A comparative study of the growth and feeding of underyearling (0+) Brown Trout (Salmo trutta Linn.) in disturbed and undisturbed stream habitats in the Avalon Peninsula, Newfoundland

Mlewa, Chrisestom Mwatete (1996) A comparative study of the growth and feeding of underyearling (0+) Brown Trout (Salmo trutta Linn.) in disturbed and undisturbed stream habitats in the Avalon Peninsula, Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

Although natural freshwater bodies on insular Newfoundland are oligotrophic, high growth and biomass of salmonids has been reported in streams within the city of St. John's. This study compared the growth and feeding of underyearling (0+) brown trout (Salmo trutta Linn.) from Juniper Brook, a headwater tributary of the Rennies River, which flows through the city; and a tributary of the Broad Cove River, outside the metropolitan area. Zero plus trout were obtained by electrofishing once every three weeks during the summer and fall of 1994 and 1995, with one sample collected in the intervening winter. In both years, fry in Juniper brook emerged later from the redds but grew at a faster rate and attained a slightly bigger size by the end of the growing season. Arithmetic growth curves for trout in each stream approximated the characteristic sigmoid curve. Within streams, growth rates were highest in early summer. Stream water temperatures showed consistent differences, with Juniper Brook warming up faster in the summer and cooling faster in the fall. -- The composition of 0+ trout diet varied between streams and seasons and was related to changes in the food available both in the streams and adjacent terrestrial vegetation. Benthic samples from Juniper Brook had fewer taxa and were dominated by chironomid larvae, whereas those from Broad Cove River had a higher taxonomic diversity but fewer numbers per taxon. Chironomids were consumed almost exclusively by 0+ trout in Juniper Brook during the summer but those in Broad Cove River had a much broader diet. Stomach contents were at times dominated by a single prey, suggesting opportunistic feeding, probably on the most abundant and available prey in the feeding environment. The higher abundance of chironomids in Juniper Brook was related to higher chemical richness resulting from the input of liquid and solid urban wastes. Thus the human disturbance that has occurred on Juniper Brook has altered the ecology of the stream resulting in higher stream temperatures in the summer and higher chemical richness which promoted the growth of 0+ trout in this stream.

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