Evidence of density-dependent cohort splitting in age-0 yellow perch, (Perca flavescens): potential behavioural mechanisms and population-level consequences

Abstract

Two sequential cohorts of age-0 yellow perch (Perca flavescens), differing approximately threefold in density, were observed for their ontogeny of spatial distribution, growth, and diet in Lake St. George, Ontario. The lower density cohort exhibited typical ontogenetic spatial behaviour patterns consisting of an early pelagic phase followed by a complete migration to the littoral zone by midsummer. The high-density cohort appeared to split into a faster growing littoral component and a slower growing pelagic component which persisted throughout the growing season and into the next spring. The differences in spatial behaviour between these two cohorts could not be explained by spatial patterns in prey availability. The overwinter mortality rate for the high-density cohort was approximately double that observed for the low-density cohort. No direct observations of behaviour were made of the two cohorts, but distribution and growth data, along with arguments from competition theory, support the hypothesis that interference competition is the density-dependent mechanism responsible for the aberrant ontogeny of spatial distribution of the high-density cohort. The occurrence of interference competition in which competitively superior individuals can monopolize optimal habitats, relegating other individuals to suboptimal habitats, infers an asymptotic stock and recruitment relationship.

Contestable shelters provoke aggression among 0+ perch, Perca fluviatilis

“…Nevertheless, low intake rate of rivals could be related to their lower social status retained from recent interactions, like it was observed in sticklebacks of different competitive rank (Milinski 1982). Our findings support the hypothesis that interference competition was the mechanism responsible for the density-dependent cohort splitting (Post et al 1997). The authors found that the high-density cohort of yellow perch, P. flavescens, split into a faster growing littoral component and a slower growing pelagic component.…”

“…Such variation in body size is often thought to be related to interference competition and social hierarchy (Metcalfe et al 1989, Skulason & Smith 1995. Post et al (1997) suggested that interference competition for the littoral zone resource (both food and refuge from predators) could explain an aberrant habitat shift when a cohort was abundant. Westerberg et al (2004) observed aggression in experiments with small groups of 0+ perch, P. fluviatilis, but no proximate cues inducing aggressive interactions and establishment of social hierarchy among juvenile perch were found until now.…”

Foraging selectivity by larval yellow perch (Perca flavescens): implications for understanding recruitment in small and large lakes

“…This diet shift resulted in a higher initial larval growth rate, and this early growth advantage was still detectable in the bimodal size distribution of larvae 30 days after peak hatch. Post et al (1997) observed a bimodality in the size structure of young perch cohorts in Lake St George, Ontario, in some years but not in others. They attributed this within-cohort size difference to density-dependent competition, but this splitting of a cohort into two size groups is also consistent with an early growth advantage for the part of the cohort that may be related to earlier onset of optimal feeding due to temporal differences in prey community composition.…”

Do models parameterized with observations from the system predict larval yellow perch (Perca flavescens) growth performance better in Lake Erie?

“…Data on larval yellow perch diet composition, growth rates, TLs, and of abiotic variables (temperature and turbidity), prey availability (zooplankton prey densities, length and mass), competition (yellow perch larval densities) and predation (potential predator densities) from 2006 and 2008 were used as potential factors to develop the Lake Erie IBM and Statistical GLM. These environmental variables were considered because previous studies have found them to be related to larval fish foraging behavior and growth (Post and Prankevicius 1987;Post and McQueen 1988;Post and Johannes 1997;Power and van den Heuvel 1999;Pangle et al 2012). We also included day of year because it can be related to factors such as cumulative degree-days or number of days in which water temperature allowed for positive growth (Post and McQueen 1988) and/or a synchronization with their prey cycles (Wu and Culver 1994) both of which are more difficult to quantify.…”