How to remove otoliths (jewels) from a mulloway (jewie)

[Jono_SS]

I just spent a week working on Fraser Island, collecting data mainly on tailor. During our travels, we spoke to a few people that had caught jewies (mulloway), and some were interested in how to take out the otoliths, so we took a few photos that might help anyone who is interested.

Step 1 - get the gills out of the way.
Step 2 - locate the bulges in the base of the skull.
Step 3 - use a pair of bone cutters/side cutters/something else suitable to crack the bone - insert just behind the bulges and use a lever motion to crack and lift.
Step 4 - expose the cavity containing the fluid-filled sac and otoliths.
Step 5 - use a pair of forceps to pull out the otoliths.

cheers.

Jono.

[MudRiverDan]

what do the otoliths look like>?
and why do people want them?

[Jono_SS]

what do the otoliths look like>?
and why do people want them?

Each species has characteristically shaped otoliths - Jewie otoliths look like this...

Scientists want them because you can use them to estimate how old the fish is (http://www.dpi.qld.gov.au/28_14762.htm).

I guess other people collect them 'cause they look interesting, rather than being useful, just like stamps, coins, shells, lures etc...

cheers.

Jono.

ps - ok, some lures are useful, but not all of them!

[MudRiverDan]

Should be a few Jewies round after with this rain ;)

[rabbi]

;D;D
Should be a few Jewies round after with this rain ;)

I wish mate.
Has not been enough rain in this area to make any difference.
I have a mate who has made earrings up for his young daughters out of Otoliths and they are different to say the least.
Reckon i could get rid of some of mine to denture makers as they would make good choppers;D
Give you a pearly white smile.
Not much good for anything else I reckon.
cheers.

[bondy99]

Each species has characteristically shaped otoliths - Jewie otoliths look like this...

Scientists want them because you can use them to estimate how old the fish is (http://www.dpi.qld.gov.au/28_14762.htm).

I guess other people collect them 'cause they look interesting, rather than being useful, just like stamps, coins, shells, lures etc...

cheers.

Jono.



ps - ok, some lures are useful, but not all of them!

Jono,

I'd like to give you a hand with this but dont have funds to go to Fraser Island or other nice areas. Send me a pm with details, I'm still at UQ - ex CMS

Cheers, Bondy

[mattooty]

Once the fish is gilled, I get a chisel and sit it at the terminal (mouth) end of the bulge and use a quick hammer hit. This way it avoids pushing them deeper into the back of the head. If you're desperate to find them and you lose them into the head, then boil the head and pick it apart.
Some people collect them as a bit of a "trophy" of sorts, similar to people collecting deer antlers or pig tusks. Some people make jewellery out of them and some just like the novelty of having something out of the fish.
The thing with jew otoliths (as well as whiting) as opposed to most other species is that they are very hard to read unless you've got both a trained eye and quality circular cutter.

[oscarbyron]

We just aged about 6 different species at uni using these otoliths, set them in resin then cut them into very very thin slices using a very expensive cutter then put under a scope. Was quite interesting, we used scales also. Its these otoliths that brought about the recent snapper regs.

[mattooty]

Oscarbyron, was that in fisheries biology? Chances are I'm in your class if you're at SCU.

[oscarbyron]

haha yeh mate, u internal or external?

[bondy99]

Sounds like same I was doing with Silverjew.

The otoliths need to be cut correctly for growth rings otherwise wasted otolith.

Colder years slows growth down and hotter years speeds up growth, a lot of variables to be considered, not everything can be based on otoliths alone to justify regs. IMO

[oscarbyron]

Its pretty easy for them to identify when ages start dropping, even if their ages are slightly off they all use the same method for consistency to eliminate issues like that. Its a very accurate method, the blokes doing it don't need several cuts to get the centre ring coz its all they do all day, every day.

[mattooty]

Internal mate. What about yourself? We'll have to catch up for a fish sometime. Once this weather quietens down there should be some stud snapper poking around.

[oscarbyron]

Yeh internal, hows your assignment 2 going? YEh I'm very much looking forward till end of semester so I just have to worry about work, and have plenty of time for fishing.

[Si]

Yeh internal, hows your assignment 2 going? YEh I'm very much looking forward till end of semester so I just have to worry about work, and have plenty of time for fishing.

Who's your lecturer these days in fisheries biology oscar?

[oscarbyron]

Danny Bucher mate. know him?

[MudRiverDan]

Yeah I know him, nice bloke very knowledgeable, pity SCU sucks dogs balls when it comes to putting good courses together.

But really is there a scientific need to kill a fish and butterfly it's head just to find out how old it is?
Surely size weight and tagging would define this (as if anyone gives a rats ass how old a Mulloway is).

Typical SCU teaching old bollocks to new youth.

[oscarbyron]

The fish they use are from recreational and commercial fisherman so they are being killed anyway. Yeh some of the courses have not been so good, but they start getting better when you start getting into your major fields.

[Si]

Danny Bucher mate. know him?

Yeah mate i did back ten years ago. He was my lecturer too. good to hear he is still there.

[Si]

Yeah I know him, nice bloke very knowledgeable, pity SCU sucks dogs balls when it comes to putting good courses together.

But really is there a scientific need to kill a fish and butterfly it's head just to find out how old it is?
Surely size weight and tagging would define this (as if anyone gives a rats ass how old a Mulloway is).

Typical SCU teaching old bollocks to new youth.

lol, sound pretty pissed off there mate. Age and growth education is not old bollocks as its still (generally) the same methodology used by fisheries today. Sure its probably doesnt have the same quality standards but in SCU instance its for educational purposes mate. its different to research.

[bondy99]

Its pretty easy for them to identify when ages start dropping, even if their ages are slightly off they all use the same method for consistency to eliminate issues like that. Its a very accurate method, the blokes doing it don't need several cuts to get the centre ring coz its all they do all day, every day.

Yeah, takes years to develope those skills especially if someone that's specialised in it and loves it otherwise somewhat repetitive and boring after awhile just like doing fish DNA - PCR work, molecular work is frustrating when things dont work.

[bondy99]

lol, sound pretty pissed off there mate. Age and growth education is not old bollocks as its still (generally) the same methodology used by fisheries today. Sure its probably doesnt have the same quality standards but in SCU instance its for educational purposes mate. its different to research.

UQ does the same thing or very similar including in its research areas where some projects require gut analysis as well as trophic ecology.

Standard procedure I would think with most uni's doing Marine Biology or related fisheries projects, freshwater and saltwater species.

Seriola, are you in Sandgate as in Newcastle way or Sandgate as in Brisbane area?

Bondy

[Si]

UQ does the same thing or very similar including in its research areas where some projects require gut analysis as well as trophic ecology.

Standard procedure I would think with most uni's doing Marine Biology or related fisheries projects, freshwater and saltwater species.

Seriola, are you in Sandgate as in Newcastle way or Sandgate as in Brisbane area?

Bondy

Sandgate, Brisbane bondy. has its postives and negatives. nice and close to the water which is handy.

[Willo]

Here's a close up pic of a couple I have,where you ca see there shape
Willo

[mattooty]

Great photo Willo! Very well defined and shows all aspects very clearly.

[supa29]

hey do any other fish have these jewels i have jar full of jew ones but didnt think any other fish had them, not that i have ever looked just thought it was limited to jewies

good luck on your coarse

kel.

[mattooty]

All fish have them. The otolith is the ear bone. Whiting have fairly large otoliths for their size, however bream/blackfish/jacks have comparatively small otoliths.

[Jono_SS]

Hey Kel.

Up your way, I'd say barra, king threadfin and reds have good solid otoliths. Grunter have very solid ones also. On the other hand, the otoliths in mackerel are pretty delicate.

cheers.

Jono.

[supa29]

shit i only thouht jewies had them, i got about 80 pairs over the years but never even looked in any other fish will in the future.

thanks for the info

kel

[Slider]

Of course, apart from being a method to identify the age of the fish and a novelty item, otoliths actually serve a purpose for the fish. And that is to assist in hearing capabilities. Jew are a fish with strong acoustic abilities - strong vocalisations and refined sense of hearing. Whiting must also possess these qualities as otolith size corresponds directly with acoustic abilities along with swim bladder size, positioning in relation to the otoliths and shape, assisting with sound detection.

Of interest, in 2008 researchers listened for spawning sounds of mulloway in the Swan River using hydrophones. They were able to listen to individual fish, identify that fish's location and movements in the stream and with a bit of practice, be able to count the number of fish that are vocalising. The hydrophones were able to detect an individual mulloway's vocalisations from 1000 metres away.