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JW Fishers - Press Release - April 7, 2005


Trying to study shellfish populations has long been a difficult task for marine biologists. Finding a way to locate and track individuals and groups of animals has proven quite a challenge for researchers. Dr. Tasman Crowe, a scientist with the Australian Centre for International Agriculture, has experienced these difficulties first hand. Dr. Crowe is involved in a stock enhancement project of trochus, a conical shaped marine gastropod (snail) that inhabits shallow tropical reefs. The shell of an mature adult can measure up to 5 inches. Smaller shells are used to make jewelry and buttons for high priced garments. The current global demand for trochus shell is over 7,000 tons annually. Like many of today’s marine resources, the trochus fishery is under stress from overfishing and scientists are investigating the feasibility of a trochus reseeding project. Dr. Crowe wrote a paper on the subject for the Secretariat of the Pacific Community. In the report he discusses the difficulty of tracking and capturing tagged animals in a complex habitat. “The trochus often move into and under the live coral or coral ruble and can not be found by visual searches. In order to conduct an accurate census, field researchers need a way to locate animals hidden by coral and disguised by debris in a marine environment of varied terrain.”

Dr. Crowe came up with the novel idea of connecting a very small metal tag to the trochus shell. He wrote, “To solve the problem we used underwater metal detectors to locate small metal tags fixed to the animals. The metal detector we used was a Pulse 8X supplied by JW Fishers Mfg.” He went on to extol the virtues of the detector for the this type of project and adds, “We found the smallest tag that could fit on the juvenile trochus and still be reliably detected was a 0.3 gram piece of aluminum. Tags were detectable within a range of 8 cm of the coil regardless of the intervening medium (e.g. air, water, rock, sand, or coral) and could be pinpointed to within 1 to 2 cm. The report concluded with, “The effectiveness of the system was tested in a series of pilot trials and the results indicated the tagging system was an effective method of finding trochus. Over 85% of a known number of juveniles were consistently recaptured.”

Another group using underwater metal detectors in a similar project are scientists at Canada’s Dept. of Fisheries and Oceans at the Maurice Lamontagne Insitute in Quebec. “I am using Fishers Pulse 8X to locate marked clams on the seashore at low tide”, says marine biologist Francois Hazel. “The detector works very well in helping us locate clams affixed with small metal tags. We can gather information on growth rates, migration patterns, and other characteristics of the population. This is an exploratory project to develop tools that will one day assist communities in monitoring their coastal zones. My hope is that in the future this equipment can be used by other groups, such as schools, in a type of “treasure hunt” to increase awareness about coastal species - mixed with some fun.”
To receive a data sheet on Fishers metal detectors or a brochure on their complete line of underwater search equipment, call (800) 822-4744, send e-mail to, or visit their website

Caption for attached photo: Diver searches for trochus

Contact information:

Christopher Combs
JW Fishers Mfg.
1953 County Street
E. Taunton, MA 02718
PH 800-822-4744
PH 508-822-7330
FAX 508-880-8949


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