Sea Grant Aquatic Nuisance Species Research Program    

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Risks of survival and establishment of tropical introduced bait species--A case study of the nuclear worm, Namalycastis sp.

Principal Investigators: Douglas Miller, University of Delaware Graduate College of Marine Studies, Lewes, Delaware and John W. Ewart, University of Delaware Sea Grant Marine Advisory Service, Lewes, Delaware

Project Period: June 1, 2003 to May 31, 2005

Nuclear worms are large, pink, semi-aquatic polychaetes imported from Vietnam and sold as fish bait. Import and sale of this species is unregulated and has received much media attention recently focused on the worms¡¦ vivid coloration, unusual size (up to 2 m long), and the potential exposure of fisherman to pathogens associated with packing material.

"While many believe the nuclear worm poses little environmental risk to temperate coastlines, this assertion is lacking any rigorous scientific basis, and certainly is not a valid extrapolation to warmer, subtropical regions of the U.S. coast," says Doug Miller, an oceanographer at the UD College of Marine Studies.

In this study funded by the National Sea Grant Aquatic Nuisance Species Program, Miller and John Ewart, aquaculture/fisheries specialist for the UD Sea Grant Marine Advisory Service, will conduct laboratory experiments to evaluate the risk of survival and establishment of nuclear worms in Mid-Atlantic waters and particularly in states farther south where warmer subtropical climates are found. Temperature and salinity experiments will be conducted in the first year. In the second year, the scientists will conduct aquarium experiments at optimal temperature and salinity to identify species of freshwater and estuarine invertebrates consumed as prey, the worm¡¦s ability to regenerate when cut for bait, and their reproductive seasonality and success (if any) in the lab. Coastline regions at risk for nuclear-worm establishment (i.e., with tolerable temperature regimes) will be identified using electronically available temperature data. This approach also will be assessed for application to other tropical imported and invasive species.

The scientists will share their research findings with the public through Web pages, a fact sheet, and lectures. The project should benefit a range of audiences, from federal agencies, state resource managers, and invasive species working groups, to bait shop owners and local fishermen.


Temperature and Salinity Tolerance of Vietnamese Bait Worms, Namalycastis Sp.: Implications for Establishment of a Tropical Import in the Southeastern USA
Miller, D. C.1, R. K. Dale1, J. R. Brown1 and P. D. Huggins2. 1Graduate College of Marine Studies, University of Delaware, Lewes, DE 19958; 2Fairmont State College, Fairmont, WV 26554.

Presented at the The 33rd Annual Marine Benthic Ecology Meeting, Mobile, Alabama, March 25-28, 2004

Large rag worms (Family Nereididae) of an undescribed species of the genus Namalycastis are imported from Vietnam and sold as fishing bait in the mid-Atlantic region of the USA. To determine where this tropical species could potentially become established, we investigated the temperature and salinity tolerances for comparison with coastal environmental data. Worms were maintained for several months in mud and plant detritus collected from mid-Atlantic salt marshes. Short-term laboratory experiments show that worms, while sluggish, survive temperatures as low as 13oC for 5 days and die quickly near 10oC. This lower limit is 7-10oC below that previously estimated for this species. Worms display a broad tolerance to salinity, surviving well from 1 to over 30 parts per thousannd (ppt) when kept at 29oC. We have observed worms to fragment spontaneously under some conditions as well as the apparent regeneration of tail ends of some individuals. We conclude that temperature represents a strong determinant of their possible range. Moreover, these data greatly increase the potential range of this species along vegetated coastlines of the southeast USA.


Vietnamese Baitworms: Great Bait or Invasive Introduction? (PowerPoint poster)


Vietnamese Baitworms: Great Bait or Invasive Introduction? (Fact Sheet)


Vietnamese Baitworms:Video Clip 1; Video Clip 2

Download Real Player     


Photos  (click on photo to enlarge)




Aquatic Nuisance Species Task Force - An intergovernmental organization dedicated to preventing and controlling aquatic nuisance species. Co-chaired by the US Fish and Wildlife Service and National Oceanic and Atmospheric Administration - the gateway to Federal efforts concerning invasive species


Sea Grant Aquatic Nuisance Species Research Program: Southeast Regional Strategic Outreach Network

Sea Grant Aquatic Nuisance Species Research and Outreach Program: Initiation of an Aquatic Nuisance Species Cooperative Education and Outreach Network in the Mid-Atlantic Region

Smithsonian Environmental Research Center MARINE INVASIONS RESEARCH LAB   PO Box 28, Edgewater, Maryland 21037 - a national and international center for research on biological invasions in coastal marine ecosystems

Forget About the Snakehead Fish, Here Comes the Nuclear Worm

Exotic new bait worms import worries - by Molly Murray, Gannett News Service

Many unwittingly helping the spread of invasive species - Bay Journal The Chesapeake bay Newspaper. Vol 12 - Number 6, September 2002


Last Updated: 14 April 2005
Please direct all questions, comments or reports of broken links to John W. Ewart