Common carp disrupt ecosystem structure and function through middle-out effects

Abstract

Middle-out effects or a combination of top-down and bottom-up processes create many theoretical and empirical challenges in the realm of trophic ecology. We propose using specific autecology or species trait (i.e. behavioural) information to help explain and understand trophic dynamics that may involve complicated and non-unidirectional trophic interactions. The common carp (Cyprinus carpio) served as our model species for whole-lake observational and experimental studies; four trophic levels were measured to assess common carp-mediated middle-out effects across multiple lakes. We hypothesised that common carp could influence aquatic ecosystems through multiple pathways (i.e. abiotic and biotic foraging, early life feeding, nutrient). Both studies revealed most trophic levels were affected by common carp, highlighting strong middle-out effects likely caused by common carp foraging activities and abiotic influence (i.e. sediment resuspension). The loss of water transparency, submersed vegetation and a shift in zooplankton dynamics were the strongest effects. Trophic levels furthest from direct pathway effects were also affected (fish life history traits). The present study demonstrates that common carp can exert substantial effects on ecosystem structure and function. Species capable of middle-out effects can greatly modify communities through a variety of available pathways and are not confined to traditional top-down or bottom-up processes.

Habitat selection and reproductive success of coot Fulica atra on ponds under different fish size and density conditions

“…In our study system, coot breeding densities were related to both water transparency and abundance of submerged vegetation; these two habitat variables are considerably interdependent (e.g. Crowder & Painter, 1991;Blindow et al, 1993; see also Kaemingk et al, 2017). Both submerged macrophytes as food resources and water transparency as a factor constraining prey detectability by diving birds (and also growth of macrophytes and charophytes) could be important for breeding waterfowl (Hanson & Butler, 1994;Hargeby et al, 1994;Svingen & Anderson, 1998;Musil, 2006;Hansson et al, 2010).…”

“…Carp may also exert substantial pressure on submerged vegetation via resuspension of sediments, herbivory and uprooting (e.g. Sidorkewicj et al, 1996;Kaemingk et al, 2017;Maceda-Veiga et al, 2017), and thus diminish food resources for coots and destroy refugia and oviposition sites for invertebrates and amphibians (Diehl & Kornijów, 1998). In our pond system, vegetation biomass was not significantly related to the fish gradient, presumably because turbidity levels during the avian breeding season only exceptionally exceeded 20 NTU (Nieoczym & Kloskowski, 2014), a critical value over which plant development can be seriously hampered (Lougheed et al, 1998; see also Fischer et al, 2013).…”

“…On the other hand, cultured and widely stocked carp species are capable of adversely affecting entire ecosystems, both via trophic influences and habitat modification (Pípa-lová, 2006;Bajer et al, 2016;Collins & Wahl, 2017). Common carp (Cyprinus carpio Linnaeus, 1758) is the most notorious for substantial top-down and bottomup effects through omnivorous feeding, mainly on detritus, benthic macroinvertebrates and zooplankton; however, the foraging-related abiotic influence of carp may create an even stronger disturbance pathway, with declines in water transparency and submerged macrophytes (Vilizzi et al, 2015;Kaemingk et al, 2017). Variation in ecosystem responses can be attributed to carp population characteristics (reviewed in Rahman, 2015;Vilizzi et al, 2015).…”

Using marketing to fish‐down bigheaded carp (Hypophthalmichthysspp.) in the United States: Eliminating the negative brand name, “carp”

“…This negative image is based on the environmental damage that ensued as the species was introduced in the past century and then spread across the country. Common carp are described as having middle‐out negative effects, a combination of top‐down (i.e., zooplankton and benthic invertebrates can be affected by predation and reduced foraging efficiency) and bottom‐up (i.e., phytoplankton abundance and diversity can be affected by modifying nutrient and turbidity concentrations), on aquatic ecosystem structure and function (Kaemingk et al, ; Weber & Brown, ).…”

Linking ecological science with management outcomes on New Zealand's longest river

“…Intentional and unintentional establishment of invasive fish is common in many large lowland rivers globally, particularly so in New Zealand which is now considered a global hotspot of freshwater fish invasion (Leprieur, Beauchard, Blanchet, Oberdorff, & Brosse, ; Lowe, Browne, Boudjelas, & De Poorter, ). Invasive fish can often dominate vertebrate biomass within a river system (Kennard, Arthington, Pusey, & Harch, ) and can substantially influence the pathway of river and lake nutrient dynamics (Kaemingk et al, ; Matsuzaki, Usio, Takamura, & Washitani, ; Morgan & Hicks, ). The generally high mobility and fecundity of large invasive species such as carp, brown bullhead catfish, and goldfish, coupled with their tolerance of degraded environmental conditions, presents a significant management challenge.…”