Biology Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2749
Browse
Search Results
Item Dynamics of ingress, hatch dates, growth, and feeding of Atlantic menhaden, Brevoortia tyrannus, larvae at the Chesapeake Bay mouth(2011) Lozano, Carlos; Houde, Edward D; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Recruitment of Atlantic menhaden to Chesapeake Bay declined in the late 1980s. Although reasons are not understood, a decline in larval supply to the Bay is one hypothesized explanation. The objective of this thesis was to evaluate levels and variability in larval ingress by conducting 18 ichthyoplankton cruises at the Bay mouth during three years at monthly intervals from fall through spring (2005-06, 2006-07, and 2007-08). The concentrations of ingressing larvae were estimated for each year and also for months within each year. Larval spatial and temporal distributions at the Bay mouth were evaluated with respect to tides and day-night differences. Age, growth rates and hatch dates were determined from otolith-aged larvae and compared among years and months. Larvae were most abundant in 2007-08, but grew fastest in 2006-07. Most ingressing larvae hatched in the November to December period. Copepods were the dominant prey in diets of larval menhaden.Item Assessment of Populations with Spatially Explicit Dynamics and the Consequences for Marine Protected Areas(2011) Barkman, Jennifer Shari; Wilberg, Michael; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Spatial processes can have important consequences in the population dynamics of fishes and marine invertebrates. Therefore fisheries management should consider space in the techniques used to understand population dynamics. The purpose of this thesis was to investigate spatial dynamics of fish populations in Maryland's coastal bays (Chapter 2) and evaluate effects of spatial management (in the form of marine protected areas (MPAs)) on accuracy of abundance estimates (Chapter 3). In Chapter 2, I examined trawl survey data from Maryland's coastal bays to estimate trends in relative abundance of four commonly caught fish species using a generalized linear model that allowed region specific estimates. Species showed different responses in the two regions, but trends over time were not related to local habitat variables. In chapter 3, I examined the effects of an MPA on the accuracy and bias of estimates from spatially aggregate and explicit surplus production models (SPMs) using a simulation experiment. I found that spatially-explicit SPMs produced more accurate estimates of biomass than spatially-aggregate SPMs, and that larger MPAs produced more accurate estimates than smaller MPAs.