Parr tagging

The tagging of a significant proportion of the autumn parr population is a key component of our ability to estimate numbers of parr and smolts, and adult marine survival. Parr are tagged using small (12-mm long by 2-mm wide) Passive Integrated Transponder (PIT) tags.

The use of PIT tags inserted inside the body cavity is widely established as a relatively benign method of tagging and identifying individual fish and the method has been used successfully in a number of studies of wild salmon parr populations both in the UK and abroad.

Trials of the tagging began in 2002 and from 2006 onward approximately 10,000 individual parr per year have been PIT tagged throughout the catchment. From previous estimates of the total Frome parr population this represents about 15-20 % of the total late autumn 0+ salmon parr population.

Salmon research such as the parr tagging carried out by our research team at East Stoke wouldn't be possible without the support of our donors. Your support can help continue this valuable scientific research.

The passage of the PIT tagged fish out to sea is recorded by equipment mounted on the East Stoke smolt counter, the main river weir at East Stoke, the Tadnoll Brook tributary and the Environment Agency fish pass at Louds Mill, Dorchester.  The main river reader at East Stoke and Louds Mill also allows the detection of the return of the PIT tagged adult fish. In 2008 the East Stoke detector recorded 42 PIT tagged salmon and several PIT tagged trout.

The use of PIT tags, and the ability to identify and follow individual fish through their complete life-cycle, enables reproductive success, smolt production and subsequent adult survival to be monitored. This includes the ability to assess riverine and marine survival from different habitat types and site/tributary origin of parr. PIT records of juveniles and returning adults will allow partitioning of freshwater and marine mortality and also the role of any augmentation or remedial measures on recovery (both in the freshwater or marine habitats).

These records together with the records from the PIT reader on the Louds Mill weir at Dorchester will give us unparallel information about marine survival rates.