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enter image description here I had a dish of fish and found 2 oval shaped nearly 1cm long bones in its head.What help does it do to the fish? what is its name? I have clicked the picture myself .

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  • $\begingroup$ perhaps you can put an arrow on one of these pics so we know where it's from google.com/… $\endgroup$ – aliential Jan 11 '20 at 10:34
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    $\begingroup$ Seems like otoliths. Put a more detailed image for better identification. $\endgroup$ – Priyanshu Das Jan 11 '20 at 15:16
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    $\begingroup$ Thanks priyanka das $\endgroup$ – user459284 Jan 11 '20 at 17:15
  • $\begingroup$ Haha, it's Priyanshu. I'm not cent percent sure if its otolith or not. Just in case you don't know what otoliths are, let me tell you we too have them. They are calcium carbonate granules present in our inner ear. They strike against the sensory hair cells present in there whenever our head moves, thus giving us a sense of movement and balance. $\endgroup$ – Priyanshu Das Jan 11 '20 at 18:03
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I am a professional fish biologist and those are otoliths; I have aged thousands of them. They are primarily used in maintaining equilibrium, hearing, and balance. The details of the shape of the otolith can vary between species but generally look very similar. They are located in the skull of the fish, usually at the back.

Here is an image of other otoliths:enter image description here Photo source: Examples of common fish otoliths found at archaeological sites in Florida. Images from the Florida Fish and Wildlife Conservation Commission http://www.flickr.com/photos/myfwc/sets/72157625872804969/

Otoliths are calcium based structures located within otolithic organs (the sacule, lagena, and utricle) and make up the inner ear of boney (teleost) fishes. They come in pairs and there are three of them: Sagittal (within the saccule), lapillali otoliths (within the utricle) and asterisci (within the lagena). They are made of calcium carbonate and are generally composed in two different crystalline formations, aragonite and vaterite; crystalline form and amount depend on the otolith and stress induce metabolic processes. Otoliths are formed as the fish grows. In periods of fast growth (warmer months) the otolith forms faster and in periods of slow growth (colder months) the otolith forms more slowly. Given the cyclical pattern of warm and cold months in the year, the otolith form annuli (growth rings); annuli can be used to age fish just like rings on a tree. Additionally, they are metabolically inert and cannot be reabsorbed as calcium reserves like other boney structures in the fish; thus, they are a permanent record of the fish's age. This permanent record can also be used to evaluate the life history (i.e., movement patterns) using trace element analysis.

Specifically, how do they work/help the fish? Within the sacule, lagena, and utricle the otoliths are suspended in endolymphatic fluid within their respective organs. The organs have hair-like sensors in them that detect vibration or movement of the otoliths within, triggering an associated nervous stimuli. The nervous stimuli are then interpreted as movement and orientation.

Here are some sources:

https://dfo-mpo.gc.ca/science/aah-saa/otoliths/info/introduction-eng.html

https://en.m.wikipedia.org/wiki/Otolith#Description

https://www.sciencedirect.com/topics/earth-and-planetary-sciences/otolith

https://www.daf.qld.gov.au/business-priorities/fisheries/monitoring-compliance/monitoring-reporting/commercial-fisheries/species-specific/estimated-fish-age

This book is also an excellent resource for a much more in-depth look:

https://fisheries.org/bookstore/all-titles/professional-and-trade/55078c/

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    $\begingroup$ Answers should be complete. It's great that you added the citations, but your post needs to indicate why it's correct without reading external links that may die or change. Either summarize these sources in your own words or find photo evidence, etc. Include this info directly in your answer so users can know why you're right without *needing" to click on your links. Citations are for support, not to send users elsewhere for answers. Also, indicating you're an expert is irrelevant -- convenient for having proper knowledge to cite, but not necessary here or adequate to use as "support" $\endgroup$ – theforestecologist Apr 15 '20 at 11:45
  • $\begingroup$ I have edited the original post to provide example photos, additional detail, and more external information if the readers wish to explore further. $\endgroup$ – OliverFishCode Apr 15 '20 at 16:40
  • $\begingroup$ Excellent. Thanks for the added effort. +1 $\endgroup$ – theforestecologist Apr 15 '20 at 17:40

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