Terms of Reference

Candidate Limit Reference Points for Pacific Herring in British Columbia using a Closed-loop Simulation Modelling Approach

Regional Peer Review Process – Pacific Region

May 27-28, 2015
Nanaimo, British Columbia

Chairperson: Nicholas Duprey

Context

British Columbia's Pacific Herring fisheries are managed based on a harvest strategy initially designed in 1986, and further refined in 1996. The harvest control rule element of the strategy prescribes a target exploitation rate of 20% when herring stock biomass is predicted in the following year to be above an operational cut-off level of 25% of the estimated unfished biomass and an exploitation rate of 0% when the predicted biomass is below the cut-off level. Closed-loop simulation tests indicated that this rule would only cause herring stock biomass to drop below the cut-off level in 5% of years (Hall et al. 1988).

Since adopting the strategy in 1986, two major herring stocks - Strait of Georgia (SOG) and Prince Rupert District (PRD) have remained above the cut-off level. However, the major stocks in West Coast Vancouver Island (WCVI), Central Coast (CC), and Haida Gwaii (HG) have been below cutoff in 32%, 21%, and 46% of years (1986-2013), respectively, which far exceeds expectations indicated by the original simulations. Long term declines in body size (weight at age) have been observed for all BC herring stocks from the early-1980s to 2010, as well as variability in estimated natural mortality rates since 1951 (DFO, 2014). Their relative contributions to stocks falling below cut-offs are currently not well understood.

One of the challenges of establishing harvest control rules and biological limit reference points for herring stocks are time-varying changes in growth and natural mortality, referred to as non-stationarity. Non-stationarity, or time-varying changes in productivity affects harvest control rule performance and the estimation and avoidance of limit references points. For Pacific herring stocks, changes in growth have been observed, and current stock assessments indicate time-varying changes in natural morality. The consequences of non-stationarity in fish stock productivity have not been explored in detail within the scientific literature nor have they been evaluated for Pacific Herring fishery management. Exploring alternative scenarios for future changes could lead to a better understanding of whether harvest control rules and biological reference points need to be adapted to improve the long-term sustainability of herring fisheries.

The existing Pacific Herring harvest strategy lacks a clearly defined set of biological limit reference points (LRPs) that reflect conservation requirements under DFO's Sustainable Fisheries Framework. Biological LRPs are used in harvest strategies as quantitative conservation benchmarks from which the probability that a management procedure (MP) that will lead to unacceptable conservation outcomes for each non-stationary productivity scenario can be computed. LRPs are, therefore, critically important because they ultimately guide the entire harvest management system and the expected conservation, economic, and social outcomes.

In this closed-loop simulation approach to exploring candidate LRPs, the operating model is nested within a simulation framework and is designed to allow testing of proposed management procedures (the combination of data, assessment model, and harvest control rule) against multiple objectives while considering alternative theories of herring stock productivity and dynamics, and the consequences of different assessment methods and data frequency scenarios (annual, biennial surveys). This approach is an extension to models published by Cox and Kronlund (2008), Cleary et al. (2010) and Cox et al. (2013).

This Canadian Science Advisory Secretariat (CSAS), Regional Peer Review (RPR) will review the simulation model developed for BC Pacific Herring, and describe the performance of alternative management procedures relative to candidate LRPs. The advice arising from this CSAS RPR will be used to inform the renewal of the management framework for BC Pacific herring in accordance with Canada’s Sustainable Fisheries Framework.

Objectives

The following working paper will be reviewed and provide the basis for discussion and advice on the specific objectives outlined below.

Benson, Cox, Cleary, Taylor. Candidate Limit Reference Points for Pacific Herring in British Columbia using a Closed-loop Simulation Modelling Approach. CSAP Working Paper 2013PEL001

The specific objectives of this review are to:

1. Identify candidate biologically-based limit reference points (LRPs) for Pacific Herring based on literature review of LRPs for pelagic species (if available), along with the data and assessment methods required to assess these for Pacific Herring.

2. Describe operating model scenarios developed for each of the five major herring stocks. Assess suitability of the modelling approach for the development of simulations that incorporate decadal scale environmental forcing (e.g. climate, tropic interactions, predator communities, etc.) through changes in natural mortality and growth, and a clear representation of uncertainty.

3. Using the modelling framework described in #2, explore the performance of existing and alternative management procedures (the combination of data, frequency of data collection, and harvest control rule) at avoiding candidate LRPs. Present outcomes using a set of performance statistics that measure yield, variability in yield, and the probability of avoiding limits for each stock area.

4. Discuss considerations for the selection of biologically-based limit reference points (LRPs) for Pacific Herring stocks and provide advice on subsequent science initiatives required to advance renewal of the management framework for BC Pacific Herring.

Expected Publications

• Science Advisory Report
• Proceedings
• Research Document

Participation

• Fisheries and Oceans Canada (DFO) (Ecosystems and Fisheries Management)
• Academia or Academics
• Aboriginal communities/organizations
• Industry (fishing industry, processors)
• Other invited experts (environmental non-government organizations)

References

Cleary, J.S., Cox, S.P., and Schweigert, J. 2010. Performance evaluation of harvest control rules for Pacific herring management in British Columbia, Canada. ICES Journal of Marine Science 67: 2005-2011.

Cox, S.P., Kronlund, A.R., and Benson, A.J. 2013. The roles of biological reference points and operational control points in management procedures for the sablefish (Anoplopoma fimbria) fishery in British Columbia, Canada . Environmental Conservation 40: 318-328.

Cox, S.P. and Kronlund, A.R. 2008. Practical stakeholder driven harvest policies for British Columbia groundfish fisheries. Fisheries Research 94: 224–237.

De La Mare, W.K. 1998. Tidier Fisheries management requires a new MOP (management-oriented paradigm). Reviews in Fish Biology and Fisheries 8: 349-356.

DFO. 2014. Stock assessment and management advice for BC Pacific herring: 2014 status and 2015 forecast. DFO Can. Sci. Advis. Sec. Sci. Advis. Rep. 2014/060.

DFO. 2009. A fishery decision-making framework incorporating the Precautionary Approach.

Hall, D. L., R. Hilborn, M. Stocker, and C. J. Walters. 1988. Alternative harvest strategies for Pacific herring (Clupea harengus pallasi). Can. J. Fish. Aquat. Sci. 45: 889-897.

Smith, A.D.M., Sainsbury, K.J., and Stevens, R.A. 1999. Implementing effective fisheries-management systems – management strategy evaluation and the Australian partnership approach. ICES Journal of Marine Science, 56: 967–979.