The abundance of Harbour Seals has been monitored in Georgia Strait since the mid-1960's. Counts are usually conducted from small aircraft at times when most of the population is hauled out. In George Strait, about 90% of the animals haul out on low tides, on calm days, in the morning and toward the end of the pupping season. Department of Fisheries and Oceans (DF) surveys conducted under these conditions indicate that the Harbour Seal population in Georgia Strait grew from about 2,100 in 1973, to 12,500 in 1987, a rate of increase of 12.4% per year. Similar increases occurred in all other areas censused. For example, in the lower Skeena River counts increased from about 400 in 1977 to 1,250 in 1987. It was estimated that the population in B.C in 1987 was about 65,000 and might be approaching historical levels.
This increase in numbers represents the recovery of a depleted population, which in the late 1960's had probably been reduced to less than 15,000. A bounty offered by DFO for each seal killed between 1913 and 1964 reduced populations to about half historic levels. Harbour Seals were also intensively hunted for their pelts between 1962 and 1969. The population could not withstand this additional hunting and declined sharply during the mid 1960's.
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Researchers at the Pacific Biological Station in Nanaimo examined the impact of the growing harbour seal population on fisheries. Data were collected on diet, seasonal movements and abundance in conflict areas to establish the extent to which seals interfere with fishing activities and their impact on important fish stocks, such as salmon and herring.
One of the main topics studied was the amount of salmon consumed by Harbour Seals. The amount of food eaten by a seal depends on its size and sex, the season and the caloric contents of the prey. On average, Harbour Seals consume about 1.8 – 3.2 kg (4 – 7 lbs) of fish daily. At present not enough is known about the diet of harbour seals to accurately estimate the amoutn of salmon eaten. Preliminary findings indicate that in most localities, Harbour Seals prey mainly on a wide variety of small fishes that occur in shallow water around reefs. These include sculpins, small flatfishes and rockfishes, greenlings, smelts and perches. During winter their diet consists mainly of hake and, to a lesser degree, herring. However, salmon may constitute an important part of the diet in some rivers and estuaries while salmon are spawning.
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These seals are typically seen in small groups resting on tidal reefs, boulders, and sandbars, but they can sleep underwater on the ocean bottom if no suitable haulout site is available. The population is traditional in the particular sites utilized as haulouts. There is little social organization in these colonies. Unlike many other pinnipeds, harbour seals do not congregate on rookeries but breed throughout most of their range. The birth season lasts about 2 months and varies from February – March to August – September, depending on location. In southern B.C., births occur in July – August and during May – June in northern B.C. Pups are usually born on tidal reefs or sandbars and begin to swim immediately. Although local movements associated with breeding and feeding may occur, harbour seals are otherwise non-migratory.
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