Annual and inter-annual trends in the zooplankton prey and growth of Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) larvae on Georges Bank

No abstracts are to be cited without prior reference to the author.

The dominant copepod taxa on Georges Bank were monitored between January and June of 1995 through 1999, using a pump sampler and a 1-M MOCNESS. Between March and May of these years over 10,000 cod and haddock larvae were collected and recent growth of individual larvae estimated using RNA/DNA ratio analysis. Undertaken as part of the US GLOBEC NW Atlantic Georges Bank Program, the zooplankton sampling was completed on broadscale cruises covering much of the Bank, while most of the larval collections were made on process cruises concentrated on the southern flank. Together the two data sets afforded the opportunity to examine prey production and larval growth over extended spatial and temporal scales. Indices of prey abundance were estimated for different size-classes of larvae. Normalized prey counts (#•M-3) and prey biomass concentration (μg dry weight•M-3) increased between January and May of each year. Following a similar trend, larval growth increased between March and May. The spring of 1995 and to a lesser extent 1996 appeared to be periods of poor growth and low prey availability for cod and haddock larvae on Georges Bank. Although no large year-class of cod was produced during the study period, the 1998 and 1999 year-classes of haddock were among the largest produced over the previous 20 years. Models relating larval growth to size, photoperiod, prey abundance and other environmental variables will be presented.