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Early Life Stage Ecology

Narragansett Lab: U.S. GLOBEC NW Atlantic/Georges Bank Study

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cod larva
Cod larva - Photo by H. Wes Pratt
Three otoliths. Credit: Jack Green

Narragansett Laboratory staff are partners in the NOAA/NSF sponsored Global Ocean Ecosystem Dynamics (GLOBEC) studies on Georges Bank initiated in 1994. The objective of the U.S. GLOBEC Georges Bank Study is to define the physical and biological processes controlling the growth and survival of gadoid larvae (cod and haddock) and their zooplankton prey species. Georges Bank has traditionally supported large fisheries for cod and haddock, however, both species have been at historically low levels in recent years. These stocks are at the southern end of the range for both species and potentially vulnerable to the effects of climate change.

The field work and data collection associated with the GLOBEC study have been conducted from 1994-1999, and focused on bank-wide studies of cod and haddock larvae and the biological and physical processes which determine their growth and survival. Studies are also conducted to determine factors controlling the prey field of gadoid larvae under different oceanographic conditions, using multiple opening and closing net systems, pumps, and advanced multi-frequency acoustic detection systems for measuring fine-scale relationships between larvae, their prey, and their environment.

Analyses are also underway at the Narragansett Laboratory to determine the age composition and growth rates of cod and haddock larvae sampled during the GLOBEC Georges Bank Program. The analyses are based on microscopic examination of larval fish otoliths to determine daily growth increments using both manual and image analysis techniques. Concurrent studies will determine the nutritional condition and recent growth rates of larvae as they are transported around the Bank. This research is expected to provide increased understanding of the inter-relations and relative importance of physical and biological variability on larval growth, survival and retention on Georges Bank.

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