Our Research Program in the Conservation Rearing Unit involves the tagging of hatchery reared salmon parr on their release into the catchment, by ‘clipping’ their adipose fin. As this fin does not grow back it is an obvious indicator, visible on adult salmon, from the facility, returning to the catchment. Over the next few years we are hoping, from this tagging, to be able to assess the return rate of salmon from the sea and the relationship between growth rate in freshwater and the timing of the migration trigger for smolts.
Our scale sampling program is also helping in this area to identify returning “Old Hatchery“ reared fish. Experience gained from the conservation rearing program has shown that those grown on parr released into the upper Cummeragh tend to smolt after their first year. Although this sounds like a good return from that program it should be noted in analyzing the Scale samples there is difficultly interpreting the freshwater stage because of damage to scales over time. Also, just because a scale is read as a 1 year old smolt does not necessarily identify it came from the Old Hatchery as it may have been produced naturally within the system.
2016 saw the end of our first five-year programme. In that time we have released over 50,000 salmon fry and parr into the catchment. With 22,000 of those tagged by fin clips. Between 2013, when the first released fish could have returned as Grilse, and the end of the 2016 season, 51 tagged salmon have been caught by rod and line in the catchment, comprising 32 grilse, 18 2SW salmon and 1 3SW fish.
Even after the short period of time that the facility has been in operation we are already gaining a better understanding of the different life histories of salmon in the the Cummeragh catchment.