Factors affecting the distribution and movement in a shallow eutrophic lake

Abstract

The role of abiotic and biotic factors in determining the distribution and movement patterns of five species of coarse fish in a shallow eutrophic lake were examined between 1987 and 1990. Early chemical analyses revealed that the lake was mildly eutrophic. Routine fish sampling showed that although bream, rudd, perch and pike were present, the fish community was numerically dominated by a stunted roach population.

Intraspecific and interspecific variations in habitat use were observed using a combination of radio telemetry, tagging techniques and C.P.U.E. data. Roach, perch and bream displayed flexible patterns of habitat use when compared to rudd and pike. Both rudd and pike showed strong preferences for littoral vegetated habitats, although older individuals of both species were occasionally recovered from open habitats. Juvenile roach, bream, rudd and perchall occupied the littoral zone during the summer months but only rudd were totally restricted to this habitat. Association and dietary overlap indices revealed that both spatial and diet overlap differs seasonally and within/between species groups. The influence of competitive and predatory interactions on observed patterns of resource utilization are discussed.

Both temporal and spatial aspects of spawning behaviour were elucidated using C.P.U.E. data for mature fish and radiotracking techniques (for pike only). All species utilized shallow vegetated areas for spawning, however no large scale movements to recognised spawning areas were observed.

Seasonal activity patterns were strongly influenced by temperature, whereas diel activity patterns were largely governed by ambient illumination levels. An analysis of diel temporal activity and foraging patterns revealed that although the feeding activity of visually oriented predators (perch and pike) was restricted to diurnal and crepuscular periods, cyprinids continued to forage at low light levels. Dielhorizontal migrations were not observed. Interpecific and Intraspecific variations in the vertical distribution of all species in relation to temperature, oxygen and light levels were also examined.

Laboratory experiments showed that predation risk by piscivorous pike influenced habitat choice and activity levels of potential prey species. The role of abiotic factors/habitat structural complexity and the importance of competitive/predatory interactions in the movement and distribution of fish populations in eutrophic lakes is discussed in relation to the 'trophic cascade' theory and biomanipulation.

Date of Award	Sept 1992
Original language	English