Determining the influence of the environment on sockeye salmon catchability in Area 12 and 13 purse seine test fisheries

This proposal seeks to address Fraser River Panel priority 5 as listed in the Southern Fund’s 2019 call for proposals: “Further work to follow-up on the Test Fishery Workshop Report’s five recommendations.” Specifically, the proposed work would address recommendation (4) from the PSC Technical Report 33 – “Evaluating and implementing potential refinements to test fisheries using a phased process (i.e., to maintain the scientific rigor and integrity of the program).
To address this Fraser River Panel priority, we propose to:
1. Compile information on test fishery catch and local environmental conditions (e.g., tides, currents, winds, diel cycle and barometric pressure) from sockeye purse seine test fishery assessment sets in Areas 12 and 13 from 1998 to 2017,
2. Quantify the ability of environmental conditions to explain variations in catch (i.e., residuals from annual relationship between catch per set and daily abundance estimates) by fitting statistical models to the data,
3. Quantify the benefit (i.e., reduction in bias and increase in precision) of accounting for environmental conditions when predicting daily abundance estimates using CPUE data; evaluate the usefulness of this method across years using a leave-one-out cross validation.
4. Evaluate the impact of using publicly available data on tides and currents instead of finer scale hydrodynamic model output by relating the two datasets to each other and quantifying the impact of using publicly available data on the bias and precision of the resulting daily abundance estimates.
We will access and compile test fishery data (e.g., catch, location, time, depth) from DFO’s Fishery Operations System (FOS) database. Corresponding tide and tidal current time series will be generated for the test fishing set locations using hydrodynamic numerical models for Johnstone Strait and the Discovery Islands in collaboration with Richard Thomson at DFO’s Institute of Ocean Sciences. Additional environmental data (e.g., winds, diel cycle, barometric pressure) will be compiled from publicly available databases.
The specific outcome of this project will be a quantitative examination of the potential benefit of incorporating environmental information into in-season assessments of Fraser River sockeye salmon abundance and run-size.