COS 214-2 - Leveraging fishery observer data and modeled environmental conditions to understand the emerging black eye syndrome in snow crab

Abstract: Black eye syndrome (BES) is an emerging syndrome of Eastern Bering Sea snow crab (Chionoecetes opilio). Characterized by darkened pigmentation beneath the eye surface in mild stages and partial or total erosion of the cornea in severe stages, BES currently lacks a known agent or cause. Nonetheless, coincident warming in the Bering Sea and observations of BES concentrated in older crab suggest pivotal roles of the environment and host in influencing BES. To assess potential demographic and environmental drivers of BES, we leverage the capacity of Alaska Department of Fish and Game observers to record BES in snow crab catches while accompanying commercial fishing vessels. Additionally, we use model outputs of temperature and carbonate chemistry from a Bering Sea implementation of the Regional Ocean Modeling System (ROMS) at 10-km resolution (Bering10K) as hypothesized environmental drivers. These model outputs and observer data are especially valuable when field sampling is logistically challenging and infrequent. We use the approximate Bayesian Integrated Nested Laplace Approximation (INLA) with stochastic partial differential equations (SPDE) approach to model BES from 2017-2021 across the Eastern Bering Sea, determining its association with likely drivers. Preliminary results show an association of crab size and shell condition with BES, suggesting potential roles of growth and molting in the condition. However, other probable drivers are unclear or unexplored. Understanding BES is critical for assessing its risk to an ecologically and commercially valuable species that is already threatened by climate change and concomitant losses of 88% and 80% of juvenile and mature crab biomass, resp., since 2018. Further, this work highlights the priority and value of incorporating disease monitoring into regular fisheries management.