Effect of temperature on growth, expression of growth regulating genes, and deformity development of juvenile European plaice (Pleuronectes platessa)

The flatfish European plaice is a demersal, temperate species and a candidate for marine aquaculture. To better understand growth and the mechanisms involved in growth regulation, juvenile plaice (initial mean weight ± SEM, 10.4 ± 0.1 g) were reared in triplicate rearing tanks at three different temperature: ambient (average of 8.6 °C), 12 °C and 16 °C, for 100 days. Interactions between growth, expression of growth regulating genes, and skeletal development were studied to determine optimal rearing conditions for juvenile plaice. Juvenile plaice grew fastest at 16 °C, followed by the 12 °C group. The condition factor was inversely correlated to increased temperatures and was highest in the 8.6 °C group. At the start of the experiment, 11% of the fish had vertebra deformities. Increasing temperature resulted in higher frequency and severity of malformations, and the 8.6 °C group had 8% less vertebra deformities at the end of the experiment compared to other two groups. The 12 °C and 16 °C groups had similar frequency of deformed fish, however, the 16 °C had more severe deformities, measured as number of deformed vertebrae per fish. Temperature affected gene transcript levels of ghr, igf-1, and igf-1r in muscle and liver tissue differently. Hepatic igf-1 transcript levels increased with increased growth and temperature. Muscular igf-1r transcript levels increased with increasing temperature in each sampling, indicating that igf-1r corresponded with muscular growth. Based on the present findings, a rearing temperature of 12 °C is recommended for on-growing of juvenile plaice.