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Why scientists tag fish

Scientists tag fish in experiments to record migratory behaviour, growth and fishing catch rates. Most of the commercial species have been subject to tagging on all of the major fishing grounds, so there is always the chance of finding a tagged fish wherever you are fishing.
Mark and recapture experiments using conventional (non-electric) tags provide a valuable insight into the structure of stocks, mixing of stocks and the implications of both for fishery management. Estimation of fishing mortality can be provided by appropriately designed tagging studies.

Electronic data storage tag (DST) development allows scientists to continuously record the horizontal and vertical movements of individual animals between the points of release and recapture and are also being used to study how their behaviour is affected by environmental variables such as temperature.
DSTs electronic tags are equipped with depth and temperature as basic sensors. Other sensors available are salinity, GPS, compass, pitch and rolll.  The detailed information is recorded in the memory of the DST along with date and time of each measurement.  The data can be used to reconstruct the movements of the fish between release and recapture, geolocation in addition to shedding light on behavioural characteristics. The tags are either placed internally or attached externally to the fish depending on species and size of tag. After recapture the data is downloaded and can be combined with tidal cycles and models of water movement to deduce the movement of the fish between release and recapture positions.

Types of tags and marks

Below you can find more information on the function and application of tags and marks. Click on a link you want to follow.

Electronic Tags
External Tags
External Marks
Internal Tags
Internal External Marks

Tagging Methods for Stock assessment and research in Fisheries
Report of Concerted Action (CATAG)

Information gathered from 


Video clips on Star-oddi website


Warning! Some of these files are large. Having ISDN or ADSL or faster is recommended.  
Click on the picture to view video clip

External tagging with DST GPS tag:
Here you can see scientist tag a brown trout and his cowerker using a Star-Oddi portable GPS transmitter. 

This is a the DST GPS system when the Simrad sonar is used onboard a research vessel in large geographic areas.


Links to interesting websites  

Marine and Freshwater Research Institutions

Organisations and Commissions  International Atlantic Salmon Research Board International Commission for the Conservation of Atlantic Tunas International Council for the Exploration of the Sea North Atlantic Salmon Conservation Organization North-East Atlantic Fisheries Commission Northwest Atlantic Fisheries Organization North Pacific Anadromous Fish Commission Pacific Salmon Commission North Pacific Marine Science Organization  American Fisheries Society

Equipment and Technology