Harbour porpoise (Pacific Ocean population) COSEWIC assessment and status report: chapter 11

Technical Summary

Phocoena phocoena

Harbour porpoise – Marsouin commun

Range of Occurrence in Canada:

Pacific Ocean

Extent and Area Information

Extent of occurrence (EO) (km²)

Throughout British Columbia (BC) coastal waters > 20,000 km²

Specify trend in EO

Unknown

Are there extreme fluctuations in EO?

Not likely

Area of occupancy (AO) (km²)

Appears to be primarily associated with shallow coastal shelf waters < 2,000 km²

Specify trend in AO

Unknown

Are there extreme fluctuations in AO?

Not likely

Number of known or inferred current locations

Not available (N/A)

Specify trend in #

N/A

Are there extreme fluctuations in number of locations?

N/A

Specify trend in area, extent or quality of habitat

Habitat decline suspected in coastal areas due to human activities, particularly in southern part of Canadian range (i.e., southern Georgia Strait, Haro Strait and eastern Juan de Fuca Strait.

Population Information

Generation time (average age of parents in the population)

  • Unknown.
  • Estimated longevity is 13 years.
  • The oldest animal aged in BC was 10 years old.

Number of mature individuals

Total population in 1996 in the Canadian Strait of Juan de Fuca, Gulf Islands, and Strait of Georgia was 2,895 individuals (all ages). These three regions are a small portion of BC. The proportion of mature individuals is unknown. Age at maturity is believed to be 3-4 years.

Total population trend

Unknown, local declines suspected in highly urbanized areas.

% decline over the last/next 10 years or 3 generations.

Decline is suspected since the 1940s-50s, but the % change is unknown.

Are there extreme fluctuations in number of mature individuals?

No

Is the total population severely fragmented?

Unknown in BC, but there is evidence for localized populations in other regions of the eastern North Pacific.

Specify trend in number of populations

Unknown

Are there extreme fluctuations in number of populations?

No

List populations with number of mature individuals in each

N/A

Threats (actual or imminent threats to populations or habitats)

  • entanglement in gillnets
  • contaminants
  • disturbance

Rescue Effect (immigration from an outside source)

Moderate

Status of outside population(s)?

USA: Washington: »15,000 (outer coastal waters, mostly along southern coastline). Alaska: »10,000

Is immigration known or possible?

Possible, but movement of animals appear limited.

Would immigrants be adapted to survive in Canada?

Yes

Is there sufficient habitat for immigrants in Canada?

Unknown

Is rescue from outside populations likely?

 

Quantitative Analysis

Unavailable

Status and Reasons for Designation

Status: Special Concern

Alpha-numeric code: not applicable

Reasons for Designation: They appear to be particularly sensitive to human activities, and are prone to becoming entrapped and killed in fishing nets. They are a short lived shy species that are now rarely seen at the highly developed areas of Victoria and Haro Strait. Continued development and use of its prime habitat by humans are some of the main threats. They are displaced by underwater noise, and could be affected by contaminants in their food chain.

Applicability of Criteria

  • Criterion A (Declining Total Population): Local declines are suspected, there is no evidence to support a population wide decline.
  • Criterion B (Small Distribution, and Decline or Fluctuation): Area of Occurrence is > 20,000 km² , but Area of Occupancy is likely < 2,000 km² given that they appear to be associated with shallow coastal shelf waters.  However, there is no evidence of population fluctuations or population wide declines.
  • Criterion C (Small Total Population Size and Decline):Total population in a small portion of the BC range is about 3,000 individuals of all ages (southern Vancouver Island).  Total population of mature individuals in BC is unknown, but there is no evidence of population declines.
  • Criterion D (Very Small Population or Restricted Distribution): Total population in BC exceeds 1,000 mature individuals.
  • Criterion E (Quantitative Analysis): Available information is insufficient to do a quantitative analysis of the probability of extinction.

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