Healthy parents provide clues to survival of young haddock on Georges Bank

Large fall phytoplankton bloom could control reproduction, future stock size

In 2003, haddock on Georges Bank experienced the largest baby boom ever documented for the stock, with an estimated 800 million new young fish entering the population. With typical annual averages of 50 to 100 million new fish in the last few decades, fisheries biologists have been puzzled by the huge increase and its ramifications for stock management. They have been looking for answers and may have found one - healthy adults.

In a study to be published in the June issue of the Canadian Journal of Fisheries and Aquatic Sciences, Dr. Kevin Friedland and colleagues from NOAA’s National Marine Fisheries Service and the University of Massachusetts suggest that the successful 2003 recruitment year is related to the fall phytoplankton bloom the year before spawning, and to the condition of the adult haddock. Phytoplankton, microscopic marine plants, form the basis of the ocean food web, and are the main source of food for many fish and other animals in the ocean. The fall 2002 bloom was significant, providing a larger than usual source of food for the ecosystem.

“Simply put, having more food to eat gives adult haddock a chance to get into better physical shape to reproduce healthy offspring with a higher chance of survival,” says Friedland, a research scientist at NOAA Fisheries’ Northeast Fisheries Science Center. “We reviewed the commonly applied factors that control recruitment, and found that the fall phytoplankton bloom the year before seems to link parental condition with a good recruitment. We call this new approach the parental condition hypothesis.”

The researchers analyzed various factors that control recruitment, from egg and larval retention, feeding conditions for larvae, size of juveniles in the fall and their estimated hatch dates, prey and time of spawning to circulation patterns and the timing and size of spring and fall phytoplankton blooms. They found that the fall phytoplankton bloom the year prior to spawning and its affect on the condition of adults to be the best supported hypothesis.