Effects of the Feeding Rate on Growth Performance, Body Composition and Hematological Properties of Juvenile Mandarin Fish Siniperca scherzeri in a Recirculating Aquaculture System

The effects of feeding rate (0.5%, 1.0%, 1.5%, 2.0%, 2.5%, and 3.0% body weight [BW] per day [BW day−1]) on the growth, body composition, and blood properties of juvenile mandarin fish, Siniperca scherzeri, (initial BW 18.4 ± 0.2 g) were investigated in a water recirculating aquaculture system. Triplicate groups of fish were fed an experimental diet (55.4% protein, 14.1% lipid) for 10 weeks. Weight gain and specific growth rate increased with increasing feeding rates of up to 2.5% BW day−1, after which no significant increase in growth was observed. Feed efficiency, protein efficiency ratio, and protein retention were not significantly different among the fish fed 1–2.5% BW day−1 but decreased significantly in those fed 3.0% BW day−1. The lipid content of fish fed 2.5% BW day−1 was significantly higher than that at 0.5–1.5% BW day−1. The total plasma cholesterol content was significantly lower in fish fed 0.5 BW day−1 than fish provided with other feeding rates. Based on the growth, feed efficiency, body composition, and blood content analyses, including regression analysis, the optimal feeding rate for juvenile S. scherzeri weighing between 18 g and 54 g was estimated at 1.88–2.80% BW day−1 depending on weight gain, specific growth rate, and feed efficiency under 26.9 °C conditions.

Mandarin fish (Sinipercidae) genomes provide insights into innate predatory feeding

Mandarin fishes (Sinipercidae) are piscivores that feed solely on live fry. Unlike higher vertebrates, teleosts exhibit feeding behavior driven mainly by genetic responses, with no modification by learning from parents. Mandarin fishes could serve as excellent model organisms for studying feeding behavior. We report a long-read, chromosomal-scale genome assembly for Siniperca chuatsi and genome assemblies for Siniperca kneri, Siniperca scherzeri and Coreoperca whiteheadi. Positive selection analysis revealed rapid adaptive evolution of genes related to predatory feeding/aggression, growth, pyloric caeca and euryhalinity. Very few gill rakers are observed in mandarin fishes; analogously, we found that zebrafish deficient in edar had a gill raker loss phenotype and a more predatory habit, with reduced intake of zooplankton but increased intake of prey fish. Higher expression of bmp4, which could inhibit edar expression and gill raker development through binding of a Xvent-1 site upstream of edar, may cause predatory feeding in Siniperca.