Effectively monitoring ecosystems given limited resources and shifting species distributions is a global challenge that must be met to uphold the NOAA Fisheries mission to manage for productive and sustainable fisheries. The Alaska Fisheries Science Center in Seattle, Washington seeks a post-doctoral scholar to develop a framework for designing efficient and flexible fishery-independent surveys to address these challenges while evaluating their expected effects on survey data. These survey data are critical inputs to stock assessments, ecosystem-based fishery management initiatives, and applied ecological research such as species distribution modeling in Alaska’s Large Marine Ecosystems. This framework would provide a quantitative basis for addressing common survey objectives of decreasing cost while minimizing information loss, and providing adequate spatial and temporal coverage to facilitate the precise and accurate estimation of abundance that is required to inform management with the best available science. This would build on progress from a recent international workshop organized by the project leaders (ICES 2020).
We propose applying this framework to the Bering Sea and other Arctic waters, which make an excellent case study given the rapid environmental change and resulting northward and shelf-slope species distribution shifts occurring in this system (e.g. Spies et al., 2018). Given these changes, we must design an approach that facilitates sampling throughout the demersal ecosystem as needed to reduce the risk of bias in indices of abundance and stock status that arises from variation in spatial availability, a key component of catchability. To avoid these pitfalls, we would develop and evaluate the expected performance of new designs for unified surveys that would include the areas of multiple existing bottom trawl surveys, including the eastern Bering Sea (EBS) shelf, slope, and northern Bering Sea (NBS). We aim to determine what further design changes would enable efficient redistribution of samples among these areas without compromising the consistency of the long-term time series and its interpretation in the context of stock and ecosystem assessments. The resulting survey design could also improve ecological understanding by providing better estimates of deep-dwelling species abundance, overlap in distributions of target and choke species (e.g. via sablefish northward range expansion), variation in species interactions (expanding coverage of stomach sampling), and seasonal variation in local abundance (via additional randomly resampled stations).
This project will evaluate the current EBS shelf survey design and potential alternatives with respect to sampling efficiency, robustness to climate and species distribution variability, and flexibility to sampling constraints. Expected performance of proposed designs will be based on metrics of the accuracy and precision of survey data products, primarily abundance indices, relative to the status quo. Specifically, we propose to determine whether and how the efficiency of the EBS shelf survey can be increased, using empirical (e.g. bootstrapping) and simulation (e.g. Oyafuso et al. 2021) approaches.
ICES (2020). ICES Workshop on unavoidable survey effort reduction (WKUSER). ICES Scientific Reports. 2:72. 92pp. http://doi.org/10.17895/ices.pub.7453
Oyafuso, Z., Barnett, L.A.K., & Kotwicki, S (2021). Incorporating spatiotemporal variability in multispecies survey design optimization addresses trade-offs in uncertainty. ICES JMS, fsab038. https://doi.org/10.1093/icesjms/fsab038
Spies, I., Gruenthal, K.M., Drinan, D.P., Hollowed, A.B., Stevenson, D.E., Tarpey, C.M., & Hauser, L. (2020). Genetic evidence of a northward range expansion in the eastern Bering Sea stock of Pacific cod. Evol. Appl., 13(2), 362-375. https://doi.org/10.1111/eva.12874
Survey design; Abundance estimation; Species distribution; Fisheries survey; Stock assessment; Fish; Spatial models