Interrelationships among Production, Density, Growth, and Mortality of Northern Pike in Seven North-Central Minnesota Lakes

Abstract

Secondary production can be an important indicator of performance for afish population. In this study we examined how density, growth, andmortality operated together to alter production of northern pike Esoxlucius in seven north-central Minnesota lakes. Estimated densities ofage-2 and older northern pike were 3-59 fish/ha and estimated productionrates were 0.77-8.31 kg.ha(-1).year(-1) across the seven lakes. Therelationship between density and production among the lakes wascurvilinear, production being moderated by slow growth rates at highnorthern pike densities. The negative relationship between indices ofindividual fish growth and production was counterintuitive anddemonstrated the overwhelming influence of density on northern pikepopulation dynamics. Relationships between total mortality and eitherdensity or production were not apparent. Recreational fisheries inMinnesota appear to be harvesting much of the annual production ofnorthern pike. Yet many northern pike populations are maintaining highdensities of small individuals in the face of such harvests. Becausenorthern pike fishing is selective for larger individuals, fishingtargets the segment of northern pike populations that is leastproductive and has the lowest turnover ratio. Because old fish appear tobe very susceptible to overfishing, management aimed at producing largefish must severely restrict the harvest of large fish.