Identifier

etd-1111103-152345

Degree

Master of Science (MS)

Department

Oceanography and Coastal Sciences

Document Type

Thesis

Abstract

Larval bay anchovy (Anchoa mitchilli) habitat quality in Chesapeake Bay was predicted using an individual-based model applied to spatially-detailed field data from Rilling and Houde (1999). Habitat quality was predicted using the ratio of instantaneous mortality rate to instantaneous growth rate. Model predictions of habitat quality were compared to field estimates of habitat quality derived from the spatially-detailed field data. Three sets of one-day simulations were performed to estimate larval growth and mortality rates throughout Chesapeake Bay during June and during July 1993. Field-based simulations used field data to estimate the model inputs of water temperature, zooplankton densities, and the densities and sizes of bay anchovy larvae and gelatinous predators (Mnemiopsis leidyi and Chrysaora quinquecirrha). Standardized larvae simulations used the same field data, but standardized larval sizes and densities throughout the Bay. A third set of simulations was performed to determine the relative importance of six factors in determining the bay-wide spatial variation in predicted growth and mortality rates. Model predictions from the field-based simulations produced spatial patterns of habitat quality in the Bay that sometimes conflicted with the otolith-based predictions of Rilling and Houde. Field estimates of anchovy egg and larvae abundances were generally high in regions predicted to have low M/G ratios, but low in regions with low otolith-estimated M/G ratios. The standardized larvae simulations generally supported the conclusions of the field-based simulations. The effect of habitat quality on larval production was evaluated using the predicted mortality rates from the two sets of simulations. Initial larval abundances dominated the percent of survivors projected 20-days into the future that a region would produce, but when larvae were standardized across the bay, differences in habitat quality among regions was important in determining the relative contributions of survivors by region. Initial larval length and zooplankton densities were the most important factors determining the spatial variation in growth rate, while predator density was most important for mortality rate. Future research should focus on field and laboratory data collection to resolve the discrepancy between model-predicted and otolith-estimated M/G ratios.

Date

2003

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Kenneth A. Rose

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