Are there two strains of grilse?

[tweedsider]

The past two weeks seem to suggest that there are two different strains of grilse in our waters. One type is lean or skinny even with a distinct swallow tail and seldom reach 4lb in weight. The other is normal shape and less distinct swallow tail and are seldom found to weigh less than 3lbs. This seems to be the case on the Tweed system, are any other members encountering this?

[minitube]

Tweedsider,

There are at least two distinctly different runs of grilse in the river Moy. Those that are bound for the Lough and those for the main Moy River.

The Moy has a run of smolts in October/November as well as the usual April/May smolt run. When the October smolts were tagged as they were caught in Eel nets and released, most turned up as small grilse in June of 2 to 3 lb.

The smaller a grilse is the more smolt like its appearance.

The two main runs of grilse in the Moy are easily distinguished. When they are being played and are alive you can see whether the back is black or brown with black spots. Black backs are the Lough grilse. The Lough grilse are more streamlined and solid, like mini springers, they have less and smaller spots. The river grilse are more rounded, less of a honed muscular appearance - though all Moy fish are of magnificent proportion, have more and larger spots.

When a river grilse is killed after a while its back turns black.

The Lough grilse run earlier, then the two runs overlap for a while, then there are only river grilse.

[tweedsider]

Hello minitube I have not studied them in as close detail as you but I agree that the smaller leaner fish are almost smolt like in appearance while the other type is small salmon. As you know there is some debate at on the forum at the moment about small lean grilse my thread was put up to see if rivers other than the Tweed were experiencing the same thing.

Thanks for your reply tweedsider

[flee]

This is a very interesting topic Tweedsider ,things like this I find are fascinating and must pay more attention .
Say there are two or more strains of grilse in a river do you think the reason the strains don't get mixed are due to them spawning in different parts of the system thus keeping the strains separate?

I hope I'm not getting in too deep here but It's amazing what you don't notice until someone brings it to your attention.

I look forward to reading more input about this subject.

[tweedsider]

Hello Flee I started that thread looking for someone with a bit more knowledge on the subject to give me some enlightenment.
Mainly I was going by the bonanza we had a week or so ago when at the risk of repeating myself saw that some grilse were lean with a distinct swallow tail. These mainly weighed in at under 4lb. Other grilse were proper small salmon the swallow tail less pronounced and seldom weighed under 3.5lbs. Of course we are handling far fewer grilse than some of the beats on the main stem where it could be possible to get a clearer picture of the situation.

Tight lines