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Cynthia Jones displays the Virginia Scientist of the Year award in her office at the Center for Quantitative Fisheries Ecology at Virginia’s Old Dominion University.

Pushing the lower limits in fisheries population dynamics research

By Pauli J. Hayes

A small sign in the labs at the Center for Quantitative Fisheries Ecology (CQFE) at Virginia’s Old Dominion University says it all: Sometimes you get bloody on the cutting edge of science.

Cynthia Jones, director of the Center and professor of biological sciences at ODU, is no stranger to science’s cutting edge. It hasn’t always been an easy road, but her internationally known work in fisheries ecology recently earned her top honors as one of two scientists who received the Virginia Scientist of the Year award from the Virginia Science Museum. She is the second woman ever to receive the award in its nearly 20-year history. She also was recently appointed to the Virginia Marine Resources Commission and is the first fisheries scientist to serve the agency in its 125-year history.

These accolades serve as an example she hopes to set for women and under-represented minority students in fisheries science. A broad-based, interdisciplinary background "has certainly allowed me, and women in science in general, to bring an unorthodox viewpoint to the field," she said.

Advocating a similar approach for her students, she heads up a program to introduce under-represented students to a broad spectrum of ocean sciences. "Knowledge of habitats, math, modeling and statistics – and the ability to understand the connections – is required for successful researchers," she said.

Juvenile and adult fish will be sampled monthly on seagrass beds in Chesapeake Bay and as far south as Florida. (After otoliths and scales are removed, freshly-caught adult fish are donated to food charities.)

Her own pioneering research spans more than two decades of studying the otoliths (earbones) of fish to track their growth and survival in various habitats during vulnerable early life stages. Most recently, she and her colleagues are using the chemistry of otoliths to track the fish’s use of different habitat throughout its life. She has also extensively studied the role of seagrass beds in the survival of the popular sportfish, the spotted sea trout. Seagrasses are an indicator of water quality in the Bay, and because spotted seatrout populations fluctuate within habitats, they also indicate water and habitat quality.

These findings clearly have important implications in helping fisheries managers determine what habitats are essential to protect key fish species in Chesapeake Bay and beyond. But defining essential habitat has until recently eluded researchers and managers.

Sectioning otoliths to reveal rings: Graphic copyright: Bob Jones, Old Dominion University

Fish-life history information is not available for many species, even some most commonly harvested. This knowledge void resulted in overly broad classification of fish habitat in which most of the coastal waters and continental shelf are "essential". "When essential habitat is ubiquitous, the concept loses its impact and ability to motivate conservation," said Jones.

Adding to the problem was the fact that traditional methods of physically tagging fish to provide habitat data were labor-intensive and deadly to young fish, many of which could not survive handling. Clearly, fisheries scientists needed methods that clarify which habitats are, in fact, essential.

Building on a wealth of foundational research by other scientists, Jones confirmed that a fish’s age can be determined from its ear bones, which have daily and annual rings much like those of trees. In addition to this registry of age, the otolith also contains a natural tag in the chemistry of its otoliths. This natural tag, formed through concentric additions of mineralized tissue around a nucleus, creates daily and permanent patterns of habitat use in almost all fish during the larval and early juvenile stages of life.

The German-engineered ICP-MS is something of a celebrity itself. Housed in ODU’s chemistry department where it benefits numerous departments, the machine is used extensively by regional scientists as well as by international researchers.

This discovery led to a chemical-analysis technique that can show where a particular fish was hatched and where it migrated in subsequent life stages – information that can help define what environmental changes a species can tolerate and what habitats are critical to its survival. To date, Jones and her student, Emmanis Dorval, can discern differences in seagrass beds just 10 miles apart, "pushing the lower limits in new research and getting down to very, very small sample sizes in which we can look at as little as five days of life," she said.

This study is important in determining how animals adapt to local conditions. Because habitats vary, fish survive and grow differently in them as they adapt – if, that is, animals survive to reproduce in the same area and pass on genotypes best suited for the given locale.

Spotted sea trout are a good research candidate because they tend to stay closer to home than some other species, said Jones. If the species proves to be a good model, local adaptation will be an important focus of future research in measuring the survival advantage in ‘higher quality’ habitats. "Once this approach is established for a few model species," said Jones, "it can then be applied more broadly and will increase our understanding of population dynamics of exploited fish whose habitats are being altered by human impact."

Funding for this research was provided in part from Virginia Sea Grant and the Virginia Marine Resources Commission.

Related Web Sites:

• Center for Quantitative Fisheries Ecology at Virginia’s Old Dominion University
• Cynthia Jones home page, Department of Biological Sciences, ODU
• View spotted seatrout otoliths, listen to a seatrout

[5/5/03]

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