FAQs about Jawfishes, Family Opistognathidae Reproduction Related Articles: Jawfishes,  Related FAQs:  Jawfishes 1, Jawfishes 2, Blue-Spotted Jawfish, Pearly Jawfish, & Jawfish Identification, Jawfish Behavior, Jawfish Compatibility, Jawfish Selection, Jawfish Systems, Jawfish Feeding, Jawfish Disease, Best not to have other fishes present.

Sexing a dead yellowhead Jawfish... 9/22/11
Hi,
I purchased a pair of yellowhead Jawfish online but unfortunately one of them didn't make it. I am able to buy another pair, but I still have the single yellowhead Jawfish. As my tank is a Nano, though, I do not think
it's a good idea - I've heard they can be very territorial (3 in 20g would fight, I'm assuming?).
<Too likely so, yes. Even two might be trouble in such a small volume>
I read on your site that it is possible to sex yellowhead Jawfish:
"<true. Its not reliable, and best done with a group to compare to. Males have larger skulls, thicker lips and larger buccal cavities (chin-pouch so-to-speak). Rather like sexing FW cichlids. Anthony>"
This got me to thinking if it's possible to pair them up without having to buy a pair and take the one I have to the LFS - perhaps I could have the vendor sex one for me as they have so many to compare to? I still have the body of the one that died in the freezer (sounds creepy even when not taken out of context!)...would it be possible for me to slice in an area and find what sex it is, therefore knowing what sex the one I current have is?
<Mmm, possibly. Though if the reproductive organs are atretic, not-developed, not easily done>
I understand this sounds a little weird...thank you!
<No worries Jane. Bob Fenner>

Jawfish Bob, thought you would enjoy a picture of this Jawfish with eggs in mouth!!! <Thanks for sending this along. Bob Fenner>

Opistognathus aurifrons breeding... sys., fdg... reference     11/9/09
About 10 months ago I purchased a mated pair of pearly Jawfish Opistognathus aurifrons to attempt breeding.
They finally started breeding in September.
My setup is as follows:
29g AGA tank drilled w/ overflow connected to a 45g sump, that also runs a 90g display and a 14g frag.
Current USA 48w T5 HO fixture
5.5" DSB, with liverock placed in the substrate to prop up the liverock on top, excellent for their burrowing.
Temp 76.5-77.5,maintained by 1/3HP chiller on the 90.
pH 8.10 minimum, maintained by Kalk Reactor/Doser in the sump (highest I have ever seen in the combined system is maybe 8.3)
Sump has a ~20g refugium with 8" DSB, tons of Chaeto, and LR w/ a 80w PC light, helping to keep the water chemistry stable.
12/12 Light Cycle
Here is the rundown of my larvae batch attempts so far.
Larvae batch #1
Male released late Sept. Died by day 4-5, probably due to lack of sufficient food, because the culture of rotifers I had (S-type) were stored to long, so the culture was not very thick.
Larvae batch #2
Eggs noticed: Oct 7
Released: Oct 22 (possibly an newer batch than the one noticed on Oct 7, 15 days incubation time is to long for this species)
This time I was better prepared. I had a L-strain rotifer culture to work with for this batch, as I couldn't get anymore S-strain on short notice, so I crossed my fingers.
Day 1 - Once they hatched, I moved them to a 5.5g AGA tank (blacked out sides), with a 25w heater set on 75, and foam filter. The foam filter is the yellow ring kind you get from Florida Aqua farms, the
ones with a yellow doughnut of foam, around a central stalk, which I slowly had bubbling, maybe 1-2 a second. I did 50% daily Water Changes on the larval tank.
Day 2 - Mortality on seemed to be a lot, but I thought the bulk was probably just some of the enviable, plus some of the weaker larvae.
Probably about 50 of the 200 or so larvae needed to be siphoned out.
Days 3-5 - Everything seemed to be going better. I fed 1/3 of my live culture a day, plus some frozen rotifers, because my culture was kind of small. Less mortality, maybe 20 a day here, but still a lot. I kind
of figured that they were eating the Rotifers, because most of the batch was still alive. On day 4 I also noticed the pH was 7.8 and the Ammonia was about .5,
<Need to address this. Is very toxic>
and then after a 50% WC, on Day 5, the Ammonia level was 1.0.
<Deadly>
I siphoned out all the rotifers from the bottom, probably mostly leftover frozen I had been feeding, and started doing larger water changes, by slowly trickling the water from my main tank into the larval tank, probably about 80% water changes at this point.
(Still a fair bit left alive at this point, even during the 1.0 Ammonia level)
Days 6-8 - On these days I continued larger water changes to keep the Ammonia level down, keeping it at or below .25, but still kept having a good bit of mortality, and I noticed something funny about some of
the dead larvae. They were pink. For some reason some of the larvae that died and ended up in the bottom of the tank had pink spreading out from them on the tank bottom. (More on this later).
Days 9-10 - By Day 9 I only had about 7 left, and I kept a good eye on water chemistry, feeding less, and doing less water changing, as it wasn't necessary, but on Day 10 I only had two larvae left, and on D11
I had none. So batch #2 was down.
Larvae Batch #3
Eggs noticed: ~10/29?
Released: 11/3
For this batch, my L-type rotifer culture was really depleted, and the little bit of S/SS-type I managed to save from my first wasn't large enough yet to be used for feeding either. I decided to try feeding the
frozen rotifers, which were Brachionus spp., just like my cultures, because I thought the larvae were eating the frozen along with the live in Batch #2.
Day 1 - At hatch, the larvae, which appeared to be about 250+ this time, were transferred to the larval tank (AGA 5.5, blacked out sides) with the same heater/foam filter as Batch #2, but I decided to raise
the temp a bit, to 77-78F. Some time over the course of the first 24h, I noticed what I think may be the cause for some of the larvae to die and possibly cause the pink decay on some of the dead. They appeared
to be attempting to eat the foam filter! I noticed some would make "jabs" at it, and back away twitching like they were trying to take bites out of the bright yellow foam ring. I really think they were nipping at it and trying to tear pieces of the foam away. I think this may be why some of them died and had a bright pink area around them on the bottom glass. Could this be the foam they swallowed being broken down?
<Possibly... these fry may have taken the foam for food, or seen food organisms w/in it>
Day 2-3 - I removed the foam filter, and replaced it with just a airstone, set to make small bubbles, and set fairly low also. I made water changes daily, about 50% a day to keep the Ammonia as low as
possible, but by the end of Day 3, I had 100% mortality again. To note the Ammonia level, without the foam filter in there, it kept rising, so it stayed around .5, even after doing massive water changes,
probably due to the use of frozen rotifers as food.
<Yes, and the lack of biofiltration>
Larvae Batch #4
So on 11/6, my male had a new batch of eggs in his mouth again. I am currently awaiting this batch, but would like to get some advice here so maybe I can finally succeed in bringing a clutch to meta, and
hopefully have some juveniles to give some of my friends. What do you guys think?
(1) Are SS/S or L-type rotifers good food for this species? I am not so sure they are. Has anyone done a gut dissection to see if rotifers are there?
<I would be culturing copepods for follow up food... Please see Frank Hoff's works, consider Algagen as a source of Calanoids:
http://algagen.com/home.htm... I would also have/leave some live phytoplankton present with the Brachionus... and leave some light on 24/7 to help/keep the young feeding>
(2) Why would they die and then some have what looks like hot pink blobs around them when decaying (keep in mind its just some, not all)?
I think its the ones eating the sponge filter that look like this.
<Death likely due to water quality issues... Any ammonia presence is very bad. I encourage you to either make DIY or buy (see Aquatic EcoSystems site e.g.) a culture vessel w/ overflow screening to do filtration in a companion, tied-in tank. The color could be just decomposers, decomposition>
(3) What about the temp for the larval tank? I think 75F might have been a bit low, so I am thinking 78F is a better setting, more
reflective of the Caribbean temperatures this species is used to.
<Either should do. I like the lower temp. to give the young more margin for growth w/o speeding up their metabolism>
(4) What are acceptable Ammonia levels for larval tanks?
<0.0>
(5) Are 50%-80% Water Changes to <too> much? Even when the replacement water comes from the main tank to keep with chemistry, and is trickled in over the course of 1-2hrs?
<... better to drip/trickle new water in... treat it and recycle it back in...>
(6) Would a bigger larval tank be better? Wouldn't a larger tank make it harder for the larvae to catch food?
<Mmm, better for rearing, but not necessary... harder in some ways to keep sufficient food densities>
(7) Should I try to get Acartia tonsa copepods as a food source?
<One species, possibility... I'd also suggest Pseudodiaptomus pelagicus>
(8) How much should I "bubble" the larval tank? I read large bubbles were bad, so I tried to use a smaller airstone, with smaller bubbles, and on a low setting.
<Not too fine... 1 mm. diameter is about right. Glass airstones are far superior. Again, shop Aquatic EcoSystems: http://www.aquaticeco.com/>
(9) Is a foam filter a bad idea? It seems to be, since they appear to be eating it! Other methods for circulation/filtration?
<I would use an "open box filter" w/ Dacron polyester media myself... though I am VERY partial to the HydroSponge line>
Sorry for such a long winded email, but I wanted to be thorough!
Thanks,
Landon
<Thank you for sharing Landon. Please do report back your further experiences, findings. Bob Fenner>

Re: Opistognathus aurifrons breeding   11/9/09
Hi Bob,
Thanks for the speedy reply. I appreciate the help. I have already found the glass airstone on AquaticEcoSystems, and sent an email to Algagen about Calanoids.
<Ah, good>
My question about your responses now are:
(1) You said that "I would also have/leave some live phytoplankton present with the Brachionus... and leave some light on 24/7 to help/ keep the young feeding", by this I assume you mean keep a light on the rotifers?
<Sorry re the lack of clarity here. I mean/t to say to leave the lights on continuously (though not bright) on the culture vessel with the Jawfishes (and algae and rotifers)>
I thought this would have negative effects on the rotifer culture water quality.
(2) You mentioned an "open box filter" setup, by this I assume you mean just a regular HOB filter, with Dacron over the intake pipe to keep larvae out? or Dacron in the filter chamber?
<Actually, an in-tank, air-driven box filter... let me see if I can find a graphic on the Net:
http://www.csupomona.edu/~jskoga/Aquariums/Cornerfilter.html>
(3) You also mentioned a larval culture vessel with overflow screening. I checked Aquatic Eco and didn't seem to find one for larval fish, most of their vessels were either for rotifers/brine/etc, or were huge commercial applications. Do you have a more specific example?
<Mmm, here:
http://www.thefishsite.com/articles/contents/05-06UMissCultureFig1.gif>
(4) What are some good filter media or overflow screening materials?
Any specific brands/types? I would assume anything such as 53um (micrometer) or so sieve material would get clogged to easily. Where could one purchase such fine screen material in the micrometer range?
<... this is too much to answer well here. Again, you'd do well to invest some time, reading in the field. Chemically inert screening for the purpose or adaptable for this application is available in many formats. Most anything that is chemically inert.>
One thing I considered was a 10 or 20 gallon tank, plumbed into my main system, using some sort of filter/screen material over the PVC overflow pipe to keep larvae from going into the sump.
<Yes!>
This should
stabilize water quality/temp/chemistry should it not? I would guess the filter/screen material would have to be smaller than 150um or so wouldn't it?
<Mmm, maybe for small larvae as in Opistognathids, yes>
Thanks for the advice on the Hydrosponge line, they look great, I must order some of those also, and thanks again for any input. If I have any success I will surely post the results to help others.
Landon
<Thank you Landon. I would also proffer it to the Breeder's Registry and MOFIB.com. BobF>

A source for Brachionus rotundiformis for feeding pearly Jawfish larvae. - 10/06/2009
Hi,
I have been searching for a source for Brachionus rotundiformis, the S- Type rotifer strain. All of the online vendors seem to only sell the L-Type strain (Brachionus plicatilis). Do you happen to know a place
I could order the S/SS strain from?
<Mmm, yes:
http://www.seahorsesource.com/cgi-bin/shop/search.cgi?&category=Foods-Live>
I am using them to feed Opistognathus aurifrons (pearly/yellowheaded Jawfish) larvae. Also, would you suggest any particular enrichment to feed the rotifers?
<Do ask the folks at Seahorsesource re... I would do a bit more looking about in the scientific literature if this is an important project>
I lost my first batch of larvae either to fact that L type rotifers are to big for them to eat, lack of nutritional value, or rotifer culture contamination/crash.
Thanks,
Landon
<Do keep good records... consider making your results, investigations more widely known. Bob Fenner>

Wife swapping Jawfish  10/14/08 Hey Crew, So there are some strange goings on in my biotope. I lost one of my female Pearly Jawfish 2 weeks ago (I believe due to her mate not letting her out of the burrow to feed). I now have 1 female and 3 males, and the female is in a different burrow every few hours! She's pretty assertive, nipping at the males tails if they try to keep her penned in, as she like to be roving the entire aquarium as much as possible. I've been looking, but have yet to find anything about this sort of behavior, more that they are pretty monogamous fish as long as their mate is alive. Ever heard of this sort of "wife swapping"/Jawfish Stud farm sort of thing? -Darby <Hello Darby. Jawfish (Opistognathidae) can be polygamous in the wild, given the chance at least, although usually described as monogamous fish. Do see "Monogamy in marine fishes", Whiteman and Cote 2004 for an overall review of monogamy/polygamy in small marine fish. It's actually pretty common for fish to switch between breeding modes depending on the circumstances, and arguably happens even supposedly monogamous animals such as humans! If one or other partner can get away with "spreading its genes", it will. Since the female doesn't brood the eggs, the male does, she can get away with (and evolution will likely favour) mating with multiple males. It's an insurance policy that means that even if some of her mates are hopeless fathers, at least some of them will be better. If she (literally!) puts all her eggs in one basket -- i.e., mates with just one male -- she's gambling everything on that male being a skilful father. This behaviour is constrained by environmental factors. For example, if both parents must work together to defend the eggs/fry, each parent is less likely to philander. But that isn't the case here, because male Jawfish have their own burrows and incubate the eggs alone. Among cichlids, many species form monogamous pairs in aquaria when forced to do so, but are polygamous in the wild (Kribs are the classic example). So in your situation, you've got a tank where the female is able to choose from multiple males, and is taking full advantage of the situation. Cheers, Neale.>

Pairing Blue Spot Jawfish 03/04/2008 I am writing to ask if it is possible to have Blue spot jaws pair up? I purchased a small BSJ and within a week found a larger specimen with a substantial size head. I rolled the dice and hoped they would form a pair. Well, little BSJ went fin to fin with large BSJ. The little one escaped alive minus a hunk of his lip. Now each has started to settle on different ends of the tank, and engage in stare downs. I have moved LR to create obstructions in their sight paths. Is there any hope they will pair? <<I Would guess not. Keeping two Jawfish such as these does need a large amount of space between them, and i imagine in your tank, they are literally at opposite ends>> or should I just be happy I don't have little bits of blue and yellow very pricey fish flesh floating about? <<Yes, be happy>> Just to add, they are alone in a species only 30 g tank. LR and deep mixed sand bed. Just hermits and cleaner crew. Both are eating fine, even the one with the missing lip. <<To be honest, i would not of recommended two of these in a tank so small>> This is my first attempt at BSJ. I have breeding pairs of pearly jaws in 2 other tanks. But these flashy fellas seem a very different beast, than their Caribbean cousins. <<Indeed. More reading for you here http://www.wetwebmedia.com/jawfishe.htm>> Thanks, Beth <<Thanks for the questions. A Nixon>>

Weaning a genderless tunnel happy Jawfish. Fdg., sys., repro.    2/17/08 Hello all, I introduced a Bluespotted Jawfish (photo attached), nearly a week ago now. Unable to quarantine at home (a fifth tank might get me murdered by my better half), I had my buddy at the shop hold him for three long weeks. I had to remove an ornery (and quite large) Mithrax crab, but the Jawfish settled in quickly, building a network of caves within mere hours. I've been feeding frozen mysis, brine, and formula one using a pipette, which the fish takes to like a baby bottle. Now here in lies my first silly question: Am I going to cause the fish to develop a dependence on food coming directly to it? <Mmm, doubtful... I have observed and even collected this Opistognathid (at the tip of Baja)... and seen it in exhibits for years (mainly in home town San Diego's Birch Aquarium)... and it doesn't seem to lose its natural "hunting behavior"> Because, as it is, the Jawfish only gets to eat once per day, unless I were able to convince my girlfriend to spend the time each morning to nurse it on the pipette, or the Jawfish decides to join the rest of the group in swimming after food that's just dropped into the water. <Mmm, do think on the addition of a plankton generating refugium here... much to be gained> Secondly, I did search the site on sexing the Bluespots, with no definitive results. So, is there any good way to determine sex of these little guys (and girls)? <Not as far as I'm aware... until they actually spawn (males are mouthbrooders)> Finally, the wonderful mountains of sand. I was planning on adding a bit more sand; the middle to the back of the 125 gal. tank is 3-5 inches of mostly sugar-fine grade sand, the front...maybe an inch, and now due to some of the tunnel construction that has occurred I'm concerned that if the Jawfish removes too much sand from the foundation of a large rock bad things could happen. <All large solid objects need to originate on solid bottom... the bits on top neatly, stably placed atop this...> So, as I understand it, these guys like varying grades of sand. But, should I keep with the sugar-fine grade, or did NNR go out the window when the Jawfish started tunneling? <To a large extent, yes> I just want to make sure this fish is as happy as a fish can be inside a glass box. Any knowledge, insight, or criticism is greatly appreciated. <I would mix in some larger grade, even rubble of varying size... makes all tunnels more stable and is a hoot to see it all get moved about. Cheers, Bob Fenner> Jules (Portland, OR)

Tiger Jawfish Keeps laying eggs, and unidentified coral 01/28/2008 Hi all, <<Hello, Andrew today>> It's been a while since I wrote last. I have a 95 wave tank with 48" metal halides (by orbit) it's also got actinics and moonlights. Everything is on a timer. I do regular water changes, about 10-20% every week. I supplement the tank with the following; Essential Elements (5 ml/week) Liquid Calcium (2 tsp/day) Microvert (5 tsp/week) Tech M (20 ml/week) Phytoplankton (10-15 ml/week) <<Sounds good>> About a year ago I purchased two Tiger Jawfish about two months apart. Initially they had a couple spats but got over themselves. After I moved and re-arranged the tank they started living with each other. Now the female stays plump and the male has a new batch of eggs in his mouth every couple of weeks. I have a brine shrimp tank where I hatch them but I haven't seen any baby jaws to feed. I use a turkey baster to feed my corals, I used that to spray some of the hatched brine shrimp into the Jawfish den. It's been about 3 months since it's started and I was hoping you had some advice about raising them. I'm moving in the next month so I don't have a lot of time. I doubt they'll start breeding again after I move. <<Your best bet to attempt to raise them is to move them to a separate aquarium as they will more than likely become a nice meal for other inhabitants>> I was also wondering what this coral is (only photo of just a coral attached) It's about the size of a volley ball and it seems happiest about a foot from the top of the tank. <<The coral is a Favites SP closed brain LPS coral. Looks bleached with a severe loss of colour. Please read more here http://www.wetwebmedia.com/faviidae2.htm >> If I need to list what's in my tank I can. I included a couple photos of where the Jawfish den is (just under the rose anemone) Thanks ahead of time! Matt <<Thanks for the questions. A Nixon>>

Yellowhead Jawfish stkg.   12/27/07 Dear Crew, Thank you for all the help you have I given me in the past. You don't know how much you have helped me. Unfortunately a new problem arises. I have been interested in Opistognathus Aurifrons for some time now and have been planning to convert my 55 gallon freshwater tank into a saltwater tank for the soul purpose of keeping these Jawfish. My question is if I kept nothing but Jawfish and some liverock in this tank could I fit four? <Mmm, possibly... but all would be happier/better with just two or three...> The reason I would like four is because I would Like to obtain a pair for breeding purposes. Any suggestions? Thanks, Tuscan Thompson <Take a bit of time reading accounts of Jawfish spawning, aquaculture... Maybe start at the Breeders Registry (.com). Bob Fenner>

Jawfish and Pod QT!  4/27/07 You have a fantastic site and very worthy of the days (yes, days) I've spent reading during the past couple months since starting a 55 gallon SW tank.   <Thank you.> My setup is:  5-7" DSB, 60# LR, 360gph canister (bio-balls removed), <Good'¦> two powerheads, SeaClone 100 skimmer, <not my first choice, or second. third'¦but better than nothing.> 130w PC 50/50 actinic & 10k daylight; and water data is:  PH 8.2; Ammonia & Nitrite 0; Nitrate 7.5; Salinity 1.025; Alk 13dKh & Calcium 375.  Inhabitants include 2 Percula clowns, 3 Chromis, 2 damsels (going back to the store as soon as I catch them), <Also Good.> 2 BTAs, <Clones of each other I hope?> several hermit crabs, feather dusters, various snails, mushrooms, Zoas & a couple leather frags.  All seem to be doing well, better now since I caught & took 2 very ornery damsels back to the store. <Sounds functional.> I have a 10 gallon quarantine tank that has sand and shells on the bottom for two Jawfish I just ordered. <Neat.> I have wanted these since I started the tank; also the main reason for the DSB in the display, although after research here, the DSB is worth much more than just a substrate for the Jawfish!   <Yes.> A couple of quick questions on the Jawfish - are they hermaphroditic?   <As far as I know, they aren't.  Breeding behavior is different depending on the species. You can usually distinguish the male of a pair during mating events by their more distinguished markings and color.  To my knowledge there have been a few successful breeding reports but almost all seen in the trade are still wild caught.> I'm guessing that they are not, but was curious & haven't been able to locate that specific info.   And I understand that the Jawfish need some shells for structure of their burrows -- <'¦Don't count out vanity,,,, yes fish can be arrogant too.> do I just put in a couple handfuls of crushed shells in a few places on top of the sand where I would prefer that they burrow? <Just place them randomly around the tank, they will put them where they want them'¦and may occasionally steal shells from each other as well'¦.which as long as no one gets hurt is actually fin to watch.> I also ordered a group of copepods, and am wondering about a quarantine procedure for them.   <Most people forgo it, but there is no 'standardized' way to do it really'¦> I'm trying to go forward with the "quarantine everything" adage, <Good!> but when I previously purchased some copepods for the display tank, the instructions were to add the entire contents of the bag directly to the tank, water and all (which I did with no ill effects).   <You don't mention which company you are getting them from, but typically the reputable folks who market these are very meticulous with their products.  Keeping the strains pure'¦.literally down to a 'science', hehehe.  There aren't (again typically) any pathogens or micro-organisms that would be a threat to your fish.> The new copepods are planned for the 20 gallon refugium I am setting up, which is not attached to the display tank yet. <Perfect, if the fuge is offline, go ahead and add the 'pods directly to the fuge, and wait a week or two before plumbing it inline'¦.if you have the space/ability to do so.> I plan to put refugium mud as a substrate covered with crushed coral, with red mangroves for nutrient export. <Mangroves are rather poor in comparison to other organisms when it comes to nutrient export, read this by Mr. Calfo: http://reefkeeping.com/issues/2004-12/ac/feature/index.htm .> I have planned on hooking up the refugium to the display tank as soon as I get it put together in order to let the display tank cycle it.  I understand (from reading here) that there are different opinions about whether the refugium should be cycled separately, but since I didn't plan to add any bioload right away, I figured it would be okay to add the refugium to the display as soon as it is set up.   <I did this, had to compensate with extra water changes. It should also be noted I precured the rock in a separate container though.> However, if I need to quarantine the pods, I would need to do that in the refugium area before I hook to the main tank, and probably before adding the substrate, right?   <Yes, as I mentioned above that would be a good way to go'¦'¦it will also give the pods sometime alone (without being preyed on) to populate the refugium.> The big question is:  Do I need to quarantine the copepods, <Probably not, but it wouldn't hurt.> & if so, what is the procedure? <See above.> Thanks for all your help. <Anytime.>   Lillian <Adam J.>

Question about male Jawfish    2/12/07 Dear Sir, French journalist for the magazine "ça m'intéresse", I'm searching data about gold-specs Jawfish. So, would you kindly please help me ? Here is the photo I have to comment : http://www.acclaimimages.com/_gallery/_print_pages/0462-0701-2210-4201.html > Is it Opistognathus gilberti ? <Mmm, no... O. gilberti is found only in the tropical West Atlantic... this fish is in Mabul, Malaysia... I have photographed it in various places in Indonesia... The species is undescribed as yet as far as I'm aware> My questions are about eggs : > Why do the male incubate eggs in the mouth ? <Mmm, likely a useful species survival technique... though this family and the Apogonids (Cardinalfishes) are the only marine fish families to employ such mouthbrooding behavior)... Much more possibility of success/survival with this technique than production of many more gametes, dispersal to the environment...> How long ? How many eggs ? <A few weeks, hundreds...> He never "eat" one of them ? What about the female ? <Not likely, and no> > Something special or surprising fact about those eggs that could interest the readers ? <Likely all sorts...> I thank you very much, Bests regards, Adeline Colonat Magazine "ça m'intéresse" <Robare Fenner>

Dusky Jawfish eggs 8/3/05 I have had 2 dusky Jawfish for a year and now I notice 1 of them (the male) has a mouthful of eggs.  Have not noticed them before, but he has turned darker on his head.  Anyway, to assure that some, if not all of these eggs have a chance in my reef tank, I am asking you for suggestions.  I have a Sailfin tang, a blue tang, a coral beauty, a niger trigger,2 percula clowns, 2 green Chromis, a fairy wrasse, a psychedelic mandarin ,a cleaner shrimp and a hitchhiker crab; some of which would love to get there little jaws around some small live meals.  What is the best way to raise some Jawfish in captivity? Dr. Ron Widen <Really need to be moved... via the male mouthbrooding parent, to another system to avoid predation, and foods cultured for... Please read here: http://www.wetwebmedia.com/jawfishe.htm and the Related FAQs file linked above, the references cited... Bob Fenner>

Jaw Fish Breeding Hi Bob, <Anthony Calfo, here in your service> As many others have said, the Conscientious Marine Aquarist, was the first in our marine library. It gave us a good start, and continues to answer our questions along with WetWebMedia. Thanks! <an important and must-have reference, indeed!> We have three yellow tail damsels (Chrysiptera parasema) and two yellow head jaw fish (Opistognathus aurifrons) in a 55 gallon tank with 6 inches of mixed substrate (aragonite sand, crushed coral, and Aruba shells) and about 30# of Fiji live rock. For external filtering we have a CPR backpack (OK) and an Eheim 2026 canister (worth every penny). Additionally there are some sponges, several Aiptasia, and various worms that came with the rock and for cleanup we have some janitors from GARF. (We also have a 75 gal reef tank with a bunch of corals from GARF and a few fish.) Today we noticed one of the jaw fish was holding its mouth slightly open and looking in we can see glistening beads. WOW! looks like we're pregnant! <Wow! you have a mouth full of eggs too?! How exciting and bizarre!...actually, Congratulations!. How wonderful.!> We are overflowing with questions about how to give the potential new arrivals the best chance to survive. Any sage advice? I can't find much of anything searching the web. We have your jaw fish bibliography, and will try to find Young's book on breeding. <yes, realistically...be prepared that this first batch is not likely to survive in the community tank with pumps, filters and predators... but do seriously consider a dedicated species-specific tank for breeding. Secondly, get set up with a live food culturing station promptly. Refer to Moe's marine handbook "Beginner to Breeder" or the Marine Aquarium Reference" for basic food culture advice. And do look up Florida Aqua Farms for algae, rotifer and shrimp culturing supplies and handbooks (they even have a plankton culturing manual)> Following are a few observations that I have not seen on the web: When the brooder needs to eat or do burrow maintenance he puts the eggs somewhere down in the burrow, does the work, then picks up the eggs when done. Since this whole operation can happen quite fast (a few seconds) the egg mass must be sort of sticky. From time to time in the past (while in quarantine and when first introduced) we would see the two sharing a burrow but lately they seem to stay separate. The burrows are about 8 inches apart along the edge of a pile of rock. At this point there is no evidence that these tunnels are connected. In quarantine, the substrate was not very deep so they had connected tunnels with several openings under a large piece of live rock. When first introduced to the 55 gallon tank we expected they would take a while to acclimate but they seemed to be right at home, maybe because we also brought in the large chunk of live rock. It did take a few weeks of excavating and trying different locations before they settled in to their current locations. They sure can move a lot of material around. <yes...and very entertaining! have you noticed them stealing shells from each other at night to cover their burrows...a hoot!> When the lights go out (sometimes a short time before lights out) both jaw fish completely cover their burrows. This cover is so complete there is no evidence that there was ever a hole there. After the lights come on they remove the covers. <ahah! I should have read further...hehehe> Have been looking for a way to tell the male from the female and don't see anything except the brooding. <difficult...but notice the enlarged folds of the buccal cavity (chin) and broader skull> Lee & Mary Powell <please write a follow-up... looking forward to future spawns! Anthony Calfo>

Breeding Pearly Jawfish Hi Bob, <cheers, friend from afar. Anthony Calfo in your service whilst Bob travels> I have a 200l tank with a pair of Pearly Jawfish in it. I have set this tank up solely for the purpose of breeding the Jawfish.  <it is very exciting to hear an aquarist with a proper system for fish breeding> I live in South Africa so we do not get the Jawfish here very often as flights are long and the losses are great.  <understood... a fascinating fish indeed> I have had the pair now for close on to a year and they have now started breeding. The female will really swell with eggs (Clearly visible behind the stomach). The female enters the males borough about 1Hr after lights on and spends about 15 to 20min with the male. When appearing again the male will be carrying eggs in his mouth. The eggs are white in color and are about 1mm in diameter. The problem is that the male eats the eggs after 1 to 3 days. <this is not at all uncommon with many young pairs... even the best suited mates often fail with the first several to a dozen spawns> I feed them once a day with a well varied diet which includes live food. I keep feeding them while he is carrying the eggs which he leaves in his borough to come and eat. Could the eggs be infertile?  <quite possibly as they are a bit clumsy with each other at first> Should I try to recover the eggs from his hole when he is eating and then try and agitate them with a small pump?  I would wait to see after several more attempts before trying to rear artificially> Could this work as I have read that some people hatch their Dottyback eggs in this manner?  <yes my friend, but it is a lot of work and very tedious. Lets see if the natural parents don't evolve> Any help would be appreciated. Tokkie. <keep up the good work! With kind regards, Anthony>

Mixing Jawfish? 3/24/03 I would be grateful for an opinion on Jawfish compatibility: <easy one... they are scary territorial> Can more than one Blue-Spotted Jawfish get along in and 80G tank? <probably... seek females (smaller head/jaw, buccal cavity)> How about one Blue-Spotted and one Yellow-Headed? <not recommended... but a very tight cover on the tank for all is... they are serious jumpers> More than one Yellow-Headed? <perhaps yes... 2... not more than 3 conspecifics. All need very deep substrates too. Some say 12" ideally. Most all say 6" minimum> What about Dusky Jawfish--can they be kept more than one to a tank? <indeed, not. Quite aggressive to each other.> Thanks! <best of luck... do try to purchase a pair/trio from the same tank/dealer for better chance of compatibility. Anthony>

Sexing Jawfishes 2/6/04  Hi (love you're site!) I was wondering if you new how to tell how to tell the difference of the Yellowheaded Jawfish.  <the one that won't stop to ask for directions is the male...>  I couldn't find it on your fish articles all it says is that it's hard to tell the with the Yellowheaded Jawfish.  <true. Its not reliable, and best done with a group to compare to. Males have larger skulls, thicker lips and larger buccal cavities (chin-pouch so-to-speak). Rather like sexing FW cichlids. Anthony> 

Breeding Jawfish Dear Mr. Fenner,      <John>        Recently, I noticed one of my Jawfish carrying eggs in its mouth. I have read the FAQ's page discussing Jawfish breeding but still have many questions. My questions are geared toward the raising of the Yellowheaded Jawfish (Opistognathus aurifrons) from eggs to larva to adults. Currently the pair is being housed in a 90 gallon display tank, with wet/dry filtration, powerheads, and a skimmer. I Don't think the larva will survive the display tank but I've been thinking of setting up a twenty gallon species tank, for the purpose of breeding. I would appreciate any thoughts and recommendations on equipment for this set-up. <A twenty might do... you should (quickly) read through Frank Hoff's works on food culture, start your gear going for same... see Florida Aquafarm's site re> Also, I have no idea what the requirements for caring for and feeding the larva and on to the fry (hoping they make it that far) should be. I would appreciate any advice you can give me, and any references to web sites or books where this may be discussed. Also, I was wondering if many people have had success raising Jawfish to adulthood. Thank you for your time, John <There are a few protocols. Take a look on the "Breeder's Registry"... Bob Fenner>

Info. on Opistognathid culture? Hi, <Hello there> First off, I want to say that this website is great! I've just stumbled across it while doing a search for info. (which brings me to my question in a second...) and it is very cool that you (Bob) and the other generous persons on this site are providing all this information. :-) <Welcome> Ok -- on to my question: Do you know where I could get information on rearing techniques for Opistognathus sp.? I saw on your site that "some species of Opistognathids have been bred and reared in captivity" and I was wondering who or what organization I could contact to possibly get details. <Mmm, Frank Hoff's works, general searches on the Net, there are some recent books... Do you read German?> I recently completed my Master's thesis project at a university on the East coast involving finfish culture and I'm now on the West coast and getting ready to start up some culturing of my own to possibly sell to LFS/warehouses in the area. <Ahh! There is much anecdotal (as opposed to more scientific) information/observational work on Jawfish reproduction... but many species have been cultured.... though the principal (aurifrons) is still mostly wild-collected...> Thanks in advance for any information or advice you can give me. Sincerely, Kristin <Will help you... more... if you'd like, on return to the States (where ref. works are). Bob Fenner, in Quito>