Performance, processing yields, and fillet composition of specific United States diploid and triploid rainbow trout (Oncorhynchus mykiss) lines reared in a semi-commercial scale freshwater recirculating aquaculture system

Authors: CROUSE, CURTIS - Freshwater Institute; KNIGHT, ANNA - Freshwater Institute; MAY, TRAVIS - Freshwater Institute; DAVIDSON, JOHN - Freshwater Institute; GOOD, CHRISTOPHER - Freshwater Institute

Submitted to: Aquaculture Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/19/2023
Publication Date: 10/23/2023
Citation: Crouse, C., Knight, A., May, T., Davidson, J., Good, C. 2023. Performance, processing yields, and fillet composition of specific United States diploid and triploid rainbow trout (Oncorhynchus mykiss) lines reared in a semi-commercial scale freshwater recirculating aquaculture system. Aquaculture Reports. 33:101794. https://doi.org/10.1016/j.aqrep.2023.101794.
DOI: https://doi.org/10.1016/j.aqrep.2023.101794

Interpretive Summary: Rainbow trout grown to larger than traditional market sizes (2-4 kg) are becoming a popular option for land-based recirculating aquaculture systems (RAS). However, growth and product quality outcomes are poorly defined for large rainbow trout of different strains and ploidy grown in commercial scale, freshwater RAS. A full scale production trial including several strains of domestically available diploid and triploid trout in a semi-commercial scale freshwater RAS quantified expected growth outcomes, survival, maturation prevalence, and product quality metrics for these trout grown to large market sizes. The results will guide producer selection of target market sizes and appropriate rainbow trout strain selection to meet production goals.

Technical Abstract: Large rainbow trout, grown to 2-4 kg and marketed as steelhead, are gaining considerable attention for production in recirculating aquaculture systems (RAS). Diploid and triploid trout with varying genetics are available from several commercial suppliers; however, performance and processing metrics of these strains have not been compared when raised in freshwater RAS. Current data on these outcomes could support more accurate cost and profitability estimates for potential RAS projects and optimize operation for existing farms. Accordingly, the objective of this study was to quantify performance metrics, processing yield, and fillet composition of six all-female rainbow trout strains (three diploid and three triploid) exposed to an artificial winter (12:12 light:dark at 40 g (Artificial Winter Photoperiod; AWP)) or continuous, 24-h light (No Winter Photoperiod; NWP) grown in a semi-commercial scale freshwater RAS to 3.5 kg. Overall, growth was impacted by strain, ploidy, and artificial winter photoperiod. Diploid and AWP trout were smaller than triploids and NWP trout at stocking and 500 g. Diploids were larger than triploids at larger harvest sizes (>3 kg); however, triploid performance varied by supplier. Mortality was lower in strains from commercial supplier 1 than strains from commercial suppler 2 and the United States Department of Agriculture (14.4 ± 0.8 vs 27.5 ± 2.0 and 29.8 ± 4.3 %, respectively). Head-on gutted and skin-on fillet yields were generally correlated with larger fish weight. Maturation prevalence was higher in diploids (0.0 to 42.9 %) compared to triploids (0.0 to 8.3 %) and likely led to differences observed between diploids and triploids in fillet lipid (10.9 ± 0.8 vs 13.3 ± 0.6 %) and moisture (67.0 ± 0.6 vs 65.1 ± 0.4 %). The results provide guidance for rainbow trout RAS producers to make informed decisions on optimal harvest size targets and tailor their rainbow trout strain or ploidy selection to those harvest sizes.