Evaluation of ultrasound imagery and body shape to predict carcass and fillet yield in farm-raised catfish

Accurate prediction of meat yield in live animals may allow more efficient genetic improvement of meat yield in farm-raised catfish. An initial trial with 30 channel catfish demonstrated significant correlations among weight- adjusted residuals for muscle area measured from transverse ultrasound imag es and transverse sections at five locations along the trunk musculature (r = 0.30 to 0.70). Relationships of weight-adjusted residuals for three meat yield traits (carcass; whole fillet, and shank fillet) with weight-adjuste d residuals for 15 external body shape measurements and five transverse ult rasound; measurements of muscle area were determined for 51 female and 91 m ale channel x blue catfish backcross hybrids. Compared to males, females ha d smaller heads; deeper, wider, shorter bodies; larger ultrasound muscle ar ea; and higher meat yield. Correlations between carcass traits and body sha pe and carcass traits and ultrasound measurements were generally higher for females than for males. Correlations among carcass traits and ultrasound m uscle area were typically higher than correlations among carcass traits and external body shape in both sexes. A single ultrasound measurement explain ed 40 to 50% and 16 to 23% of the variation in meat yield traits of females and males respectively; The best three-variable model using ultrasound and body shape traits explained 48 to 56% and 31 to 38% of the variation in me at yield traits in females and males, respectively. Differences between mal es and females for the variability in meat yield traits explained by the mo dels may be related to sexual dimorphism for body shape and fillet; yield o bserved in catfish. Ultrasound has potential for predicting meat yield in l ive fish, but improved prediction accuracy is needed. Differences in meat y ield traits between males and females and among individuals within sexes su ggest that selecting for fish with smaller heads and deeper, shorter body s hape posterior to the visceral cavity will increase meat yield in catfish.