Euphausiids in the eastern Bering Sea: A synthesis of recent studies of euphausiid production, consumption and population control

Euphausiids are an important component of the eastern Bering Sea marine ecosystem. We synthesized information on the ecological roles of two species, Thysanoessa raschii, which predominates over the Middle and Inner Shelf Domains, and Thysanoessa inermis, which predominates over the Outer Shelf Domain. Although estimates of euphausiid biomass across the shelf are not well constrained, we estimated that, between April and July, 2004–2010, euphausiid biomass was 3.08–5.25gCm−2 on the outer shelf and 1.95–3.92gCm−2 on the middle shelf. Modeled estimates of euphausiid production, for spring and summer combined, varied between 0.043gCm−2d−1 and 0.051gCm−2d−1, depending on location, with a mean of 0.048gCm−2d−1. Recently reported field measurements of annual primary production over the southeastern Bering Sea in 2008–2009 vary between 0.06 and 6.65gCm−2d−1, with a mean of 1.262gCm−2d−1±2.049gCm−2d−1 in spring and summer combined, a level sufficient to support euphausiids, at least on an annualized basis. Walleye pollock (Gadus chalcogrammus, hereafter pollock) is the single most important consumer of euphausiids over the eastern Bering Sea shelf. We estimated that pollock consumed between 0.0042 and 0.019.7gCm−2d−1 of euphausiids, depending on year, with a mean of 0.011gCm−2d−1 in summer averaged over 1999–2009. This consumption is equivalent to between 17% and 29% of summer euphausiid production, depending on location.