. The Canadian field-naturalist. 444 The Canadian Field-Naturalist Vol. 99 Present Zone of Abundance Seasonal Occurrence QUEBEC. Figure 4. Present distribution of Beluga in the St. Lawrence River and Gulf (from Pippard and Malcolm 1978). tide. As well, Ilet Rouge has been found to serve as a travel corridor for groups passing back and forth between habitats upstream and downstream of the Saguenay River. Changes in Amount of Critical Habitat The amount of critical habitat available to the St. Lawrence Beluga has undergone severe reduction. This is mainly a result of the loss of the combined Man
. The Canadian field-naturalist. 444 The Canadian Field-Naturalist Vol. 99 Present Zone of Abundance Seasonal Occurrence QUEBEC. Figure 4. Present distribution of Beluga in the St. Lawrence River and Gulf (from Pippard and Malcolm 1978). tide. As well, Ilet Rouge has been found to serve as a travel corridor for groups passing back and forth between habitats upstream and downstream of the Saguenay River. Changes in Amount of Critical Habitat The amount of critical habitat available to the St. Lawrence Beluga has undergone severe reduction. This is mainly a result of the loss of the combined Mani- couagan and Outardes river mouths (see Limiting Fac- tors), which until the 1960's were a major summer con- gregating area for the white whales. Within the remaining area of critical habitat, one locality of former importance is known to no longer be used in the summer; this is Baie Tadoussac at the mouth of the Saguenay River. Changes in Quality of Critical Habitat Quality of the Belugas' critical habitat has deterio- rated in recent years as a result of extensive municipal, agricultural and industrial pollution discharged to the St. Lawrence and Saguenay Rivers and their tributaries from the many urban centres concentrated in the St. Lawrence drainage basin. Mercury released from chloralkaH plants and pulp mills at the head of the Saguenay Fjord has resulted in particularly high concentrations in sediments of the Saguenay River, downstream into the estuary of the St. Lawrence (Loring 1975). There are also high concentra- tions of mercury in commercial fish in the estuary and Saguenay River (Bligh 1970; Tam and Armstrong 1972). Mercury levels in certain species of shellfish, such as shrimp, clams and mussels, have reached high enough levels for the government to post notices throughout the region warning the public not to eat the shellfish. With shipping annually increasing on the St. Law- rence and Saguenay Rivers, there has also been an increase in incidences of oil spill
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