Rearing the unrearable - Stegastes partitus

[MattMan4te]

Hello Wise People,

Our University lab has taken upon itself to attempt to rear the bicolor damselfish, Stegastes partitus, and we're seeking advice on getting the larvae to survive.

After giving our wild-caught brood stock (we have 2 adult females, 2 adult males, and 5 juveniles in a large colony tank) plenty of love for several months, they have begun to lay eggs. I should mention this is a flow-through tank that receives water directly from the bay adjacent to our university in Miami, and it is set up with 4 distinct piles of rocks/conch shells. The eggs are laid approximately weekly, and they consistently prefer to lay the eggs on the outer lips of two of the larger conch shells that are in the tank.

When the eggs appear near-hatch (day 3-4, it seems to vary), we have been removing the conch shells from the tanks, keeping them submerged in water in a bucket, and transferring them to black rearing bin. This is set up with a very low surface flow and a vertical PVC pipe (topped with a fine mesh) fitted into a bulkhead at the bin's center that allows overflow to drain out from the surface. Temperature is around 80-82 F and salinity is 35 ppt, similar to the colony tanks, though the temperature is controlled so that there is no variation throughout the day.

We have rotifer colonies which we sample, enrich, and stock in the rearing bin at an approximate density of 10 rotifers/mL once a day. We do this on the night before the eggs hatch and then again every night at approximately 5pm.

We can't get our larvae to live past 3 days.

We are fairly new to rearing, and are absolutely novices with rearing damselfish larvae. We are also well aware that this species has been attempted (without success) in the past. We would GREATLY appreciate any advice that anyone on this forum has to offer (colony care, rearing conditions, rotifer densities, whatever). We have a few ideas we will be testing in the next few months, but I'd prefer to hear what you all have to say without feeding any of our ideas first!

Thanks!!!

 

[Sniperhank]

Far from an expert, but my two questions right away are tied together.
Is there a continual food source of Rotifers and algae in the larvae tank?
If so, how are the parameters in such am easily polluted tank?
This is a great topic for Andy Sager. He is mostly a freshwater guy, but knows his stuff. A pm to him might help you out.


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[Gregcoyote]

I agree with Sniper. Andy might be the guy.

Raising the fry in a non-polluted environment heavy with foods is the trick IMO. Look at threads where folks have raised clownfish fry as they also are damsels.


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[Andy Sager]

Geez, I keep trying to get out but you all keep pulling me back in!!!! ( That's from the movie Godfather part 3 )

Tho I am more a freshwater breeder, I do have some experience with microfoods but not that were or are commonly used for marine fish HOWEVER, it seems to me that a history of only 3 days means either the conditions in the tank are not right or the food you are trying to feed is not the right food. So the first question is: Which one is the problem? My gut says it's the food source. Either not enough or not the right kind. Have you taken any samples post feeding to see if the larvae are feeding? That may confirm my suspicion.
That said, I did find a couple of articles that may help.
On the following page: https://scholar.google.com/scholar?...ved=0CBsQgQMwAGoVChMI_8SVhd2nyAIVAqCACh1PZwtL
I saw 2 articles that may explain your dilemma. I would suggest reading through article : Linking larval history to juvenile demography..... and Role of Isopod on the health, behavior and breeding ..... I skimmed through them both and saw in the first one that there may be a correlation between using smaller planktonic foods longer and successful transition to juvenile and from the second article that the isopod may have done damage to your females making your failed efforts not your fault but making the need for a larger brood stock ( IMO) necessary to eliminate that possibility for you.

Wish I could be of more help but the marine breeding successes happened more after I was out of breeding or I would be more on top of things. You may want to try to contact Martin Moe ( if he is still alive) and see if he has any other suggestions. He started with Clowns a long time ago. He used to be in the Keys. Not sure if he is still there or not.

Hope this helps

 

[Gregcoyote]

That guy in Australia propagates clams. Bet he knows. I agree with Andy, I too had a FW hatchery and the food was the key.


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[MattMan4te]

Hey Greg,

Thank you for answering, and I apologize for the delayed response. I will reach out to Andy and try to get his feedback on the issue.

We are indeed adding rotifers (10/mL) and algae (1mL green water solution per 100L) daily. We pump water in/out of the tank at about 250mL/min for 2 hours a day, in the morning. We haven't seen any spikes in ammonia, nitrates, etc.

 

[MattMan4te]

Andy,

Well look at that, you found me before I could find you!

Thanks a lot for the detailed response. I'm going to give your effort and attention all the respect it deserves by reading up on what you suggested before I come back at you with questions.

We also have the suspicion that the food is the issue. It seems like the density of rotifers in the tank isn't really being depleted much in that first 3 days. We're going to look into filtered plankton tows, commercial microfoods, etc. and see what works better for us.

On the bright side the adults are laying like crazy, so we should have many opportunities to "practice".

Again, I greatly appreciate the feedback. Expect to (most likely) hear from me again in the near future!

- Matt

 

[Andy Sager]

Andy,

Well look at that, you found me before I could find you!

Thanks a lot for the detailed response. I'm going to give your effort and attention all the respect it deserves by reading up on what you suggested before I come back at you with questions.

We also have the suspicion that the food is the issue. It seems like the density of rotifers in the tank isn't really being depleted much in that first 3 days. We're going to look into filtered plankton tows, commercial microfoods, etc. and see what works better for us.

On the bright side the adults are laying like crazy, so we should have many opportunities to "practice".

Again, I greatly appreciate the feedback. Expect to (most likely) hear from me again in the near future!

- Matt

Glad to help. I have a long history with the Rosenstiel school back in the 70s and 80s so I am more than happy to pay it back with whatever I can.
One of the things I've learned with breeding fish is timing. Usually, if you go a certain amount of time, certain things correlate to those times. 3 days, for freshwater fry at least, is usually food or lack of feeding. It sounds like that's the answer if you are not seeing a reduction in food supplied. My suggestion would be to try to get the Rotifer's food ( what rotifers eat) and try them on that smaller food. The rotifers may actually be too large for the fry? Just a guess but worth trying. I see this with some of my freshwater fish. The young pairs produce smaller eggs which makes for smaller fry but as they get older, and their eggs get larger, the fry are larger and can go straight for the larger foods. Maybe it's the same with these fish?

Just give me a shout if you need more ideas.

 

[Gregcoyote]

I think the Rotifers live off of live plankton. Green water is what it's called and keeping a culture going is a exercise in hospital style sterility. You can get sieves that are graded to sort out large Rotifers from the babies. My guess is they need protein and not planktons when hatched. They will be very size sensitive to the food. They are also pretty blind, so a smaller softer light is helpful. At least that's the routine with clown fish fry.

There is no prepared food I have heard of that works on SW fry.


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