EVALUATION OF IMAGE ANALYSIS AS A METHOD FOR EXAMINING CARCASS COMPOSITION OF RAINBOW TROUT

Abstract

Two year groups (1+ and 2+; n = 10/group) of rainbow trout (Oncorhynchus mykiss) were sampled from a Danish marine fish farm. Fish were selected to span the same weight range (1+: 2643 - 3875 g; 2+: 2651 - 3912 g). During production (April to November) fish were fed identical commercial diets. Visual fat depots of faster and slower growing animals were examined by image analysis of directly scanned cutlets. No significant (P > 0.05) correlation between meat percentage and fish size (length, weight, condition factor, dressed weight) was found, and t-tests failed to expose any difference in fat: meat ratio between 1+ and 2+ yr old rainbow trout. However, a significant difference (P < 0.05) between variances for the two groups was observed, being approximately four-fold larger for 1+ yr animals compared to 2+ yr. This finding indicates that selection for faster growth results in less uniform products from a compositional perspective. Where specific product specifications should be met, this might complicate production management.

Keywords

• fat
• pigmentation
• meat ratio
• product quality
• growth rate