Conventional Tags

Posted on May 21, 2010 in Articles | Comments Off on Conventional Tags

Conventional tags are essentially fish identification tags. These take many forms and may consist of a long piece of plastic tubing, a disc, or small coded wire. Generally they contain a unique number, identifying the individual fish as well as contact information from the sponsoring organization. They can be secured with a plastic or stainless steel dart or may be inserted under the skin entirely.

A tag is secured to an individual fish at time A. When a fish is recaptured at time B we have a location at two separate times and can make a rough estimate of movements and stock structure. Documenting the associated changes in size provides researchers with the growth rates of tagged fish. Recording the percentage of tagged fish that are re-caught can indicate population size. Conventional tag databases have provided a wealth of biological information for many species and have been critical for management.

However, conventional tags do have some limitations:

  • The resolution is coarse; you have no idea where the fish went between A and B
  • They are fishery dependent; data is only obtained when and where people fish
  • The fish must be recaptured to recover the tag, which has limited the use of conventional tags to those species for which a fishery exists and tag returns are reasonable. For some species (i.e. Marlin) tag return rates are less than 1%

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