Science Response 2016/026

Review of a Method for Identifying a Window of Principle Striped Bass (Morone saxatilis) Spawning in the Shubenacadie River Estuary

Context

The Alton Natural Gas storage facility is to consist of an underground hydrocarbon (i.e., natural gas) storage facility near Alton, Nova Scotia (see NSDOE 2007). A water intake facility will draw water from the main stem of the Shubencadie River estuary to create cavern spaces for natural gas storage through dissolution of salt within a subsurface salt deposit. The resulting brine solution will be brought back to the surface and stored in a holding pond for eventual discharge back into the estuary in a manner that aligns with natural salinity fluctuations. Release of the salt brine will be via a diffuser pipe located in a mixing channel that has been constructed along the shore of the estuary.

The Stewiacke River estuary, which joins the tidal main stem of the Shubenacadie River approximately 2 km upstream of the mixing channel, is the primary spawning site for Shubenacadie River Striped Bass. This population is the only one of the three member populations of the Bay of Fundy Striped Bass Designatable Unit (DU) that is known to be reproductively viable (DFO 2014). Accordingly, they are of high conservation significance. The Environmental Registration Document for the Proposed Alton Natural Gas Storage Project acknowledges that Striped Bass eggs and larvae may occur in significant numbers in the vicinity of the mixing channel during May-June spawning events (Jacques Whitford 2007). Annual May-August ichthyoplankton surveys during the years 2008-2015, conducted under the supervision of Dr. J. Duston, Agricultural Campus, Dalhousie University, have confirmed the presence of Striped Bass eggs and larvae in the vicinity of the mixing channel in all years.

In light of uncertainties concerning the potential for brine release infrastructure and effluent to negatively influence Striped Bass productivity (DFO 2007), Alton Natural Gas LP. has proposed to cease brining operations during peak Striped Bass spawning events. However, no definition for “peak spawning events” for Shubenacadie River Striped Bass has been developed (Conestoga-Rovers & Associates 2015). Guidance provided to the proponents on August 11, 2015, following discussions between Fisheries and Oceans Canada (DFO) Science and DFO Fisheries Protection Program (FPP) on August 10, 2015, recommended that any analyses of existing data to identify ’principle’ spawning events should 1) consider use of water temperature as an indicator of onset of spawning; and 2) be conducted within the context of the overall timing and duration of annual spawning activity. Subsequent analysis by the proponent was provided to DFO Science in support of a peer-review of a proposed protocol for ensuring that the period when brining would cease aligned with natural spawning activity by Shubenacadie River Striped Bass, such that eggs and larvae would not be exposed to effluent or be at risk of entrainment during principle spawning events.

This review is to consider whether the portrayal of the timing and duration of spawning activity as outlined in the proponent’s analysis is accurate and whether knowledge gaps remain. The outcomes of the review will be used by the DFO FPP to help guide determination of when the project proponent might suspend brining operations in line with Shubenacadie River principle Striped Bass spawning events.

The objectives of this Science Response Process are to provide peer-reviewed science advice on:

1. a proposed method to define timing and duration of the annual window of principle spawning events for Shubenacadie River Striped Bass; and
2. the accuracy and gaps in the proponent’s analysis of timing and duration of Shubenacadie River Striped Bass spawning activity.

This Science Response Report results from the Science Response Process of September 21, 2015, on the Review of a Method to Define the Timing and Duration of Spawning Activity for Shubenacadie River Striped Bass.

Complete document (PDF, 208 KB)

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