Roughhead grenadier (Macrourus berglax) COSEWIC assessment and status report: chapter 12
Technical Summary
Macrourus berglax Lacépède, 1801
roughhead grenadier – grenadier berglax
Range of Occurrence in Canada:
Atlantic Ocean
Extent and Area Information
Extent of occurrence (EO) (km²)
> 120,000 km²; Continental shelf and slopes of the North Atlantic Ocean minimum estimate, based on surveys covering part of the distribution
Specify trend in EO
Unknown
Are there extreme fluctuations in EO?
No
Area of occupancy (AO) (km²)
> 120,000 km² for all sizes; > 13,000-22,000 km² for adult females minimum estimate, based on surveys covering part of the distribution
Specify trend in AO
Unknown: change in distribution 1980s and early 1990s, stable since 1995
Are there extreme fluctuations in AO?
No
Number of known or inferred current locations
Continuous distribution
Specify trend in #
Continuous distribution
Are there extreme fluctuations in number of locations?
No
Specify trend in area, extent or quality of habitat
Unknown
Population Information
Generation time (average age of parents in the population)
19 years
Number of mature individuals
Minimum estimate > 1.4 million (adult females) minimum estimate, based on surveys covering part of the distribution
Total population trend:
Unknown
% decline over 15 years (< 1 generation)
Survey catch rates for adult females declined by 95-96% over 13 - 15 years (yr), in the 1980s – early 1990s, stable over past 10 yr, but survey declines reflect some combination of population declines and distribution changes
Are there extreme fluctuations in number of mature individuals?
Unlikely
Is the total population severely fragmented?
No
Specify trend in number of populations
Single continuous population
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)
By-catch in fisheries in combination with conservative life-history traits
Rescue Effect (immigration from an outside source)
Status of outside population(s)?
Unknown
Is immigration known or possible?
Possible
Would immigrants be adapted to survive in Canada?
Probably
Is there sufficient habitat for immigrants in Canada
Yes
Is rescue from outside population likely?
Unknown
Current Status
COSEWIC: Special Concern (2007)
Status and Reasons for Designation
Status: Special Concern
Alpha-numeric code:
Reasons for Designation: This species is widespread on the upper continental slope and deep continental shelf throughout the North Atlantic. Females mature at 13-15 years with a generation time of approximately 20 years. The species is distributed from Davis Strait in the north to Georges Bank in the south, occurring both inside and outside 200 n. miles, primarily in depths between 400 and 1500 m. Research vessel surveys have not consistently covered deep portions of the range and catch a low proportion (ca. 2%) of mature adults. Canadian survey index decline rates over 15 years (< one generation) of > 90% occurred in the 1980s and early 1990s, but the surveys only covered depths to 1000 m. This decline is probably due to a combination of distributional change and abundance decline: there is evidence for movement of fish into deeper water as a result of the cooling of the shelf in the 1980s, and reduction in population size due to fishing pressure is also a possible factor. The species is caught primarily as bycatch in the Greenland halibut fishery, which has experienced reduced Total Allowable Catch and greater restrictions on areas of operation since 2000. However, there are no catch limits or management plans for the species in Canadian waters, and catch reporting of foreign vessels is often unreliable. Survey indices (Canadian and European Union) for adults have been stable over the past decade. The species is of concern because of late maturation, lack of evidence of return of adults to shallower depths with return to environmental conditions prevailing prior to the 1980s, a probable decline in abundance in the 1980s and 1990s, and the lack of a management plan for directed and incidental harvest.
Applicability of Criteria
- Criterion A: Although the survey index for adults declined > 90% over less than one generation in the 1980s and early 1990s, exceeding the criterion threshold for Endangered status, it is not considered to have tracked abundance accurately during this period because it was influenced both by distribution changes and abundance changes. Accordingly it is not considered "an index of abundance appropriate for the taxon" as required in the definition for Criterion A-b.
- Criterion B: Does not apply because extent of occurrence exceeds 20,000 km² and the area of occupancy is greater than 2,000 km².
- Criterion C: Does not apply because the estimated population size exceeds 10,000 individuals.
- Criterion D: Does not apply because the number of mature individuals exceeds 1,000 and area of occupancy is grater than 20 km².
- Criterion E: Not undertaken.