Diverse Foraging in Small‐Bodied Fishes: Effects on Water Quality and Submerged Macrophytes in Shallow Subtropical Lake Ecosystems

ABSTRACT The proliferation of small‐bodied fishes and their foraging effects within food webs can limit the growth of submerged macrophytes and degrade water quality in shallow lake ecosystems. The foraging habits of small‐bodied fishes vary, and, therefore, ecosystem responses may differ depending on which species or feeding guild that dominates the fish community. Yet, species and feeding guild‐specific foraging effects remain poorly understood. Here, we used an experimental mesocosm to evaluate how water quality and submerged macrophytes respond to different species of small‐bodied fishes, including omnivorous bitterling Acheilognathus macropterus (AMA), crucian carp Carassius auratus (CAU), sharpbelly Hemiculter leucisculus (HLE), zooplanktivorous thin sharpbelly Toxabramis swinhonis (TSW) and their mixes (1:1:1:1) (MIX). Our results showed that the mean weekly total nitrogen, total phosphorus, turbidity, chlorophyll‐ a and trophic level index values were significantly higher in treatments with fish compared to fish‐free controls during the experiment. At the end of the experiment, mean values for the number of submerged macrophyte shoots, leaf number, dry mass and the relative growth rate of shoots were significantly lower in the treatments with than without fish. In addition, mean values for leaf height, leaf width and the dry mass of submerged macrophytes in the TSW treatment were significantly greater than in the CAU, HLE and AMA treatments. Structural equation modelling revealed that small‐bodied omnivorous fishes (i.e., crucian carp, sharpbelly and bitterling) affected submerged macrophyte growth more than zooplanktivorous fishes (i.e., thin sharpbelly), driven by their different foraging habits. Our findings indicated that high abundances of small‐bodied fishes have negative effects on water quality and the growth of submerged macrophytes in subtropical shallow lake ecosystems, but the effects differed with fish foraging guild. Control of overabundant small‐bodied fishes (especially omnivorous fishes) may facilitate maintenance or effective restoration of submerged macrophytes and subtropical shallow lake ecosystem structure and function.