Seasonal and diurnal patterns of littoral microhabitat use by fish in gravel pit lakes, with special reference to supplemented deadwood brush piles

Abstract

The habitat quality of the littoral zone is of key importance for almost all lentic fish species. In anthropogenically created gravel pit lakes, the littoral zone is often structurally homogenized with limited fish habitats. We supplemented deadwood brush piles in the littoral zone of eight gravel pit lakes and investigated the diurnal and seasonal use of this and other typical microhabitats by six dominant fish species. Shoreline habitats were sampled using point abundance electrofishing during day and night in all four seasons, and patterns of fish abundance were compared amongst unstructured littoral habitats, emerged macrophytes and brush piles. We caught a total of 14,458 specimens from 15 species in the gravel pit lakes. Complex shoreline structures were used by all fish species that we examined, especially during daytime, whilst the use of unstructured habitats was highest during night. The newly added brush piles constituted suitable microhabitats for selected fish species, perch (Perca fluviatilis), roach (Rutilus rutilus) and pike (Esox lucius), particularly during winter. Supplemented deadwood provides suitable fish habitat in gravel pit lakes and may to some degree compensate for the loss of submerged macrophytes in winter by offering refuge and foraging habitat for selected fish species.

Lake depth alters the trajectory of ontogenetic niche shifts in Eurasian perch (Perca fluviatilis) in small lakes

“…Our study examined a relatively small sample size of small, structurally simple gravel pit lakes, and so had several additional limitations. Littoral structures concentrate food sources for fish communities and provide refuges and spawning habitat (Radinger et al, 2023), but the effects on fish populations of adding woody structure to lakes vary depending on lake characteristics (Maday et al, 2023; Sass et al, 2022). Littoral structure may, therefore, have more influence on perch trophic niche in larger or more complex lakes.…”

A call to action: The need for evaluation of carbon storage by lacustrine large woody debris

“…Fish are attracted to structure and use sunken LWD and floating woody debris for shelter, spawning, feeding, and nursery habitat (Sass et al., 2009). Anglers and managers frequently use small branches and pruned shrubby material to aggregate fish in ponds and impoundments (e.g., Maday et al., 2023), and rafts constructed of floating vegetation are used as fish aggregating devices in marine environments (Everett & Ruiz, 1993). Thus, processes that decrease inputs of LWD to lacustrine systems impact biological, chemical, and physical aspects of lakes in addition to affecting carbon storage.…”