Data from: Separating intrinsic and environmental contributions to growth and their population consequences

Among-individual heterogeneity in growth is a commonly observed phenomenon that has clear consequences for population and community dynamics yet has proved difficult to quantify in practice. In particular, observed among-individual variation in growth can be difficult to link to any given mechanism. Here, we develop a Bayesian state-space framework for modeling growth that bridges the complexity of bioenergetic models and the statistical simplicity of phenomenological growth models. The model allows for intrinsic individual variation in traits, a shared environment, process stochasticity, and measurement error. We apply the model to two populations of steelhead trout (Oncorhynchus mykiss) grown under common but temporally varying food conditions. Models allowing for individual variation match available data better than models that assume a single shared trait for all individuals. Estimated individual variation translated into a roughly twofold range in realized growth rates within populations. Comparisons between populations showed strong differences in trait means, trait variability, and responses to a shared environment. Together, individual- and population-level variation have substantial implications for variation in size and growth rates among and within populations. State-dependent life-history models predict that this variation can lead to differences in individual life-history expression, lifetime reproductive output, and population life-history diversity.Steelhead Size DataThis file contains length and weight time series for individual steelhead trout raised in tanks in Santa Cruz California during 2006. Individual fish were measured on a series of days starting in spring 2006 to spring 2007. The fish were derived from two hatcheries (Scott Creek Hatchery and Coleman National Fish Hatchery, denoted as "Scott" and "Coleman" respectively) and raised in set of tanks. The tank number in which each fish grew is noted in the file. The fish were fed two rations levels (high or low) and the ration associated with each time is noted in the column labeled "Ration." The sequence of feeding treatments determine the "Treatment" column which has four levels (1,2,3, or 4). See the publication for more detailed information.Steelhead Ration ScheduleThis file shows the sequence of high and low ration treatments for each tank and the date at which changes in ration occurred