Life Between Tide-Marks in North America: Vancouver Island, I

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Abstract
An account of the distribution of algae and animals on rocky substrata between tide-marks at Brandon Island, in Departure Bay, British Columbia, as seen in 1947; with a note on other comparable shores in the vicinity. This island is situated in a sheltered position far from the ocean, in water of variable salinity, lower in summer than in winter, and ranging between 18.1 and 29.5 [degree]/oo (monthly means: day-to-day variations cover a wider range). The shore population isof a cold-temperature type, and in 1947 showed a particularly neat zonation. But as the island is elongate, with a cliffed and shaded northern coast and a sloping, sunny southern coast, both apparently subject to similar amounts of (reduced) wave-action, the zonation on the sunny south coast was markedly different from that on the shady north coast. These differences are described in detail and are related accurately to tidal levels; and their causes are discussed. The region described contrasts with Nova Scotia in that ice-action in winter is not a factor regularly affecting shore organisms in southeast Vancouver Island. Also, echinoderms form a particularly important constituent of the population in Departure Bay, and this applies especially to the large starfish Pisaster ochraceus. A note on the natural history of this species is supplied. In 1947 the imported oyster Crassostrea gigas was not a dominant animal in Departure Bay, whereas at present (1960) it has become one.

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