Survival and growth of young Gammarus Lawrencianus Bousfield at different temperatures and on different diets in Newfoundland

Survival, growth and egg production of Gammarus lawrencianus was determined for newly released young kept without food and maintained on diets of TetraMin, the Blue Mussel (Mytilus edulis)k, and the algae Dictyosiphon foeniculaceus, Pilayella littoralis and Enteromorpha intestinalis, at 15°C. Similar experiments were performed on animals fed TetraMin at 5°, 10°, 12° and 15°C. concurrent field collections were made at Witless Bay Pond and North Arm Holyrood, Newfoundland. The selectivity of immature and adult G. lawrencianus were also investigated and the energy and amino acid content of the diets determined. -- Survival was inversely proportional and growth directly proportional to temperature. Temperature also significantly influenced fecundity and age at maturity, but not maturation size in the range of the temperatures tested. Higher temperatures reduced the maturation age and increased the number of eggs produced. Diet significantly influence survival, growth, fecundity as well as size and age at maturation. Survival was enhanced by fine algae but growth, fecundity and age, and size at maturation were optimized on a diet of Mytilus. Size in maturity in the field was comparable to animals fed diets of TetraMin or Mytilus, but diets of filamentous algae produced a much larger maturation size. Maturation size in the filed decreased as the summer progressed, probably due to changes in the quality of the available diet. -- The total energy content of the food appeared to be an important variable in the quality of the diet. Texture probably had a large influence on the amount of energy actually available to the animals, especially when algae were a major part of the diet. -- No obvious correlation between the quality or quantity of amino acids in the diet and the growth, survival and fecundity was found except in the case of TetraMin. TetraMin was deficient in a great number of amino acids when compared to G. lawrencianus. Animals fed TetraMin had a very low survival rate when compared to the other diets, but growth and fecundity were similar to Mytilus, the diet that most closely corresponded to the amino acid makeup of G. lawrencianus