A Vaguely Interesting Observation About The Way Water Sticks To the Flanks Of A Salmon

bobmiddlepoint

Well-known member
Joined
Sep 28, 2017
Messages
3,698
Location
Where I want to be
How's that for a snappy thread title?

Anyway, while out today trying to get some pictures of spawning fish in poor light and high water I took the following shots. The way the film of water follows the underlying scales on the flanks/back when they are whizzing about half out of the water is something that stands out. I've seen it many times on salmon but never on sea trout (even double figure ones) which I guess is just down to the size of the scales. I did warn you that it was only vaguely interesting...

Scale Pattern 1.JPG




Scale Pattern 2.JPG




Scale Pattern.JPG




Job done (hopefully!)

Job done 1.JPG




Andy
 

Bobfly2

Well-known member
Joined
Jul 11, 2015
Messages
1,043
Flowing on the surface of the outer "slime" layer which I assume is like a hydroscopic gel ?
 

NAHMINT

Active member
Joined
Nov 11, 2021
Messages
28
Location
Nanaimo/VANCOUVER ISLAND. B.C. CANADA
Interesting photos .....at this time of year, still have salmon running up the streams, but one has to watch for the bleeding bears !!!
pouring cold rain again today........I am sure my good wife will find something to keep me from being bored!!:rolleyes:
 

Cap'n Fishy

Well-known member
Joined
Sep 29, 2008
Messages
31,571
Location
Embra
You may have something there, Andy, though exactly what, I am not sure. If I cherry-pick through the leaping salmon shots I have taken over the years...

CP18Oct14_8087.jpg


BuchantyOct21_1153.jpg


BuchantyOct21_1263.jpg


BuchantySep19_2192.jpg


Buchanty21Sep18_3852.jpg


Buchanty21Sep18_3861.jpg


Buchanty21Sep18_4045.jpg


Buchanty21Sep18_4171.jpg


Buchanty21Sep18_4210.jpg


Buchanty25Oct2017_2816.jpg


Buchanty19Oct16_1361.jpg


Buchanty19Oct16_1649.jpg
Buchanty19Oct16_1743.jpg


Buchanty2013_7083.jpg


Same thing visible in a few of them. While they are selected from a few hundred shots, the interesting thing is that I don't see it in any of the leaping trout shots!

Another skin-related observation. I seem to notice foam in the net any time a summer grilse comes on board from a loch...

Hope4-6Aug20_0440.jpg


Hope4-6Aug20_0459.jpg


Or the grilse comes out the net frothy...

3427.jpg


Uist2014_2929.jpg


Uist2014_3224.jpg


What's all that about??? :unsure:

C.
 

Bobfly2

Well-known member
Joined
Jul 11, 2015
Messages
1,043
I was surmising that that final surface coating has the critical characteristics for water flow.
 

bobmiddlepoint

Well-known member
Joined
Sep 28, 2017
Messages
3,698
Location
Where I want to be
You may have something there, Andy, though exactly what, I am not sure.

That was exactly what I was thinking, I don't really know but was assuming it was something like Bobfly's point.

I was surmising that that final surface coating has the critical characteristics for water flow.

Something do do with boundary layers and reduced drag.


Another skin-related observation. I seem to notice foam in the net any time a summer grilse comes on board from a loch...

Can't say I've noticed that but then I've not netted many loch salmon. I guess it's something to do with slime/oils from the fish mixing with the water, fresh grilse (and salmon) are certainly give off a strong smell so there is something coming off them.


Andy
 

Cap'n Fishy

Well-known member
Joined
Sep 29, 2008
Messages
31,571
Location
Embra
Can't say I've noticed that but then I've not netted many loch salmon. I guess it's something to do with slime/oils from the fish mixing with the water, fresh grilse (and salmon) are certainly give off a strong smell so there is something coming off them.

I have only ever noted it with grilse.

Not with salmon...

Brora-2019_0318.jpg


Not with sea trout...

Hope2-4Aug21_1794.jpg


Not with brown trout...

Orkney2019_7433.jpg


And not with rainbow trout...

Menteith24Jun16_5310.jpg


Something about the slime on grilse???
 

raphael

Well-known member
Joined
Feb 13, 2010
Messages
461
Location
France, by the banks of river Loire
Hi!

I've took many pictures of my fish, mainly grisles and a few salmon. I've checked many pictures from miscellaneous Irish rivers (Moy, Erriff, Finn, Drowes, M.Blackwater) and there are only a couple with the so called "foam"... but it happens the picture is taken just below rapids or falls where the water is already foamy.

Regarding the pattern of the scales of spawning salmon, I guess that it may be due to the use of scales as source of calcium by the fish during their freshwater stay. They do not feed but metabolism of all vertebrates requires calcium and it is known that salmon scales are used for that and tend to seriously fade away. Then the scales may change in shape and design due to that natural wear, and the water flow on them is showing that effect?
Just a supposition from what I've learnt.

R
 

bobmiddlepoint

Well-known member
Joined
Sep 28, 2017
Messages
3,698
Location
Where I want to be
I have only ever noted it with grilse.

'tis a mystery!


Regarding the pattern of the scales of spawning salmon, I guess that it may be due to the use of scales as source of calcium by the fish during their freshwater stay. They do not feed but metabolism of all vertebrates requires calcium and it is known that salmon scales are used for that and tend to seriously fade away. Then the scales may change in shape and design due to that natural wear, and the water flow on them is showing that effect?
Just a supposition from what I've learnt.

You might have a point there, I've tried to find a similar effect on pictures of fresh fish battling up the falls and rapids here in May/June or leaping about in the tidal water in July but I don't have anything clear enough to see.


Andy
 

codyarrow

Well-known member
Joined
Feb 6, 2010
Messages
5,126
It looks like badly applied or aged varnish. Can we call it 'varnishing'?

Anyhoo my tuppence half baked theory based on no facts is it will be something to do with the starvation process rather than eco streamlining. You won't see it in sea trout or trout because they are not in the process of consuming their body fats to the same extent. Basically my guess is the skin reacts differently after the colour change, whether that aids some part of the process or is just a consequence???
 

bobmiddlepoint

Well-known member
Joined
Sep 28, 2017
Messages
3,698
Location
Where I want to be
It looks like badly applied or aged varnish. Can we call it 'varnishing'?

Anyhoo my tuppence half baked theory based on no facts is it will be something to do with the starvation process rather than eco streamlining. You won't see it in sea trout or trout because they are not in the process of consuming their body fats to the same extent. Basically my guess is the skin reacts differently after the colour change, whether that aids some part of the process or is just a consequence???

I like your thinking here, both on the name and the mechanism behind it.
I propose that the phenomenon be known as Middlepoint Yarrow 'n Fishy Varnishing, there's a Phd in it for someone!


Andy
 

Bobfly2

Well-known member
Joined
Jul 11, 2015
Messages
1,043
Look at the flanks and shoulder area on a post spawning dead fish and you may be able to see the scavenging of the minerals from the scales. Not uncommon for animals to "conserve resources" and even autumn leaf colour change is chlorophyll recovery removing green and allowing carotenoids to show that were swamped before.
 
Top