. The Canadian field-naturalist. SERENDIPITY. Figure I. Representative specimens of Gasterosieus aculeatus. Boulton Lake stickleback (not shown) similar to those from Serendipity Lake, ap = ascending branch of pelvic skeleton, as - anal spine, bp = basal plate of dorsal spine, ct = clei- thrum, ds3 - third dorsal spine, Ip = lateral plates, ps = pelvic spine, vp = ventral plate of pelvic skeleton. Magnifica- tion X2. Population Size and Trends Total numbers of fish in each lake have not been determined; however, it was possible to obtain crude estimates of density by using a range of sampling
. The Canadian field-naturalist. SERENDIPITY. Figure I. Representative specimens of Gasterosieus aculeatus. Boulton Lake stickleback (not shown) similar to those from Serendipity Lake, ap = ascending branch of pelvic skeleton, as - anal spine, bp = basal plate of dorsal spine, ct = clei- thrum, ds3 - third dorsal spine, Ip = lateral plates, ps = pelvic spine, vp = ventral plate of pelvic skeleton. Magnifica- tion X2. Population Size and Trends Total numbers of fish in each lake have not been determined; however, it was possible to obtain crude estimates of density by using a range of sampling techniques. Such estimates give a total population of 350 000 for Boulton Lake; 17 500 for Rouge Lake; and 22 000 for Serendipity Lake. As assessed from trap success (numbers offish per trap hour), there had been no obvious changes in the abundance of fish during the sampling period (Boulton: 1970-1981; Rouge: 1976, 1978, 1980, 1981; Serendipity: 1979- 1981). The expansion of the Beaver (Castor canaden- sis), as discussed below, may have an adverse effect on population numbers in the future. Habitat The broad characteristics of the three small lakes are summarized in Table 1. The watersheds are not connected and have separate drainages to marine waters. Each lake is surrounded by Sphagnum bog and scrub coniferous forest; these watersheds are sim- ilar to adjacent areas where lakes with "normal" stickleback are found. In the last 20 years, the natural drainage system in the area has changed due to the activities of the Beaver. Beaver were introduced onto the Queen Charlotte Islands by the British Columbia Game Commission in 1949. Since that time, they have extended their range throughout much of Graham Island. In the lowland region, the alteration of habitat has been extensive. Water levels have risen, resulting in submergence of large areas of Sphagnum bog and inundation of cedar forest. Previously isolated lakes have been connected and small creeks where Coho Salmon
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