Comparison of muscle quality of rainbow trout (Oncorhynchus mykiss) raised in two open and partial water reuse systems

At present, many cold water fish farms in the country use reused water to produce fish, but the effects of its using on fish muscle quality are not well known. The aim of the present study was to compare the muscle quality of rainbow trout (Oncorhynchus mykiss) raised in two open and partial reuse water systems. For this purpose, young trout with a stocking density of 20 kg/m3 and a loading density of 1 L/min/kg of fish was studied in two an open system (100% make-up water) and a designed partial water reuse system (with a reduction of 80% make-up water and its replacement with the reused water) for 45 days. Four times of water recirculation caused an increase of 6.7 and 6.5 times in the amount of water total ammonia and total phosphorus compared to an open treatment, respectively. Crude protein, crude fat, pH and moisture percentage showed significant differences between two treatments. In contrast, there were no significant differences in water holding capacity, cooking loss, texture analysis (hardness, adhesiveness, resilience, cohesiveness, springiness, gumminess and chewiness) and color indices of L*, a* and b* between two treatments. Consequently, the reuse of water to the same extent as the present designed protocol does not have very obvious changes on many studied muscle quality factors of fish.