Harbour porpoise (Northwest Atlantic population) COSEWIC assessment and status report: chapter 15

Technical summary

Phocoena phocoena
Harbour porpoise
Northwest Atlantic population

Marsouin commun
Population de l’Atlantique Nord-Ouest


Extent and area information

Extent of occurrence (EO) (km 2 ).
> ~150 000 km 2
Specify trend (decline, stable, increasing, unknown).
Stable
Are there extreme fluctuations in EO (> 1 order of magnitude)?
No
Area of occupancy (AO) (km 2 ).
>~ 250 000 km 2
Specify trend (decline, stable, increasing, unknown).
Unknown
Are there extreme fluctuations in AO (> 1 order of magnitude)?
No
Number of extant locations.
N/A
Specify trend in # locations (decline, stable, increasing, unknown).
N/A
Are there extreme fluctuations in # locations (>1 order of magnitude)?
N/A
Habitat trend: specify declining, stable, increasing or unknown trend in area, extent or quality of habitat.
May be declining due to noise from acoustic harassment devices associated with aquaculture facilities


Population information

Generation time (average age of parents in the population) (indicate years, months, days, etc.).
ca 7 years
Number of mature individuals (capable of reproduction) in the Canadian population (or, specify a range of plausible values).
> 50 000 (all-age estimates of 89 000 in 1999 in Bay of Fundy/Gulf of Maine, >22 000 in 1990s in Gulf of St. Lawrence, no estimates for other parts of range)
Total population trend: specify declining, stable, increasing or unknown trend in number of mature individuals.
Unknown
If decline, % decline over the last/next 10 years or 3 generations, whichever is greater (or specify if for shorter time period).
N/A
Are there extreme fluctuations in number of mature individuals (> 1 order of magnitude)?
No
Is the total population severely fragmented (most individuals found within small and relatively isolated (geographically or otherwise) populations between which there is little exchange, i.e., ≤ 1 successful migrant / year)?
No
List each population and the number of mature individuals in each.
N/A
Specify trend in number of populations (decline, stable, increasing, unknown).
N/A
Are there extreme fluctuations in number of populations (>1 order of magnitude)?
No


Threats (actual or imminent threats to populations or habitats)

  • Bycatches in commercial fisheries
  • Habitat degradation and loss caused by acoustic harassment devices


Rescue effect (immigration from an outside source): Low

Does species exist elsewhere (in Canada or outside)?
Yes
Status of the outside population(s)?
Unknown (West Greenland)
Is immigration known or possible?
Possible
Would immigrants be adapted to survive here?
Yes
Is there sufficient habitat for immigrants here?
Likely


Quantitative Analysis

Yes for Bay of Fundy/Gulf of Maine subpopulation


Current status

Committee on the Status of Endangered Wildlife in Canada (COSEWIC): Designated Threatened in April 1990. Status re-examined and confirmed in April 1991. Status re-examined and designated Special Concern in May 2003. Status re-examined and confirmed in April 2006.


Status and reasons for designation

Status: Special concern
Alpha-numeric code: Not applicable


Reasons for Designation: The species is widely distributed in eastern Canadian marine waters. Surveys of portions of the range (Bay of Fundy/Gulf of Maine and the Gulf of St. Lawrence) during the late 1990s indicated more than 100 000 porpoises. Incidental catch (bycatch) in fishing gear, especially gillnets, is a major source of mortality. Bycatch probably has declined in areas where use of gillnets has decreased. Management measures in the Bay of Fundy and Gulf of Maine have been shown to reduce porpoise bycatch rates in gillnets. However, these measures have not been implemented in much of the species’ range, including the Gulf of St. Lawrence and Newfoundland and Labrador, where annual mortality in several gillnet fisheries is still estimated to be in the thousands. There is also some concern that porpoises in the Bay of Fundy and possibly other areas may be excluded from portions of their habitat by acoustic harassment devices associated with aquaculture. Although the population remains abundant, the particular susceptibility of harbour porpoises to bycatch in fishing gear represents an incipient threat. Given that, the lack of good abundance information in some parts of the range and the lack of porpoise bycatch monitoring and mitigation in many of the relevant fisheries are reasons for concern.


Applicability of criteria

Criterion A (Declining Total Population): Not applicable.

Criterion B (Small Distribution, and Decline or Fluctuation): Not applicable.

Criterion C (Small Total Population Size and Decline): Not applicable.

Criterion D (Very Small Population or Restricted Distribution): Not applicable.

Criterion E (Quantitative Analysis): Not available.

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