Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: Georges Bank; Atlantic cod; environmental quality. Includes bibliographical references (p. 38-42).

Thesis (Ph. D.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 1999. / Includes bibliographical references. / The thesis investigates the circulation at a 76-m deep study site on the southern flank of Georges Bank, a shallow submarine bank located between the deeper Gulf of Maine and the continental slope. Emphasis is placed on the vertical structure of the bottom boundary layer driven by the semidiurnal tides and the flow field's response to wind forcing. The observational analysis presented here is based on a combination of moored array and bottom tripod-mounted current, temperature, conductivity, and meteorological data taken between February and August 1995. Results from the bottom boundary layer analysis are compared to numerical model predictions for tidal flow over rough bottom topography. The flow response to wind forcing is examined and brought into context with the existing understanding of the wind-induced circulation in the Georges Bank region. Particular attention is given to the vertical distribution of the wind-driven currents, whose variation with background stratification is discussed and compared to observations from open ocean studies. / by Sandra Regina Warner. / Ph.D.

The Georges Bank area in the northwest Atlantic Ocean plays an important role in New England's economy. Overfishing has led to a rapid decrease in cod population numbers, leading to a collapse in certain stocks. Currently, the rate of decrease in cod numbers has slowed; however, population numbers are still low. In this study, I use Growth Rate Potential (GRP) to assess the current environmental quality of Georges Bank and its suitability to support a cod population. GRP is the amount of growth predicted for a fish with known prey availability and environmental conditions. With prey availability and temperature data obtained during the fall fisheries acoustics surveys in 2000, 2001 and 2002, I developed spatially explicit GRP maps, using bioenergetic and foraging models, for Atlantic cod to determine the ability of the Georges Bank environment to support a cod population. Results show that Georges Bank is able to support growth for adult Atlantic cod. In addition to GRP analysis, I studied nucleic acid concentrations of Atlantic herring. Nucleic acids play an important role in growth and development, and have been used to assess physical condition of fish as well as and current growth rates. In this study, I determine total nucleic acid concentrations of Atlantic herring caught during three different spawning stages: pre-, post-, and non-spawning, to determine how nucleic acid concentrations and energy allocation vary seasonally. Results support the hypothesis that nucleic acid concentrations can be used as condition indicators, and are highly sensitive to the spawning stage of fish showing a significant difference between the three groups, which may affect their ability as condition indicators.

Thesis (Ph. D.)--University of Rhode Island, 2006. / Typescript. Includes bibliographical references (leaves 129-143).

Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Biology; and the Woods Hole Oceanographic Institution), 2011. / Cataloged from PDF version of thesis. / Includes bibliographical references. / The ultimate goal of early life studies of fish over the past century has been to better understand recruitment variability. Recruitment is the single most important natural event controlling year-class strength and biomass in fish populations. As evident in Georges Bank haddock, Melanogrammus aeglefinus, there is a strong relationship between recruitment success and processes occurring during the planktonic larval stage. Spatially explicit coupled biological-physical individual-based models are ideal for studying the processes of feeding, growth, and predation during the larval stage. This thesis sought new insights into the mechanisms controlling the recruitment process in fish populations by using recent advances in biological-physical modeling methods together with laboratory and field data sets. Interactions between feeding, metabolism and growth, vertical behavior, advection, predation, and the oceanic environment of larval haddock were quantitatively investigated using individual-based models. A mechanistic feeding model illustrated that species-specific behavioral characteristics of copepod prey are critically important in determining food availability to the haddock larvae. Experiments conducted with a one-dimensional vertical behavior model suggested that larval haddock should focus on avoiding visual predation when they are small and vulnerable and food is readily available. Coupled hydrodynamics, concentration-based copepod species, and individual-based larval haddock models demonstrated that the increased egg hatching rates and lower predation rates on larvae in 1998 contributed to its larger year-class. Additionally, results from these coupled models imply that losses to predation may be responsible for interannual variability in recruitment and larval survival. The findings of this thesis can be used to better manage the haddock population on Georges Bank by providing insights into how changes in the physical and biological environment of haddock affect their survival and recruitment, and more generally about the processes significant for larval fish survival. / by Colleen Mary Petrik. / Ph.D.