Contrasting strategies of ova lipid provisioning in relation to maternal characteristics in three walleye (Sander vitreus) populations

Abstract

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

Hatching success of walleye embryos in relation to maternal and ova characteristics

“…Females ranged in age from 5 to 18 years, and from 6 to 18 years in the Lake Manitoba and Lake Ontario trials, respectively. However, profiles for Lake Manitoba polar lipids (Table 2) were similar to those seen in other walleye populations (Wiegand et al 2004), and profiles for Lake Ontario total lipids (Table 2) were also similar to those seen in other walleye populations (Wiegand et al 2007). The two populations produced ova of similar size, but the Lake Ontario walleye produced ova with a higher lipid content (t-test, P < 0.001; Table 1).…”

“…In walleye, some ova traits are correlated with maternal age and/or size, most notably ovum size (Johnston & Leggett 2002) and fatty acid composition (Wiegand et al 2004;Wiegand et al 2007) although the strengths of these relationships vary among populations (Wiegand et al 2007). In walleye, some ova traits are correlated with maternal age and/or size, most notably ovum size (Johnston & Leggett 2002) and fatty acid composition (Wiegand et al 2004;Wiegand et al 2007) although the strengths of these relationships vary among populations (Wiegand et al 2007).…”

Maternal and stock effects on egg-size variation among walleye Sander vitreus stocks from the Great Lakes region

“…To facilitate comparisons with CART models and past studies using a similar analytical approach (Johnston and Leggett, 2002;Wiegand et al, 2007), we initially analyzed data using multiple linear regression. We natural log-transformed female length data to examine the relationship between egg size and female length (R 2 increased about 0.01 with Log e -transformed female length).…”

Abundance, growth, and life history characteristics of sympatric walleye (Sander vitreus) and sauger (Sander canadensis) in Lake Winnipeg, Manitoba

“…possible explanation for this discrepancy between available energy and reproductive effort is that the forage base available to walleye in Lake Winnipeg is energetically rich but low in particular constituents, such as essential nutrients, that may be limiting for reproduction. Female walleye of Lake Winnipeg appear to produce ova with relatively low levels of arachidonic acid (20:4(n-6), AA), an essential fatty acid (Wiegand et al, 2007). Determining whether AA, or any other nutrients, are limiting growth and reproduction in Lake Winnipeg percids may be worthy of further investigation.…”