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Similar to the zebra mussel (Dreissena polymorpha) and the quagga mussel (Dreissena bugensis), the Asian clam (Corbicula fluminea) is an invasive bivalve that has colonized many waterbodies in the United States and Europe. So far, low water temperature and ice formation during winter appear to have limited its northern distribution, especially in Eastern North America. This paper documents the recent discovery of a Corbicula fluminea population in the St. Lawrence River, in the thermal plume produced by the Gentilly-2 nuclear power plant (Bécancour, Québec, Canada). Based on a benthic samples obtained during November 2009 from 21 sites, both upstream and downstream of the power plant outlet, average density (± standard error) of this non-indigenous species was 368 ± 176 living individuals/m². Additional samples collected in 2010 showed an increase in density to 3,380 ± 1,315 living individuals/m² downstream the power station, and established the range limit at 4 km downstream. The species was present only downstream of the power plant and its distribution appears to be associated with the warm water plume. The influence of the thermal plume at 4 km from the power station was however fairly limited. The size of individuals varied from < 1 mm to 24 mm in length. These results confirm the establishment of the species in the St. Lawrence River, thereby extending the northern boundary of its distribution in North America. [ABSTRACT FROM AUTHOR]

Limiting factors of caribou (Rangifer tarandus) populations vary regionally. In tundra environments, this species appears to be regulated by food, either because wolves (Canis lupus) are absent or because migration of caribou allows escape from predation during part of the year. In the boreal forest, the main limiting factors are hunting and predation but because of low caribou densities, no regulation mechanism seems to exist between caribou and wolves. Moose (AIces alces) is the primary prey species of wolves and consequently, if moose abundance increases, wolves should also increase, independently of the caribou population. Thus, caribou could experience high predation rates and be eliminated in high wolf densities. Here we attempted to identify the necessary conditions to maintain caribou numbers in the presence of moose. To do so, we built a deterministic model that simulated the relationship between a caribou population regulated by food competition and limited by predation, a moose population regulated by predation, and a wolf population, the abundance of which is determined by moose abundance. At current hunting rates for caribou and moose in the boreal forest, and in the absence of wolf trapping, the model predicted that the caribou population would be extirpated in approximately 100 years. Wolf trapping was not adequate to conserve the caribou population unless very intensive control was undertaken. In the absence of trapping, cessation of caribou hunting allowed a 3-fold increase in caribou numbers over the long term, if the moose population remained low. According to our model, the best management measure for caribou consisted of maintaining a low moose density through appropriate population and habitat management strategies, which prevented expansion of the wolf population and limited predation on caribou. [ABSTRACT FROM AUTHOR]