Hi Coralite,
Ahhh, you ask some very good questions. I am currently writing another article that describes the challenges I face when trying to answer them. Because this is a new approach to farming corals, there really aren’t a whole lot of answers yet...
Spawning and brooding of corals is not something I instigate among corals. Corals, like all organisms, strive to reproduce. We don’t see it (enough) in captivity because many times there are not an excess of resources that would allow corals to allocate them to reproduction. Further, many corals need some type of environmental cue (water temp or lunar cycles for example) to trigger the release of their gametes or planulae. It may sound complicated but you do not need to be an expert at coral spawning or sexual reproduction since corals will spawn or brood if you have created a good environment for them and provide plenty of resources. I have Pocillopora damicornis that broods in captivity and my Acropora are out on the reef (I have been using the same colony for 3 years now). The P. dams use lunar cues and the Acropora use seasonal cues (temp mostly, but I suspect day lengths may be important as well). The trick is how to collect the planulae and larvae. I use plankton netting for the Acropora and I have designed a flow-through catchment system for the P. dams, although this month I simply placed them in a bucket with an air stone over night and was successful with that as well. Pretty basic stuff really
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Taking it a step further, settling corals is also fairly academic. It has been studied for decades now and many scientists have a good handle on what type of metamorphic cues are needed for coral settlement. I don’t want to talk too specifically about how I make the chips, but they are not magical in any way. As I mentioned, there is plenty of literature out there (especially from Australia where they have been settling larvae and planulae since the 80’s) that I use to form the substrates for larvae settlement. Crustose coralline algae is one particular type of metamorphic inducer that works great for Acropora, however, ceramic tiles that have been soaking in seawater for a few weeks can work just as well. P. dams will settle on most anything that has a bio-film. As a matter of fact, I have recently switched to ceramic chips for the settlement of P. dam. They are cheap, sturdy, and work just fine. I will be talking a bit about the wide range of settlement cues for P. dam as a challenge at MACNA. A challenge? Yes, settling them isn’t the hard part; it’s how to get them to settle where you want them to. The challenge is also in the question of how you can do it on a commercial scale. For example, if you have 1000 planulae and throw those all into a big tub full of chips that contain metamorphic inducers you might get 90% of them to settle. That would be fantastic results, however, what if they all settle on three chips? Then you would have three corals for sale within the industry. From these examples, you can see the expertise is not in how to make them spawn or settle, it is how set up the commercial operation so that it is competitive (in terms of numbers) with other farms or can be self supported.
Colony morphology is subjective. I try and raise them to match the sizes of the average fragment that is market ready. Right now, I am shooting for sizes around the 2-3 inch diameter range. This may be on the smallish size, but since this is a new type of endeavor, this is one area where experience in the marketplace will define it for me. I can send you photos of some types of morphology that I think would be attractive in the industry. The idea is to create corals that are similar to those out on the natural reef. A linear, un-branched Acropora fragment is not as natural looking as a whole colony. With corals grown from larvae, you get the whole colony because the coral is genetically programmed to grow that way. A fragment will eventually branch, but its overall morphology will still be ‘awkward’. I have a great photo of Porites cylindrica which demonstrates this idea perfectly. Please let me know (anyone out there) and I will send it.
Planulae from brooded corals are usually replete with zooxanthellae they received from their parent. Larvae that are produced from spawned gametes require zooxanthellae once they settle and metamorphose. I believe (and I will be talking about this at MACNA) that this is a good reason why brooded corals are good candidates for this type of farming. With that being said, I will be running a zooxanthellae inoculation experiment this summer. In the past, simply placing the new recruit in the open seawater system at the lab has been adequate for zoot uptake. Dr. Robert Richmond used to place large adult colonies of similar species in the tank to act as a donor for zooxanthellae. Both of these techniques are fine. For example, last season 90 out of 110 individual Acropora surculosa were able to acquire zooxanthellae using this technique. However, these techniques can be time consuming (i.e. it may take up to two weeks before the coral has acquired zooxanthellae). Last year, we lost what I believe to be unacceptable numbers of A. surculosa (for research and not for grow out) because they perished before they acquired zooxanthellae. Many of them that had acquired early on survived. This is what prompted the call for the experiment on inoculating zooxanthellae. I will borrow some of the techniques from Tridacna clam farmers and see if they are viable for corals as well. Further, I have a few resources in the form of scientists who are true zooxanthellae experts. They have outlined a good technique that they use to isolate zooxanthellae for inoculating corals.
I realize I may not have a checklist of procedures here and I strongly recommend you look out for future issues of Advanced Aquarist Online as I hope to offer an article on why these questions are not easy to answer yet. I must admit that I am trying to hold back on publishing some of my techniques until I can prove their effectiveness.
I can tell you this; my success is due to the careful observations on the habitat that juvenile corals thrive in. This is the key to success. Think of how far we have come in maintaining adult corals in captivity. Much of the success is due to aquarists who spent years observing their corals and writing about them.
Finally, I am familiar with Dirk’s work. Although our goals are different, it’s nice to see other people interested in pursuing this form of coral propagation.
