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The biology, economic status and control of the harbour seal (Phoca vitulina richardli) in British Columbia, with particular reference to the Skeena River area

University of British Columbia

Distribution of the harbour seal in British Columbia is extensive and includes at least 20 rivers and 6 lakes. An estimated 450 individuals utilize 8 hauling out sites in the area at the mouth of the Skeena River. A seasonal upriver movement in the Skeena River begins with the onset of the eulachon run in March, developing to a maximum in the fall and apparently dependent in its extent upon the available salmon supply. The extent and manner of daily movements is dealt with in some detail. Harbour seal habitats are described. Mating in the Skeena area takes place in September and October. Sexual maturity is inferred to occur at the end of the third year. The birth season in the Skeena area begins in the last part of May at the earliest and ends in the latter half of June. Parturition in upriver areas appears to be adjusted to the tidal exposure of the bars. The weight of the pups is doubled in the first 5 or 6 weeks of life, and a weight decrease of about 20 per cent occurs during the weaning period in the fall. Very few parasites or cases of disease were noted. Damage to gill-nets from seal action in the Skeena estuary was found to be negligible. The monetary loss suffered by fishermen from seal depredation upon salmon caught in nets is at its worst in the early part of the spring salmon fishing season in April and May, when it may be 12 per cent or more of the money made. The contents of 20 adult seal stomachs from British Columbia are recorded. Rockfish (Sebastodes) and octopus, unidentifiable fish, salmon, herring and shrimp occurred, in the above order of frequency. Salmon formed 28.5 per cent of the total volume, herring 20 per cent and rockfish 19 per cent. The only localities where seal predation upon salmon is felt to approach significant proportions are in upriver areas. The bounty system for control of harbour seals in British Columbia is concluded to be inefficient, the chief reason reason being that that the control exercised is too widespread, the majority of kills taking place in marine areas where control does not appear to be essential. It is suggested that the employment of one or more crews of trained hunters equipped with proper facilities should accomplish far better results at control than does the bounty system.

Text

2012-03-28

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http://hdl.handle.net/2429/41819

Zoology

University of British Columbia

Graduate