We examined how the lipid content and fatty acid composition of walleye (Sander vitreus) ova varied with respect to maternal characteristics, particularly indices of body nutrient reserves, within three spawning populations that varied in maternal age, size, and somatic lipid reserves. We also compared the variability in ova lipid composition among three populations with that observed among spawning years within one of these populations. Maternal characteristics had little influence on ova lipid content. In Lake Ontario, percentages of docosahexaenoic acid (22:6(n-3), DHA) and arachidonic acid (20:4(n-6), AA) increased with maternal length, while those of eicosapentaenoic acid (20:5(n-3), EPA) declined. In Lake Nipissing, maternal age had similar effects on AA and EPA, but not DHA. The Lake Winnipeg population did not conform to the trends of the other two populations, and ova from this population had very low levels of AA. We hypothesize that there are similar selection pressures on the Lake Ontario and Lake Nipissing populations with respect to desirable ova fatty acid profiles. Lake Winnipeg walleye may experience different selection pressures or may be unable to conform to the trends observed in the other two lakes.Résumé : Nous examinons la variation du contenu lipidique et de la composition en acides gras des oeufs de dorés (Sander vitreus) en fonction des caractéristiques maternelles, en particulier des indices de réserves nutritives corporelles, chez trois populations reproductives qui diffèrent par l'âge maternel, la taille et les réserves lipidiques somatiques. Nous comparons aussi la variabilité de la composition lipidique des oeufs chez les trois populations avec celle obtenue au cours des années de fraie chez l'une de ces populations. Les caractéristiques maternelles ont peu d'influence sur le contenu lipidique des oeufs. Au lac Ontario, les pourcentages d'acides docosahéxaénoïque (22:6(n-3), DHA) et arachidonique (20:4(n-6), AA) augmentent en fonction de la longueur de la mère, alors que celui de l'acide eicosapentaé-noïque (20:5(n-3), EPA) décline. Au lac Nipissing, l'âge de la mère a le même effet sur AA et EPA, mais non sur DHA. La population du lac Winnipeg ne suit pas les tendances des autres populations et les oeufs de cette populations contiennent de très faibles concentrations d'AA. Nous formulons l'hypothèse selon laquelle les pressions de sélection concernant les profils souhaitables d'acides gras dans les oeufs sont semblables dans les populations des lacs Ontario et Nipissing. Les dorés du lac Winnipeg peuvent subir des pressions sélectives différentes ou alors ils sont incapables de suivre les tendances observées dans les deux autres lacs.[Traduit par la Rédaction] Wiegand et al. 712

Differences in reproductive strategies of male and female fishes are presumably accompanied by differences in nutrient allocation and predicted to lead to divergence in body composition between the sexes. We compared patterns of variation in fatty acid profiles of lipids extracted from ova, liver, muscle and visceral fat between mature male and female walleye (Sander vitreus) sampled from two wild spawning stocks. Fatty acid profiles differed significantly among body tissues in both males and females, with the strongest contrast between muscle and visceral fat. Significant differences in fatty acid composition between the sexes were found in liver, muscle and visceral fat tissues. Variation among sexes and populations was greater in liver than in the other tissues. Female livers had lower relative abundances of palmitic acid (PA, 16:0) and oleic acid (OA, 18:1(n‐9)), and higher relative abundances of arachidonic acid (ARA, 20:4(n‐6)), eicosapentaenoic acid (EPA, 20:5(n‐3)) and docosahexaenoic acid (DHA, 22:6(n‐3)) compared to male livers. In addition, female muscle had higher relative abundance of OA and lower relative abundance of DHA compared to male muscle. Our results illustrate the differential effects of reproductive demands on the biochemical composition of males and females and have implications for the analysis of fatty acid profiles in studies of wild fish populations.

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