Life history variation and divergence of walleye (Sander vitreus)

Moles, Matthew David
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University of Guelph

I tested whether whole body lipid reserves determine gonadal investment within and among populations of walleye ('Sander vitreus') to better understand recruitment variability. I accomplished this by comparing body lipid concentration with reproductive traits in seven populations across Canada. Among populations, I found weak trends that suggest possible relationships, however, within populations I found relationships to be highly variable. My results suggest that lipid may not be as limiting to reproductive effort as was previously thought. I also investigated ecological and life history differences between morphotypes in a polymorphic form of walleye in Lake Winnipeg. Between morphotypes, I found strong differences in gonad size and female fecundity, but minor differences in other egg traits. I found 'dwarf' individuals to be morphologically distinct from the 'normal' form, but individuals of similar size seem to use the same resources. I discount some common diversifying mechanisms and suggest this polymorphism may be fishery-induced.

walleye, Sander vitreus, life history variation, divergence, reproduction traits