Re:Raising Erectus fry

Pete Giwojna

Dear Nigel:

I’ll do my best to answer your questions about raising Hippocampus erectus one by one below:

How long are they in the prolific stage?

Newborn H. erectus goes through an abbreviated pelagic phase or free-swimming stage that last several days as opposed to several weeks for H. reidi or H. ingens. There is considerable variation among the fry in the same brood, however. Some of the newborn H. erectus may begin seeking out hitching posts after just a day or two, whereas others will not begin to orient to the substrate and begin to hitch until they are 1-3 weeks old. H. erectus fry are considered moderately easy to raise because they can accept newly-hatched brine shrimp (Artemia nauplii) as their first food and the high-risk pelagic period they go through is relatively short.

Could I use a fish breeder with a net for the expecting fater or would a refugium be better?

Neither of those options is a good idea. You want to avoid handling or stressing out a gravid male unless absolutely necessary, and it is never advisable to separate expectant seahorses from their mates. Isolating a pregnant male in a paternity tank as his delivery date approaches is a bad idea for a number of reasons that are discussed in more detail in the following discussion thread, so please check it out and avoid that all-too-common mistake, sir:

Click here: – Seahorse, Sea Life, Marine Life, Aquafarm Sales, Feeds and Accessories – Re:Possibly Pregnant / Swi,com_simpleboard/Itemid,/func,view/catid,2/id,1856/#1856

Can I still use a siphen when clean the fry tank?

Yes, sir, and it is advisable to siphon off fecal pellets and debris from the bottom of the nursery tank AT LEAST twice a day. Of course you must be careful to avoid inadvertently sucking up the fry, and I like to use a small diameter siphon hose (a length of ordinary airline tubing, actually) for this purpose. But larger diameter siphons also work very well and if you accidentally suck up any of the fry, they are usually none the worse for wear as long as you retrieve them from the bucket and return them to the nursery tank without exposing them to the air.

How often do the erectus sp. court and pass eggs?

The gestation period for H. erectus can be anywhere from 14-30 days, dependent on water temperature and a number of other factors, but a gestation of around 20 days is fairly typical at standard aquarium temperatures. Gravid males normally remate within a day or two after they deliver their latest brood, so once they begin breeding, mature males are more or less permanently pregnant and will present you with a new brood of fry about once every month.

If the dreaded white tail disease comes what can I use and will they survive?

When provided with good care and proper water quality, white tail disease or tail rot is uncommon in highly domesticated Mustang and Sunbursts (H. erectus) as long as they are not subjected to heat stress or temperatures spikes. If white tail disease should occur, it should be treated in isolation using broad-spectrum antibiotics and reduced water temperature. Using an aminoglycoside antibiotic (e.g., neomycin or kanamycin) with Triple Sulfa compounds forms a potent synergistic combination of antibiotics that works well as long as the condition is detected early and treatment is begun at the first sign of a problem. With prompt, proper treatment, hardy H. erectus will often survive an outbreak of white tail disease, although some of the affected individuals may lose the most distal segments of their tails to the disease. Providing seahorses with a daily dose of beta-glucan, a potent immunostimulant, can help prevent white tail disease and other health problems. Beta-glucan is a primary ingredient in both of the Vibrance formulations, so feeding your seahorses with vibrance-enriched frozen Mysis is a simple way to assure that received a daily dose of the immune system booster. If you maintain optimum water quality, feed your seahorses properly, maintain water temperatures in their comfort zone, and provide them with a stress-free environment, you should have no problems with white tail disease.

On average what is the brood size?

A brood size of 100-800 fry is typical for experienced H. erectus males that are actively breeding. However, The first few broods produced by virgin males are often inordinately small in number. This has to do with a number of factors including the smaller size of the young studs, their inexperience at executing the copulatory rise and transfer of the eggs, and differences in the level of key hormones resulting from their relative unfamiliarity with the female.

For example, when Bart Goedegebuur was breeding H. barbouri in the Netherlands,
he found that brood size was directly related to body size. A small, 4-inch male typically produced an average brood of about 25 fry, while a large 8-inch stallion regularly produced broods of 120 or more offspring (Goedegebuur, pers. comm.).

Clumsy, inexperienced males are more likely to drop eggs during the copulatory rise, reducing the number of young they are carrying accordingly. And, most importantly, virgin males are less physiologically synchronized and attuned to the reproductive status of their mates, and their hormonal levels and the physiological responses those formal control are not yet fully in sync with those of their mates during their first attempts at meeting, as described below.

Pair bonding serves to increase reproductive efficiency (Vincent, 1990). Not only does it tend to increase brood size over time, it also shortens the length of time between successive broods by keeping the partners closely attuned to one another’s condition and helping to synchronize their reproductive activity (Vincent, 1990). Thanks to their daily greeting ritual, the female is always acutely aware of how advanced the male’s pregnancy is, allowing her to begin ripening her eggs well before her mate is due to deliver, thereby enabling the pair to re-mate a short while after the male has recovered from giving birth.
Furthermore, after mating repeatedly with the same partner, the pair becomes more accomplished at achieving coitus — after all, practice makes perfect — thus reducing the number of copulatory attempts needed to successfully transfer the eggs and the number of eggs that are successfully deposited in the pouch when coitus is achieved. So experienced breeders naturally produce larger broods that inexperienced pairs.

When can they start eating enriched brine or mysis?

The current thinking is that the fry can remain on a steady diet of newly hatched Artemia until you are ready to begin weaning them onto a diet of frozen foods (usually minced Mysids and/or Cyclop-eeze). Aquaculturists are now converting the fry to frozen foods earlier than ever, often beginning around 3-4 weeks old. Jeff Mitchell reports that the fry are healthier and grow faster the sooner they make the transition to enriched frozen foods, and he expects the young seahorses to have made the transition to frozen foods by the age of 4-1/2 weeks.

The best way to prepare the Mysis for this is to mince the frozen Mysis coarsely rather than putting it through a blender. How fine or coarse you need to chop it depends on the size of your fry, since you want to wind up with bite-size pieces of Mysis. Initially, many breeders prefer to shave small pieces of Mysis off of a cube while it’s still frozen.

When the fry have grown a little larger and can accommodate bigger pieces of Mysis, I find it convenient to carefully thaw whole Mysis individually and then carefully chop them into several pieces.

Either way, it is very important to be extra diligent about vacuuming up leftovers (and any fecal pellets) while the fry are making the transition to frozen Mysis. Otherwise, the minced Mysis that doesn’t get eaten right away while it’s still suspended in the water column or shortly after it has settled on the bottom will begin to degrade the water quality in your nursery tank.

It’s important to overlap the fry food when they are making the transition. Offer them shaved or minced Mysis along with the newly hatched brine shrimp they are accustomed to eating. (Many times it’s better to offer the minced Mysis first, while the fry is still the hungriest, and then add the baby brine shrimp.) Once they begin eating the bits of frozen Mysis well, gradually increase the amount of minced Mysis and decreased the amount of baby brine shrimp you offer at every feeding until they are finally eating the shaved Mysis almost entirely.

Overlapping the feedings this way, offering newly-hatched brine shrimp as usual along with just a little frozen Mysis at first, assures that there is familiar food available to the fry while they are making the transition and makes sure that the slow learners still get enough to eat.

Some hobbyists find it helpful to begin soaking the newly hatched brine shrimp in Mysis juice for a week or two before they actually began offering the bits of minced Mysis along with the bbs. That way, the juveniles get used to the scent of the frozen Mysis and associate it with food before you start to add the bits of frozen Mysis.

Here’s a previous post from Patti that describes how she weaned her erectus fry onto frozen to Kari Mysis:

[open quote]
I’m wondering if nutrition is your problem.
Could you train them onto frozen mysis? My 4 week old erectus are
eating shaved Hikari frozen mysis already. They started not eating
much of the BBS and looking around the bottom of the bowl. I
enriched the shaved mysis w/Vibrance & put it in the bowl. It goes
to the bottom and they’re on the hunt. They’ll look at it a good
while and then snick. It only took 1 day to train them. I swish it
around a little at first to get them interested.

I think the mysis is better for them nutritionally and they don’t
have to spend so much energy eating all those tiny BBS. Give it a
try. It may take a few days. I gave mine the mysis 1st – before
adding the BBS. That way they were pretty hungry. Then I gave them
some BBS for desert to make sure each one got something to eat if
they weren’t eating enough mysis yet.
Patti [close quote]

Notice that Patti’s erectus fry were all hitching and beginning to look around on the bottom for things to eat, indicating that they were ready to give up their planktonic existence (the high-risk pelagic phase) and make the transition from live brine shrimp suspended in the water column to frozen foods.

When the newborns are the right age, don’t hesitate to try them on frozen Cyclop-Eze first if you aren’t having any luck with the frozen Mysis.

Bonus tip: adding one or two older juveniles that are already eating the frozen Mysis well to the nursery tank along with with the inexperienced fry in order to act as their mentors can hasten the transition. Many hobbyists report that fry learn to take frozen minced mysids much faster and easier when they are provided with teachers to show them the way. These teachers are usually a few of the older fry from a previous brood, which have already become proficient at feeding on the frozen mysids (Liisa Coit, pers. com.). The younger fry are quick to copy them, learning from their example.

Would a 5 gallon tank sufice for 1 brood of healthy fry?

The recommended stocking density for pelagic seahorse fry such as H. erectus is no more than 6 fry per liter, or a maximum stocking density of about 25 fry per gallon. If your nursery tank holds 5 gallons, for example, it can hold about 125 fry when stocked to capacity, and for best results I would keep it understocked. But that should certainly be adequate for the first few broods produced by an inexperienced pair.

When the fry get about 1 inch or greater will they be too crowded in a 5gallon?

Yes, sir, depending on the survival rate, there could come a time when the youngsters outgrow your five-gallon nursery tank and it would be appropriate to transfer the juveniles to a larger grow-out tank when that time comes. However, losses are likely to be high (75% mortality is common), particularly during the pelagic period, and after several weeks you may have only a handful of juveniles left, in which case a five-gallon aquarium could certainly still accommodate all the survivors. Bear in mind that it is not at all uncommon to lose the entire brood in your first few attempts at rearing seahorses that go through a pelagic phase.

Best wishes with all your fishes, Nigel!

Happy Trails!
Pete Giwojna

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