Populations of Clethrionomys rutilus were studied on two islands (Island 2 and Green Island) in the Mackenzie River during the summers of 1976 to 1978. This was done to examine the demographic parameters related to confinement of northern red-backed vole populations on islands.The number of voles on Island 2 in 1977 increased until late June and then remained nearly constant until trapping ceased in late August. On Green Island in 1977 and 1978 and Island 2 in 1978, populations grew all summer and even in August had not reached the densities found during the 1977 high on Island 2. Island 2 in 1977 had an unusually low number of maturing young voles. Higher wounding rates and shorter adjusted range lengths were associated with higher population densities.Although high densities of voles were reached early in the summer of 1977 on Island 2, numbers stopped increasing before the end of the breeding season. Restraint of growth potential was seen in poor maturation of the young and in declining juvenile survival and recruitment of young through summer.
In the summers of 1974 and 1975, profiles of temperature, salinity, and dissolved oxygen were made monthly at four stations in Kennebecasis Bay. Samples of the benthic fauna and substrate were also taken.Sediment particle size distribution did not vary between stations. Combustible organic content of sediments was highest at the head of the bay and lowest near the mouth.Surface water was generally of low salinity, high dissolved oxygen, and seasonally variable temperature. Bottom water showed a stable salinity of 18 to 20‰, stable temperature of 4 to 7 °C, and stable oxygen concentrations of 1.5 to 4.5 mg/ℓ.While the parameters just mentioned are thought to be uniform throughout Kennebecasis Bay, the observed distribution pattern of species and individuals in the benthic fauna was not uniform. Samples taken at the mouth of the bay produced greater numbers of taxa and abundance of fauna than samples from the head of the bay. It is proposed that this bay mouth-to-head gradient is related to infrequent saline water inflows reaching only lower parts of Kennebecasis Bay.
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