Abstract
Transferrin (Tf) phenotype was associated with weight gain in 147- and 230-day-old rainbow trout, but no association was found between lactate dehydrogenase (LDH) phenotype and weight gain. A total of 2038 progeny were examined from two different environments. Progeny lots were reared at densities below those known to affect mean fish weights. Differential survival among progeny with respect to their Tf of LDH phenotype was not detected. Key words: biochemical genetic markers, economic performance, transferrin, lactate dehydrogenase, weight gain