Hallprint's range of body cavity internal anchor tags (type IEX) provide the researcher with an option that is really worth contemplating if extremely long term tag retention is desired, such as for population size or exploitation rate estimates. These tags, developed by Michael Hall in the early 1990s, have now been successfully applied to a number of freshwater and saltwater fish and show excellent tag retention properties while having minimal apparent impact on fish behaviour and condition.
IEX tags provided an excellent internal anchor in the abdomen while requiring only a needle prick in the body cavity wall to accomodate the tag. The tag is designed such that the anchor lies parallel with the inside abdomen wall and the external marker lays backwards along the line of the fish.
The IEX tag may take a longer time to apply that the T-bar or dart tags and may be less suitable for high volume tagging operations, especially when holding time is critical. It is favoured by some researchers tagging finfish species for the following reasons -
1. Tag retention appears to be excellent in most species
2. Algal growth on the tag is minimised through the ventral positioning of the tag which reduces light exposure levels
3. No damage to edible muscle tissue.
As a result of these features, it is expected that use of these tags may increase for use in aquaculture operations and for studies of exploitation rates and population size. These tags are now available in a range of possible anchor or marker lengths in 0.8 mm (IEXX), 1.3 mm (IEXS) or 1.8 mm (IEXA) diameter and, as for all Hallprint tags a wide range of colours is available.
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