Alberto Rovellini, UW School of Aquatic and Fishery Sciences

Abstract TBA

Murdoch McAllister, UBC Institute for the Oceans and Fisheries

Both short-lived and long-lived fishes are known to exhibit so-called spasmodic recruitment, a population dynamics pattern in fisheries characterized by long, consecutive periods of low recruitment interrupted by infrequent, irregular, and intense pulses of high recruitment. For up to several decades such fish stocks may remain at low abundance. Very large recruitment events typically arrive unanticipated and come as a surprise to both industry and managers. Spasmodic behaviors have been observed recently on both coasts of North America, for example, in Pacific Ocean Bocaccio Rockfish, California Sardine and Anchovy, and Canadian Atlantic redfish and capelin. Given their highly unpredictable behaviors, spasmodic fish stocks present substantial challenges and also new opportunities for the design of fishery management plans for fisheries for such stocks when large recruitment events are confirmed. I summarize findings from my research group’s study of Canadian Atlantic redfish on characterizing stock trends and evaluating candidate management procedures.

James Thorson, NOAA Northwest Fisheries Science Center

Dynamic structural equation models (DSEM) provide a fast and general approach to incorporate ecological knowledge in multivariate time-series analysis, e.g., when linking covariates to stock-assessment models. However, DSEM has previously been restricted to stationary, linear, and additive relationships, whereas many ecological systems are nonstationary, nonlinear, and include statistical interactions.
In this workshop, we introduce “moderated SEM” and quickly summarize how moderated DSEM can incorporate nonstationarity, nonlinearity, and statistical interactions. We will then walk through three R-package vignettes in package dsem, showing (1) random slopes linking the Pacific Decadal Oscillation to local temperature, (2) nonlinear (Lotka-Volterra) predator-prey interactions for Wolf-Moose or Paramecium-Didinium systems, and (3) quadratic temperature-
dependence in zooplankton dynamics for Lake Washington. We encourage participants to have a laptop with R and Rtools installed, and/or pre-installing the dsem@dev branch using `remotes::install_github(“james-thorson-NOAA/dsem@dev”)`.