Encouraging early grilse run

It has been encouraging for all to see what appears to be a reasonably good early run of grilse in the river. The run of two sea winter fish this season has been excellent, the best for a number of years, but for the continuation of good sport into the latter half of the season the grilse are really important. Most of the grilse so far, although not all,  have been of good size (for June) and well conditioned. In recent years we have become accustomed to small, poorly fed grilse, although 2015 marked a change in that regard with a many much better quality fish present.

Of course it is easy to jump to the wrong conclusion regarding the age of a fish; one example of this would be the so called “grilse error”. Knowing the characteritics of the run of fish each and every year has always been important but never more so that now following the introduction of conservation limits and egg deposition targets.  We had the opportunity to look at the first grilse scale sample received in the office the other day. The scales were from a 3.5lb fish, one that was assumed to be a grilse at the time of capture. A few scales were collected before returning the fish. In this case there was no grilse error as can be seen from the picture below.

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The scale had one winter check (the band of closer rings below the red arrow) but of interest was the extent of the “plus growth” – the new growth put on in the spring after the winter check. This fish clearly had experienced good growing conditions, and presumably a plentiful supply of food in the last month or two, including on its return journey back to Scotland.

Good feeding and good survival at sea are likely to be correlated so the presence of a decent early run of well conditioned grilse if a promising sign. All the more so considering that the grilse returning this year were derived from the 2015 smolt year class; a cohort potentially affected by the fish kill in the aftermath of the Bertha storm in August 2014.

It was a three year old smolt which suggests that it was an upper river grilse, as would be expected for the early runners. That particular fish is likely to be heading for the Truim, upper Avon, Feshie or somewhere similar. Extreme flows could have a differential impact on fish originating in different parts of the catchment or in different stream order tributaries. We hope that the grilse run will continue to develop from this promising start.

There are 2 comments for this article
  1. Alan at 10:18 pm

    It will be interesting if there is a good grilse run this year. If so it may well indicate that smolt quality is at least as important as quantity.

    • Brian Shaw Author at 10:28 pm

      An interesting point Alan. We should not forget that marine survival is a major factor affecting the returns as well, although I suppose your point is that better quality smolts are more likely to return. Thanks for the comment
      Brian

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