This project is an effort to use the different roles, half-lives and properties of messenger ribonucleic acid (mRNA) and ribosomal (rRNA) to develop new indices of recent growth and physiological status of larval Atlantic cod (Gadus morhua) and the copepod Calanus finmarchicus. The concentration of rRNA and selected mRNAs will be determined using nucleic acid hybridization probes developed for these species. Larval Atlantic cod (G. morhua) and C finmarchicus will be cultured under conditions producing widely different growth and development rates. The relations among mRNA and rRNA levels, feeding conditions, growth and development will be determined.