Science Advisory Report  2009/041

Recovery assessment of canary rockfish in British Columbia waters

Summary

• The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) has assessed the canary rockfish population in B.C. as Threatened. A final decision by the Government of Canada is required by December 2010. If the threatened listing is accepted, a Recovery Strategy will be required within two years from the date of acceptance.
• This document provides the scientific advice required for development of the Recovery Strategy. It follows the outline provided in the Revised Protocol for Conducting Recovery Potential Assessment (RPA). The specific intent of this RPA is to predict the impact of future harvest levels on canary rockfish abundance relative to attaining a target stock status. The stock status and forecasting advice are framed to be consistent with the current DFO policy on the Precautionary Approach (PA).
• Canary rockfish is one of over 39 species of rockfish present in B.C. waters.Vernacular names for canary rockfish include rockcod, red snapper, and snapper; however these names are also shared with other species. Female canary rockfish mature at about 14 years of age with a generation time of 20.4 years. The population is assumed to be one designatable unit in B.C.
• Little is known about the distribution of young canary rockfish in B.C. waters although they have been captured by gillnets in nearshore sub-tidal depths. They appear to move deeper as they become older and larger. Most of the late stage juveniles and adult specimens are caught over depths of 100-225 m on the continental shelf. Most canary rockfish will probably die if released after capture. Canary rockfish does not appear to exhibit residence requirements as defined in the SARA legislation.
• A coastwide assessment of canary rockfish was conducted using a catch at age model tuned to five fishery-independent surveys and to age composition data from the commercial fishery. A Bayesian approach was used to explicitly incorporate model and data uncertainty in the assessment results.The model was started from an equilibrium state in 1940 and the available fishery-independent survey data span a period from 1967 to 2007, although not all intervening years are represented with surveys. The full model and results were reviewed in the fall of 2007 at the Pacific Science Advisory Review Committee (PSARC). This RPA was reviewed by PSARC in June 2008.
• The three model runs accepted by PSARC indicate that current spawning biomass is most likely within the cautious zone as defined by the reference points in the draft DFO PA policy documents. The mean expected values for current spawning biomass are estimated to be between approximately 0.15-0.22 of B₀, while the credible range for stock status is broader, spanning between 0.07 and 0.31. The mean estimate of B₂₀₀₈/B_MSY ranges from 0.49-0.73 for the three runs. There is, however, large uncertainty around these estimates.
• Harvests in the commercial groundfish fisheries are assumed to be the major current source of human-induced mortality. Total groundfish commercial catch (retained and discarded) was 751 t in the 2007/2008 fishing year. Landings and at-sea catches (retained and discarded) are monitored in all commercial groundfish fisheries with 100% coverage. There is negligible discarding of undersized fish. The catches of canary rockfish in the salmon troll, First Nations’, and recreational fisheries are unknown but are probably relatively small in comparison with commercial groundfish catches.
• Catches in U.S. waters may have an impact on the population of canary rockfish in B.C. waters, but the size of this impact is unknown. Recent U.S. assessments have indicated slow rebuilding of the canary population in U.S. waters.
• Given that canary rockfish appear to be predominantly a semi-pelagic and aggregating species with areas of highest density (for adults) along the edge of the continental shelf; and they appear to be much reduced in abundance from pre-exploitation levels, we know of no basis for assuming that the current quantity of physical habitat is limiting abundance. However, recent unpublished information on observed declines in dissolved oxygen, which appear to be correlated with apparent shifts in distribution of many groundfishes species to shallower depths, may be a source of concern. These observations are preliminary and their longterm significance is unknown. There is no information available to suggest that canary rockfish have residence requirements, as defined in SARA.
• Controlling the commercial harvest of canary rockfish appears to be the most effective way to mitigate threats to this population. It is possible that, under special circumstances, regulation changes to the gear used, or to fishing patterns, might provide modest benefits in addition to general steps to reduce catch. Such scenarios are best discussed during consultation with harvesters.
• While restricting commercial catches appears to be the most practical means at present to minimize harm to canary rockfish in B.C. waters, the mechanisms for implementing catch restriction proposals should be developed in consultation with industry.
• A series of decision tables provided in the document give predictions of stock trends under several fixed harvest rules under a range of modelling assumptions. These tables capture the relative trade-offs required when considering the three recovery targets (i.e. target biomass, time frame, and likelihood of reaching the target). These targets will be developed during the consultation phase.
• While the Bayesian approach used in the assessment provides a mechanism to include uncertainty in estimating the current status of the population, managers and stakeholders are advised that not all sources of uncertainty have been addressed. The true uncertainty is even greater with forecasting adding even more uncertainty. These projections assume the population will respond to the future environment as it did in the past, an assumption which may not hold due the effects of climate change and/or other external processes.
• Notwithstanding the uncertainty in the assessment and forecasts, short-term projections of 1 to 2 years predict that current commercial groundfish catches of about 750 t per year will not place the population in significant additional jeopardy, suggesting that it is not necessary to accelerate the time frame required to implement a Recovery Strategy and Action Plan (if required). However, longer term predictions based on the decision tables suggest that a reduction in harvest from current levels is required to significantly increase the probability of a population increase, as well as to increase the speed of the rebuild.

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