What to do if you find a Cefas tagged fish
Why scientists tag fish and shellfish
Cefas and other European 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.
More information about the numbers of different fish species released by Cefas can be found in the Cefas Technical Report: A summary of demersal fish tagging data maintained and published by Cefas (2006) (PDF, 4.75 MB).
Types of Tag
There are two types of tags utilised by Cefas for tagging fish, which can be broadly classified, as conventional or electronic.
Whole ranges of conventional tags have been used to tag a variety of species. The tags are often specific to particular types of fish. Simple button "Peterson" discs are used primarily for flatfish, skates and rays, plastic flags (often "howitt" tags) for roundfish and T-bar type tags for bass and crustaceans (edible crabs and lobsters). Conventional tags are uniquely numbered, prefixed by the letter "E" which denotes "English" and can be used in conjunction with electronic tags that are not always numbered uniquely. Although conventional tagging experiments can give us a lot of information they can only tell us about the location of the fish at the time of release and recapture.
Data storage tags (DSTs) are electronic tags which record and store detailed depth, light and temperature information that can be used to reconstruct the movements of the fish between release and recapture in addition to shedding light on behavioural characteristics. They are either placed internally or attached externally to the fish depending on species and size of tag. After recapture the data is downloaded and combined with tidal cycles and models of water movement to deduce the movement of the fish between release and recapture positions.
Satellite and acoustic tags are also utilised to track movements of fish.
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The principal types of conventional tags used by Cefas
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The Cefas G5 data storage tag
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2007-2008 Cefas tagging programmes
