Science Response 2013/017

A Review of Sablefish Population Structure in the Northeast Pacific Ocean and Implications for Canadian Seamount Fisheries

Context

On the west coast of Canada, many commercial fish populations are delineated into separate "stocks" for some combination of biological and operational reasons.  For example, biological attributes of a fish population may suggest genotypic and/or phenotypic differentiation from other populations of the same species in nearby areas.  Management practice may separate a population into stocks because of constraints to area-specific monitoring of catch and discards, enforcement, and assessment.  Requirements for population-specific analysis of biological, catch, and abundance data typically dictate stock separation from a larger population.  Finally, fish populations that straddle national boundaries, or exist in whole or part within international waters, can be delineated into stocks purely for policy reasons.

Canadian Sablefish (Anoplopoma fimbria) fisheries at seamounts located within and outside of the Pacific Canadian Exclusive Economic Zone are managed independently of Sablefish fisheries along the continental shelf and slope of British Columbia.  While the total allowable catch for the coastal fishery is determined annually via quantitative analysis of coastal fishery catch and abundance data, Sablefish harvests from seamount populations are regulated by monthly vessel limits and input control tactics involving limited entry licensing, seasonal closures, and gear restrictions.  Emergence of this distinct form of harvest management for seamounts was not based on biological evidence of stock structure differences between seamount Sablefish and coastal populations.  Rather, differences arose from the contrasting origins of these fisheries; coastal fisheries grew into large-scale industrial operations in the 1970s, while seamount fisheries developed from experimental activities in the 1980s.

Fisheries and Oceans Canada’s Pacific Region Ecosystem Management Branch and Fisheries and Aquaculture Management Branch requested Pacific Region Science Branch to provide science information and advice to assist evaluation of fishery compliance with the Sustainable Fisheries Framework policy and to support development of management plans for the Sgaan Kinghlas - Bowie Seamount Marine Protected Area (SK-B MPA).  Sablefish fishing by longline trap gear is permitted within Zone 2 of the SK-B MPA by the Bowie Seamount Marine Protected Area Regulations.  Specifically three questions were posed:

1. Do Sablefish located at seamounts and the continental shelf and slope of coastal British Columbia represent different biological populations?
2. What is the nature [e.g., frequency and magnitude] of Sablefish exchange between seamount and coastal populations? and
3. What are the benefits and risks of alternative approaches to managing seamount and coastal Sablefish as a single stock?

This paper reviews life history, genetic, and tag release-recovery studies throughout the Sablefish range in the northeast Pacific Ocean and presents previously unpublished tag release-recovery data to determine the degree of empirical support for biologically distinct Sablefish populations on seamounts and in coastal areas.  Following synthesis of this information, a summary of three alternative options for management of seamount Sablefish in British Columbia is provided; however detailed evaluation of their relative efficacy requires knowledge of the complete range of objectives for seamount ecosystems.  Some objectives are only indirectly related to the status of Sablefish, such as those pertaining to habitat and species diversity, but may impose constraints on Sablefish harvest.

This Science Response Report results from the Science Special Response Process of May 30, 2013 on A Review of Sablefish Population Structure in the Northeast Pacific Ocean and Implications for Canadian Seamount Fisheries.  There has been no past advice provided on this issue, and at this time there is no expectation of further advice on Sablefish population structure.

Complete document (PDF, 634 KB)

Accessibility Notice

This document is available in PDF format. If the document is not accessible to you, please contact the Secretariat to obtain another appropriate format, such as regular print, large print, Braille or audio version.