Correlations between bottom fauna in Murray's and Butler's Ponds and the food of rainbow trout, Salmo gairdneri Richardson

Limnological conditions were studied in two Newfoundland ponds having areas of 16 and 21 acres, and mean depths of 4.7 and 5.6 feet. The water was slightly acid in each and there was no dissolved oxygen deficiency; both are eutrophic and lie in an area of sedimentary rock. Rooted aquatic vegetation was not a major feature. The ponds are continuously stocked with rainbow trout and it is the most abundant of the three species of fish present. Numerically dominant bottom organisms were amphipods, dipteran larvae, sphaeriid clams, and amnicolid snails, while gravimetric analysis indicated the dominance of anisopteran nymphs. Seasonal variations in the bottom faunae were also studied. One pond has been fertilized experimentally and it revealed a standing crop of benthic organisms (46.0 kilograms per hectare) which tripled that of the control pond. Rainbow trout in one pond were feeding on a variety of bottom organisms while those in the other fed more intensely on a less varied diet of zooplankton. Seasonal differences in food consumption were studied along with the utilization of benthic organisms by the fish. Food preference was briefly discussed. Angler catch in one pond was shown to have a tendency to vary inversely with the amount of food available in the environment and that present in the stomachs of the rainbow trout