Annual ice blocks erosion characterizes James Bay coastline. Within the sampled area, the estuarine Rupert Bay shores are flooded by fresh or brackish tides, and James Bay shores by saline water. Nineteen mosquito species were found in typical larval associations, related to the vegetation of their temporary shallow water breeding sites. In the tidal zone, Ae. implicatus is characteristic of fresh or brackish water marshes, while Ae. cantator and then Ae. dorsalis are dominant in the salt pitted marshes. In the supra-littoral zone Ae. punctor is characteristic of Salix Candida and S. pellita unit; at the foot of the supra-littoral slope, Ae. communis and Ae. pionips characterize the S. planifolia unit. An ecological map of a section of Rupert Bay illustrates where are located the typical littoral mosquito species. The ecological status of each mosquito species found in this area is also discussed, taking into account previous data from all the subarctic continental zones.