Scientists to study bay as ecosystem

Va. institute gets $629,000 to develop model of food web


GLOUCESTER POINT, Va. - Scientists at the Virginia Institute of Marine Science will soon launch a three-year project to develop a model for multi-species management of sustainable fisheries within the Chesapeake Bay.

Bay fisheries traditionally have been managed on a species-by-species basis, with management plans that do not take into account factors such as the abundance of competitors, predators and forage species.

With a $629,000 grant from the Virginia Environmental Endowment, scientists at the Virginia Institute of Marine Science will try a new approach that will consider the entire ecosystem and be based on the development of a food web model for the lower Chesapeake Bay.

Scientists know that populations of commercially important fish are greatly affected by the abundance of their prey, their predators and their competitors. These relationships change over the life history of a species, and can be greatly influenced by the environment.

Fishing, as well as environmental fluctuations, can seriously alter community structure, affecting the abundance of predator and prey species.

Managing the ecosystem

"The delineation and understanding of such interactions are critical to the sustainable management of the lower bay ecosystem," said Dr. John Graves, head of the Department of Fisheries Science at VIMS. "The award from the Virginia Environmental Endowment provides us with a unique opportunity to develop a model that will allow fishery managers to forecast the impacts of various actions on the ecosystem as a whole."

This work will build on VIMS' Juvenile Trawl Survey, a 46-year series monitoring the abundance of juvenile fishes in Chesapeake Bay and tributaries and some environmental conditions.

The project will be coordinated with researchers at other institutions on the bay who are also working on various aspects of the food web within Chesapeake Bay.

Rockfish questions

The data will be used to develop a more comprehensive model for fishery managers, allowing them to predict the outcome of various management scenarios. For example, striped bass populations are up. What impact do elevated levels of striped bass have on their prey species such as bay anchovy, blue crab, and menhaden? How do these impacts affect other species such as bluefish, red drum, and weakfish that also feed on bay anchovy, blue crab and menhaden?

Scientists feel that some of the data necessary to understand these kinds of food-web interactions are not known. As the model is developed, the needs for further food web research will be highlighted.

"Building a dynamic model will force us to take inventory, to see where information is needed to develop predictive capabilities," explained Dr. Richard Wetzel, head of the Department of Biological Sciences at VIMS and co-director of the project.

The grant from the Virginia Environmental Endowment will also permit researchers at VIMS to update the Status of Stocks and Species Information document they developed in 1995.

The original document, which included a synopsis of information on important recreational fishes of Chesapeake Bay, will be revised and expanded to include data on the feeding habits and relationships of many important forage species, as well several non-resident species in the lower Chesapeake Bay.

Gerald P. McCarthy, executive director of the Virginia Environmental Endowment, said, "This work will enable scientists to develop the knowledge and applications needed by managers to make decisions based on a complex and far more complete suite of information."

The goal of the work is to develop an ecosystem based fisheries management plan with models that will provide better tools to forecast the impact of a management act or environmental event.

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