Limnological changes in a pond ecosystem caused by grass carp (Ctenopharyngodon idella Val.) low stocking density

Abstract

Grass carp (Ctenopharyngodon idella Val.) stocked (29 kg/ha) in a small pond reduced the biomass of aquatic macrophytes from 109 g/m 2 to 33 g/m 2 during one growing season. The only changes in hydrochemical parameters (pH, alkalinity, acidity, BOD 5 , COD Mn , NH 4 -N, NO 2 -N, NO 3 -N, TN, PO 4 -P and TP) associated with the grass carp stocking were a decrease in pH (from 8.43 to 7.57) and in NO 3 -N concentration (from 0.99 mg/l to 0.56 mg/l). The increases in organic matter content and NO 3 -N concentration in the surface sediment layer were higher in the control pond than in the pond stocked with grass carp. No changes were detected in the other parameters (NH 4 -N, PO 4 -P and TP) in the upper sediment layer and between all parameters measured in the lower inorganic layer. The grass carp grazing had no impact on phytoplankton biomass (concentration of chlorophyll-a) or species composition. There were no changes either in the abundance or in the species composition of zooplankton and zoobenthos induced by grass carp. Statistically significant indirect changes (in water and sediment chemistry) following the grass carp stocking were connected especially with a reduction in the biomass of the filamentous alga (Cladophora globulina) or rather with its maintenance in the control pond.

The feeding ecology of grass carp: A review

“…Red frame represents the 0 < fold change <3; fold change was calculated using the data in stocking grass carp to divide the data from control group. All data were collected from relevant studies 76–78,81,83,86,91,111–114,118 (Table S4)…”

Status of Chinese Carp Fisheries in Tunisian Freshwater Reservoirs: Threats and Opportunities

“…About half of the ingested nutrients contained in aquatic plants are used and digested by carps, the other half passes through the digestive tract in part digested and, in another part, fragmented [5,31,49,64]. These nutrient-rich feces can either remain in the water body or accumulate in the sediment [64].…”

“…About half of the ingested nutrients contained in aquatic plants are used and digested by carps, the other half passes through the digestive tract in part digested and, in another part, fragmented [5,31,49,64]. These nutrient-rich feces can either remain in the water body or accumulate in the sediment [64]. This increase in nutrient abundance can also lead to an increase in phytoplankton and consequently in the whole food chain: zooplankton and zoobenthos, which are favorable to planktivorous species [5,31,64].…”

“…These nutrient-rich feces can either remain in the water body or accumulate in the sediment [64]. This increase in nutrient abundance can also lead to an increase in phytoplankton and consequently in the whole food chain: zooplankton and zoobenthos, which are favorable to planktivorous species [5,31,64]. The introduction of carp may also indirectly favor the increase in growth and survival of fi sh species due to the increase in planktivorous or faecal-feeding species [31].…”

“…Several authors have confi rmed that current knowledge does not allow to accurately predict the long-term eff ects of the Chinese carp introduction. The negative impacts of introduction of C. idella, A. nobilis and H. molitrix are complex to evaluate and depend on many factors, such as the native fi sh community, the structure and the ecosystem functioning [5,28,31,35,52,58,64,68,71]. However, it is clear that the density of fi sh introduced into a reservoir strongly controls the impacts.…”