Research Document 2020/027
A Technical Review of the Management Approach for Stream-Type Fraser River Chinook
By Dobson, D., Holt, K. and Davis, B.
Abstract
Starting in 2008, Fisheries and Oceans Canada (DFO) implemented a series of fisheries closures and restrictions to protect Fraser Spring 42 Chinook Salmon stocks. These restrictions were expanded in 2010, and again in 2012, to allow additional protections for Fraser Spring 52 and Summer 52 Chinook Salmon stocks. The 2012 management approach was documented in a letter written by the Regional Director for DFO’s Pacific Region Fisheries Management Branch to First Nations and stakeholder groups (RD directive). An objective of the 2012 management approach was to ensure that First Nations fishing for food, social, and ceremonial purposes had priority over other use. In this paper, we present a technical review of the available data and methods with which to evaluate recent management outcomes relative to the objectives laid out in the 2012 RD directive. We summarize recent patterns in spawner abundance, biological properties, and annual exploitation rates for Fraser River Spring 42, Spring 52, Summer 52 Chinook stock management units. We then compare two alternative approaches for estimating fishery- and sector-specific exploitation rate indices using readily available data and assessment tools. The first of these approaches relies on the coded wire tag (CWT) mark and recovery program for the Spring 42 Nicola River CWT indicator stock, while the second combines an existing Fraser River Chinook Run Reconstruction model with genetic stock identification (GSI) catch composition estimates from marine fisheries. We then use predicted exploitation rate indices from the Run Reconstruction approach to evaluate management outcomes relative the objectives stated in the 2012 RD directive. Results show that all three stream-type Fraser Chinook stock management units (SMUs) show depressed escapement in recent years and consistent declines over the last four years. Time series of exploitation rate indices for the Spring 42 SMU were similar for the CWT and Run Reconstruction methods, but with higher values for the Run Reconstruction approach. Results from the Run Reconstruction approach show that stream-type Fraser Chinook have experienced a reduction in exploitation rates in recent years, and that First Nations fisheries have experienced a larger reduction in harvest impacts than other sectors. However, data were insufficient to fully evaluate management performance relative to harvest reduction and allocation objectives. The reliance on an exploitation rate index, as opposed to a complete estimate of total mortality, meant that exploitation rate indices were underestimates. Furthermore, an uncertainty analysis highlighted that measurement of sector-specific changes in exploitation rates were highly uncertain, especially for lower impact recreational and commercial fisheries, whose estimates relied on GSI sampling. The fact that we cannot estimate reductions in commercial and recreational fisheries with reasonable error, using the available data, does not mean that they did not occur. The management measures implemented in various fisheries, such as time and area closures during periods of peak stream-type Fraser Chinook migration, were reasonably expected to reduce impacts on stream-type Fraser Chinook. We make recommendations for future work to address key gaps in the management and assessment framework for stream-type Fraser Chinook.
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