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

Abstract

1. Gravel pit lakes are common across Europe. These novel ecosystems serve as model systems to study human-induced and natural colonisation of isolated lakes by fish. Fisheries-management activities can quickly spread species over large distances, possibly homogenising fish communities across ecosystems, while fostering local fish diversity.2. Our objective was to evaluate the effects of lake genesis (gravel pit lakes < 100 years old vs. natural lakes of glacial genesis ~10,000 years old) and fisheries management (fish stocking activities present vs. absent) on the fish community in small lakes, while controlling for key environmental variables known to affect lake fish communities.3. We sampled fish communities by electrofishing and multimesh gillnetting in 47 isolated lakes managed for fisheries, and 19 unmanaged and isolated lakes of both natural and artificial origin in northern Germany. Unmanaged lakes were used as reference to assess fisheries-management impacts in small natural and artificial lakes. 4. We caught 178,506 fish from 30 species and found that the accumulation of native lake fish species in lakes was associated with fisheries management, which increased local species richness (α-diversity) and number of predatory species, and reduced among-lake variation in fish community composition (β-diversity; i.e., homogenisation). The homogenisation-effect associated with fisheries happened with introduced native fish species, whereas non-native species were rarely detected. 5. In unmanaged gravel pit lakes, the littoral fish community composition was substantially different to the communities present in both types of managed lakes and unmanaged natural lakes. Therefore, the relatively young unmanaged gravel pit lakes revealed evidence of ongoing, stochastic colonisation processes that resulted in comparatively species-poor fish communities.

Environmental predictors of lake fish diversity across gradients in lake age and spatial scale

“…However, our study shows that game species such as carp and goldfish are nevertheless frequent in the new lakes, probably as a consequence of illegal release of these species for recreational fishing. These different patterns call for larger scale studies, beyond a single country or region, of fish species richness and the role of management (Matern et al, 2022). The carp is often released by humans due to its recreational value as a game fish (Arlinghaus & Mehner, 2003; Vilizzi, 2012) and has also been observed in Danish gravel pit lakes (Søndergaard et al, 2018).…”

“…Recreational fishing is known to influence non-native fish species richness patterns in Europe (Zhao et al, 2016) and North America (Davis & Darling, 2017), where several catchments experienced an increase of almost 50% in richness due to the transferring of game fish to areas where the species were not found previously (Peoples et al, 2020). Studies in Europe have found different patterns in lakes managed for recreational fishing, showing that fish communities are subject to homogenisation (Matern et al, 2019(Matern et al, , 2022 with cases of both elevated (Zhao et al, 2016) and unchanged non-native richness (Matern et al, 2019). While many of the investigated lakes are used for recreational fishing, they are not managed for this purpose, in a way similar to fisheries in other countries (Arlinghaus et al, 2021).…”

“…However, our study shows that game species such as carp and goldfish are nevertheless frequent in the new lakes, probably as a consequence of illegal release of these species for recreational fishing. These different patterns call for larger scale studies, beyond a single country or region, of fish species richness and the role of management (Matern et al, 2022).…”

“…The development of freshwater fish communities has been studied in reservoirs (Agostinho et al, 2016; Paller et al, 1992), new lakes (Degani et al, 1998; Kristensen et al, 2020), ponds (Ray et al, 2004), and wetlands (Langston & Kent, 1997). To our knowledge, Emmrich et al (2014) and Matern et al (2022) are the only studies investigating S lake and assemblages in natural and new lakes, however, these studies only include gravel pit lakes as new lakes and did not evaluate the effect of connectivity. We hypothesised that: (1) S basin is influenced by lake habitat area, landscape history, and anthropogenic pressure; (2) S lake is structured by a combination of dispersal and environmental filters; and (3) rapid dispersal of most fish species will result in rapid development of fish communities in new lakes connected to a stream network, resulting in minor differences between new and natural lakes, while disconnected new lakes will have fewer species than comparable natural lakes.…”

River connectivity increases the diversity of fish communities in gravel pit lakes

“…In some gravel pit lake systems, fisheries management interventions such as stocking speed up colonization and promote species‐rich communities that resemble those in natural lakes (Matern et al 2022). We expected that the initial fish community would primarily include stocked fishes; however, these species had a surprisingly small presence in the lake communities despite yearly stocking from 2006 to 2019.…”