Flank marks on sea trout?

Cap'n Fishy

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Noted the number of sea trout that have a mark on their flank in the same place...

Hope23-25Aug21_2603.jpg


pic6.jpg


A bit further back...

Hope2-4Aug21_1806.jpg


850_0141-Edit-Edit.jpg


Subtle, but it's there...

hope_aug2020_2-76.jpg


Hope2019_9376.jpg


A finnock, further back...

Hope18_2529.jpg


Shiel2014_1494.jpg


What's catching them in the same spot all the time?

Col
 

loxie

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It looks a bit like heron on some, cormorant on others. Perhaps a bit of seal and maybe otter. I think the positioning is probably more to do with the fish still be alive than any single type of predator. The ones hit further forward have been eaten.
 

aldot

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Interesting observation

I don't think any of these fish have been damaged by a cormorant.

I've had quite a few interactions with cormorants, they have distinctive bite characteristics: damage is equally inflicted to both sides of a fish, not just on one flank. Also all of the fish I've ever encountered with cormorant marks (that I can think of) have been gripped between the head and the dorsal, they know the optimum point to grip a fish and are very good at it.

Some of the wounds on your fish look very narrow and 'speary', very unlike cormorant beaks which are surprisingly wide at the mouth, taper steeply, and cause a lot of damage. I'd imagine these narrow wounds have been inflicted at sea by plunge-diving sea birds which are known to target all types of shoaling fish inc smolts and finnock given the opportunity.

Just for info, here are some recent pics to help demonstrate what I'm talking about above;

This is a 2lb trout that a cormorant had a hold of for only 20 seconds or so, the abrasion caused is phenominal. I caught this particular cormorant red handed, it released the fish as soon as it spotted me and flew off, note the equal damage to the flanks. The trout, unsurprisingly, died quickly.
Screenshot_20210906-220044_Gallery.jpg


This is a fish I caught showing the triangular profile of the beak (and replicated on the other side)
Screenshot_20210906-220028_Gallery.jpg


This is another fish I caught showing the patternation joining up over the back
Screenshot_20210906-220014_Gallery.jpg
 
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bobmiddlepoint

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It looks a bit like heron on some, cormorant on others. Perhaps a bit of seal and maybe otter. I think the positioning is probably more to do with the fish still be alive than any single type of predator. The ones hit further forward have been eaten.

I'd generally go along with this.
Heron seems unlikely on so many fish, herons are about and might have hit a few fish as they scrambled through the river when it was very low but it isn't something you see often.

Another possibility is lesser and greater black backed gulls, they do hang about the shallows in greater numbers than herons when fish are running and are capable of dragging out fairly big fish (grilse get pulled out on occasions).

No legal nets in the area, which isn't the same as no nets but they are not net marks.


Andy
 

whitehorses

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i have an aquarium and theres definetly a pecking order ,the most agressive dominant one constantly biting and nipping tails could it be a pecking order ie trout bullying other trout , just a suggestion ,
 

Cap'n Fishy

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In general I'd say the damage is not inflicted by a cormorant.

I've had a few interactions with cormorants, their bite is devastating, do a huge amount of damage even to bigger fish.
They have distinctive bite profile, the beak tapering quickly to the tip unlike, say, a heron which is pointy and dagger-like. Any damage affects both sides of a fish and the abrasion goes all the way over the top of the fish, see some of my pics below;

All of the fish I've encountered with cormorant marks have been gripped between the dorsal and the head, I have personally never seen any cormorant marks outside of that area, they know the optimum point to grip a fish and are very good at it. I've caught a few fish with wounds in that specific area so not all are eaten, quite a few escape (pic 2 and 3 are caught fish)

Some of the wounds in your pics look old so not necessarily inflicted when the fish was at its current size. Also some (1,2,6,7) look 'speary' so quite possibly damage done at sea by birds; shags which have a narrower beak than their big cousins, or by diving birds, gulls, gannets, common terns, fulmar, kittiwakes which will no doubt target shoaling smolts or finnock.

This is a 2lb trout that a cormorant had a hold of for less that 20 seconds, the abrasion is phenominal. I caught this cormorant red handed, it released the fish as soon as it spotted me and flew off, note the equal damage to the flanks
View attachment 43198

This is another fish showing the triangular profile of the beak (and replicated on the other side)
View attachment 43199

This is.another fish shows the abrasion joining up over the back
View attachment 43200

I agree. They don't look typical of cormorant damage. I've caught plenty rainbows from our club water with typical cormorant damage, and it is quite different.

Col
 

bobmiddlepoint

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Then in that case its damage caused getting over weir at Hope bridge.

I'm not aware that the low weirs on the Hope being an sort of problem to upstream migration. They are not high steep weirs but are more croys built to provide pools on the very short river.
I've seen a lot of fish that have gone over very difficult weirs and falls and marks like these aren't something I've seen as a result. "Gravel rash", a running sore under between the pectoral fins and ragged/reddened lower tail edge are the sort of things you see with some weirs. It is difficult to see how so many fish would damage themselves between dorsal and tail (and nowhere else) from weir running.

I see what people are saying about it not looking like classic cormorant marks. With cormorant you usually get some sort of break right through the skin from the hook on the top jaw. But I wouldn't rule out cormorant just because of that, they aren't going to hit every fish right (we see plenty that they drop).

I'm sure they are all predator marks of some sort with most being birds of one sort or another. There were a lot of fish hanging around the coast for a long time waiting for rain this summer with plenty of time for everything to have a stab at them.


Andy
 

morangiedave

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In previous years on Hope ever fish I caught had these marks on the flank in exactly the same position. This year on the one visit I managed none of them had any marks. I did notice how clean the fish were and was going to comment. I've never seen these marks on fish from Ulladale, voshmid or Clachan so maybe something hanging about the mainland coast but not the islands. Is it evident on Uist fish ?
 

Vintage Badger

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Anyone who's seen the teeth on an otter or seal will know the damage on those fish photographed is highly unlikely to have been caused by a bite from either of those two... unless it hadn't got its dentures in. ;)
 

bobmiddlepoint

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In previous years on Hope ever fish I caught had these marks on the flank in exactly the same position. This year on the one visit I managed none of them had any marks. I did notice how clean the fish were and was going to comment. I've never seen these marks on fish from Ulladale, voshmid or Clachan so maybe something hanging about the mainland coast but not the islands. Is it evident on Uist fish ?

I can't say I ever noticed it as being a feature of South Uist fish.

I still think gulls might be responsible for some of the marks. In low water here we always get black backs hanging around shallow stickles waiting for running fish.


Andy
 

Rhithrogena

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When a fish gets wrapped after twisting as it tries to free the hook the mono leader can cause abrasions along the flanks towards the tail. The pelvic and anal fins can catch the leader and the taught mono grating along the flanks causes these marks. The fish unrolls before netting. I have just looked back through dozens of photos of browns I have caught this season and many have the same marks.
I can post some here when I get the chance to resize them.
Rich
 

Wee Jimmy

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Interesting observation

I don't think any of these fish have been damaged by a cormorant.

I've had quite a few interactions with cormorants, they have distinctive bite characteristics: damage is equally inflicted to both sides of a fish, not just on one flank. Also all of the fish I've ever encountered with cormorant marks (that I can think of) have been gripped between the head and the dorsal, they know the optimum point to grip a fish and are very good at it.

Some of the wounds on your fish look very narrow and 'speary', very unlike cormorant beaks which are surprisingly wide at the mouth, taper steeply, and cause a lot of damage. I'd imagine these narrow wounds have been inflicted at sea by plunge-diving sea birds which are known to target all types of shoaling fish inc smolts and finnock given the opportunity.

Just for info, here are some recent pics to help demonstrate what I'm talking about above;

This is a 2lb trout that a cormorant had a hold of for only 20 seconds or so, the abrasion caused is phenominal. I caught this particular cormorant red handed, it released the fish as soon as it spotted me and flew off, note the equal damage to the flanks. The trout, unsurprisingly, died quickly.
View attachment 43198

This is a fish I caught showing the triangular profile of the beak (and replicated on the other side)
View attachment 43199

This is another fish I caught showing the patternation joining up over the back
View attachment 43200
Alan, was the top fish still alive.....it looks as if the front end of it has already been soaking in the birds stomach acid for a good while.?
 

Cap'n Fishy

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When a fish gets wrapped after twisting as it tries to free the hook the mono leader can cause abrasions along the flanks towards the tail. The pelvic and anal fins can catch the leader and the taught mono grating along the flanks causes these marks. The fish unrolls before netting. I have just looked back through dozens of photos of browns I have caught this season and many have the same marks.
I can post some here when I get the chance to resize them.
Rich

What I would say, Rich, is that the fish 2nd from top was just a couple of weeks ago on the dap, and I would have remembered if it had managed to do any wrapping at any stage. It's just not something that tends to happen with the dap. Also, the damage in the 1st and 3rd fish is clearly not fresh?

Thanks to all for the very interesting input on this. (y)

Col
 
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