Hello all, not necessarily the best subject for a Monday morning but I wonder if someone could help me identify these objects please? They were in the stomach of a good sized still water caught Rainbow trout which was also pretty stuffed with crayfish. I have looked at the internal organs of a crayfish and can't find these (feel free to correct me) so what are they? They feel cold to touch like stone, feel heavier than bone and are identical in shape, just vary in size.

I am new here so please forgive me if I have made any errors regarding this post or the photo's.

They look like mushrooms but why they are solid I wouldn't know unless they have been fossilised in some way.

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Sandy
Carried it in full, then carry it out empty.

I have no idea what they are. Interesting tho

How big are they?.....Are they hard like stone?.....Can you cut them or crush them?.....Do they float or sink?......Are there any symetrical patterns that would suggest they may be from a mollusc or crustacean?....Can you see these on the lake bed or in the silt where you caught the trout from?....Do you know where the trout came from originally and if you do can you find out if these exist from there?.....

I had an idea and then did a bit googling.

I am taking an educated guess here but I think they could be "Otoliths" ie (ear bones from fish).

I believe this because they are very similar to Otoliths in colour and shape, the size I do not know. The Otoliths appear to have more defined edges but I am factoring in that they have been inside a Trouts stomach and have been subjected to digestive juices. I am too thick to work out how to set a link up to google but there are picture of Otoliths that look similar to your photos.

They may be Otoliths from other fish species present in the lake you fish or they may be Otoliths from dead Trout which have been eaten in the stew ponds.

Hope this helps

Thank you for the responses Steveow, here are a couple more photo's. Yes they can be crushed (see pic) three of the are just over 1cm across and the small two are .5cm. I have not seen them on the lake bed. Your 'otolith' theory is an interesting one, though having googled them they are similar(ish) but I am not 100% convinced. Glad someone else thinks these are as interesting as me!





BTW these were from a fin perfect 'overwintered' fish not a recent stockie.

They might be stones or bits of gravel from the lake bed perhaps? You say they are hard and can be crushed and that the fish was full of crayfish too. I know that here in Taupo the bigger fish fish that feed on koura (small, lake crayfish) also eat a lot of pumice from the lake bed to help them digest and 'pass' the hard shells of the beasties. Whatever they are it could be that your fish was doing something similar.

Possibles? Could be pic on bottom right? These are gastroliths from a crayfish. Today such gastroliths are found in freshwater crayfish of the family Astacidae as paired disc-shaped structures. They are thought to be the way the animal sequesters calcium prior to ecdysis (molting) as a way of conserving this precious resource The gastroliths are then broken down to facilitate hardening of the new exoskeleton.

Opalized Crayfish Gastroliths Fossils

crayfish gastroliths

All crayfish have a hard outer shell (exoskeleton) composed of calcium carbonate but no internal skeleton. Their body is formed of three parts; head, thorax (the section with legs), and tail (the edible section). The carapace protects the both head and thorax. As the crayfish grows it must moult/shed its shell and grow a larger one. However, to do this it has to have a store of calcium to draw upon. It achieves this by growing a pair of gastroliths in its stomach prior to moulting. The gastroliths are composed of calcium carbonate and are used to build the new shell. The process is repeated throughout the life of the crayfish. Two pairs of gastroliths are shown in the image. Also the discarded shell may be eaten by the crayfish (or another crayfish) as an additional source of calcium. Just after moulting the crayfish is extremely vulnerable to predators as it no longer has its 'armour plating' to protect it. If the predator is a bird, such as a cormorant or heron, the two unedible gastroliths may be left behind beside the water to be found by a passer-by.

Image search on google with give you plent pics.

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Thank you Stonepark! This is exactly what they are, mystery solved

Used your link to find this picture...



Many thanks to all for contributing I am very grateful.

Best wishes,

Andrew

Wow, thats pretty cool!

I like the way the mystery was solved in less than two hours!

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PawPrinT
"I'd rather be fishing"

Ok so who is going to tie some up? get in quick and claim the pattern.