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1. Growth rate is of considerable importance to the life histories of indeterminately growing organisms. Its determination of size at age can generate positive associations with several traits, although the rate at which size increases with time has been negatively linked with survival. Such a trade-off may not, however, be evident at growth rates considerably less than species-specific maxima, nor need links between growth and life history be similar for both sexes. 2. Based on a 5-year, mark–recapture study of an unexploited population of Brook Trout ( Salvelinus fontinalis) near the edge of the species’ range, I tested the null hypotheses that seasonal growth does not differ between sexes and that survival is independent of growth rate. Both hypotheses were rejected. 3. Faster growth by males during summer, and by females during winter, can be explained by seasonal differences, by sex, in the proportional allocation of energy to gonads and soma. 4. Survival increased with growth rate per se, independently of the latter's effects on size at age; survival among males appears more dependent on growth than that of females. 5. The results indicate that there can be fitness costs associated with slow growth, that these costs can differ between sexes, and that they may be exacerbated during periods of energetic stress. Trade-offs between growth and survival may depend on the behavioural and developmental contexts in which they are examined, need not be ubiquitous and may vary throughout a species’ geographical range. [ABSTRACT FROM AUTHOR]

Polymorphism at five microsatellite genetic markers (genotyped n = 496) and mark-recapture tagging data (tagged n = 9813) were used to define the population structure of brook charr, Salvelinus fontinalis from the Indian Bay watershed, Newfoundland, Canada. Despite the absence of physical barriers to migration among lakes, both genetic and tagging data suggest that brook charr in each lake represent reproductively isolated populations. Exact tests comparing allele frequencies, θ (global value = 0·063), R st (global value = 0·052), individual assignment tests, and Nei's genetic distance provided congruent estimates of population subdivision in agreement with the tagging data (only 2·2% of recaptures were lake-to-lake). The genetic structure of the brook charr populations corresponded with the geographic structure of the drainage basin on a qualitative level, although linear distance over water was not significantly correlated with the tagging data or the genetic distance measures. The agreement between the tagging and the genetic data suggest that microsatellite markers can be useful tools for defining real biological units. The results also suggest that brook charr exhibit microgeographic population structure at the watershed scale, and that this is the scale at which conservation and management of this salmonid might best be implemented. [ABSTRACT FROM AUTHOR]