Posted by: AAPGAI | April 2, 2010

Note on: Blue Salmon caught at Upper Mertoun : 22nd March 2010

The following report & pictures are provided by the fisheries biologist of the Tweed Foundation, sourced and forwarded by Ron Holloway – AAPGAI 

This is a Blue Salmon, caught at Upper Mertoun, 22nd March 2010

(“Spring-Spawning Autumn Fish”)

     84cms, 12lbs, Mature Male , silver flanks, reddish upper back

1) Appearance: Silvery along the flanks, but coloured along the back. Fully developed kype and teeth, running milt when landed.

Blue Salmon

2) Inside the body, gonads fully developed and running the whole length of the cavity

image

3) The scales showed that:

a) It was a fresh run fish – the edges of its scales were completely smooth, so it had spent very little time in fresh water. (As adult salmon do not eat while in fresh water, they re-absorb their body tissues to “feed”. As material is re-absorbed from the roots of scales, their edges become increasingly ragged or “eroded”)

b) There was spawning mark for last season. When a fish survives spawning and returns to the sea and starts growing again, the old, eroded edges of its scales remain as scars despite the new growth. It is known from tagging recaptures that when salmon spawn for a second time, they do so at much the same time that they did for the first. Since this fish had only recently spawned this year, it follows therefore that it must have spawned around February / early March last year as well. This is of particular interest as such fish must spend only a short time in fresh water, entering in January / February, spawning almost immediately and (presumably) leaving soon afterwards. It was not known, for the Tweed, what sort of a spawning mark, if any, such a short freshwater period would create – but on this fish it can be seen that the mark is distinct.

Blue Salmon 

4) It was also of interest that this fish was a male as repeat spawners are largely females. This is because while females “spawn and go”, males wait around on the spawning beds for more females to turn up until they are too weak to survive and return to the sea. It may be that very late male spawners, such as this fish, might however survive more often than earlier spawning fish because of the shorter period between entry and spawning.

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