The gammarid amphipod Eogammarus confervicolus (Stimpson) was investigated as a potential mass culture organism, with utility as a diet supplement for artificially reared fish. Suitable conditions for large-scale culture were determined in a series of experiments. E. confervicolus demonstrated wide salinity and temperature tolerances, with best survival at low salinities (5 - 10⁰/00) and temperatures (5⁰ - 10⁰C). Population densities greater than 2 mg/1 reduced amphipod growth and survival, although densities may be increased with a flow-through system. E. confervicolus showed good growth and survival on a variety of algae and associated epiphytes, demonstrating the broad diet of the species. Clumping diatoms or phytodetritus were suggested as suitable foods for mass culture. Maintenance of populations over three generations showed the feasibility of long term culture of this amphipod. Short term growth rates of juvenile coho at 12°C were similar on live amphipods (3.2%/day), freeze-dried amphipods (2.4%/day) and Oregon Moist Pellets (3.1%/day). Protein analysis showed E. confervicolus to have a well-balanced amino acid spectrum, and proximate analysis indicated that the amphipod was a nutritionally satisfactory component of fish diets. A Leslie matrix model was developed from information about growth, mortality and fecundity of Eogammarus confervicolus under optimal conditions, and was used to test various harvest strategies. Highest yield of the strategies examined was produced by a weekly 41% harvest applied to amphipods between 0.6 and 2.2 mg dry weight. Further experiments testing the predictions of the Leslie matrix model were recommended. / Science, Faculty of / Zoology, Department of / Graduate