Smolt trap reports 2012

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.

There are 9 comments for this article
  1. Anthony Tinsley at 3:53 pm

    Good work, Brian. It is very encouraging to see such healthy, and natural, smolt production from what are unstocked tributaries.

    We have been smolt trapping for a number of years now and a lack of smolts has yet to be revealed by the rotary traps, although I would expect it at Spey Dam.

    Given the finite amount of food available to juvenile salmon in the Spey, there’s as much salmon biomass leaving it as could reasonably be expected.

    Unfortunately the biomass returning is not as great as we would all like due to problems at sea we would all like to know more about.

    • henry spence at 10:44 pm

      Hi Brian,

      Are you of the same view as Anthony that given the amount of food available for juvenile salmon in the Spey then there is as much Salmon biomass leaving as can be expected?

      • Brian Shaw Author at 12:01 am

        Hi Henry, in four years of smolt trapping in the Tromie we found that the smolt output varies by a factor of two at least. That might suggest that there are other limiting factors than just the food resource but Anthony may be right in what he said about food availability. I read an Irish study which found that warm spring weather was positively correlated with good smolt outputs in long term monitored rivers. Parr destined to smolt in the spring make that decision in the back end of the previous year and then tend to keep on feeding and growing throughout the winter. An open winter and good early spring weather will be good for invertebrates activity which means they will be available to the fish, leading to better parr to smolt overwinter survival. I think thats what we saw last winter. So in that case Anthony was spot on; food availability contributed to the high smolt output.
        Is that always the case across the Spey? I doubt it, we surveyed plenty sites where there should have been more fry/parr. Possibly lack of spawning fish is an issue but we will learn more about that this summer with some of the repeat surveys planned to follow up on the 2012 monitoring. Regarding inverebrates we are starting to look into this but some of the sites in the mainstem support rich and diverse populations, no shortage of food in these areas. A multitude of other factors affect juvenile salmon biomass: predation, habitat, spawners, climate, you name it. Other rivers have outperformed the Spey in recent years; are there factors unique to the Spey? If there are, surely they are unlikely to include food availability specifically on the Spey?

        • Simon Crozier at 8:55 pm

          Hi,I am a very keen trout fisherand a keen amateur entomologist so when a fisher of mine who was a pro trout guide and seriously into entomology suggested thst we do a kick sample on my beat , i jumped at the chance, to cut a long story short, we conducted a 1 min kick sample , he was astounded at the richness and diversity of what he found , he had conducted similar surveys on some of the most renowned trout streams in England and he told me that the spey was far and away the best he had seen, heptogenid, baetis, gammarus, ephemerids, damsels, bloodworm , stonefly and the most caddis he said he had ever found were all present, i know that this was in the upper mainstem and not the Tromie but i thought you may find it of interest, cheers Simon.

          • Brian Shaw Author at 7:27 pm

            That’s good to hear Simon. I was highly impressed by the March Brown and olive hatch on your beat a couple years ago; never forget that day, my first Spey salmon!

            I have had a look at some of the SEPA invertebrate data from the Spey over the last 30 years. The Grantown area appears to have some of the most diverse invertebrate populations in the Spey, and as you mention there is a big range of caddis species. I’ll not say too much more on this issue as I will make a blog post next week.


  2. Gordon Mackenzie at 12:34 pm

    Hi Brian
    Did you get a chance to monitor spawning activity in these burns in 2012?
    And if you did, how did numbers of redds compare relative to similar upland burns on the Spey catchment?

    • Brian Shaw Author at 2:24 pm

      Hi Gordon, We didn’t do full counts on the Truim nor Tromie. We had a look at a couple sections of the Truim where there were a good number of redds but no more than I saw elsewhere. No doubt the Truim is above average for an upland river with good habitat and what appears to be wee bit of enrichment (the conductivity is high in comparison to other burns nearby). The Tromie has lower conductivity and a lesser availability of good spawning gravel but it is universally good parr habitat. Fry numbers are generally only moderate in the Tromie with better parr densities. We will be surveying the Truim in detail this summer so it will be interesting to see if the electrofishing results support the good smolt production.

  3. Graham Ritchie at 7:38 pm

    Those figures are very encouraging Brian, hopefully they are replicated on other tributaries and the main river.

    • Brian Shaw Author at 8:48 am

      Hi Graham,

      They are adjacent tributaries but it is good that both showed similar increases in smolt output that might indicate that other tributaries could be similar.

      Best regards


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