Science Advisory Report  2015/055

Arrowtooth Flounder (Atheresthes stomias) stock assessment for the west coast of British Columbia

Summary

• Arrowtooth Flounder (Atheresthes stomias) is a commercially important flatfish species in British Columbia, which occurs throughout the entire coast. It is caught primarily using bottom trawl gear, with a mean annual coastwide catch (landings + at-sea releases) of 8,532 t between 2010 and 2014.
• All areas of Canada’s Pacific coast, excluding waters between Vancouver Island and the British Columbia mainland, were assessed as a single stock, using an annual female-only catch-at-age model, implemented in a Bayesian framework to quantify uncertainty of estimated quantities.
• The model was fit to catch and survey data from 1996 to 2014. Catch data prior to 1996 were not used in the assessment due to unknown levels of releasing at sea prior to the introduction of Total Allowable Catches (TACs).
• The median spawning biomass (mature females only) at the beginning of 2015 (B2015) is estimated to be 296,271 t (95% credibility interval: 146,337-760,905 t).
• Decision tables are presented using two sets of reference points:
• the provisional DFO Limit Reference Point (LRP) 0.4BMSY and Upper Stock Reference (USR) Point 0.8BMSY (DFO 2009); and
• alternative LRP′ = 0.2B0 and USR′ = 0.4B0.
• Advice to management is presented in the form of decision tables, using a one-year projection for a range of catches up to 50,000 t/year (average coastwide catch over 2010-2014 was 8,532 t). The probability of dropping below the LRP at the beginning of 2016 is estimated to be zero for all catches tested. The probability of dropping below the USR at the beginning of 2016 is estimated to be close to zero. Stock size is not likely to decrease at any of the projected catch levels tested.
• All model-based results are expressed in terms of female Arrowtooth Flounder. Where appropriate, catch advice is scaled up using an average proportion of females caught by fishery and survey.
• The magnitude of at-sea releases prior to 1996 is a major source of uncertainty in this assessment. Reconstruction of historical releases based on advice from the fishing industry is recommended.
• There was uncertainty in the estimated age composition of the population, given the current availability of age data. There remain unaged samples from the commercial fleet and some surveys, and it is recommended that these samples, particularly those from the freezer trawl fleet, be aged before the next assessment of this species.

This Science Advisory Report is from the May 12-13, 2015 regional peer review on Coastwide Assessment of Arrowtooth Flounder (Atheresthes stomias) in 2014 and recommendations for 2015. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

Complete document (PDF, 310 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.