Jawfish Breeding/Spawning Overview - Opistognathidae

Jawfish Breeding/Spawning Overview - Opistognathidae

Postby mpedersen » Sun Mar 11, 2007 12:01 pm

Opistognathidae - Jawfish - Breeding, Mating, Spawning and Rearing Overview

1 - Species covered in this forum:

The Family Opistognathidae - fish in this family may sometimes be casually referred to as gobies, but in fact this family is a distinctive group of fish commonly referred to as Jawfish. There are 5 species which are available relatively frequently:
Opistognathus aurifrons - the "Pearly" or "Yellowhead" Jawfish
Opistognathus lonchurus - the "Blackcap" or "Moustache" Jawfish - Possibly a synonym or often confused with the Tiger Jawfish below...
Opistognathus rosenblatti - the "Blue Spot", "Blue Spotted", or "Blue Dot" Jawfish - imports come and go like flicking a switch, and may have high mortality rates upon import, thus the high prices
Opistognathus whitehursti - the "Dusky Jawfish"
Opistognathus sp. - the "Tiger Jawfish" (occasionally listed as O. gilberti, howerver O. gilberti is a very small Carribean species, the Tiger Jawfish hails from Bali, Indonesia)

There are MANY other species of jawfish that are infrequently or rarely available, often coming as somewhat of a mixed / misc bag of fish. I personally briefly encountered a stunning RED Jawfish shipped out of Bali only twice in 2005...haven't seen it since (but I'm not privy to that exporter's lists anymore). It seems that there may be some confusion on species names as well, especially considering that I've seen things like the "gilberti" situation above, as well as citations that O. lonchurus is from the Atlantic OR Indo-Pacific...take your pick I suppose!

For an overview of the Opistognathids, see http://www.fishbase.org/identification/ ... nes=&fins=

2 – Common characteristics:
Jawfish are commonly thought of as Gobies, although they are most assuredly a distinct family of fish and are more closely related to Dottybacks and Grammas. All jawfish share a characteristic "bulldog" type apperance, long slender body with a large mouth. Jawfish all build and reside in burrows, which they hover out of snatching meals as it floats by.

Martin Moe cites the average lifespan of Yellowheaded Jawfish in the wild as 2-3 years.

For more basic information, visit - http://www.wetwebmedia.com/jawfishe.htm

3 – Reproduction:

3.1 – Sex determination:
Separate sexes - I have found no information suggesting that any jawfish are protogynous or protandric, so for now, consider their sex fixed from the get-go. It would NOT surprise me to find out that they are hermaphrodites, especially given their sedentary nature (afterall, if you live in the same spot your entire life, why risk 50/50 odds that your neighbor ISN'T the opposite sex?)

3.2 – Sexual organization:
Pairs - Mated Pairs of Yellowhead Jawfish (O. aurifrons) are available from Florida collectors. Information suggests that during breeding seasons, jawfish form pairs, but I do not currently know that these pairings represent ongoing or lifelong monogamous pair ponds.

3.3 – Sexing:
Sexual dimorphism; - at times, especially during breeding seasons, male Jawfish are said to have enlarged heads. In general, males are said to have proportionally larger heads and buccal cavities. In reality, these are very difficult traits to discern, especially without many fish for comparisons. It is also suggested that in O. aurifrons, the male is larger than the female.

Sexual dichromatism - During times of courtship or sexual activity, Male Jawfish may undergo a color change. In O. rosenblattii, the male's anterior half to 2/3rds turns white. In O. gilbertii, it appears that the male darkens dramatically.

Sexual dichromatic traits associated with O. aurifrons (Pearly Jawfish) may not be reliable. It is sometimes said that MALE O. aurifrons will have 2 black dots on the underside of the lower jaw. However, it is apparent that ALL "Yellowhead Jawfish", or O. aurifrons collected in Florida, lack these black dots. It would be wise to exercise caution in trying to use the "Black dot" trait to identify sexes in O. aurifrons.

3.4 - Pairing / Setting Up Broodstock:
Very little, if any data or annedoctes, are available regarding any reliable means of pair formation. I.e. you can't just put 2 together and expect things to work out. The creation of pairs likely involves housing several individuals separately and trying this fish with that fish, methodically working out the pairs. The one suggest I've encountered is that if a large group of fish is available, selecing the largest and smallest from the group will likely get you a male and female (based on the suggestion that in O. aurifrons, males are larger than females). It is also suggested that purchasing a large group and letting them form their own pairs in a large tank will work.

Better yet, try to buy a mated pair whenever possible!

If ANYONE has suggestions on good, reliable means of creating Jawfish pairs, please share!!!

3.5 – Courtship:
Courtship seems to focus on the male. The male spends more time burrowing, coloration changes. Most all literature cites the male's head being "swollen" or "puffed up / puffed out". The male is also said to display high in the water column, flaring fins and gills, which occurs in the evening before lights out.

O. aurifrons is a Winter/Spring spawner in Florida (Moe).

3.6 – Spawning:
For O. aurifrons, there is conflicting information. Some suggests spawning occurs in the "den". Both fish enter the den, the male appears a short while later with a mouthful of eggs if all has gone well. At least one report on the Breeder's Registry suggests that spawning actually occurs in the water column.

As far as I am currently aware, all Jawfish are paternal mouthbrooders.

4 – Eggs:

4.1 – Size:
Reports suggest 2-3 mm, but may be "ballpark estimates".

4.2 – Quantity:
At least a few hundred in O. aurifrons.

4.3 – Characteristics
It´s not know if there´s an oil globule in their eggs.

Include items like egg shape, color, are there oil droplets (and if so, how many), are the eggs boyant or do they sink, are they adhesive? List out by species if appropriate

4.4 – Incubation period/Hatching temp:
If I remember from Martin's presentation at IMAC, they expected hatch at 7-8 days but it took 9 in O. aurifrons. Martin also discribed a periodic "egg toss" where the male will spit the egg mass into the open water and then re-take it, presumeably to aerate / change position of the egg mass within his mouth.

5 – Larvae:

5.1 – Size at hatching: 2-3 mm
5.2 – Yolk sac present at hatch: Yes
5.3 – Mouth present at hatch: Yes
5.4 – Eyes developed at hatch: Yes

6 - Rearing:

6.1 - Breeding & Rearing Techniques
Martin Moe recently reared O. aurifrons (again)...first time was MANY years back. Bill Addison (C-Quest) has also reared many O. aurifrons in the past.

It is my understanding that Martin's rearing successess have utilized shaded tanks (black sides and bottom), with wild collected plankton as the first food source. Basically, similar to the simple "greenwater" techinque, minus the green water (and replaced with freshly collected plankton from the Florida Keys).

6.2 – Day at first feeding:
I believe larvae are ready to feed immediately upon hatching.

6.3 - Starvation Time:
If known, include the time post-hatch that larval will live without feeding. This can often be found in larval studies where scientists do not feed the larvae, as well a accounts of failed larval rearing attempts.

6.4 – Feeding scheme:
Martin Moe fed wild-collected plankton in clean (sterile) tanks...no phytoplankton additions were made.

It is suggested that copepod nauplii were the food of choice as no rotifers were found in the guts of discected fish. Other reports suggest limited success with Rotifers (possibly S or even SS Strain) enriched with Selcon/Selco as a first food, followed by Brine Shrimp nauplii.

Matthew Wittenrich suggests enriched rotifers for the first 14 days, with BBS starting at day 10.

6.5 – Age at meta:
In O. aurifrons, larvae start to settle as early as 18 days, and may take as long as 26. They will be between 6 and 9 mm at settlement. Martin Moe describes O. aurifrons as settling with a "Dark Headed" phase first, in which larvae develop a dark head and then orient themselves benthically, starting to dig their burrows (yes, sand, gravel and rubble would need to be present in the larval tank). The Yellow Headed adult coloration appears a day after settlement.

It appears that once settled, Jawfish can grow very quickly, reaching saleable size (2 inches TL?) in as little as 2 months post settlement!

7 – Species been reared successfully

Opistognathus aurifrons - To my knowledge, only the Pearly / Yellowhead Jawfish has been reared in captivity. Martin Moe has reared this species on two distinct occasions (2006/7 and many years ago), and I believe C-Quest reared this species as well. In 2007, Martin Moe's Captive Bred Yellowhead (Florida) Jawfish are available (as of May) at retail through Ken Nedimyer of Sea Life Inc (www.sealifeinc.net) - retail price is $20 US vs. $12.50 for the same fish as WC.

8 – References

8.1 - Articles / Books

"The Complete Illustrated Breeder's Guide To Marine Aquarium Fishes" - Matthew L. Wittenrich. See pages 209-212.

8.2 - Web Content
Jawfish Reproduction on Wet Web Media - http://www.wetwebmedia.com/jawfishreprofaqs.htm

Martin Moe's Thread on Jawfish Rearing on Reef Central - http://www.reefcentral.com/forums/showt ... id=1053375

1993 Breeder's Registry Report for O. aurifrons - http://www.breedersregistry.org/database/OPIAUR01.htm

1995 Breeder's Registry Report for O. aurifrons - http://www.breedersregistry.org/database/OPIAUR02.htm

8.3 - Books
List any books that contain "Breeding-Relevant" information to this group.

9 - Compiled By
Matt Pedersen - mpedersen - matt (at) cichlidrecipe.com
Last Update: July 9th, 2007
mpedersen
Read-Only
 
Posts: 9215
Joined: Sun Sep 09, 2012 10:53 am

Postby mpedersen » Tue Jan 13, 2009 1:30 am

Need to add this old Article by Forrest Young on Dynasty Marine's Website

http://www.dynastymarine.net/Publicatio ... tivity.pdf

Also need to list Thresher and Wittenrich in the new books section...
mpedersen
Read-Only
 
Posts: 9215
Joined: Sun Sep 09, 2012 10:53 am


Return to Opistognathidae - Jawfish



Who is online

Users browsing this forum: No registered users and 2 guests

cron