Research Document 1998/122

Observations of Temporal and Spatial Variability in Density and Relative Condition Factor of Juvenile Atlantic Salmon (Salmo salar L.) in the Harry's River Drainage System, Insular Newfoundland, from 1987-1997

By J.L. FitzGerald, R. Knoechel, and C.C. Mullins

Abstract

Spatial and temporal variability of juvenile population densities and juvenile relative condition in Harry's River, Newfoundland were examined for 1987-1997. Apparent differences in growth allometry (slopes from log weight : log forklength regressions) among sites and years were attributable to variability in stomach contents of the smaller fish and to sex and maturity status of the largest fish. Pooling of all weight : length data permitted comparison among relative condition factors (regression intercepts for specific sites/years) for all years and locations. The most extreme (low) relative condition factors observed were confined to headwater streams in 1987 which was an unusually dry year. The data indicated that fish of all sizes and ages were under stress at those sites. There was no significant correlation between density and relative juvenile condition overall, however one site (site 12) with consistently high total densities displayed average to above average relative condition in all years. Total densities for each "closed" site in 1997 were higher (except site 12) than those observed in 1996. No significant correlations were found between relative juvenile condition and habitat factors in 1996, however potential relationships with benthic invertebrate abundance remain to be explored. A declining proportion of females with increasing age class indicated that females made greater use of pond habitats than males. Observation of a high proportion (73%) of precociously mature males in the streams was consistent with the observed low proportion of males (29% in 1995) in adults returning from the sea.

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