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Walleye fishery threatened; Puerto Rico aquaculture, calling ALVIN on ocean bottom

News from NOAA's National Sea Grant Program

National Sea Grant College Program

Some male fish that dwell in Minnesota waters are developing female characteristics, according to a study by Sea Grant researchers. Smaller sex organs, female proteins and sterility were some of the characteristics found among populations of walleye, fathead minnow and carp. The mix-up is caused when chemicals get into waterways and then interferes with the fishes' development and reproductive systems. The chemicals, known as environmental estrogens, act the same as natural estrogen, a female hormone. Trace amounts of the chemicals are enough to change the male fish. If too many fish lose their male traits, a drop in the fish population could lead to major ecological problems and impact the economically important recreational walleye fishing industry.

University of Minnesota Sea Grant researcher Deb Swackhamer and her team are studying two Minnesota waterways (Duluth-Superior Harbor and the Mississippi River near St. Paul) to learn more about the source of the environmental estrogens, as well as their effects on fish. Considered endocrine disruptors, the chemicals can reach the environment through sewage systems, paper mills, feed lots or industrial waste. Environmental estrogens can come from the natural hormone estrogen (found in animals, including humans), or from synthetic hormones like those found in birth control pills and industrial products such as detergents, packaging plastics and insecticides.

Many questions still remain. So far, researchers have been unable to pinpoint a specific chemical as the cause of the sexual changes. The team has found that some wild male walleye taken from waters near a sewage outflow of the Mississippi River had high levels of the female egg protein vitellogenin, decreased gonad size and no sperm. But laboratory goldfish exposed to the same water experienced much lesser effects. "Even these subtle effects may have an impact on wild fish," says Swackhamer, "where reproductive opportunities are limited and competition is severe." Further study of fish in Duluth, and eventually the entire Great Lakes, should give her team a better idea of what causes the fish to develop female characteristics.
CONTACT: Deb Swackhamer, Minnesota Sea Grant Researcher and University of Minnesota Professor, School of Public Health 612-626-0435, Email:

Off the Puerto Rican Island of Culebra, researchers are testing new aquaculture technology that could reduce the environmental impact of such fish farming operations. By using offshore aquaculture cages, Snapperfarm, Inc, and Dr. Daniel Benetti, Director of the Aquaculture Program at the Rosenstiel School of Marine and Atmospheric Science, at the University of Miami, hope to grow fish in offshore waters with minimal environmental impact. A group of Puerto Rico Sea Grant scientists will conduct a study to monitor the environmental impact of this innovative technology as well as its social impact.

Two cages were stocked in August, one with 12,000 cobia (the first time this has ever been done for this species) and the other with 4,000 mutton snapper. So far the fish are doing well-- they grew to three times their original size in just two weeks.

Currently, only five percent of Puerto Rico's seafood supply comes from aquaculture fisheries. Inshore aquaculture projects are subject to domestic and industrial runoff, and its own wastes can impact the local environment. Offshore, limited technology previously prevented deployments from being harmed by ocean elements. The new cage technology, developed by Ocean Spar, can resist the elements and is cleaner for the environment. In addition to monitoring the caged fish and their development, future studies will include environmental monitoring and determining the cage's social impact on the area. If successful, the aquaculture project should pave the way for clean, economical fisheries operations in the Caribbean.
CONTACT: Alexis Cabarcas, Puerto Rico Sea Grant, University of Puerto Rico Marine Sciences Department, Email:; 787-832-4040 ext. 5491
Dallas Alston, Puerto Rico Sea Grant, University of Puerto Rico Marine Sciences Department, Email:; 787-832-4040 ext. 5491.

Sea Grant Web Spotlight: "Extreme 2002: Mission to the Abyss"
Beginning October 21 nearly 42,000 middle and high school students in 525 schools in 49 states and five foreign countries will begin a virtual journey to the depths of the Pacific Ocean through Delaware Sea Grant's "Mission to the Abyss" education program. Students and teachers will follow the action as University of Delaware scientist Craig Cary explores hydrothermal vents in the Pacific Ocean. Cary and his team will study the vents and the creatures that inhabit them, including the Pompeii worm, the "hottest" animals on the planet, as it can withstand temperatures of up to 176 degrees F. Scientists will use the submersible ALVIN and research vessel ATLANTIS to perform their work. As part of the National Science Foundation research, Delaware Sea Grant is helping to sponsor classroom materials that will allow students and teachers to participate in the action. While the research team explores, students can tune in to an interactive website that will be updated daily throughout the 24-day voyage. More than 450 schools from across the U.S. and several other countries will use the provided resource guides, curricula and video about the deep sea to guide them through Cary's expedition. A select group of 48 classrooms will have the opportunity to participate in one of four live conference calls, over the next month, with the scientists as they conduct research in ALVIN on the seafloor.
CONTACT: Tracey Bryant, University of Delaware Sea Grant, Marine Public Education Office, 302-831-8185, Email:; Craig Cary, Delaware Sea Grant Researcher, Associate Professor of Marine Biology-Biochemistry, University of Delaware, Email:

Sea Grant Calendar Spotlight: 2nd International Seafood Byproduct Conference, Nov. 10-13, 2002, Anchorage, Alaska
The Alaska seafood industry harvests over 60% of the food fish caught in United States waters. The amount of fish processing wastes generated from human food processing wastes generates in excess of 1.1 million metric tons annually. Since the first such gathering in 1990 a wide range of new advances in medical sciences, and the development of new secondary products for human, animal, and industrial uses from seafood processing byproducts have been developed. This conference looks at issues of fish byproduct utilization and environmentally sound fish waste disposal.
Contact: Donald Kramer, Alaska Sea Grant Marine Advisory Program, 907-274-9691 ext. 5, Email: ; Website:


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.

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