Publication Date:
2006-01-01
Description:
We describe a tagging method using underwater-tagging equipment (UTE), developed in collaboration between the Icelandic Marine Research Institute and the marine-device manufacturer STAR–ODDI. The tagging device can be attached to a pelagic or demersal trawl, immediately in front of the codend. Fish that enter the trawl are guided through the UTE, where they enter a tagging chamber to be held, tagged, and then released. The tagging equipment is electronically controlled from the vessel by a computer with a hard-wire, sonar cable link between the ship and the device. The same cable carries signals from four video cameras in the UTE, and a researcher can view images of the fish on a computer screen and control the tagging equipment simultaneously. The motivation for this project is the need to be able to tag fish, in situ, underwater, so avoiding the problem of swimbladder expansion that for physoclists such as redfish precludes conventional tagging. The UTE has been used to tag redfish in the size range 32–52 cm. Other species, such as saithe, have also entered the equipment and have been tagged with success. The tagging equipment could therefore be an alternative for tagging any medium-size roundfish, such as cod, haddock, and saithe, as well as many deep-sea species in their natural environment without subjecting them to the hazardous journey from deep water to the surface. In all, 752 redfish were tagged with the UTE in 2003 and 2004. Of these, 29 (3.9%) have been recaptured, most with reliable information on date, position, and condition at the time of capture. The tags used in 2003 and 2004 were dummy tags identical in size and shape to the external housings of electronic data-storage tags. In 2005, real DSTs were used of the type DST-micro from STAR–ODDI. These will in future provide time-series of ambient temperature and depth.
Print ISSN:
1054-3139
Electronic ISSN:
1095-9289
Topics:
Biology
,
Geosciences
,
Physics
Permalink