Further Analysis of Population Trends in the Northwest Atlantic Harp Seal ( Phoca groenlandica ) from 1967 to 1985

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Authors: Roff, Derek, Bowen, W. Don
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1986
• Subjects: Aquatic Science; Ecology, Evolution, Behavior and Systematics; Harp Seal; Northwest Atlantic; Phoca groenlandica
• Online Access: http://dx.doi.org/10.1139/f86-066; http://www.nrcresearchpress.com/doi/pdf/10.1139/f86-066

We examined changes in the age structure of the northwest Atlantic harp seal (Phoca groenlandica) population from 1967 to 1983. Through this period there has been a statistically significant population increase in the proportion of seals aged 2–6 yr. Precise estimation of the rate of increase is hindered by a tendency for immature seals to be overrepresented in samples of molting males. Two methods were developed to correct for this bias; these provide a minimum estimate of the proportion of seals aged 2–6 yr present in 1967. Utilizing a simulation model, we showed that the unadjusted and adjusted age distributions are both extremes and that the correct distribution probably lies between them. In both cases the data are more consistent with an increasing than a decreasing population, given the level of catch experienced by this population up to 1982. Recent total catches of 75 000 or less in 1983 and 1984 are substantially below the most conservative estimates of replacement yield in 1985 and will result in a further, more rapid population increase.