Terms of Reference

Framework Review and Assessment of Alewife (Alosa pseudoharengus) in the Gaspereau River, Nova Scotia

Regional Peer Review - Maritimes Region

February 17-19, 2025

Dartmouth, NS

Chairperson: Kristian Curran

Context

Alewife (Alosa pseudoharengus) and blueback herring (Alosa aestivalis) are diadromous species of fish that collectively are referred to as river herring or gaspereau. In the spring, they return to many of the river systems in Nova Scotia and Southwest New Brunswick to spawn, where they are fished together in tidal and freshwater environments. The fishery is geographically widespread, with fishing practices and gear types that differ among rivers. The fishery is managed primarily through effort controls. In the Fisheries and Oceans Canada (DFO) Maritimes Region, the last science framework of river herring was completed in 2017, in an effort to develop an on-going assessment and monitoring program for these stocks (see: Gibson et al., 2017). The framework was developed to provide an overview of the spatial scale for assessment and identification of stock units, reference points against which stock status could be evaluated, monitoring methods, analytic methods, and research recommendations, which took into account DFO’s precautionary approach framework for the sustainable management of fisheries. For Gaspereau River, Nova Scotia, the reference points used for assessing the status of the alewife stock, referred to at the time as an escapement target and later adopted as the Upper Stock Reference (USR), were developed when abundance was low and fishing mortality rates were high (DFO 2007).

The primary goals of this science peer-review process are:

1. review and update the science framework for the assessment of the Gaspereau River alewife stock;
2. use the framework to update reference points for the Gaspereau River alewife stock; and
3. describe the impacts of fishing and other anthropogenic activities on the abundance and population dynamics of the Gaspereau River alewife stock.

The advice will be used by DFO Resource Management to manage the commercial, communal commercial, and recreational gaspereau fisheries on the Gaspereau River and by DFO Fish and Fish Habitat Protection Program to inform the regulatory review of hydroelectric operations and fish passage requirements.

Objectives

The objectives of this process are:

Describe the Gaspereau River alewife stock

1. Define the Gaspereau River alewife stock.
2. Describe the life cycle of Gaspereau River alewife, including the timing of fishing and other anthropogenic activities, such as hydroelectric infrastructure and operations, in the life cycle.
3. Describe historical and current data collection, estimation procedures, trends and associated estimates of uncertainty, and caveats for the count, catch and age data, as well as any other data used in the science framework.

Review and update the science framework used to estimate Gaspereau River alewife stock parameters

1. Develop models to estimate Gaspereau River alewife stock parameters (e.g., fishing mortality [F], biomass, abundance) and biological reference points, as well as analyze model performance.
1. Explain model assumptions, strengths, and limitations.
2. Describe history of model usage, its theory and framework, and document associated peer-reviewed literature.
3. Present different versions of the model and input data. Present the results with diagnostics for all versions of the model considered.
4. If multiple models were considered, justify the choice of a preferred model and the explanation of any differences in results among models.
2. Describe the process for annual updates and how it may differ from the reference point estimation model.
3. Characterize uncertainty of model estimates and biological or empirical reference points.

Evaluate Gaspereau River alewife reference points and estimate stock parameters

1. Provide an estimate of the unfished equilibrium population size for Gaspereau River alewife in the absence of fishing or other human-induced impacts on the stock.
2. Evaluate reference points (i.e., Limit Reference Point, Upper Stock Reference, Removal Reference) consistent with DFO’s precautionary approach for the management of the Gaspereau River alewife stock.
3. Assess status of the Gaspereau River alewife stock in relation to reference points and consistent with DFO’s precautionary approach.
4. Describe sources of uncertainty that are not already described or accounted for in the model; specifically, those that would affect the conclusions drawn from the results of the model.
5. Describe the effects of hydroelectric infrastructure on the Gaspereau River alewife stock, reference points, and model parameters
6. Recommend timing of the next stock assessment and interim stock updates, if necessary, relative to biology and current management of the Gaspereau River alewife stock.

Expected Publications

• Science Advisory Report
• Research Document

Expected Participation

• DFO Science
• DFO Resource Management
• DFO Fish and Fish Habitat Protection Program
• Indigenous Communities and Organizations
• Provincial government
• Academia
• Industry
• Non-government organizations

References

• DFO, 2007. Assessment of Gaspereau River Alewife. DFO Can. Sci. Advis. Sec. Sci. Advis. Rep. 2007/030.
• Gibson, A.J.F., Bowlby, H.D., and Keyser, F.M. 2017. A Framework for the Assessment of the Status of River Herring Populations and Fisheries in DFO’s Maritimes Region. DFO Can. Sci. Advis. Sec. Res. Doc. 2016/105. vi + 69 p.