More fish survive if plankton bloom early

Data collected by Earth-orbiting satellites and oceangoing trawlers suggest that juvenile haddock off Nova Scotia are more abundant in years when plankton populations peak earlier than normal.

Scientists have been surveying the abundance of fish off the eastern coast of Nova Scotia since 1970, says Trevor Platt of the Bedford Institute of Oceanography in Dartmouth, Nova Scotia. One index used to characterize fish survival is the number of fish less than 2 years old in a catch divided by the weight of older fish taken. That index was particularly high in 1981 and 1999, indicating an abundant juvenile population.

Satellite observations of the region show that in those 2 years, populations of phytoplankton peaked at least 2 weeks earlier than average. For the years when such satellite data were available–1979 through 1981 and 1997 through 2001–the timing of the spring phytoplankton bloom accounted for 89 percent of the variation in the fish-survival index.

Platt and his colleagues speculate that when phytoplankton bloom earlier than normal, larval haddock have access to more food and may be shielded from predators more effectively in the cloudy water. The researchers report their analyses in the May 22 Nature.


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