Re:New Seahorses

Pete Giwojna

Dear Lisa:

Congratulations on your new seahorses, especially your pregnant male! It sounds like you must have done a fine job of acclimating them, since they obviously felt right at home in their new surroundings and wasted no time at all getting down to business and setting up housekeeping. And it is really neat that your entire family was able to witness the courtship and mating.

The differences in the feeding habits of your seahorses could simply be an indication of broody behavior from your stallion. Gravid males do behave somewhat differently; as their pregnancy progresses, they are less mobile and become real home bodies, since they cannot expose their developing brood to any unnecessary risks. They tend to hole up and may even go into hiding; they may go off their feed and miss a meal or two or fail to show up at the feeding station now and then. A pregnant male’s pouch typically becomes increasingly distended as his pregnancy progresses and the embryonic young develop, and the pouch will often change color somewhat due to the elaboration of the internal structures, increased vascularization as a result of the placenta-like changes taking place internally, and thickening of the walls of the pouch.

You can expect your Sunburst stallion to give birth between 2-4 weeks after he mated. 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. So if it’s been two weeks already, he could be ready to pop almost any day now. Once he does give birth, his gestation should remain the same for his subsequent broods, and you’ll be able to predict his delivery date with pretty good accuracy thereafter.

So it may be that your new male will have more of an appetite and begin eating more aggressively after he delivers, Lisa. If not, if the problem is not a lack of appetite but rather that the male is simply having difficulty swallowing large prey items, it’s possible that he may have suffered a minor injury to his hyoid bone feeding mechanism or the associated musculature. In that case, he may do better with smaller prey items such as the tiny Hikari frozen Mysis or softbodied adult brine shrimp while the injury heals, as discussed below:

Another common cause of weak snick in many instances is a mechanical injury to the seahorse’s hyoid-bone "trigger" mechanism. This sometimes happens when a seahorse accidentally ingests a foreign object when feeding off the bottom. The offending particle is often a piece of gravel or crushed shell. When a hard, sizable foreign object such as this is ingested, it can lodge in the throat or snout, and the seahorse may have difficulty expelling it again. (The seahorse’s feeding mechanism is much better suited for sucking things in than spitting them out again.) When that happens, the seahorse is almost always able to clear the offending object eventually, but sometimes not before it causes considerable irritation or the repeated efforts to eject it cause a muscular strain to the hyoid trigger mechanism. The seahorse then acts as though it has a very bad sore throat. The suction it generates is weak and both the act of pulling the trigger and the act of swallowing appear to be painful. The seahorse feeds reluctantly or halfheartedly as a result, and may eventually stop feeding altogether. Such mechanical injuries can also open the door for snout rot.

Suspect a mechanical injury when the weak snick or sticky trigger is not accompanied by respiratory distress, when only one of your seahorses is affected and exhibiting unusual symptoms, or when you witnessed the seahorse struggling to expel a foreign object. In such cases, most often the problem clears up on its own after two weeks to two months as the injury heals. No treatment is necessary and the key to a successful outcome is keeping the patient eating while the healing takes place. That’s what treatment should concentrate on.

When these feeding difficulties arise, it’s a good idea to try tempting the affected seahorse with live adult brine shrimp. Seahorses suffering from weak snick induced by an injury may have better luck slurping up smaller, lighter, soft-bodied prey like brine shrimp; if so, that will be enough to keep them going while they heal. You’ll want to enrich the brine shrimp to maximize its nutritional value, and gutloading the shrimp with an enrichment product high in HUFA such as Vibrance is a good way to fortify it beforehand. Brine shrimp are filter feeders that will ingest whatever is suspended in the water with them, so all you need to do is add a pinch or two (or drop or two) of the enrichment formula to a small container of freshwater swarming with brine shrimp at least 30 minutes before you offer the shrimp to your seahorse. The freshwater disinfects the brine shrimp while they are being fortified.

If you want to try your luck at raising the newborns Sunbursts, Lisa, now is the time to prepare a suitable nursery tank and to get a battery of brine shrimp hatcheries ready. Let’s go over some of the basics in that regard.

As you know, all seahorse babies are challenging to raise and Ocean Riders are no exception. How difficult or challenging the offspring may be to raise depends on the type of seahorses you have. Two main factors determine how easy or hard seahorse fry are to raise: (1) their size at birth and (2) whether or not they undergo a prolonged pelagic phase. The bigger and better developed the newborns are, the easier they are to raise. Seahorse fry whose average length at birth is 10 mm (0.4 inches) or more are able to take enriched Artemia as their first foods and are relatively easy to rear. Seahorse fry that are significantly smaller than 10 mm (0.4 inches) at birth need to be started on smaller foods that are more difficult to provide in copious amounts on a daily basis, such as rotifers, copepods, and larval Mysis, making them more difficult to raise. Likewise, seahorse fry that undergo an extended pelagic phase, during which they drift freely with the plankton, are much more troublesome to raise than benthic seahorse fry, which orient to the substrate and seek out hitching posts straightaway. The pelagic fry are difficult because the surface huggers tend to gulp air and suffer fatal buoyancy problems, and may even become entrapped by surface tension. As a result, most hobbyists find that mortality is very high during the pelagic phase.

The easiest seahorse fry to rear are therefore benthic fry that are large and well developed at birth. Dwarf seahorses or Pixies (Hippocampus zosterae) fall into this category, and indeed many hobbyists have closed the life cycle with zosterae. The most difficult seahorse fry to raise are relatively small and underdeveloped at birth, and must pass through a lengthy pelagic stage. Brazilian seahorse fry (Hippocampus reidi) are a good example of this category, and are notoriously difficult to raise.

Ocean Riders span the gamut in that regard, including both those species that are the easiest of all to raise and those that are the most difficult to rear, and everything in between. At the one extreme, there are Mo’Olios (Hippocampus fisheri), which produce very large broods of tiny fry that are barely 3-4 mm at birth and remain pelagic all their lives, even as adults. Mo’Olios are very challenging for even expert aquaculturists with state-of-the-art facilities to raise. Brazileros (H. reidi) and Gigantes (H. ingens) likewise have enormous broods of relatively small (6-7 mm) fry that undergo a rather protracted pelagic phase lasting weeks. The average hobbyist would still be hard-pressed to regularly raise any of their fry.

At the other extreme, there are pixies, H. zosterae), which produce small broods of large, well-developed benthic fry that hitch from day one. Pixies are probably the easiest seahorses to rear, and no doubt more hobbyists have closed the life cycle with this species than all other seahorses combined. Zulu-lulus (Hippocampus capensis), Spikeys or Barbs (H. barbouri) and the Sydney seahorse (H. whitei) likewise produce large benthic babies that are relatively easy to raise.

Most of the remaining Ocean Rider types (Mustangs, Sunbursts, Pintos, Fire Reds) produce fry that are fairly good sized (about 8-10 mm) and whose pelagic phase is fairly short (several days rather than weeks), and which are therefore intermediate in difficulty.

In short, Lisa, your Sunbursts (Hippocampus erectus) will produce fry that are moderately difficult to raise. They will be able to eat newly hatched brine shrimp right away, but they will go through a pelagic phase lasting anywhere from several days to a week or two. The link below will take you to an article that discusses how to set up a basic nursery tank, simple feeding regimens, and rearing the fry in greater detail (your Sunburst babies are suitable for the "easy" rearing method outlined in the article):


Aside from the very basic nursery setup described in the article, many other ingenious nursery tank designs have been tried to improve the survivorship of pelagic seahorse fry like Sunbursts babies. I would be happy to review some of the more sophisticated nursery tanks and discuss feeding the newborn seahorses with you in more detail if you would like more information before the big day arrives.

In the meantime, best of luck with your Sunbursts and their future progeny, Lisa!

Pete Giwojna

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