Consequences of fish for cladoceran, water beetle and macrophyte communities in a farmland pond landscape: implications for conservation

Abstract

Traditionally, fish have been neglected in pond ecology and conservation studies although it has been often been assumed that they have a detrimental impact on pond biodiversity and ecosystem function. In order to assess the consequences of fish for pond biodiversity and ecosystem structure we sampled a set of 40 small farmland ponds (20 with and 20 without fish) in eastern England and compared their water chemistry as well as the assemblage characteristics (abundance, diversity, species composition) of three biological groups: cladocerans (zooplankton), water beetles and macrophytes. Water depth was significantly greater in fish ponds, while pond bottom oxygen levels and pH were significantly higher in the ponds without fish. The presence of fish significantly reduced the abundance of macrophytes and altered the community composition of cladocerans and macrophytes, but had no detectable influence on water beetles. Variation partitioning using environmental and spatial variables, indicated all three biological groups were spatially structured. The inclusion of fish however, reduced the importance attributed to space in the case of both cladocerans and macrophytes, suggesting that space effects for these two groups were at least partly the result of a spatially structured predator (i.e. fish) and not because of dispersal limitation or mass effects. In most cases fish did not have an effect on cladoceran and water beetle alpha diversity (number of species, Shannon's and Simpson's index), although the opposite was true for macrophytes. Nevertheless, at the landscape level, gamma diversity (i.e. total number of species) was enhanced for all three biological groups. Our results suggest that fish, at least small pond-associated species, are an important component of heterogeneity in farmland pond networks, thereby increasing landscapescale diversity of several faunal and floral elements. Consequently, we propose that fish should be more fully included in future pond biodiversity surveys and conservation strategies.

Generating and testing ecological hypotheses at the pondscape with environmental DNA metabarcoding: a case study on a threatened amphibian

“…Although we observed fewer detections from ponds for C. carassius than C. carpio, G. aculeatus or E. lucius , previous research also indicates large and/or predatory fish are more detrimental to T. cristatus occurrence (Skei et al, 2006; Hartel et al, 2010; Chan, 2011). C. carassius does not hinder T. cristatus oviposition, larval behaviour, or recruitment success (Chan, 2011; Jarvis, 2012), or pond invertebrate and macrophyte diversity (Stefanoudis et al, 2017). In contrast, C. carpio foraging reduces invertebrate density and macrophyte cover (Maceda-Veiga, López & Green, 2017), which lowers T. cristatus reproductive and foraging success and heightens predator exposure (Rannap & Briggs, 2006; Gustafson et al, 2006; Chan, 2011).…”

Assessing the impact of the threatened crucian carp (Carassius carassius) on pond invertebrate diversity - a comparison of conventional and molecular tools

“…commercial farming, artificial feeding, pond depth and bank alteration, removal of aquatic vegetation and sediment) associated with angling activity (Lemmens et al, 2013;Maceda-Veiga, López, & Green, 2017;Schilling et al, 2009a;Wood et al, 2001). However, the impact of fish stocking can be negligible or even beneficial to invertebrate diversity, particularly at a regional-scale, provided that fish species are carefully selected and managed (Gee, Smith, Lee, & Griffiths, 1997;Hassall, Hollinshead, & Hull, 2011;Lemmens et al, 2013;Stefanoudis et al, 2017).…”

Development and application of environmental DNA surveillance for the threatened crucian carp (Carassius carassius)

“…The crucian carp (Carassius carassius; Figure 1) is an elusive, benthic fish species popular with anglers (Copp, Warrington, & Wesley, 2008;Sayer et al, 2011). As one of few fish associated with small ponds, this species may have an important ecological role but its relationship with other lentic biodiversity is understudied (Copp & Sayer, 2010;Stefanoudis et al, 2017). Although listed as 'Least Concern' on the International Union for Conservation of Nature Red List of Threatened Species, the species has declined throughout its native range of Northwest and Central Europe (Copp, Warrington, & Wesley, 2008;Sayer et al, 2011), with local extinctions across the UK (Copp & Sayer, 2010).…”