Date Awarded

Winter 2016

Document Type

Thesis

Degree Name

Master of Science (M.Sc.)

Department

Virginia Institute of Marine Science

Advisor

Eric J Hilton

Committee Member

Mary C. Fabrizio

Committee Member

Robert J. Latour

Committee Member

Kenneth A. Moore

Committee Member

Edward D. Houde

Abstract

This thesis developed from the VIMS Larval Fish Monitoring Program, which began in 2007 as part of a study comparing the larval fish assemblages of Chesapeake and Delaware Bays. Ribeiro et al. (2015) analyzed data from the first three years of this time series to describe the temporal variation in the larval fish assemblages. After this initial study was completed (three years in duration), the sampling continued at the fixed station near the mouth of the York River, which was used to represent the Chesapeake Bay. For this thesis, therefore, eight years of data (2007-2015) were available to investigate temporal changes in the larval fish assemblage, and to better evaluate intra-annual variation of the larval fish assemblage. Further, larval fish indexes of five target species of commercial and recreational importance in the Chesapeake Bay, were examined, including Anchovy (Anchoa spp.), Atlantic Menhaden (Brevoortia tyrannus), American Eel (Anguilla rostrata), Summer Flounder (Paralichthys dentatus), and Atlantic Croaker (Micropogonias undulatus). Regression models were used to evaluate the effect of different environmental and temporal variables on the larval fish density from the York River system. Results show a stable assemblage in the York River since 2007, with marked seasonal patterns in terms of composition and abundance of larval fishes. The assemblage from May to August is formed by estuarine species with high number of larval fishes (e.g., Anchovy, Green Goby, Naked Goby); the assemblage from September to April is characterized by a lower number of species, mainly coastal spawners such as Atlantic Croaker, Summer Flounder, and Atlantic Menhaden. At the species level, slight annual variations were found, although in general abundances were stable across the time series. Because the larval fish monitoring program sampled at a single fixed station located in the lower portion of the York River system, it is limited spatially even though it has good temporal resolution (eight years). One fixed station may capture only localized patterns and it is unclear if this is comparable to the larval fish assemblage in southern portion of the Chesapeake Bay generally. The second chapter of this thesis addresses the question of spatial variation of the larval fish assemblage, principally between the York River system and the mouth of the Chesapeake Bay. Samples taken in three locations were compared to determine if the assemblage varied among the sampling locations. Larval stages of two coastal spawners, Atlantic Menhaden and Atlantic Croaker, were the two most abundant at both all locations. Results indicate species specific differences among the locations, for example, Atlantic Croaker larvae were more abundant in the York River mouth (YRM) than in the Chesapeake Bay mouth (CBM), indicating significant spatial variation in larval fish assemblage composition over a distance of approximately 40 km, the distance between the YRM and CBM. This variation should be taken into account when generalizing the structure of the larval fish assemblage of the York River spatially.

DOI

http://dx.doi.org/10.21220/M2432W

Rights

© The Author