Status of aquatic and riparian biodiversity in artificial lake ecosystems with and without management for recreational fisheries: Implications for conservation

Abstract

Humanity is facing a biodiversity crisis, with freshwater‐associated biodiversity in a particularly dire state. Novel ecosystems created through human use of mineral resources, such as gravel pit lakes, can provide substitute habitats for the conservation of freshwater and riparian biodiversity. Many of these artificial ecosystems are subject to a high intensity of recreational use, however, which may limit their biodiversity potential. The species richness of several taxa (plants, amphibians, dragonflies, damselflies, waterfowl, and songbirds) was assessed and a range of taxonomic biodiversity metrics were compared between gravel pit lakes managed for recreational fisheries (n = 16) and unmanaged reference lakes (n = 10), controlling for non‐fishing‐related environmental variation. The average species richness of all the taxa examined was similar among lakes in both lake types and no substantial differences in species composition were found when examining the pooled species inventory. Similarly, there were no differences between lake types in the presence of rare species and in the Simpson diversity index across all of the taxa assessed. Variation in species richness among lakes was correlated with woody habitat, lake morphology (surface area and steepness), and land use, but was not correlated with the presence of recreational fisheries. Thus, non‐fishing‐related environmental variables had stronger effects on local species presence than recreational fisheries management or the presence of recreational anglers. Collectively, no evidence was found that anglers and recreational fisheries management constrain the development of aquatic and riparian biodiversity in gravel pit lakes in the study region; however, the conservation of species diversity in gravel pit lakes could benefit from an increasing reliance on habitat enhancement activities.

Fish community composition in small lakes: The impact of lake genesis and fisheries management

“…Yet, in previous studies in the same study area, recreational-fisheries management and stocking in gravel pit lakes did not negatively affect local species richness and the presence of threatened taxa across a wide range of riparian and aquatic taxa (e.g., dragonflies, macrophytes; Nikolaus et al, 2021). However, predation impacts on selected species of zooplankton and macrozoobenthos (not studied by Nikolaus et al, 2021) are still plausible, as the presence of fish repeatedly has been shown to shape composition, size structure and abundance of lower trophic levels in previously fish-free lake ecosystems (Knapp et al, 2001;Lemmens et al, 2015). Some taxa, such as amphibians, are particularly sensitive to fish predation and thus would benefit from fish-free waters (Leu et al, 2009;Schmidt et al, 2021).…”

Stocking practices shape the taxonomic and functional diversity of fish communities in gravel pit lakes

“…Nevertheless, repeated stocking of a limited number of species could lead to biotic homogenization of taxonomic (Matern et al, 2019, 2022; Radomski & Goeman, 1995) and functional diversity among lakes managed for fishery purposes. Fishery managers must account for this potential risk of loss of community diversity at the regional level, especially because gravel pit lakes are primarily managed for recreational fisheries, as in Central Europe (Matern et al, 2019; Nikolaus et al, 2021).…”

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

“…Aquatic vegetation coverage (both submerged and emergent) of each lake was estimated between June and August of 2016 using snorkel surveys along equidistant transects following Schaumburg et al (2014) and described in detail in Nikolaus et al (2021). Surveys were completed on equidistant sampling units surrounding the shoreline of each lake and then transformed into percent of the lake area covered by vegetation (hereafter, percent vegetation coverage).…”

“…A large gravel pit lake, Meitzer See, with a surface area of 19.5 ha, was, therefore, designated as a reference lake. This lake was not sampled for this analysis, but it was one of a full set of 16 lakes sampled for a wider project (see Höhne et al, 2020;Matern et al, 2019Matern et al, , 2022Nikolaus et al, 2021;Radinger et al, 2023). On this reference lake, 16 nets were deployed to correspond with the standards for 20 ha lakes.…”