Food resource utilisation by Tenagomysis chiltoni (Crustacea, Mysidacea)
Degree GrantorUniversity of Canterbury
Degree NameMaster of Science
The interrelationships existing between some different parameters which may have influenced the diet of Tenagomysis chiZtoni (Crustacea, Mysidacea) were investigated in Lake Ellesmere, South Canterbury, New Zealand (43°48'S, 172°22'E). The mysid was found to be omnivorous and ingested foods having both aquatic and terrestrial origins. The stomach contents of 1113 mysids were examined. The diet was mainly composed of macrophyte detritus, filamentous algae, diatoms, calanoid and harpacticoid copepods, chironomids, amphipods and ostracods. Seasonal variations in the length-frequency structure of T. chiltoni populations were observed. These variations were due to the emergence and development of successive broods. An associated variation in the male:female ratios was found, and may be due to males dying out before females belonging to the same cohort. The most important intrinsic factor exerting an influence on the diet of an individual was the length of a mysid which was partly dependent on the sex of an individual. Hunger did not affect the nature of the food ingested. Changes in the length-frequency structure of the population were observed which influenced the quality and quantity of the diet of T. chiltoni. Some environmental parameters also influenced the quantity ingested. The nature of the water column and, to a lesser extent, benthic, food resources, regulated the selection of diet by the mysid which was controlled by physical considerations. Seasonal cyclical variations in the availability of some food resources caused changes in the diet of T. chiltoni. The observed diet of T. chiltoni is a product of the complex interaction of intrinsic and extrinsic factors and varies in space and time.