Utilization of natural and artificial habitats by YOY pike in a biomanipulated lake

Abstract

Biomanipulation by stocking with YOY pike Esox luciushas been shown to be a useful tool in the restoration of shallow hypertrophic lakes. The success of such stocking depends partly on the standing stock of the YOY pike in the first 2–3 months following stocking, this in turn depending on habitat type and abundance in the lake. The present study evaluated the general habitat use and preferences of YOY pike and the suitability of artificial submerged habitats formed by small laid out spruce trees Picea omoricausing Point Abundance Sampling by Electrofishing (PASE). This sampling method was assessed as being suitable for catching and quantifying small pike. While very few pike were present in either the dominant emergent vegetation Phragmites australisor the subdominant vegetation Typhaspp. in June and July, they were present in significantly greater numbers in the artificial habitats. This suggests that the use of spruce trees as artificial habitats in biomanipulation projects could potentially enhance the standing stock of YOY pike. In August, in contrast, habitat utilization by the YOY pike did not differ from that expected if they used the habitats randomly. This suggests that YOY pike change their habitat utilization as a function of their size. Thus they use habitats with a complex structure in the early summer, but in late summer when they are larger, they use habitats with a less complex structure such as Phragmitesand Typha.