Terms of Reference

Assessment Framework for SW Nova Scotia / Bay of Fundy Herring: Fall 2006 – Winter 2011

Maritimes Regional Science Advisory Process

24-28 January 2011
Dartmouth, NS

Chairperson: Ross Claytor

Context

The current management plan for the 4VWX herring stock complex pursues three conservation objectives:

1. To maintain the reproductive capacity of herring in each management unit through:
• persistence of all spawning components in the management unit
• maintenance of biomass of each spawning component above a minimum threshold
• maintenance of a broad age composition for each spawning component
• maintenance of a long spawning period for each spawning component
  
  
2. To prevent growth overfishing
• continue to strive for fishing mortality at or below F_0.1
  
  
3. To maintain ecosystem integrity/ ecological relationships (“ecosystem balance”)
• maintain spatial and temporal diversity of spawning
• maintain herring biomass at moderate to high levels

If during the current review, biological processes become apparent for which additional objectives might be required, these would be proposed to the Scotia-Fundy Herring Advisory Committee for approval.

The 2005 and 2006 assessments of the status of the SW Nova Scotia / Bay of Fundy Management Unit (SWNS/BoF) of the 4VWX stock complex highlighted the need for an in-depth review of the data and models used to assess progress against these objectives. For instance, the population model (VPA) and acoustic surveys estimates of current biomass differ substantially, which has focused attention on whether or not the acoustic survey biomass estimates should be considered absolute or relative as well as the veracity of the VPA.

This framework review was to be conducted over three sequential meetings scheduled to ensure that modifications identified in a meeting can be incorporated into the preparations and deliberations of the following meeting. Two review meetings were held in 2006/07 to: 1) Define the management unit and fishery data inputs (31 October – 1 November 2006), and 2) to review the indices of abundance (9 – 11 January 2007). Proceedings: Proceedings of the Maritime Provinces Regional Advisory Process on the Assessment Framework for 4VWX Herring Stocks. During this review process a serious error in ageing was uncovered and the third meeting, the assessment review, was postponed until the age issue could be resolved. The catch at age and the age disaggregated index of abundance for the past 10 years are now corrected so that the third and final framework meeting can proceed

The main objective of the third framework meeting will be to review the current ADAPT formulation and to investigate alternative assessment models for providing advice on stock status.  This meeting will also outline the assessment procedure to follow until the next framework review. The framework will be used for the first time in March/April 2011 in support of the 2010/11 fishery. 

The hope is that a range of assessment models can be explored, including ADAPT, to recommend a modelling approach for future evaluations. In this context there will be a comparison of the output and diagnostics of models commonly used for the assessment of pelagic fish stocks.  To achieve this goal a number of national and international experts have been engaged to take the input data and explore assessment formulations using a suite of models from a simple no-catch model, to a length-based approach, in addition to various age-based models. 

Objectives

Review of Models to Assess Status and Productivity (24-28 January 2011)

• Determine the methodology, exploring a range of models, to estimate the current state of the stock.
• Determine the methodology to provide short, medium and long-term yield forecasts.
• Provide guidance on the assessment procedure to be used during subsequent years, recommended timing of future framework reviews, as well as procedures to verify the on-going efficacy of the framework.

Expected publications

CSAS Science Advisory Report outlining the assessment framework
CSAS Proceedings of the discussion of the third framework meeting
CSAS Research Documents

Participation

DFO Science Maritimes and other regions
DFO Maritimes FAM
Scotia-Fundy Herring Advisory Committee
Provincial representatives
National and International modelling experts
External/Internal reviewers