Density-Dependent Reproduction of Two Dominant Small-Bodied Fish Species in Reservoirs and Their Top-Down Effects on Plankton Biomass

ORCID

Chen: https://orcid.org/0009-0003-5369-0957; Mehner: https://orcid.org/0000-0002-3619-165X; Correa: https://orcid.org/0000-0003-4466-6923

MSU Affiliation

College of Forest Resources; Department of Wildlife, Fisheries and Aquaculture

Creation Date

2026-03-30

Abstract

In recent years, small-bodied fishes have become increasingly dominant in many subtropical reservoirs due to climate change and overfishing of predatory species. Their rising populations can disrupt aquatic ecosystem balance and increase eutrophication risk. This study investigated the density-dependent effects on the reproductive traits of two dominant small-bodied fish species (sharpbelly Hemiculter leucisculus and thin sharpbelly Toxabramis swinhonis), and their subsequent impacts on plankton biomass in three large Chinese reservoirs during 2022–2023. We observed significant variation in reproductive traits of the two fish species; both species exhibited the lowest fecundity, largest egg diameter, and smallest length at 50% maturity in the Liuxihe Reservoir, which had the highest density of thin sharpbelly. Density-dependent responses differed between species: sharpbelly fecundity was primarily affected by interspecific competition with thin sharpbelly, whereas thin sharpbelly fecundity was mainly influenced by intraspecific competition. Both species affected realised zooplankton biomass (as indicated by the ratio of zooplankton biomass to phytoplankton biomass) and positively promoted realised phytoplankton biomass (as indicated by the ratio of chlorophyll a to total phosphorus content). These results suggest that both species exert top-down control on zooplankton, which indirectly promote phytoplankton growth and negatively affect water quality. Our findings highlight that the reproductive traits of these small-bodied fish species were closely linked to species-specific densities, which in turn drove top-down impacts within freshwater food webs. These findings underscore the ecological risks posed by high densities of small zooplanktivorous fish and emphasise the importance for population regulation in freshwater ecosystems management.

Publication Date

1-10-2026

Publication Title

Ecology of Freshwater Fish

Publisher

Wiley

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Digital Object Identifier (DOI)

https://doi.org/10.1111/eff.70038