Life-history variation within a three-spined stickleback population in the Camargue

Among individuals of female three-spined sticklebacks Gasterosteus aculeatus from a population in the Camargue, southern France, studied in 12 successive years, adult L _T ranged from 31–64 mm, clutch size ranged from 33–660 eggs, and mean egg diameter per clutch ranged from 1.15–1.67 mm. Because the population was strictly annual, inter-annual variation corresponded to variation among generations having experienced different environmental conditions. Body mass varied significantly among years, suggesting an effect of varying environmental conditions. Gonad mass and clutch size increased with body mass, but mean egg diameter was not correlated to body mass. Body mass-adjusted gonad mass, interpreted as reproductive effort per clutch, did not vary significantly among years, suggesting that this trait was not influenced by environmental conditions. Body mass-adjusted clutch size and egg size varied significantly among years. Inter-annual variation in body length at breeding, clutch size and egg size was of the same order of magnitude as inter-population variation reported by other authors for this species. During the breeding season, reproductive effort and clutch size tended to increase. Egg size tended to decrease during the breeding season but this seasonal pattern varied among years. Observed life-history variation is discussed both in terms of its evolutionary significance and methodological implications in the study of life-history variation among populations.