Flesh characteristics of pan-size triploid and diploid rainbow trout (Oncorhynchus mykiss) reared in a commercial fish farm

Abstract. Sexual maturation of rainbow trout during production has a negative effect on the slaughter yields and flesh quality. Induction of triploidy is a method to prevent the development of fertile trout. In many investigations sexually mature triploid and diploid rainbow trout had been compared. In the present study the slaughter characteristics and flesh quality of female immature diploid and triploid rainbow trout reared up to 66 and 75 weeks (pan-size-format) were compared. Considering the age the old fish had significantly higher body and fillet weights accompanied with larger muscle fibres. The fillets of the old trout were brighter and redder, had a reduced water-holding capacity (WHC) and contained more fat and protein. With regard to the ploidy status the triploid trout had higher body and fillet weights and larger muscle fibres. The fillets of the triploid fish were brighter, had a reduced WHC and lower fat contents. With regard to the age-ploidy status interaction the young and old triploid trout had better growth characteristics but the WHC and the fillet fat concentration was reduced in these animals. The colour values were inconsistent. The pH and electrical conductivity values indicated no higher pre- or peri-mortal stress and/or different stress susceptibility of the investigated young as well as old triploid and diploid trout. In conclusion, it could be suggested that induction of triploidy positively influences body and fillet development mainly by muscle fibre hypertrophy, but the triploid fillets showed slightly worse flesh characteristics (Brightness, WHC).