Meristic variation, asymmetry, and aspects of the habitat of Culaea inconstans (Kirtland), the brook stickleback, in Manitoba

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Abstract
Phenetic traits were compared in 45 Culaea inconstans populations in southern Manitoba. Small body size characterized individuals of populations exposed to potentially predatory fishes. Skewing of the gill-raker distributions was greatest among populations sympatric with Umbra limi, a potential food competitor and predator. These patterns of variation are in some aspects similar to and in others contrast with those found in another stickleback, Gasterosteus aculeatus. Less fluctuating asymmetry occurred in the pectoral fin rays of stream-dwelling populations than in those of lakes. Care will be required in using fluctuating asymmetry as an indicator of environmental stress.