So does anyone know what I should be feeding the larvae if I can catch the release into the water column? If I'm home when she releases the larvae, my plan is to catch with shrimp net & also suction out with a small python syphon into an isolation tank. There I was going to aerate with a bio sponge filter and add copepods. But what else could I do if I can catch these larval cave Basslets? Thanks everyone!
Just for clarification here, if they are mating, then the fish will be releasing eggs and sperm into the water - they will not be releasing live larvae. From the source I listed above, which succeeded in rearing
Liopropoma rubre, and has been working to rear the larvae of
Liopropoma carmabi too:
"We collected the pelagic eggs in a 120-micron Nitex bag attached to the overflow of each tank. The bottom of the bag rested in a small container of water so that the eggs would remain immersed. In the morning we would rinse the eggs into a beaker and lightly aerate them for the rest of the day, then pour the partly-hatched eggs into a rearing tank,"
For feeding the young, they used the following three copepod species -
Parvocalanus crassirostris,
Pseudodiaptomus pelagicus, and
Acartia tonsa. I would assume - based on how infrequently these basslet species have been aquacultured - that you'll need first stage
Parvocalanus crassirostris nauplii (newborn parvo pods) with the older pods sieved out to feed the newly hatched larvae (i.e. I'm guessing the older pods will be too big, and you'll need only the smallest pods available to feed the young).
Yeah, the one I'm familiar with is "
Apogon quadrifasciatus" (with the accepted name of
Ostorhinchus fasciatus). They were kept at 29C (84.2F) and the eggs hatched after 5 days (I'd imagine at normal temps 7-8 would be about right).
"The average total length of the newly hatched larvae was 2.6mm with an average mouth gape of 160 μm."*
"most marine fish larvae consume prey that are only 20% of their total gape."**
So, assuming these guys are in a similar boat because they're in the same genus, they're likely going to need tiny feeds. As a note here, Bangaii Cardinals,
Pterapogon kauderni, are actually in a different genus and - as mentioned above - seem to have different reproductive strategies than the "average" cardinalfish.
*Source:
The present study describes captive breeding, reproductive behavior and larval/juvenile rearing of Apogon quadrifasciatus. Spawning occurred 25 days after stocking in the breeding tank. Clutch size varied from 2500 to 3100. The males incubated the eggs, the incubation period was approximately...
pubmed.ncbi.nlm.nih.gov
**Source:
The reproductive behavior, embryonic development and early larvae of Priolepis nocturna are described. Three pairs of P. nocturna began spawning 41 days after acquisition and maintained a 5-10 day spawning cycle lasting beyond several months.
www.academia.edu
Yeah, you'd need to screen the Parvocalanus culture prior to feeding them so that you're only offering the baby Parvocalanus pods (the 1st stage nauplii) to the fish larvae. This is what I was meaning when I brought up sieving the culture if the feeders were too large.
Adult Parvocalanus pods get up to 400 microns, whereas stage 1nauplii are about 40 microns. This means that they should be ~1/10 the size of the adult pods (which looks like it would fit with the ~20% gape rule). So, basically, before offering the feeders to the fish, strain them through a 45 or 50 micron mesh - this ensures that you're only getting the smallest available feeders (those that are small enough to fall through a 45 or 50 micron mesh), which should be more appropriately sized for the larval fish.
I'm assuming you'll have the rearing tank heated to match the broodstock tank:
Water temperature directly impacts the development time and survival rates of eggs; lower temps = longer development time (in some cases, dropping the temperature a few degrees can change the hatch date by a few days, so as long as it was within a tolerable range for the chromis, your eggs may still hatch). Most fish have an ideal temperature range for the larval development, growth, and survival (for most tropical reef fish, right around 78-83F seems to be considered ideal from what I’ve seen, so you probably want to keep temps above 75F).
And, here's some general aquaculture advice:
"Based on this, I'd assume you'll probably need more than rotifers - I'd guess you'd need
Parvocalanus crassirostris pods (or other, super tiny pods - but Parvocalanus are by far the easiest to find on the market at the moment), and you'll probably build up slowly from Parvo nauplii to Artemia nauplii over the course of the rearing.
Some general advice that might help:
- Have a tank ready to move the larvae into (basically a tank with an air stone, a dim light, and a heater - a kreisel tank is ideal, but not necessary; you don't want a filter, a skimmer, uncovered pumps/powerheads, etc. - it needs to be as pelagic larvae safe as possible).
- Be prepared to catch the young when they hatch (ideally, you'd be able to move the eggs immediately before hatching into the new tank, but I'm assuming you don't know exactly when they'll hatch) - catch them and move them into the larval rearing tank as soon as possible.
ISpeakForTheSeas said:
Assuming you have fertile eggs, the advice I would give is this:
- if possible, get some Parvocalanus crassirostris pods too (rotifers are great, and I would expect the larvae to go for them, but some fish larvae are picky and prefer pods over rotifers - having both seems like a good way to ensure you have good, small foods for them... Artemia and other larger pod species would likely be good to have on hand too for the larvae as they grow.
- Get various sizes of very fine sieves so you can control the size of the feeders being offered to the larvae as/if needed.
- Add phyto directly to the larval rearing tank. It’s a good method of ensuring that the feeders are gut-loaded and healthy, and it makes them easier for the fish to see (better feeding/survival rates are typically observed with this method).
- Observe and note information about the larvae (things like how big the eggs are, how big the larvae are, when the larvae settle, when coloration comes in, etc.) and the larval behaviors (stuff like if they are attracted to light, how they react to light, if they are attracted to certain colors, what feeders they eat and what what sizes of feeders they eat at what days post hatch, what kind of substrate they prefer to settle on, are they cannibalistic, etc.).
- Watch for developmental bottlenecks and issues with your rearing methods.
- A lot of people run into feeder issues their first few times breeding, so I’d have a backup plan in place to be able to get some feeders quickly if you find yourself needing some.
With regards to the sieves and feeder sizes:
- You may need to screen the feed initially to only offer Parvocalanus nauplii.
- Observing the larvae eating when/if possible is important for telling if they are accepting/able to eat the food you are offering them.
ISpeakForTheSeas said:
Generally the main thing to watch for at this stage is a bottleneck where the young start dying off - these usually happen after a few days (day three post hatch seems to be one of the most common bottleneck days for fish that hatch with a yolk they can feed off of - if the rots and phyto don’t provide the proper nutrition for these guys, you might see a die off sometime around here). Some fish run into multiple bottlenecks, including some that happen around/after 2-3 weeks post hatch, so you really need to keep an eye on how things are going. Bottlenecks typically occur because the food the fry is eating isn’t nutritious enough for them, or they’re not interested in eating the food offered, or the food isn’t the proper size for them to eat.
ISpeakForTheSeas said:
if you do run into a bottleneck and lose this batch, don’t get too disappointed by it - this happens frequently in trying to breed a new species (even to the professionals), and every attempt gets one step closer to success.
With regards to the substrate settlement:
- Some species need sand, rock, dark areas, specific colors, or other oddly specific things to settle on/in (from what I've seen, inverts are usually a lot more picky with this), so it may help to have a ledge or cave (PVC should be fine for this, if it's even needed, which I honestly kind of doubt) and a little sand in the larval rearing tank.
That’s all I can think of at the moment - hope it helps!"
reefs.com
