The Marine Research Institute (MRI) of Iceland recently conducted a redfish tagging cruise using Underwater Tagging Equipment (UTE) from Star-Oddi.
The objective of the deepwater tagging studies is to gather information on the relations between redfish stocks around Iceland and oceanic areas around Reykjanes Ridge. Fish tagging is a major factor in the biology of fish and provides invaluable information on their behaviour.
The use of UTE is of necessity for tagging deepwater species like the redfish, which do not survive being brought to the surface for tagging, due to differences in pressure and temperature.
The UTE is mounted inside a fishing trawl, at the cod-end. As the fish swims into the equipment, it gets trapped inside a tagging chamber, where it is tagged and released. Live video images are transferred through the cable wire onboard the vessel, where it is remotely controlled.
Two types of tags have been used in the UTE. Majority of the tags are dummy tags (2,335 pcs), giving information on migration distance between release and recapture point as well as the growth of the fish. 87 DST micro tags have also been applied, giving additional information on the depth and temperature of the fish through its migration route, where approximate geolocation at different times can be obtained.
In the three tagging cruises 2003-2005, a total of 1776 redfish were tagged around Iceland, 49 with DST micro electronic tags. Tagging was performed at depths down to 800m. So far 37 redfish have been recaptured with dummy tags, most of them close to the release area. But a few recaptures indicate a long distance migration. Fish released SW of the country have been recaptured NW and SE, and two fish released SW at the boundaries of the 200 miles EEZ have been recaptured NW of the country.
This most recent cruise’s objective was to tag oceanic perch, which stay in the upper layers in the area south of Greenland (in Greenland Sea). Due to low accessibility of the fish, only 76 fish were tagged in the area, nine with DST micro electronic tags. Therefore the cruise moved to the area where fish had been tagged in 2004 and 2005. The tagging went well and total of 570 fish were tagged in that area, 29 with electronic tags.
