Corps Fish Tagging Study in the HARS Could Net Valuable Data

Below the waters off the coast of New Jersey, fish are busy moving about as they unknowingly assist the U.S. Army Corps of Engineers in a complex fish tagging study that could net valuable data for the Corps and the environmental community.

For over a century, the U.S. Army Corps of Engineers, New York District, has dredged the channels within the port of New York and New Jersey to help facilitate navigation that is crucial to our economy. Dredging the port is necessary because fine-grained sediments accumulate on the bottom of the channels that can cause shoaling and interfere with safe navigation.

Historically, dredged material from the port has been disposed in the Atlantic Ocean, in and around a 2.2 square nautical mile area off the shore of New Jersey, commonly referred to as the "mud dump site" (MDS).

In 1997, the U.S. Environmental Protection Agency (EPA) terminated the use of the MDS and redesignated the site and surrounding area that was historically used to dump dredged material as the Historic Area Remediation Site (HARS). The HARS is an approximately 15.7 square nautical mile area—3.5 nautical miles east of Highlands, New Jersey, and 7.7 nautical miles south of Rockaway, New York.

Transmitter covered in beeswax is inserted into peritoneal cavity of fish through incision (made by surgeon using a scalpel).

Suturing of incision area.<br>Transmitter has been implanted.

Suturing of incision area.
Transmitter has been implanted.

Application of Vetbond, a type of super-glue used by veterinarians to ensure the closure of tissues after suturing is complete.

Male black sea bass after surgery is being placed into a recovery tank.

Only dredged sediment that has been tested and meets EPA's strict biological and chemical criteria can be used as remediation material. These sediments are placed in the HARS to cover or "cap" dredged materials previously placed there. This cap remediates the site and improves the habitat conditions for aquatic life in the HARS by covering historic sediments whose contaminant levels may potentially cause environmental concern. The EPA has determined that a cap of at least one meter in thickness is required to effectively cover the HARS.

"The criteria used to determine whether dredged sediment can be placed at the HARS is among the most stringent in the United States," said Monte Greges, chief of Dredged Material Management Section, New York District. To evaluate the potential changes the EPA proposes to make to the current criteria, the Corps' New York District initiated and is funding a fish tagging study that is being conducted and managed by the Corps' U.S. Engineer Research and Development Center—Waterways Experimental Station (WES), in the Vicksburg, Mississippi District. The Waterways Experimental Station contracted the Northeast Fisheries Science Center to perform the study that will determine the residency time of fish in the HARS.

In summer 2003, the 18-month study began, and 153 healthy adult fish were tagged in the HARS, including 129 black sea bass (Centropristis striata) and 24 summer flounder (Paralichthys dentatus), also known as "fluke," important recreational and commercial fish.

The fish were tagged with two different tags—an ultrasonic transmitter that was surgically implanted in their abdominal cavities and an external tag placed below their dorsal fins. These external tags are labeled, "Not for Human Consumption" on one side and have the study manager's phone number on the other.

To pick up the signals from the fish's ultrasonic transmitters, 72 receivers were strategically moored throughout the HARS site, 800 meters apart. According to Dr. Mary Fabrizio, the study's principal investigator and chief of the Behavioral Ecology Branch, Northeast Fisheries Science Center, "The signals produced by the transmitters will be detected by the receivers when a fish swims within 400 meters of the receivers.

"The transmitters, which are only 30 millimeters long and 9 millimeters in diameter, are programmed to send 68 KHz signals (pings) once every three to five minutes for about one full year. Every signal detected by a receiver is 'decoded' electronically, and the receiver records the identification number of the transmitter, the date, and the time of day the signal was detected. These records accumulate in the memory of the receiver and when the receiver is retrieved, scientists download the data to a laptop computer using an interface between the receiver and one of the communication ports on the laptop.

She continued, "The next step is to associate a particular receiver and all its data with a particular location, that is, the station where the receiver was moored. We do this by assigning a station identification number to the electronic file associated with each receiver." She added, "Based on retrievals completed in September 2003, we know that over a period of about three months, 68 receivers detected over 1.3 million transmissions!"

In June 2004, the study will be completed and the scientists will retrieve the receivers for the last time and download the remaining data. A final report will be completed in December 2004.

Greges said, "In addition to providing a better estimate of residency time of these two fish species at the HARS, this study will also provide data to correlate fish movement and behavior with changes in bottom topography from disposals, changes in water temperature and salinity and storm events. This will be extremely helpful to fishery biologists." Greges added, "This study will also help the New York district develop an environmental risk assessment for the HARS that will more realistically portray the effect that certain contaminants have on aquatic life. Knowing how much time fish spend in the HARS will provide information on the potential level of exposure."

This study is considered "cutting edge." "Most tagging studies of this kind are relegated to bays, lakes, streams, and other relatively small 'closed areas.' This study is the only one performed in a mid-Atlantic continental shelf area," said Fabrizio. She continued, "In addition, this is the first use of ultrasonic transmitters to monitor movement and habitat use by two fish species that are closely associated with the bottom of the ocean. Also, most studies tag one to two dozen fish and use maybe a dozen receivers. In this context, this may be the largest study of this type ever performed. The amount of technical data that can be gleaned from it is unprecedented."

JoAnne Castagna is a technical writer/editor with the U.S. Army Corps of Engineers, New York district. In this position, she writes articles about the district's civil works projects. Presently, she is completing a dissertation in cooperation with Cornell University. She can be reached at Joanne.castagna@usace.army.mil.

—JoAnne Castagna