News Release

Sex, flounder and donuts

Sea Grant News & Notes February 4, 2003

Peer-Reviewed Publication

National Sea Grant College Program


Sex, Warm Water and Southern Flounder May Mean New Aquaculture Operations
A four-man flounder Sea Grant researcher team at North Carolina State University is turning up the heat on Southern flounder to produce all-female cultured stocks. The controlled-breeding method relies on water temperature manipulation to control sex during the flounder's early development - not on genetic engineering. From a pure scientific perspective, their finding is important because most temperature-dependent sex determination has been documented in reptiles such as turtles and alligators, but the finding may have significant economic impact.

Russell Borski, a zoology professor and one of the research team members, notes that the production of all-female stocks will push the Southern flounder up a notch as a candidate for aquaculture in the United States. Studies show that female flounder grow two to three times larger than male flounder within two years. Given high consumer demand and world-market value, the ability to produce larger flounder in a short period of time could mean handsome investment returns. Clustered in the zoology department in the NC State College of Agriculture and Life Sciences, the team, along with Borski, includes fellow faculty members Harry Daniels and John Godwin and Adam Luckenbach, a doctoral student.

"Aquaculture can be a lucrative alternative to tobacco farming," says Daniels, who eyes tobacco greenhouses as potential settings for growing Southern flounder in recirculating systems. Not suited for outdoor pond culture, Southern flounder do better in the warm, protected greenhouse environment. There are no Southern flounder-farming operations that rear fish from egg to market-size anywhere in the U.S. Japan leads the way in technology for producing farm-reared flounder. They are rewarded with a market price that more than doubles that of hybrid striped bass, tilapia or trout.

"This research brings us one step closer to realizing profitable, large-scale aquaculture operations for Southern flounder," says Ronald G. Hodson, director of North Carolina Sea Grant, which has provided ongoing funding for the research.

Such operations also may hold economic potential for traditional commercial fishing. Reports of dwindling Southern flounder stocks by both national and state marine fisheries groups have resulted in more regulations - and less profit for commercial fishing fleets. In Japan, natural fisheries get a boost from the annual release of hatchery-reared juveniles. The use of farm-reared fish for stock enhancement is not on the policy agenda here. Should it become an option, then the NC State team's methods could be key to determining the optimal water temperature to produce fingerling populations with 50:50 female:male sex ratios for restocking efforts, says Godwin.

CONTACT: Russell Borski, North Carolina Sea Grant Researcher, Associate Professor of Zoology, North Carolina State University, Phone: 919-515-8105; Email: Note to editors: Photos are available upon request. Contact Pam Smith, North Carolina Sea Grant at, or 919-515-9098. For addition information, go online to:

Lake Superior's Deep-Water Donut Mystery
"It's as if someone pressed giant donuts into the soft sediment on the floor of Lake Superior, then took the donuts away," says Minnesota Sea Grant researcher Nigel Wattrus, associate professor of geological sciences at the University of Minnesota's Large Lakes Observatory. "All that remains are huge ring-shaped impressions and unanswered questions."

Measuring up to nearly 1000-feet in diameter and up to 16 feet deep, the rings are found in soft fine-grained clay found in the deepest parts of the lake, and are believed to be less than 10,000 years old. This clay is known to exhibit dramatic changes in volume and may be tied to the origins of petroleum and of life itself. What is undetermined is how they were formed. Wattrus, working with Joe Cartwright, a professor at the University of Cardiff in Wales who studies distinctive honeycomb-like Polygonal Fault Systems (PFS) around the world's ocean floors has been using high-resolution seismic data to examine the structure of the sediments below Lake Superior's rings, thinking that these rings could be immature PFS. "We think the rings are the surface expression of this developing fault system," says Wattrus.

Wattrus and Cartwright believe that the mechanism responsible for these unique deep-water features involves "syneresis." This is the same process that creates curds and whey in cheese production, and the polygonal-shaped cracks in dried mud. Wattrus and his colleagues conclude that the water squeezed out by syneresis through a more compact crust may be the trigger that formed the rings. Geologic conditions associated with retreating glaciers and processes like syneresis caused the lower sediment layer to become mobile and the overlying sediments to collapse.

Wattrus hopes that by studying the immature Lake Superior's deep-water donut rings the scientists will be able to shed light on what triggers volumetric contraction in sediments and more about the processes that shape our planet. But for now, the rings remain a testament to unanswered questions and one of Lake Superior's deepest mysteries.

CONTACT: Nigel Wattrus, Minnesota Sea Grant Researcher, Associate Professor, Geological Sciences, University of Minnesota, Phone: 218-726-7154; E-mail:

University of Delaware Professor, and Delaware Sea Grant researcher Nancy Targett has been named a National Associate of the National Academy of Science, a lifetime appointment made in recognition of her service on the Ocean Studies Board. Targett has been researching ways to develop an artificial bait to replace the use of horseshoe crabs by fishermen.

Brian Allee will take over as director of the Alaska Sea Grant College Program. Allee returns to Alaska from Portland, Oregon, where he has served the Northwest Power Planning Council as Manager of Policy and Program Implementation, Fish and Wildlife Division. Allee has served in an advisory capacity for three Sea Grant programs, Washington, Oregon, and Alaska.

Robert Stickney, Texas Sea Grant Director has been elected as President of the Sea Grant Association, which assists in coordinating the activities of the 30-state Sea Grant programs, including assistance in setting program priorities at both the regional and national level, and in providing a unified voice for these institutions on issues of importance to the oceans and coasts.


Survival in Cold Water: Hypothermia Prevention
Hypothermia is a risk for anyone who enjoys activities like boating, fishing, swimming, hiking, or skiing. It can occur quickly and it can be fatal. Learn how to be safe from this threat by visiting this Minnesota Sea Grant site.


The Role of Marine Protected Areas in Fisheries Management
February 27, 2003, Samoset Resort, Rockport, Maine
Event Web Site:
This all-day session is part of the annual Maine Fishermen's Forum. The program will include; an overview of MPAs, a discussion of the scientific evidence related to the efficacy of MPAs as a tool in fisheries manageament, presentations on the successes and failures in the processes of implementing MPAs around the country in recent years and facilitated discussion of how we might develop an inclusive process for moving towards a system of MPAs in the Gulf of Maine based on consensus. Sponsored by The Maine Fishermen's Forum and Maine Sea Grant

CONTACT: Paul Anderson, Maine Sea Grant, 207-581-1435,

Sea Grant is a nationwide network of 30 university-based programs that works with coastal communities and is supported by NOAA. Sea Grant research and outreach programs promote better understanding, conservation, and use of America's coastal resources. For more information about Sea Grant visit the Sea Grant Media Center Website at: , which includes on-line keyword searchable database of academic experts in over 30 topical areas.


Sea Grant Research News:
Sex, Warm Water and Southern Flounder May Mean New Aquaculture Operations
Lake Superior's Deep-Water Donut Mystery

Sea Grant Web Spotlight:
Survival in Cold Water: Hypothermia Prevention

Sea Grant Calendar Spotlight:
The Role of Marine Protected Areas in Fisheries Management
February 27, 2003, Samoset Resort, Rockport, Maine

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