Density-dependent compensatory growth in brown trout (Salmo trutta) in nature.

Density-dependence is a major ecological mechanism that is known to limit individual growth. To examine if compensatory growth (unusually rapid growth following a period of imposed slow growth) in nature is density-dependent, one-year-old brown trout (Salmo trutta L.) were first starved in the laboratory, and then released back into their natural stream, either at natural or at experimentally increased population density.

Modes of competition: adding and removing brown trout in the wild to understand the mechanisms of density-dependence.

While the prevalence of density-dependence is well-established in population ecology, few field studies have investigated its underlying mechanisms and their relative population-level importance. Here, we address these issues, and more specifically, how differences in body-size influence population regulation. For this purpose, two experiments were performed in a small coastal stream on the Swedish west coast, using juvenile brown trout (Salmo trutta) as a study species.

Habitat exclusion and reduced growth: a field experiment on the effects of inter-cohort competition in young-of-the-year brown trout.

Competition during the juvenile phase is a key process for regulating density in organisms with high fecundity. Juvenile density-dependent bottlenecks may become even more pronounced if several cohorts compete, but this has received relatively limited attention in previous literature. We performed a manipulation experiment in seven coastal streams to investigate the presence of inter-cohort competition, using habitat selection, body-size and density of newly emerged (age-0) brown trout (Salmo trutta) as response variables.