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Understanding how environmental productivity and resource competition influence somatic growth rates and plasticity in life-history traits is a critical component of population ecology. However, evolutionary effects often confound the relationship between plasticity in life-history characteristics and environmental productivity. We used a unique set of experimentally stocked populations of rainbow trout (Oncorhynchus mykiss) to empirically test predictions from life-history theory relating to patterns in immature growth rates, age- and size-at-maturity, and the energy allocated into reproduction across climatic and fish density gradients. Our results support theoretical predictions that plasticity in life-history characteristics is a function of environmental variables. In particular, we demonstrate that immature growth rates are best explained by climatic and density-dependent competition effects and that age-at-maturity and the energy allocated to reproduction depends on juvenile growth conditions. Empirical evidence of these relationships helps to improve our understanding of optimal life-history strategies of fish populations. La comprehension de l'influence qu'exercent la productivity environnementale et la concurrence pour les ressources sur les taux de croissance somatique et la plasticite des caracteres du cycle biologique constitue une composante cle de l'ecologie des populations. Des effets evolutifs confondent toutefois souvent le lien entre la plasticite de caracteristiques du cycle biologique et la productivite environnementale. Nous avons utilise un ensemble unique de populations de truites arc-en-ciel (Oncorhynchus mykiss) ensemencees experimentalement pour verifier de maniere empirique des predictions de la theorie du cycle biologique concernant des motifs des taux de croissance des individus immatures, de l'age et de la taille a la maturite, et de l'energie affectee a la reproduction le long de gradients climatiques et de densite de poissons. Nos resultats appuient des predictions theoriques selon lesquelles la plasticite de caracteres du cycle biologique serait une fonction de variables environnementales. En particulier, nous demontrons que des effets climatiques et de la concurrence dependante de la densite expliquent le mieux les taux de croissance des individus immatures et que l'age a la maturite et l'energie affectee a la reproduction dependent des conditions de croissance des juveniles. Les preuves empiriques a l'appui de ces relations aident a ameliorer la comprehension des strategies de cycle biologique optimales de populations de poissons. [Traduit par la Redaction], Introduction Density-dependent growth among fish populations is well-documented and is hypothesized to be a function of competition for food resources (Post et al. 1999; Lorenzen and Enberg 2002; de Roos [...]

Angler effort responses to the stocking of sterile rainbow trout were evaluated using a historical data set consisting of 63,000 angler boat counts, which were used to develop indices of annual angler effort for 513 lakes representing 3396 lake-years of data over a period of 25 years. Included in this data set were 173 lakes that were supported by put-and-grow stocking of rainbow trout, and that received diploid (2n) stocking in earlier years and triploid (3n) stocking in later years. A stocking-size-dependent, ploidy-independent, growth and survival model was used to estimate the number of fish available to anglers one and two years post-stocking. Following a change to triploid stocking, boat counts increased by 31%, with larger increases in more remote Regions. Boat counts declined through time by 0.988x/yr, but with substantial variation among years (SD = 0.124). A principal component synthesized from four correlated variables (license cost, license sales, gas price, Can$:US$) explained 35% of the residual variation in boat counts among years. The boat count response to fish abundance was positive for rainbow trout, at 0.20x of the proportional change in abundance. An index of size-and-quota regulation intensity ranging from 0 (general restrictions only) to 1 (catch and release only), indicated that boat count response was positive, at 1.17x of the proportional increase in regulation intensity. [ABSTRACT FROM AUTHOR]