Coexistence of behavioural types in an aquatic top predator: a response to resource limitation?

Abstract

Intra-population variation in behaviour unrelated to sex, size or age exists in a variety of species. The mechanisms behind behavioural diversification have only been partly understood, but density-dependent resource availability may play a crucial role. To explore the potential coexistence of different behavioural types within a natural fish population, we conducted a radio telemetry study, measuring habitat use and swimming activity patterns of pike (Esox lucius), a sit-and-wait predatory fish. Three behavioural types co-occurred in the study lake. While two types of fish only selected vegetated littoral habitats, the third type opportunistically used all habitats and increased its pelagic occurrence in response to decreasing resource biomasses. There were no differences in size, age or lifetime growth between the three behavioural types. However, habitat-opportunistic pike were substantially more active than the other two behavioural types, which is energetically costly. The identical growth rates exhibited by all behavioural types indicate that these higher activity costs of opportunistic behaviour were compensated for by increased prey consumption in the less favourable pelagic habitat resulting in approximately equal fitness of all pike groups. We conclude that behavioural diversification in habitat use and activity reduces intraspecific competition in preferred littoral habitats. This may facilitate the emergence of an ideal free distribution of pike along resource gradients.

Between- and within-individual variation in activity increases with water temperature in wild perch

“…The perch population was natural and self-reproducing, and no commercial and recreational fishing took place before and during the study period. Other relevant top predators in the study lake were northern pike, Esox Lucius, and European catfish, Silurus glanis (Kobler et al 2009). The average data yield (i.e., the percentage of transmissions yielding a valid position) of the wholelake telemetry system was 40%, and the accuracy was 3.1 m for horizontal position and 0.3 m for vertical position.…”

Behavioural and fitness consequences of direct and indirect non-lethal disturbances in a catch-and-release northern pike (Esox lucius) fishery

“…Prey fish abundance and biomass were estimated by monthly gill-netting (8, 12, 16 and 20 mm mesh size) in the littoral of both lake sides during two-hour surveys at both day and night between May and November, 2005. The mesh sizes used caught prey fish in a size range between 46 and 245 mm T L , which is a size range preferentially and commonly consumed by adult pike 450 mm T L (Raat, 1988;Kobler et al, 2009). During each survey, three floating net fleets (each with all mesh sizes) were placed in the littoral zone of the disturbed and the undisturbed lake side (about 2 m deep) at the edge to the reed belts, each placed on the opposite sides of the lake along its greatest dimension.…”

Intrapopulation variation in habitat use by two abundant coastal fish species

“…The activity space of individual fish also differed based on spatial orientation and location. Such intrapopulation variation has been shown to be important in several freshwater fish taxa (Bourke et al 1997, Morbey et al 2006, Kobler et al 2009), and we provide one of the first extensions of this research framework to marine fishes (cf. Egli & Babcock 2004).…”