The consumption of zooplankton by early life stages of fish in the North Sea

Previous work has shown that during the 1970s, fish and carnivorous macrozooplankton together consumed ~22 gC m-2 year-1 of mesozooplankton, principally copepods. Consumption declined to ~17 gC m-2 year-1 during the 1990s, mainly because of a reduction in fish production. The zooplankton production required to meet this demand seems to be approximately accounted for by estimates of new primary production, but there are additional sinks for zooplankton production attributable to predation by, for example, gelatinous species. Additionally, the consumption of zooplankton by early life stages of fish is difficult to assess and could be larger than implied by the earlier analysis. Here, the role of fish early life stages in zooplankton consumption is reassessed, and found to be approximately double that previously estimated. Some 28% of the zooplankton consumption by fish is now estimated to be attributable to early life stages, resulting in an estimate of zooplankton consumption by the fish community as a whole 14% higher. Taken overall, the consumption of zooplankton production by fish and other planktivorous predators is now estimated to be 19-25 gC m-2 year-1