Spatial dynamics of snow crab (Chionoecetes opilio) in the eastern Bering Sea-putting together the pieces of the puzzle

Landings of the snow crab Chionoecetes opilio (J. C. Fabricius, 1788), which supports a lucrative fishery in the eastern Bering Sea (EBS), dropped to historical lows by 2000, and the geographic range of reproductive females contracted to the north-west. Resilience of the mature female range through larval advection may be hampered because hatching now occurs downstream. These changes have been punctuated by four pulses of recruitment, with a remarkably regular period of 6-7 yrs. Major pulses of the fishery, during the 1990s, were sustained by recruitment pulses that originated in regions of the northwest section of the EBS shelf beyond the reach of the fishery. Here we present, for the first time, a conceptual model of snow-crab spatial dynamics that integrates empirical information with new results from modeling of circulation and larval transport. The geographic region of interest, defined by means of biophysical modeling and tracking ontogenetic migrations, consists of the middle and outer domains of the EBS shelf, bounded by the 50- and 200-m isobaths. Connectivity analysis highlights the significance of subsystems in the southeast and northwest sections of the EBS's middle domain. Predicted settlement regions match historical regions of abundance of immature crabs and are consistent with observed fields of suitable near-bottom temperature. Our study, together with others, highlights the significance of climate change for the fate of important high-latitude fisheries.