Timothy Targett, professor of marine biology–biochemistry at the University of Delaware College of Marine Studies, and Dominic Di Toro, Edward C. Davis Professor of Civil and Environmental Engineering at the University, have received a $548,273 grant from the National Oceanic and Atmospheric Administration (NOAA). The three-year grant will support their research to determine the impact of fluctuating water quality on fish that use estuaries and coastal bays as nursery grounds during their first few months of life.
Part of the work will be conducted in two of Delaware’s Inland Bays — Rehoboth and Indian River. During the summer months, these sheltered bays provide valuable nursery habitat for key recreational and commercial fisheries including summer flounder and weakfish. Yet significant reductions in dissolved oxygen levels often occur daily during summer in the tidal tributaries used by young fish as nursery grounds.
According to Targett, scientists do not understand why juvenile fish use these waters in such high abundance when low dissolved oxygen can adversely affect their growth and survival. In addition, fish have the ability to swim to other areas where the water quality is better.
“We don’t know why the fish are even in some of these areas,” says Targett. “Is there such a great source of food that they just go in, stay as long as possible, grab some food, and then make a run for it?”
To answer this question, Targett and Di Toro will use a unique modeling approach that combines the results of two different models. One model will predict how the water quality changes over space and time. This water-quality model will be constructed using detailed measurements of salinity, temperature, and levels of dissolved oxygen in the water.
The second model will predict the growth, behavior, and survival of an individual fish to changes in these parameters. This individual-based model was developed in previous laboratory and field experiments done by Targett. It will be validated in the current study by directly tracking fish movement with acoustic tags in Pepper Creek, a tributary of Indian River Bay.
By coupling the two models together, the scientists can predict the behavior of juvenile fish to the water quality at a specific location throughout the summer months — something that has never been done before. Damian Brady, a doctoral candidate in marine biology–biochemistry, will assist Targett and Di Toro in the research.
The field study in Pepper Creek also will look at the effect of dissolved oxygen on the benthic community as well as the effect that the prey abundance (amount of food) has on the response of fish. The benthic community consists of crabs, worms, and other marine organisms that live in and on the bottom sediments and provide juvenile fish with food.
This portion of the study will be led by Robert Diaz, professor of marine science at the Virginia Institute of Marine Science (VIMS) in Gloucester Point. VIMS received an additional $135,314 in grant money, bringing the total award to $683,587. Danielle Tuzzolino, a master’s student in marine biology–biochemistry will assist Targett and Diaz in completing this work.
“It is truly an integrated and cooperative approach that links marine biology with engineering,” says Targett. “None of us could do this project by ourselves. In particular, Damian has been very instrumental in bridging this gap by taking modeling courses from Dominic in addition to his courses in marine sciences.”
Targett says the research is designed to provide fisheries managers with a tool that predicts the impact of changing water quality on the growth and survival of juvenile weakfish and summer flounder. In addition, the modeling approach is not site specific, but can be applied to many other coastal ecosystems.
Specifically, the research will address how various scenarios, which affect water quality, influence the behavior of juvenile fish. This information will enable fisheries managers to minimize the adverse effects that a project might have on the marine environment. For example, the model can help determine how altering nutrient input or tidal flushing in an area would impact the fish living in that environment.
“The results will help management officials spend money where it is needed the most,” says Di Toro. “It can cost a lot of money to improve the water quality once it has been degraded, and you don’t want to spend money to correct something that isn’t really a problem to begin with.”
A member of UD’s faculty since 1986, Targett was appointed to the Atlantic States Marine Fisheries Commission as the governor’s appointee representing Delaware in 1987. The commission coordinates the conservation and management of near-shore fishery resources among the 15 Atlantic coastal states. He has published 45 technical papers on fish ecology.
Di Toro joined UD’s faculty in January 2003 after serving on the faculty at Manhattan College for more than 30 years. This past year, Di Toro was elected to the National Academy of Engineering, an honor he shares with fewer than 2,200 engineers nationwide. In electing him, the academy cited his “leadership in the development and application of mathematical models for establishing water-quality criteria and making management decisions.”