Status of Unarmoured and Spine-deficient populations (Charlotte Unarmoured Stickleback) of the Threespine Stickleback, Gasterosteus sp., on the Queen Charlotte Islands, British Columbia

Abstract

Endemic populations of the threespine stickleback (Gasterosteus aculeatus ) with major loss of spines and lateral plates and tolerance to naturally acidic waters occur in three small lakes in the Sphagnum dominated lowlands of the Queen Charlotte Islands, British Columbia. Recent range extension of the Beaver (Castor canadensis ), an introduced species on the islands, has resulted in increased water levels and organic debris in two of the lakes. Population numbers of stickleback appear to be stable, although the increase in organics may influence the reproduction of the fish. Introduction of Cutthroat Trout, Salmo clarki , a predator on stickleback, could seriously decrease numbers in these small populations, or, more likely, significantly modify their genetic structure. These populations can be categorized as "rare".