Growth-Related Dynamics of Muscle Protein Degradation in Reared Oncorhynchus Mykiss during Growing Season

Abstract

Although temperature influence on the physiology of rainbow trout have been widely studied, there is little information about the responses of muscle growth and overall protein turnover to temperatures. Therefore, body growth rate and muscle protein turnover of cultivated rainbow trout (Oncorhynchus mykiss) of 0+ and 1+ year-classes were studied within a growing season since June to October. Fish grown on cages on a natural lake does not face with food shortage or other growth-retarding factors, and the environmental water temperature affects fish growth primarily. There were detected that water temperature increase in-season results in maximal growth increments and maximal protein turnover rate in trout muscles. Since protein synthesis recognized to be similar between individuals, high overall protein turnover rate depended on increased protein-degrading activities mostly relying on calpain system. Trout of different year classes significantly differs in growth rate and calpain activity coordinately decreasing with age while their temperature responses are quite similar. New data expands on aquaculture practice since based on our observations on coincidence of peak water temperatures (mid-summer) and increased muscle protease activities in trout we can recommend excluding this period for fish slaughter to avoid postmortem flesh deterioration and excessive fillet softening.