Abstract
Although the stock relationships among harbour porpoise (Phocoena phocoena) in the Northwest Atlantic are unknown, it has been postulated that there are 4 local populations: Bay of Fundy/Gulf of Maine, Gulf of St. Lawrence, Newfoundland, and west Greenland. Data on the Newfoundland population are extremely limited. To determine growth rates and examine if these animals can be differentiated from other sub-populations on the basis of growth characteristics, 94 porpoises caught incidentally in fishing gear along the southeast coast of Newfoundland during the summers of 1990 and 1991 were examined. Most porpoises (56%) were ≤ 4 years of age. Maximum age was 9 for females and 12 for males. Growth rates were similar for both sexes until one year of age, after which females grew longer and weighed more than males of similar ages. Using the Gompertz growth model, asymptotic values for body length were 156.3 cm for females and 142.9 cm for males. Asymptotic weights were 61.6 kg and 49.1 kg for females and males respectively. With the exception of West Greenland porpoise that were shorter and females from Norway that were lighter, Newfoundland porpoises could not be differentiated from animals collected in other areas based on growth data. However, differences in dental deposition patterns were noted suggesting that Newfoundland porpoise may belong to a separate population.
Highlights
The harbour porpoise, Phocoena phocoena, (Linnaeus 1758), is one of the smallest oceanic odontocetes, rarely exceeding a length of 1.8 m (Harrison 1971)
The North Atlantic population is divided into west Atlantic and east Atlantic populations based on skull measurements (Yurick and Gaskin 1987), allele frequency (Andersen 1993), and haplotype frequency (Rosel et al 1995, 1999)
The objective of the present study is to describe growth parameters of harbour porpoises in Newfoundland to improve our limited knowledge of this sub-population
Summary
The harbour porpoise, Phocoena phocoena, (Linnaeus 1758), is one of the smallest oceanic odontocetes, rarely exceeding a length of 1.8 m (Harrison 1971). Distributed widely throughout the Arctic, North Atlantic, and North Pacific Oceans, harbour porpoise populations in many regions are thought to be declining due to direct and/or indirect exploitation, habitat degradation in the form of pollution, ship traffic disturbance, and/or a diminished food source (Read and Gaskin 1988, Lien 1989, Gaskin 1992). Mitochondrial DNA data (Wang et al 1996) and organochlorine contaminant composition (Westgate and Tolley 1999) support the existence of 3 local sub-populations of harbour porpoise in eastern Canadian waters: 1) Bay of Fundy/Gulf of Maine, 2) Gulf of St. Lawrence, and 3) Newfoundland and Labrador (Gaskin 1984, IWC 1996, Wang et al 1996, Rosel et al 1999)
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