Another survival index relates to first-feeding pollock larvae, a key survival stage when they have exhausted their yolk sacs and need to capture food. Possibly because increased turbulence interferes with larvae s ability to feed, strong wind mixing events during the first-feeding period are detrimental to survival of pollock larvae. As with precipitation at Kodiak, there is wide interannual variability with a less noticeable and shorter trend to increasing survival potential from 1962 to the late 1970s. Index of pollock survival potential based on estimated wind mixing energy at a location south of Shelikof Strait from 1962 through 1999. The extent and timing of seasonal sea ice over the Bering Sea shelf plays an important role, if not the determining role, in the timing of the spring bloom and modifies the temperature and salinity of the water column.
Sea ice is formed in polynyas and advected southward across the shelf.
The leading edge continues to melt as it encounters above freezing waters. The ice pack acts as a conveyor belt with more saline waters occurring as a result of brine rejection in the polynyas and freshening occurring at the leading edge as the ice melts. Over the southern shelf, the timing of the spring bloom is directly related to the presence of ice. If ice is present in mid-March or later, a phytoplankton bloom will be triggered that consumes the available nutrients. If ice is not present during this time, the bloom occurs later, typically during May, after the water column has stratified.