Recreational darkhouse spearing for northern pike in Minnesota: historical changes in effort and harvest and comparisons with angling

摘要

A traditional form of harvest for northern pike Esox lucius during winter is darkhouse spearing through the ice. Using a comprehensive evaluation of creel surveys and license sales in Minnesota, we document a long-term decline in this unique sport fishery. The decline in recreational spear fishing effort cannot be blamed on catch rates because spearing catch rates have not changed perceptibly with time. Catch rates for spearing (mean = 0.175 fish/h) are similar to harvest rates by anglers that are targeting northern pike. Conflicts between spearers and anglers have led to questions about relative harvests by each group and their effects on northern pike populations. Creel survey data since 1980 show that summer and winter angling account for most of the northern pike harvest. Spearing accounted for 15 percent of the average yield of northern pike by number, but spearing is selective for the larger fish. In comparison with population estimates, spearing removes a small proportion of the total population and biomass of northern pike but an increasing proportion of fish with increasing size. Recreational angling, by comparison, removes an even greater proportion of all fish sizes in a population. Management designed to improve the size structure of northern pike populations will need to be directed at reducing harvest by all methods.