Date of Award

12-2012

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Marine Biology

Advisor

Jeffrey Runge

Second Committee Member

Teresa Johnson

Third Committee Member

James Wilson

Abstract

Calanus finmarchicus is a widely distributed copepod species that dominants the zooplankton community in the Gulf of Maine. It is of particular interest in its role as a major food source for the endangered northern right whale and stocks of herring, mackerel and cod. More accurate coupled models to predict its distribution requires better life history models. However, due to the difficulty in estimating it, mortality is often used as a closure term in those models; the value is justified mathematically rather than ecologically. Instantaneous mortality is difficult to measure, but the Vertical Life Table method (VLT) has gained some acceptance as an effective estimation technique. Calculations are made using the stage structure of the population and development rates. The VLT mortality estimations are heavily dependent upon development rates determined from temperature dependent functions and several assumptions. The limitations imposed by the VLT and inadvertent violations of assumptions prevented a spatial analysis of mortality. However, a new technique is presented to provide a much more explicit array of instantaneous mortalities that vary with season, stage and distance from shore. The Structured Population Molting rate method uses in situ incubations to directly observe the progressing stage structure and calculate the molting rates. The observed C. finmarchicus demography suggests that there is size selective predation mortality corresponding with bathymetry. Near shore regions host various visual predators of late stage C. finmarchicus and lack a depth refuge through vertical migration. These factors could explain the paucity of later stages when compared to offshore regions, but an alternative hypothesis suggests that the Maine coastal currents are responsible for transporting C. finmarchicus to the deep off shore basins where they are found in great abundance.

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