Sex Ratios of Black Crappies Harvested during Spring Fisheries on Two Minnesota Lakes: Are Males in the Majority?

Abstract

AbstractSex‐selective fishing mortality can alter the demographics and life history patterns of fish populations, yet the extent of this mortality is rarely investigated in harvest‐oriented recreational fisheries. Potential differences in habitat use between sexes and nest‐guarding behavior suggest that male black crappies Pomoxis nigromaculatus could dominate angler harvest during spring fisheries. We examined the potential for male‐dominated harvest in spring (late April to mid‐June) recreational fisheries for black crappies occurring on two north‐central Minnesota lakes. In the three spring fisheries we examined, males represented between 45% and 57% of all black crappies harvested by anglers, but sex ratios (expressed as the percentages of males) did not significantly deviate from 1:1. However, a temporal pattern in sex ratios was observed on Lake Hubert, where female black crappies dominated angler harvest before 19 May in both 2005 and 2006 (41–42% male) while the harvest on or after 19 May was dominated by males (69–75% male); this shift appeared to coincide with peak nesting periods. In fall electrofishing samples, the sex ratios of black crappies that had been exposed to exploitation during spring fisheries (i.e., fish age 4 and older) did not significantly deviate from 1:1, suggesting that total annual mortality rates were similar between sexes. The sex ratios of black crappies harvested by anglers during spring can vary within and among lakes and will not always be skewed toward male fish. Estimating population sex ratios and the sex ratio of black crappies harvested by anglers may improve our understanding of the effects of exploitation on crappie populations, particularly when fishing intensity during nesting is high and nests are easily located by anglers.