• Environmental cues for Pacific herring (Clupea pallasi) spawning in northern Bristol Bay

      Tojo, Naoki (2006-05)
      Pacific herring, Clupea pallasi, is an important forage fish species, which interfaces with various trophic levels including human beings. There have been many herring studies about reproductive biology and migration dynamics, but not many studies about the underlying mechanisms. For fisheries management, reliable spawning prediction models are necessary. I sought to understand the mechanisms behind the variability in northern Bristol Bay herring spawning variability and migration dynamics in the eastern Bering Sea (EBS). Through a combination of spatio-temporal approaches and statistical methods, I found significant statistical relationships between herring spawning and spring environmental variables. All the best models include air-sea-ice interactions through their effects on gonad maturation and migration. EBS herring undergo a pseudo-clockwise seasonal migration with adjustments in response to changes in oceanographic conditions along the ice edge. Ocean temperature changes near the ice edge, which are controlled by atmospheric gradients over the North Pacific Ocean, explain most of the interannual variability of herring spawning in northern Bristol Bay.