Comments for ART Blog

Comment on River Ayr smolt trap update 24th May by Ayrshire Rivers Trust

Ayrshire Rivers Trust — Thu, 27 May 2010 18:24:35 +0000

Good of you to have a stab anyway Michael!
As I said we didn’t set out to estimate the run but we may be able to give a rough estimate once the trapping is finished. However the smolt run on the River North Esk in Angus has average out at about 180,000 over the last 40 years. The smolt run there is the most intensively monitored in the country and is the best set of data available (http://www.marlab.ac.uk/FRS.Web/Uploads/Documents/FW26Marine%20FH10.pdf ) .
Good though the Ayr is as a salmon river it isn’t quite in the same league as the North Esk so it is probably safe to say that the smolt run, and adult salmon run, will be quite a bit less.
Your estimate for marine mortality are similar that that recorded for the Esk, about 92-95% lost at sea.
The trap is quite far up the mainstem so we aren’t recording any smolts produced in the lower reaches. However, if we feel confident enough to publish a figure for the total smolt run it will appear on here!
There is no fish counter on the river so we don’t know the size of the adult run. Figures I have seen for exploitation rate suggest that anglers take more then 10%. In a relatively small river like the Ayr, with it’s high angling pressure, and beats well up the river I wouldn’t be surprised if the exploitation rate to anglers was around 20%. That means that your rod catch could be produced from a smolt run a good bit smaller then your estimate.
Thanks for posting!
Brian Shaw

Comment on River Ayr smolt trap update 24th May by Michael Canning

Michael Canning — Thu, 27 May 2010 16:43:15 +0000

I am going to get the belt for this, but on the principle that fools rush in I will have a stab at it.
In order to stave of madness I have rounded this figures off.
Assuming ? that 9k salmon spawn in the Ayr system @ 2.2k eggs per fish this gives us a total of 20m eggs laid with a 99% mortality rate we would get [ 200k SMOLTS ]. with a further 95% mortality rate at sea we would get 10k salmon returning. an additional 10% loss to anglers gives 9k salmon spawning.
This would suggest that if the trap catches 5k smolts that would work out at a 2.5% capture rate.
I am of now to look for a high bridge.

Comment on River Ayr smolt trap update 24th May by Ayrshire Rivers Trust

Ayrshire Rivers Trust — Thu, 27 May 2010 08:33:39 +0000

Thanks for the comment Michael. We didn’t set out to quantify the run, although that can be done using mark and recapture techniques. However we have carried three individual recapture trials, two earlier in the month and one this week. We re-released 29 marked fish back upstream on Tuesday, two were recaptured yesterday and more could be caught this week. The results of the first two trials were consistent so if this last trial is similar it will give us some confidence if producing an estimate of the total run. Out of interest how many smolts do you think would be produced in the Ayr in a typical year?
Brian Shaw

Comment on River Ayr smolt trap update 24th May by Michael Canning

Michael Canning — Thu, 27 May 2010 05:10:05 +0000

Facinating data, amazed at numbers of smolts particulary salmon. Has anyone every produced a formula for estimating total smolt production based on the traps results. I would think that the trap would only intercept a small percentage of migrating fish.

Comment on Late spawning by Michael Canning

Michael Canning — Sat, 20 Feb 2010 12:28:59 +0000

Good to hear, I walked what would be busy redds at new year and found them frozen over with no fish present, as you say just goes to show how adaptable the species is.