Fish ID help needed

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science_fox
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Re: Fish ID help needed

Post by science_fox » Thu Oct 22, 2020 8:43 pm

tenchboy wrote:
Thu Oct 22, 2020 6:57 pm
But you would have to invent a story to excuse its not being green.
I know noting at all about fish ID, I've eaten a few and that's it. But colour/pattern is very variable in everything else that I do know about birds and animals, in some ways it's the least reliable indicator. So maybe it's just a bit of a odd colour? I'm sure the scales/lack thereof massively effect perceived colour too. That's my invented story anyway.

And as a contrast to the brilliance thread, this has been informing on just how difficult the details are once you do know them.
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Fishnut
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Re: Fish ID help needed

Post by Fishnut » Thu Oct 22, 2020 9:10 pm

tenchboy wrote:
Thu Oct 22, 2020 6:57 pm
You know it could be a tench.
But for it being silver it would be a tench.
The wrist of the tail is deep, although the wrist of a trout is deep this is very deep: like a tench.
Deep in the body as you say: notable 'shoulder' like a tench, too deep for a trout.
And there is some green on the gill cover, but it should be green all over if it is a tench.
And if it were a tench you wouldn't have to invent a story to excuse the lack of adipose tissue.
But you would have to invent a story to excuse its not being green.
As science fox has wisely noted, colour isn't hugely reliable in these types of situations. In my experience it's one of the things that gets damaged quickest when the fish suffers abrasion so I don't think the lack of green should be a negative mark. Comparing with the fishbase image again, the operculum looks like it should be slightly golden on the edge, moving to more olive green in the middle and there's definitely the golden edge in my fish, though admittedly more silvery as you move towards the centre but that's also an area that would be more likely to be abraded.
operculum.png
operculum.png (692.56 KiB) Viewed 1415 times
Around the remaining lateral line I think there's some original colouration remaining and that's got an olive-green tinge to it too
Lateral.line.colouration.jpg
Lateral.line.colouration.jpg (31.11 KiB) Viewed 1415 times
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Re: Fish ID help needed

Post by Fishnut » Sat Oct 31, 2020 10:46 pm

The saga continues...

I got my hands on a rainbow trout (Oncorhynchus mykis) from Tesco and finally got round to dissecting it today. I know it's a different genus to brown trout (Salmo trutta) but they're both salmonids and it's the closest I've managed to get so far. The otoliths are very different from my fish.
otoliths.jpg
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From a brief googling salmonids all have similar shaped otoliths which the rainbow trout fits into nicely, and my fish is definitely different. My fish was about twice the size of the rainbow trout I bought (it was undersized and the guy on the counter didn't know why they'd been sent it) and otoliths get bigger with age/length so you'd expect my fish to have the bigger otolith of the two if they were similar species. The photo isn't the clearest (they're bl..dy tiny and I'm not set up properly for macro photos) but there are distinct differences that, though they aren't clear in the photos, are clear irl, and make me pretty sure that my fish isn't a salmonid. So I'm formally ruling out brown trout as an ID (though I'd still like to get my hands on a brown trout to compare their otoliths).

To that end, I've emailed the angling club asking if it's possible to get unwanted heads of fish they catch so I can build a bit of an otolith reference collection for fish in the area. I don't know if they'll help or if they think I'm crazy and block me. Time will tell.
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Re: Fish ID help needed

Post by tenchboy » Sat Oct 31, 2020 11:21 pm

Fishnut wrote:
Sat Oct 31, 2020 10:46 pm
The saga continues...

I got my hands on a rainbow trout (Oncorhynchus mykis) from Tesco and finally got round to dissecting it today. I know it's a different genus to brown trout (Salmo trutta) but they're both salmonids and it's the closest I've managed to get so far. The otoliths are very different from my fish.
otoliths.jpg

From a brief googling salmonids all have similar shaped otoliths which the rainbow trout fits into nicely, and my fish is definitely different. My fish was about twice the size of the rainbow trout I bought (it was undersized and the guy on the counter didn't know why they'd been sent it) and otoliths get bigger with age/length so you'd expect my fish to have the bigger otolith of the two if they were similar species. The photo isn't the clearest (they're bl..dy tiny and I'm not set up properly for macro photos) but there are distinct differences that, though they aren't clear in the photos, are clear irl, and make me pretty sure that my fish isn't a salmonid. So I'm formally ruling out brown trout as an ID (though I'd still like to get my hands on a brown trout to compare their otoliths).

To that end, I've emailed the angling club asking if it's possible to get unwanted heads of fish they catch so I can build a bit of an otolith reference collection for fish in the area. I don't know if they'll help or if they think I'm crazy and block me. Time will tell.
Stick with it being a tench.
And try to think up a reason for it's being silver rather than green.
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Re: Fish ID help needed

Post by Cousin Itt » Sat Oct 31, 2020 11:33 pm

I have a brown trout in the freezer, it's about twice the length of your mystery piscine but you're welcome to the otolith (if you can tell me where to find it).

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Re: Fish ID help needed

Post by Fishnut » Sun Nov 01, 2020 11:00 am

Cousin Itt wrote:
Sat Oct 31, 2020 11:33 pm
I have a brown trout in the freezer, it's about twice the length of your mystery piscine but you're welcome to the otolith (if you can tell me where to find it).
That would be fantastic! I'll get you some instructions later. It's a bit fiddly but I find it very satisfying. You'll need a strong knife and some tweezers/forceps.
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Re: Fish ID help needed

Post by Fishnut » Sun Nov 01, 2020 9:18 pm

Cousin Itt wrote:
Sat Oct 31, 2020 11:33 pm
I have a brown trout in the freezer, it's about twice the length of your mystery piscine but you're welcome to the otolith (if you can tell me where to find it).
I've found a couple of videos showing the two main techniques for taking otoliths. The first is the 'top down' method. This is the method I was taught, though I don't normally remove the face like the guy did in the video. I normally go at a shallower angle, to try and expose the brain and then you can pull out the brain and then normally see the otoliths sitting in their little cavities. (If you're doing it with a really fresh fish, when you remove the brain sometimes you can activate the nerves and get the fish to twitch which is kinda creepy but fun). I like this method on fish I've not worked with before because you can go in gradually, shaving off layers of head until you reach the brain/otic capsule without having to know exactly where it is in advance.

The second one is the 'bottom up' method. It's a technique I only learned a few years ago and is really good though I'm less comfortable with it. I suspect part of that is lack of familiarity (I've only done it on a couple of hundred fish, compared to a few thousand for the first) but It also feels like a technique where, if you're unfamiliar with the fish or there's some damage to that area, it's really easy to get lost in bone fragments and not be able to find the otoliths (especially if they're small).

If your trout is a decent size, which sounds like it is, they should be fairly large (I'm going to guess just under a centimetre in length). They are white like the bone but they are a different texture - much harder. You can hear when you've got them with your forceps, even if you can't see them, and they are much more inflexible than the surrounding bone. If you go with the top-down method then they can be difficult to remove from the capsule but if you've found them and can't get them out then you can use either your knife to cut or the forceps to break the capsule open. If you go with the knife do fine slivers - it should open up quite quickly and if you cut too deep you'll cut the otolith in half.

If those videos aren't clear enough I can try and make my own. I did go to Tesco today to see if I could get some heads but the fish counter is closed until wednesday so I won't be able to do anything until then.
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Re: Fish ID help needed

Post by Cousin Itt » Wed Nov 04, 2020 5:30 pm

"Top down" looks safer for a noob. I'll give it a go in the next few days. Watch this space.

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Re: Fish ID help needed

Post by Fishnut » Wed Nov 04, 2020 6:58 pm

Cousin Itt wrote:
Wed Nov 04, 2020 5:30 pm
"Top down" looks safer for a noob. I'll give it a go in the next few days. Watch this space.
Awesome! Thanks so much :D
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Re: Fish ID help needed

Post by Fishnut » Mon Mar 29, 2021 7:27 pm

I have another fish I need help identifying. I think it might be a brown trout rainbow trout but I'm really not sure. I saw it today swimming in a local river (North Somerset). I think it was about 30cm long but that's a very rough estimate. It was significantly bigger than the other fish around. It had some pink colouration on the operculum and along what I'm guessing may be the lateral line - it was really quite beautiful! Tail and fins appear to be quite fleshy. It was swimming near the water's surface which is why the picture is fairly clear and was just hovering above a spot, facing into the current.

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Re: Fish ID help needed

Post by tenchboy » Mon Mar 29, 2021 8:25 pm

Fishnut wrote:
Mon Mar 29, 2021 7:27 pm
I have another fish I need help identifying. I think it might be a brown trout rainbow trout but I'm really not sure. I saw it today swimming in a local river (North Somerset). I think it was about 30cm long but that's a very rough estimate. It was significantly bigger than the other fish around. It had some pink colouration on the operculum and along what I'm guessing may be the lateral line - it was really quite beautiful! Tail and fins appear to be quite fleshy. It was swimming near the water's surface which is why the picture is fairly clear and was just hovering above a spot, facing into the current.


Fish.jpg
Yep! spot on (what?) Rainbow trout.
Right colour this time! :D
Oh and being alive really helps too :lol:
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Re: Fish ID help needed

Post by Fishnut » Mon Mar 29, 2021 8:59 pm

Thanks! And yes, being alive is a huge help :D

I also saw chub and perch but I got out my uncle's Observer Book of Freshwater Fish and was able to work them out myself. A second look through also turned up the rainbow trout, I don't know why I didn't see it first time round.
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Re: Fish ID help needed

Post by Grumble » Tue Mar 30, 2021 7:57 am

Fishnut wrote:
Mon Mar 29, 2021 8:59 pm
Thanks! And yes, being alive is a huge help :D

I also saw chub and perch but I got out my uncle's Observer Book of Freshwater Fish and was able to work them out myself. A second look through also turned up the rainbow trout, I don't know why I didn't see it first time round.
I find myself doing that with spotting guides. I suspect it’s a case of focusing on the wrong thing and maybe seeing what you expect to see, subconsciously.
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