The Truim and Tromie Smolt trap reports for 2012 can be viewed by clicking the following links Truim and Tromie. We have operated Rotary Screw Traps on the Truim and Tromie for 3 and 4 years respectively to provide baseline information regarding the licence application to modify the flow in these two important upland tributaties.
The number of smolts trapped in 2012 was approximately double that trapped in any previous year. The trapping conditions were excellent in 2012 with stable flows throughout the main smolt run period and there were very few days when the traps had to be lifted due to high flows, this no doubt contributed to the excellent smolt production estimates obtained. However comparing the operational days in 2012 with 2011 shows that 2011 was also a good trapping season with the trap operational throughout the main smolt run. There were more days missed in 2011 but they were mainly in March, a month that marks the start of the smolt run but never high numbers. Tables showing operational days for each year are included in the reports.
The 2012 trapping season was dominated by relatively low and stable flows. On the Tromie almost 55% of the smolts were trapped in a four day period between the 7-10th April when the river level rose 6.6cm, a very modest rise. Increasing flows are a well known trigger for smolt movements and ideally a good spate in early to mid April would occur to help the smolts downstream. All the major upper Spey tributaries have regulated flows and a proper big spate in the upper catchment can be a rare thing in the spring, especially in a year with little snow on the hills. These smolts migrating on the back of a small rise in river levels may be exposed to high predation as they travel through the low gradient reaches before Grantown but at least they were moving on mass, always a good predator avoidance strategy.
The reports conclude that the high numbers of smolts trapped in 2012 were more than just the product of the good trapping conditions. The 2012 smolt output from these two upper tributaries appears to have been significantly up on previous years. The smolt run in both was also the earliest recorded with the half way point in the smolt run occuring three weeks earlier in 2012 than in 2010. Average temperatures in 2012 were much higher than in 2010, one of the coldest winters in recent decades, and this no doubt influenced the run timing. The mild and open winter may also have contributed to the high smolt output although there was no evidence of increased numbers of two year old smolts migrating. At 8 salmon smolts/100m2 the output from the Truim in 2012 was exceptional for an upland tributary and the 6.3/100m2 from the Tromie was also good. 5/100m2 is typical for a Scottish highland river, including low altitude sites. Similar upland tributaries in the North Esk produced between 3-5 smolts/100m2. The accessible areas of both rivers lies between 240m-450m altitude approximately and they are known spawning destinations for early running fish. It is encouraging to see that these two monitored upper Spey tributaries are producing good smolt outputs, however they have a few trials and tribulations before they return as spawning adults.