneficial management concept was quantitatively examined by employing unique isozyme phenotypes of the enzyme malate dehydrogenase in skeletal muscle as biological markers. Walleye fry plants in the spring of 1971 and 1972 and a fingerling plant in the fall of 1972 were monitored in monthly gillnet samples by starch-gel electrophoresis to determine their relative survival, contribution to the year-classes, and effects on production of the native walleye population. The 1971 fry plant augmented the year-class by 43% but averaged only 2.2% of the total catch during 1974-1975. In contrast, the 1972 fry and fingerling plants comprised the entire year-class (98.5%) and contributed 35.5% of the total catch in 1974-1975. The fingerling plant was marginally successful contributing only 7.75% to 1972 year-class abundance. Annual population production was 341 kg from August 1974-August 1975. The introduced fish contributed the majority of this production (51.5%) of which the 1972 fry introduction comprised 95%. The 1971 fry and 1972 fingerling introductions contributed equally to the remainder - about 1% of total annual population production. Fry planting is preferential to fingerling plants as a means of increasing population production. The isozyme marking system is virtually flawless and deserves consideration in other suitable population dynamics studies.