Broad-scale Studies

The objective of this component of the program is to provide a basic description of the primary physical and biological properties of the Bank and the surrounding waters, as well as their spatial and temporal variability. This will be accomplished through a combination of ship surveys, moored instrumentation, and satellite observations. Of particular importance is documenting the life histories of the target species (cod, haddock, Calanus, and Pseudocalanus) in relation to the physical oceanographic conditions on the bank (Figure 3).

Two approaches exist to study the life history and population dynamics of the target species. First is life table or cohort analysis in which the abundance of successive stages in the life history of the population is determined. Mortality rates can be calculated directly calculated as recruitment rates and/or development times are known). These rates can be compared to likely mortality mechanisms (e.g., predation, starvation, advective loss/ exchange). This approach requires frequent, intensive sampling, along with measurements of development time. The second approach, which requires less intensive sampling, is survivorship analysis in which the characteristics of individuals are measured in several life stages to determine the characteristics which favored survival (e.g., birthdate, growth rate, genetic parentage). Both cohort and survivorship analysis can be used in this study because of: 1) the relatively discrete nature of the cod/haddock spawning on Georges Bank (in both space and time); 2) the relatively higher abundance of Calanus and Pseudocalanus on Georges Bank than in surrounding waters; 3) the general retention of plankton within the confines of the Bank; 4) the relatively small size of the Bank; and 5) the high probability of a cohort age structure for Calanus finmarchicus driven by a large, discrete egg production "event" associated with the spring bloom.