Caspian Sea gamarus (Pontogammarus maeoticus) as a carotenoid source for muscle pigmentation of rainbow trout (Oncorhynchus mykiss)

The red coloration of rainbow trout muscle is an important quality criterion. Duplicate groups of rainbow trout (Oncorhynchus mykiss; initial weight of 200&plusmn;10g) were fed diets either supplemented 0 (control), 0.5, 2, or 4%, of the Caspian Sea gammarus (Pontogammarus maeoticus) respectively as a prospective alternative carotenoid source. The feeding trial lasted for 39 days. No significant differences (p>0.05) in specific growth rate (SGR), or condition factor (CF) were found between treatments. Carotenoid concentrations were determined in the dorsal region and the Norwegian Quality Cut (NQC). The correlation between mean total carotenoid content of the Norwegian quality cut per treatment and dietary inclusion level of P. maeoticus was high (R2=0.99; p<0.01). Less correlation was found between total carotenoid content of the dorsal cut and inclusion level of P. maeoticus (R2=0.80; P=0.10). The total carotenoid concentrations were significantly higher (p<0.05) in male (4.26&plusmn;0.39 mg/kg) than in female (3.38&plusmn;0.23 mg/kg) rainbow trout. In conclusion, it was found that dietary supplementation of the Caspian Sea gammarus at levels of 2 and 4% effectively improved muscle pigmentation of rainbow trout.&nbsp;