Rearing Abudefduf; comparing those round black tanks

Rearing Abudefduf; comparing those round black tanks

Postby Witt » Tue Jul 10, 2007 9:48 pm

Every aquarist interested in marine fish propagation undertakes challenges and vexations that can prove dreadfully annoying; this can often last years. Here is a brief synopsis of my epic battle with Abudefduf saxatilis. I thought this might be a good one to post owing to the rearing tanks used and the frustrations encountered.

Each year, as the water temperature slowly rises from the cooling of winter I patiently polish the glass on my diving mask in anxious preparation for the sergeant major spawning season. Usually in late May brooding male sergeants can be seen a good distance away underwater, their bright blue nuptial colors being a dead give away as to the location of their nests. Once the nests are located I place 12" ceramic tiles in a variety of locations near the brooding males. Eventually, one of the males will give and spawn on the tile.

After placing a new tile in place of the old, the tile containing the spawn is transferred back to the lab, inverted and supplied with a steady stream of air. Collecting eggs and hatching larvae is non-problematic and I can usually get over 1,000 larvae from a single spawn. This is an egg shortly before hatching.
Image
I first attempted to raise sergeants 3 years ago. I hatched the larvae in black laundry sinks, fed them rotifers and watched them die. At 5 days there was a massive mortality. I added some wild plankton to the mix and routinely brought them to day 15. There was still a big drop at day 5, but I still got some to day 15. Then, I tried raising some with live microalgae, some with paste, some without rotifers, and several different densities and sizes of plankton, and I was beginning to see progress. Numbers would slowly dwindle until there were 2 or 3 left in the tanks by day 17. Flexion was just barely initiated and I kept thinking I was going to raise at least 1. Then, the next day they would be dead. By the time I thought I was getting somewhere the spawning season would be over and I was out of eggs until the next year. Well, finally this year I have good news. It turns out this is one of the pickiest little fish I have come across. Earlier this year I set up a bunch of experiments in three systems to get a little closer to my goal. All of the tanks are round and black, but they are vastly different.
Image
These are simple whiskey barrel liners from Lowes. Tanks are plumbed to a central system with UV, skimmer and Bio-tower. CONSTANT slow drip into the system. These tanks are roughly 24" in diameter and 18" deep (about 20 gal. volume).
Image
This is a new system I just set up to get more replication out of my experiments. Personally, I think these tanks are limited to hardy larvae such as clowns, some gobies and blennies and a few dottybacks. They are the same volume as the whiskey barrel liners, but notice the shape. These are taller and narrower. About 16" diameter, 24" depth.
Image
This is my personal favorite; two 50 gallon tanks connected to central system with external gated standpipes.

So here is the real quick run down. Everything in the tall, narrow tanks died at day 5 - 9 no matter what diet they were being fed. Greenwater had no effect on survival. Larvae in the whiskey barrel liners survived to metamorphosis, but experienced a large die off at 5 dph and around 15 - 17 dph. Larvae in the 50 gal. survived to metamorphosis, still experiencin g a noticeable die off at 5 - 9 and 15 - 17, but decent numbers pulling through. In the larger systems greenwater definitely reduced mortality. Paste or live, didn't matter.

Food is THE major constraint. I put hours into watching these little guys. Swimming in a soup of potential organisms and they want nothing to do with most of them. While they do consume rotifers, dinoflagellates and a bunch of other organisms they definitely do not survive on it. Copepods...they will hold out for, inspect everything around them, but unless it jerks, jostles or tries to escape they don't seem to be interested. I watched one larva for about 20 minutes the other day inspecting and casting aside roughly 50 potential meals before it came across a copepod. At the sight of the copepod, the larva stopped, curled up into an S pattern, but the copepod moved. The larva relaxed, repositioned and tried again. This went on for over 2 minutes. That larva tracked and stalked that copepod until he finally captured it.

With a good density of copepod nauplii growth is quick and flexion is achieved around day 15. metamorphosis is complete by day 20, usually.
Diet has extreme effects on growth and metamorphosis. In earlier trials no larvae hit flexion until day 17 and the tip was barely flexed up.

Image
Rearing tank design and food..... I hope this helps some of you in your personal quests.

Matt Wittenrich
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Postby KathyL » Tue Jul 10, 2007 10:14 pm

Very interesting, would be good to see the pictures instead of the square ? boxes.....
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Postby Witt » Wed Jul 11, 2007 1:33 am

OK, I got somethin'. If I open the thread in Mozilla Firefox I get the pics every time. Using Internet Explorer I get little red squares. Any ideas?
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Postby Witt » Wed Jul 11, 2007 1:55 am

Sorry for the eye melting little squares. Pics should be up for good now.
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Postby "Umm, fish?" » Wed Jul 11, 2007 2:26 am

Damn. :shock:



I need a new microscope.... :(
Andy

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Postby FuEl » Wed Jul 11, 2007 2:48 am

Hats off to you Matt! I've always wished I could have rearing systems like that in my house. I'm sure the photos of the larval rearing systems are helping many others with regards to system design.

As fish larvae rely on visual cues to identify prey, the effective hunting depth is probably rather similar for all rearing vessels since the illumination seems similar for all treatments. In the narrow vessels, larvae might be limited to successful feeding in maybe the top 1/3 or 1/2 of the vessel? In contrast, rearing vessels with a larger surface area might exhibit less intraspecific competition for food resources by fish larvae and give better results? :idea: In the large vessel (the one on the right), illumination seems to be closer to the larvae. Perhaps this could have also favoured the larvae in the larger vessel?
Last edited by FuEl on Wed Jul 11, 2007 10:18 pm, edited 1 time in total.
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Postby mpedersen » Wed Jul 11, 2007 4:18 am

Stunning thread...if I wasn't embroiled in trying to finalize my wedding reading I'd have more time to soak this up and comment further ;)

The one thing I noticed, Witt, your comments about the tall & narrow might rule out my thought of using 5 gallon buckets as an inexpensive solution for the home breeder...hmm.

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Postby KathyL » Wed Jul 11, 2007 8:03 am

OMG, the pictures are fabulous.
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Postby Clownfish75 » Wed Jul 11, 2007 8:23 am

Hi Matt W

Thats very interesting

The university hear, has/does rear Pomacentrus amboinensis, and they do it often and profusely.

I remember that they alwayss aid that survival was a bit of a hit and miss affair, I do remember that the most successful person was rearing in large 1.5m dia 1.5m deep black walled fiberglass tanks. With Live nano and wild caught plankton. amazing the similarities.

May i ask what is the aspect ratio of the wiskey barrel vs that of the fibreglass tank? Any other idea son the disparity?

Have you ever tried to culture or propagate copepods to influence survival? I surpose really thats the next step.

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Postby Witt » Wed Jul 11, 2007 10:44 am

You all bring up fantastic ideas about rearing. This is key to larval rearing!
FuEl, your comments on lighting are spot on. I did forget to mention that. In the last pic of the 50 gallon tanks I placed a fluorescent strip RIGHT on top of the tank. This helped out with amazing results. Lighting is VERY important. The picture was taken a while ago, but right now the tank on the left is filled with thousands of sargassumfish to day 8. On day 9 in all the other tanks they died with only about 1% actually consuming prey. I will keep you posted if these ones live.

5 gallon buckets are used by at least 4 people that I know of to grow larvae. The problem is the size. Clownfish, dottybacks (at least one person has been successful) and a few hardy blennies have survived this. Otherwise, I feel their use is limited. Commercial facilities experience dramatic die offs in all but the largest tank. That is probably why JCU uses large ones. I can't imagine anyone would try raising foodfish in anything less than 250 gallon volumes. This could be part of the problem. Throw a million angelfish eggs in a 200 gallon tank and see what happens. Red Snapper, snook, cobia, flounder...if you try raising them in a small tank you get massive mortality before day 12. large tanks just seem to work.

In the tall and narrow tanks I am sure it has everything to do with water flow and surface to volume ratio. I tried some of these tanks on an up-welling system, but it yields the same result. My personal favorite rearing tanks for home culture are the whiskey barrel liners from Lowes or plastic utility sinks. The sinks come with legs so they can placed in a row, fitted with standpipes, and plumbed to a system. The inside should be painted black. I use black spray-paint. Don't laugh. Hard acrylic like Krylon in high gloss. Then, i paint over it with a high gloss acrylic clear coat (Krylon).

Cultured copepods are definitely the next step. I will actually be setting up a collaboration in a week or so to see if first-feeding sergeants will take a few cultured cops and what species they prefer.
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Re:

Postby mpedersen » Wed Jul 11, 2007 11:54 am

Witt wrote:Throw a million angelfish eggs in a 200 gallon tank and see what happens


Is a million angelfish eggs in a 200 gallon tank feasible? If so, 0.0002 gallons per egg? But what about throwing 600 angelfish eggs in a 5 gallon tank (closer to 0.008 gallons per egg)? What about only 100 eggs in a 10 gallon tank (0.1 gallons per egg). I guess the core question is what makes a larger tank any better than a smaller one? We all know the obvious reasons, i.e. slower fluctuations in water parameters, but is that the actual issue we're facing? Or is the reality that one might put 2000 eggs in a 200 gallon tank, which when scaled down would still be approximately 0.1 gallons per egg.

It seems when we deal with first foods like calanoid copepods, we tend to get hung up on the fact that we can't raise enough of them for the larvae we have. Maybe we're going about this from the wrong angle, i.e. trying to raise every last larvae that hatches? If perhaps instead we focused on smaller scale using only a portion of a spawn or hatch, we might have better results? So perhaps when my angelfish spawn 600 eggs, I should only try to rear 50 of the prolarvae? In larger tanks, and we're talking pelagic spawner larvae now, how many prolarvae might make it to the first feeding stage?

FWIW,

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Postby Witt » Wed Jul 11, 2007 7:46 pm

My million eggs in a barrel speech was aimed toward curious motivation. Commercial finfish hatcheries routinely stock upwards of 100 eggs / liter into larval rearing tanks. It sounds like a lot, but the goal is to combat mortality. With most pelagic spawners (at least the ones that have been raised) you can expect less than 1% to survive to metamorphosis. The panther grouper for example; millions of eggs are stocked into large concrete or earthen ponds. Hundreds make it, but out of how many...If we applied this same concept (large tanks and lots of larvae) like the commercial food fish guys use, how many species of ornamentals do you think we could rais?

If we kept going on the down scaling theme we could end up with one egg in a liter soda bottle or 5 eggs in a thermos. Feeding selectivity trials conducted in different size vessels suggest that feeding is largely influenced by larval tank design. As an example, larval orchid dottybacks feed reliably in 3 - liter black bowls. Comparing these results to those left in 20 gallon larval tanks show amazingly different results. Which one reflects the true feeding behaviour of the larvae? Again, if I see that larval sergeants are feeding in a 50 gallon tub, does that mean this is how they would behave in nature? The answer is probably no. Bottom line is that when we scale up the size of the rearing tank larvae behave differently, develop faster and survive longer. This is the case with the sergeants and I am still a long, long way away from achieving great, reliable success. Everything from hyrodynamic flow, contact with side walls, Reynolds numbers, surface to volume ratio, all the environmental parameters that saltwater can tease apart, illumination and food all influence how well a larval tank will work.

And Matt, you bring up a fantastic point. Often, we simply try to raise too many larvae. This is usually good with a species that will consume what we offer. There are bound to be mortalities. Stocking more, assuming our larval tanks and feed cultures can sustain them, assures we bring more through. BUT, when copepods are limited what do you do?

With the sergeants they are eating certain things from the plankton. I haven't opened too many up yet, but it looks like they prefer a copepod nauplii and metanauplii of a distinct calanoid. So I have run into a great many problems with this. First, everything else in the tank needs to be flushed. I have a constant drip from a central system, but my standpipe only has 150 micron mesh screen. So along with the fish larvae I am now growing shrimp, jellyfish, nudibranchs, barnacles, you name it. When I add more plankton to introduce the preferred prey I inevitably add more of the stuff they wont eat. So as the larval period goes on I get an increase in the density of the stuff they wont eat and a decrease in the ones they will.

Intraspecific competition is high in these larval tanks; they are all competing for a limited resource, that darn copepod. Mortality eventually weans the population down to a level that can be sustained by the amount of copepods I offer. Who knows what would have happened if I only started with one or two hundred larvae??

I brought back some more eggs today for another go. I will try things a little different this time around. Now that I kind of know what they are eating and what they are not, I set up another system with a fast turnover to flush all the other stuff out.
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Postby FuEl » Wed Jul 11, 2007 10:24 pm

Spot on! The crazy larval rearing syndrome whereby one tries to rear every single larvae. :lol:
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Postby Peter Schmiedel » Thu Jul 12, 2007 11:06 am

Matt,

but what are according to you the main reasons for better results in bigger tanks?

I could assume:

1. More liter per larvae reduces water quality issues
2. More liter per larvae reduces impact of pheromone produced by the larvae
3: More liter means more phytoplankton and maybe more stabil water conditions
4. The already mentioned surface / hight ratio
5. Water movement improvement

BTW Really awesome pictures !!
Take care
Peter
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Re: Rearing Abudefduf; comparing those round black tanks

Postby Luis A M » Thu Jul 12, 2007 7:59 pm

Fascinating thread,Witt!(or Mark W.,whatever you like more) :)
And neat pics!Is that FIT?BTW,you met Andy R:there?
What are your plans,will you keep researching larval culture as a pro?

Witt wrote:Every aquarist interested in marine fish propagation undertakes challenges and vexations that can prove dreadfully annoying; this can often last years. Here is a brief synopsis of my epic battle with Abudefduf saxatilis. I thought this might be a good one to post owing to the rearing tanks used and the frustrations encountered.


I feel very identified with this.Only that my battle with Chrysiptera lasted not three but thirty years! :)

Each year, as the water temperature slowly rises from the cooling of winter I patiently polish the glass on my diving mask in anxious preparation for the sergeant major spawning season. Usually in late May brooding male sergeants can be seen a good distance away underwater, their bright blue nuptial colors being a dead give away as to the location of their nests. Once the nests are located I place 12" ceramic tiles in a variety of locations near the brooding males. Eventually, one of the males will give and spawn on the tile.

After placing a new tile in place of the old, the tile containing the spawn is transferred back to the lab, inverted and supplied with a steady stream of air. Collecting eggs and hatching larvae is non-problematic and I can usually get over 1,000 larvae from a single spawn. This is an egg shortly before hatching.


Great aproach!Eco-friendly,and you avoid variables related to broodstock management.I think this is how Martin M.and Forrest Y.could raise the jewelfish,M.chrysurus,one of the few reports of damsel raising available.

I first attempted to raise sergeants 3 years ago. I hatched the larvae in black laundry sinks, fed them rotifers and watched them die. At 5 days there was a massive mortality. I added some wild plankton to the mix and routinely brought them to day 15. There was still a big drop at day 5, but I still got some to day 15. Then, I tried raising some with live microalgae, some with paste, some without rotifers, and several different densities and sizes of plankton, and I was beginning to see progress. Numbers would slowly dwindle until there were 2 or 3 left in the tanks by day 17. Flexion was just barely initiated and I kept thinking I was going to raise at least 1. Then, the next day they would be dead. By the time I thought I was getting somewhere the spawning season would be over and I was out of eggs until the next year. Well, finally this year I have good news. It turns out this is one of the pickiest little fish I have come across.
In the larger systems greenwater definitely reduced mortality. Paste or live, didn't matter.

I also crash against the 5th day barrier,and for years they´d never make it thru it.It must be nutritional,though my starving controls died sooner.

Food is THE major constraint. I put hours into watching these little guys. Swimming in a soup of potential organisms and they want nothing to do with most of them. While they do consume rotifers, dinoflagellates and a bunch of other organisms they definitely do not survive on it. Copepods...they will hold out for, inspect everything around them, but unless it jerks, jostles or tries to escape they don't seem to be interested. I watched one larva for about 20 minutes the other day inspecting and casting aside roughly 50 potential meals before it came across a copepod. At the sight of the copepod, the larva stopped, curled up into an S pattern, but the copepod moved. The larva relaxed, repositioned and tried again. This went on for over 2 minutes. That larva tracked and stalked that copepod until he finally captured it.

With a good density of copepod nauplii growth is quick and flexion is achieved around day 15. metamorphosis is complete by day 20, usually.
Diet has extreme effects on growth and metamorphosis. In earlier trials no larvae hit flexion until day 17 and the tip was barely flexed up.

I only once tried nauplii of two copepod species and results were not particularly good,but it was just once,and there are so many variables...

It seems damsels hatch in four different larval development stages,the less developed being Dascyllus,almost prolarval,with unpigmented eyes,then Chromis,Pomacentrus and Chrysiptera.
Where would A.saxatilis fit?.They look very well developed in your pics but they measure 2.2mm TL according to the scale?.C.taupou hatches at 3.19 mm TL.

The most frustrating part was that when some larvae passed the 5th day death toll,and began to grow well and take bbs,when they were ready to meta,around day 20,they died suddenly.The larger died,the smaller kept growing until they were ready...to die :(And they died in perfect health and nutritional conditions,suddenly,sometimes under my eyes.
Somehow I came to the conclusion that they died because they could not resist stress,being meta time a stressful time;and correlated this condition to being fed on bs.
So I tried to raise them "bs less" which was not particularly difficult,and for the first time I was presented with the wonderful blue glimpse of newly meta juvs.(getting poetic here:) )

So I agree about the copepod way and will try to explore it.But landlocked hobbyists have severe handicaps regarding volumes of ASW,algae and copepod mass culturing.But no challenge,no fun,right?8)
Luis
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Postby Witt » Thu Jul 12, 2007 8:35 pm

Luis,
You bring up some very interesting points about damsel culture. For some strange reason these little fish are extremely tough to raise. One would think that their nearly ubiquitous occupation in marine environments would bode well for captive propagation. Who knows.
The pics are of some larval systems I set up in a lab here at FIT. And yes, Andy Rhyne, an ambitious and enthusiastic young soul, I met here.

Sergeants hatch out small. 2.2 mm NL is about right for newly hatched larvae. The picture is actually of a 2dph speci