Effects of Formulated Feed and Forage Fish Feeds on Phytoplankton Community Structure in Mandarin Fish (Siniperca chuatsi) Culture Ponds

Abstract

The mandarin fish (Siniperca chuatsi) is an economically important carnivorous freshwater fish native to China. Recent studies have explored physiological adaptation mechanisms of mandarin fish to artificial feed. However, diverse feed regimes exerted distinct influences on the aquaculture water environment, and few reports have investigated the phytoplankton community and environmental conditions of mandarin fish (Siniperca chuatsi) aquaculture ponds fed with formulated feed and forage fish. To explore the effects of various feed patterns on phytoplankton community structure and water properties in aquaculture ponds, the experiment was conducted in formulated feed (WF) and forage fish (WB) culturing patterns in Dadukou town, Anhui, China from July to November in 2023. Significant differences in environmental parameters and phytoplankton communities were detected between the two feeding treatments. The WF treatment maintained higher pH, dissolved oxygen, and nutrient concentrations relative to the WB group, whereas chlorophyll a was markedly lower in the WF group. The Shannon diversity index was persistently high and stable in the WF group. The results revealed that the phytoplankton community exhibited distinct patterns between the two groups across all sampling times. The results of nonmetric multidimensional scaling (NMDS) analysis and redundancy analysis (RDA) demonstrated that phytoplankton community composition in the WB group was primarily governed by pH, dissolved oxygen, and ammonia nitrogen. In the WF group, ammonia nitrogen and total phosphorus constituted the key driving environmental factors instead. The study confirmed that variations in feed patterns induced fluctuations in aquaculture water systems. Comparative analysis of two feed patterns demonstrated that the WF group possessed markedly higher phytoplankton species richness and taxonomic diversity relative to the WB group (p < 0.05). Our study recommended formulated feed as the optimal feeding strategy for mandarin fish aquaculture, given its beneficial effects on water quality and phytoplankton community stability. These results facilitated aquatic microecological regulation and optimized formulated feed substitution in mandarin fish cultivation.