From field data on growth and population numbers, production of T. raschii, excluding molts, was calculated to be about 1.8 mg dry wt .cntdot. m-3 .cntdot. yr-1 in the Gulf of St. Lawrence. The mean annual biomass of T. raschii was 0.47 mg dry wt .cntdot. m-3, comprising about 1% of the total zooplankton biomass in the Gulf, and giving a production to biomass (P:B) ratio of about 4. Production and biomass were probably underestimated due to some sampler avoidance, lack of egg to nauplius-metanauplius interval of population production and loss of weight due to leaching in preserved samples.