Date Awarded

2014

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Virginia Institute of Marine Science

Advisor

Robert J. Latour

Abstract

Management of fisheries resources is increasingly broadening its scope from single-species approaches to more holistic, ecosystem-based approaches that account for interactions of fish with a variety of ecological factors, such as predators, prey, and habitat. This ecosystem based fisheries management (EBFM) approach requires thorough biological and ecological understanding of systems pertaining to community structure, habitat suitability, and food web interactions. to strengthen the ecological underpinnings of EBFM efforts in Chesapeake Bay, the largest estuary in the USA, I conducted synoptic analyses examining the structure, function, and patterns of the bay's demersal fish community. This research relied on I0 years of data from a multi-species, bimonthly bottom trawl survey of the Chesapeake Bay mainstem. The unifying objectives of this work were to 1) synthesize basic biological and ecological information of many Chesapeake Bay fishes, and 2) examine the environmental drivers of community structure and trophic interactions in the Bay. One major hypothesis underlying the more detailed research objectives for each component was that bay-wide patterns in biomass and feeding habits of Chesapeake Bay fishes were mostly driven through bottom-up processes governed by a blend of small- and large-scale environmental factors. as food web structure and trophic interactions are governed by the presence, distribution, abundance, and behavior of species, Chapter 1 focused on evaluating patterns for these basic biological characteristics for a large suite of 50 species and investigating environmental factors that influence the community trends. Univariate and multivariate statistical modeling revealed that the demersal fish community (dominated by five species) was strongly structured along a salinity gradient, and other factors (e.g. dissolved oxygen, temperature, month, and year) helped regulate biomass and diversity trends. Chapter 2 synthesized diet information for 47 fish species, demonstrated the role of five prey groups (mysids, fishes, bivalves, polychaete worms, and crustaceans) in differentiating feeding guilds, and highlighted the importance of non-pelagic prey groups (especially the hyper-benthic mysids) in supporting the nutritional needs of fishes. Diets of 12 predator species were investigated in more detail in Chapter 3 to infer the dynamics of four important prey groups (mysids, bay anchovy, polychaetes, and bivalves) using advanced statistical modeling techniques. Results revealed generally coherent consumption trends across predators for a given prey, suggestive of prey availability driving consumptive patterns. Synchronous annual peaks in prey consumption were indicative of pulses in prey production (particularly mysids and bivalves) that were exploited by predator populations. to evaluate the population-scale effects of these bottom-up alterations in prey productivity, Chapter 4 relied on a simulation model to examine the potential effects that these annual changes in prey availability could have on consumption and production of one representative predator species. The model indicated that enhanced individual growth resulting from pulses in prey production could generate substantial gains in predator spawning stock biomass, recruitment, and fishery yield. However, the bottom-up effects on predator production had only modest effects on rebuilding times of a depleted population relative to controls on fishing mortality. This research represents one of the largest studies on community structure and trophic interactions for demersal fishes in an estuarine environment, contributing to a broader understanding of fish ecology within a complex and dynamic system. By filling research gaps identified for EBFM in Chesapeake Bay, this body of work also supports a more holistic management approach for the sustainable use of resources from the Chesapeake Bay and coastal waters of the Northwest Atlantic Ocean.

DOI

https://dx.doi.org/doi:10.25773/v5-8fhg-xq05

Rights

© The Author

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