The relationship between Pacific hake (Merluccius productus) distribution and poleward subsurface flow in the California Current System

In a search for ocean conditions potentially affecting the extent of Pacific hake (Merluccius productus) feeding migrations, we analyzed data collected in 1995 and 1998 by the National Marine Fisheries Service on abundance and distribution of hake (by echo integration), intensity and distribution of alongshore flow (from acoustic Doppler current profiler), and temperature (conductivity–temperature–depth profiles). Our results show that Pacific hake are associated with subsurface poleward flow and not a specific temperature range. Temporal and spatial patterns characterize both hake distribution and undercurrent characteristics during the two years of this study. We suggest that poleward flow in this area defines adult hake habitat, with flow properties aiding or impeding the poleward migration of the population. We conclude that although physical processes may not directly affect fish production, they may be the link between large-scale ocean–atmosphere variability and pelagic fish distribution.