 |
|
 |
 |
 |
 |
Beth Phelan and John Manderson are using ultrasound to track the movement of fish in a small river in New Jersey. Employing a technology similar to the EZ Pass tollbooth systems on highways, the NEFSC scientists are monitoring the peregrinations of bluefish, striped bass, and weakfish in the Navesink River.“We’re trying to understand how physical variables in an estuary – things such as temperature and salinity and turbidity – affect the movement of animals in and out of the estuary,” said Phelan, a biologist in the Behavioral Ecology Branch at the James J. Howard Laboratory in Sandy Hook, NJ. Specifically, Drs. Phelan and Manderson are trying to determine what parts of the Navesink River bluefish, striped bass, and weakfish use for feeding, and why they use different parts of the river at different times of day and in different seasons. The research began in early May when the Howard Lab ecologists worked with NOAA scuba divers to plant two dozen listening devices up and down the river. The receivers are attached to orange buoys and anchored in at least three feet of water.The next step is to catch fish and insert acoustic tags about half the size of a triple-A battery – an operation that is now underway.“You make a small cut in the abdominal cavity, insert the tag, and close the wound with a couple of stitches,” Phelan said. “It takes less than five minutes when you get good at it.”
The fish are also marked with external identification tags and then released. For the rest of the summer, the acoustic tags will emit signals every 40-90 seconds. The receivers scattered through the river will gather and store the signals, data that will eventually enable the scientists to track the movement of individual fish up and down the river. The Howard Lab group plans to tag approximately 30-40 adult striped bass, weakfish and bluefish in May and June, and a similar number of young-of-the-year bluefish in August and September (“young-of-the-year” fish are less than one year old). All three species in the study are important to both recreational and commercial fishermen.“We will be in the field at least once a week, and usually more often,” Phelan said. In addition to tagging fish and downloading data from the receivers, the researchers will be working in the river to gather information about physical conditions of the water and about the smaller fish that serve as prey for bluefish and striped bass. Instruments attached to some of the listening stations will constantly be gathering data on water temperature, salinity, dissolved oxygen, current and speed, tidal height and turbidity. The scientists will use nets to survey prey species such as anchovies and silversides. In a joint venture with scientists from Rutgers University, the NEFSC team will use hydroacoustic “fish finders” to locate schools of prey.
The research team asks that anyone who catches a bluefish, striped bass, or weakfish with an external tag call the telephone number on the tag to report where and when they caught the fish, and how large it was. If an angler keeps one of the tagged fish, the biologists would appreciate having the internal tag returned so they can re-use it. |
||||
In that 2005 study, a team led by Dr. Mary Fabrizio used acoustics to determine how many months sea bass and summer flounder spend at the site where contaminated sludge from New York Harbor was dumped until the 1990s. Farther up the coast, the NEFSC Atlantic salmon team began using the technology in 1997 to track the movement of endangered Atlantic salmon headed downstream to the ocean. The salmon group began by tagging smolts in the Narraguagus River, and has gone on to monitor salmon migration in four Maine rivers and in the estuaries and bays where those salmon encounter salt water and begin their journey to the coast of Greenland. Tagging as many as 300 fish and placing up to 100 receivers per year, the salmon group has gathered data on fish movement that is helping them understand how long it takes smolts to migrate downstream, their preferred passage-ways, and where some of the fish are eaten by predators or otherwise lost to the population.  When
the salmon group began its acoustics work nine years ago, few researchers
were using the technology. Today, the technology is increasingly
popular with government and academic researchers in Canada and
the U.S. – including one group hoping to tag sturgeon and
another that wants to tag lampreys. With the receivers in one project
able to pick up signals from tagged fish in other projects, fishery
scientists are increasingly apt to find unfamiliar signals on their
receivers. Each tag has its own unique signal, according to the NEFSC’s salmon team member Jim Hawkes, so a research group should know when their receiver picks up a signal from someone else’s study. “”We need to keep open lines of communication with other groups using the technology, to create synergy and stem confusion” Hawkes said. |
||||
Posted June 13, 2006 |
by 
By
combining data on river conditions, prey movement, and movement of
tagged fish, the biologists hope to piece together a detailed understanding
of how and why fish use different parts of the river. The team chose
the Navesink as a model system in part because scientists from the
Howard Lab and others have done a number of previous studies in the
little river, and there is already a good base of knowledge about the
system.“Everything
we learn here about how fish use habitat can be applied to other estuaries
with similar physical properties,” Phelan said.
Home | News | Features | Checker | Site Map | Story Tips | About Us | NEFSC
|
www.nefsc.noaa.gov |
Search |
Link Disclaimer |
webMASTER |
Privacy Policy |
(Modified Feb. 16 2007) |