Analyzed with regard to their slaughter weights and flesh quality 78-month-old diploid and triploid rainbow trout (full sibs) were reared together in a pond after tagging at an age of 12 months. Triploids had higher body weights and carcass percentages than diploids (6 kg vs 4 kg and 66% vs 52%). Triploid fish also displayed lower electrical conductivity values and darker (L* value) and redder (a* value) flesh color. The fillets of the triploid trout contained more crude fat and less moisture than the diploids (6% vs 3% and 68% vs 74%, respectively). No effect of ploidy was found with regard to the protein contents. Triploid rainbow trout had larger mean white and intermediate muscle fiber areas than diploid fish in the dorsal and pelvic fin regions. In the pelvic fin part, the white muscle fiber areas were larger than in the dorsal fin part. In conclusion, adult triploid rainbow trout grow faster especially by fiber hypertrophy and have better flesh quality parameters than diploid fish.

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