Raising Seahorse Fry

Dear Grant:

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, Grant, Mustangs and 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 Mustang babies are suitable for the "easy" rearing method outlined in the article):

<http://www.seahorse.com/FAMA_-_Freshwater_and_Marine_Aquarium_magazine/Horse_Forum_-_Nutrition/Nutrition_-_Feeding_%26_Rearing_the_Fry_-_Part_IV/&gt;

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 Mustang babies. I would be happy to discuss a number of more sophisticated nursery design as with you if you contact me off list ([email protected]), Grant. Nurseries can be as simple or sophisticated as you like, depending on how much time, effort, and expense you can afford to devote to rearing.

Here are some tips on hatching and enriching the baby brine shrimp you’ll need to feed the newborns, Grant:

Hatching Out Brine Shrimp (Artemia)

Many commercially made hatcheries are available or you can easily improvise your own from 2-liter soda pop bottles or quart jars. Fill the jars or bottles about 4/5 full with saltwater or brine solution and equip each container with an airstone connected to a length of rigid airline tubing that reaches all the way to the bottom. An inexpensive vibrator air pump with a set of gang valves with put out enough air for the entire battery of hatching containers. Add 1/8-1/4 teaspoon of brine shrimp eggs to each container and adjust the valves so the airstones bubble vigorously, keeping the eggs in suspension at all times. Shine a light directly on the hatching bottles and keep them illuminated 24 hours a day. A temperature of 80°F-82°F optimum for hatching brine shrimp.

The eggs will begin hatching after 1-24 hours, and the emerging nauplii should be harvested and used as soon as possible after incubation while they still retain their full nutritional value. (The yolk supply lasts about 6-8 hours after hatching, and the food value of the nauplii deteriorates steadily as the yolk sac is consumed. Once it has been exhausted after about 8 hours, the nutritional worth of the nauplii drops drastically.)

However, before they can be used as food, the nauplii must first be separated from the indigestible egg shells. Otherwise the empty shells may be accidentally ingested by the seahorse fry, which has been known to cause intestinal blockages and death.

The brine shrimp nauplii can be separated from the eggs simply by turning off the air for a few minutes and allowing the water to settle. The unhatched eggs will sink to the bottom of the hatching jar while the empty egg shells will float to the top. The nauplii can then be concentrated in the center of the jar by darkening the room and shining a flashlight on the jar’s midsection. (Brine shrimp are attracted to light and will be drawn together in midwater where the light is focused.) Harvest the nauplii by using a siphon or turkey baster to suck up the concentrated mass of shrimp. The shrimp-laden water can then be strained through a plankton screen or fine-meshed brine shrimp net.

Return the strained water to the hatching container, add more eggs, and readjust the aeration. The same hatching solution can be used for a week’s worth of hatchings before it has to be replaced.

Alternating the hatching container from which you harvest each day’s supply of nauplii will assure that you have a nonstop supply of newly hatched brine shrimp available at all times.

If you’re still uncertain about how to proceed, the information at the following link should make everything perfectly clear:

Click here: Brine Shrimp Technical Information 1
http://www.brineshrimpdirect.com/brineshrimpdirect-faq-1-2-13.html#hatching

The best eggs or cysts to use for your brine shrimp factory are decapsulated eggs which have had their hard, outer shells stripped away. These shell-less eggs have many advantages over ordinary Artemia cysts. For starters, they simplify the task of separating the live nauplii from the unhatched eggs, since there are no empty shells, and the decapsulated eggs eliminate the possibility of clogged intestines due to the indigestible cysts. Secondly, the decapsulation process destroys virtually all known pathogenic organisms. Since the shell-less eggs have been disinfected, there is much less risk of introducing disease or parasites to the aquarium when you feed your seahorses with brine shrimp from decapsulated cysts. More importantly, the nauplii produced from decapsulated eggs have greater caloric value than the nauplii from unaltered cysts. This is because the nauplii from decapsulated eggs do not have to waste energy struggling to break free of their shells, and thus emerge with 20% greater food value, primarily in the form of additional amino acids and essential fatty acids. This extra nutritional value can make a crucial difference to the rapidly growing seahorses.

Decapsulated brine shrimp eggs are now available from some manufacturers. Although the shell-less eggs are expensive to buy, it is easy for the serious hobbyist to decapsulate his own brine shrimp eggs at home.

Decapsulating Brine Shrimp Eggs.

Decapsulating brine shrimp cysts — the process of dissolving away their hard outer shell — may sound intimidating at first and may seem awkward when you first attempt it. No doubt you will have these instructions open, your eyes glued to the page, with all of your supplies at the ready the first few times you perform this procedure. Relax, this is not difficult at all, and after you’ve done it a couple of times, you will see how truly easy it is and realize decapping is well worth the extra few steps. I will walk you through each numbered step. Measurements do not have to be exact. Regular strength bleach is best, but ultra bleach can be used at lesser portions. You can estimate this yourself. Decapsulating your cysts is beneficial for a number of reasons:

• Reduces the risk of hydroids.
• Removes the outer shell, which means less mess and no fouling of your tank.
• Eliminates intestinal blockages from accidental ingestion of indigestible shells.
• Kills off any and all unwanted contaminants.
• Slightly quicker hatching times.
• Better hatch rates.
• Increased nutritional value secondary to less energy expenditure during hatching.

Supplies Needed for Decapsulating:

• Brine shrimp net
• Air pump
• plastic clip or paper clip wrapped in baggie to clip airline into the container
• Approximately 2 teaspoons brine cysts.
• Approximately 2/3 cup of bleach
• Approximately 2 cups of water

Procedure:

1. Pour your water into a container and clip airline tubing to the side. (No air stone is needed for this). This will keep the cysts in motion. Allow the cysts to aerate this way for approximately 1 hour or a little more.

2. Add in your bleach and continue aerating. As the outer shell gradually dissolves, the eggs go through a series of color changes from brown to gray to white and finally to orange–the color of the nauplii within. This process takes about 7 minutes. The decapsulation process is complete when your cysts become an orange-yellowish color.

3. Pour decapsulated eggs into a brine shrimp net. Add a dechlorination product if you want and rinse until you no longer smell bleach.

4. Drop eggs into your hatching container. You can also refrigerate eggs for about 1 week prior to use in a supersaturated saline solution.

Once you get your brine shrimp hatcheries cranked up and running in high gear, you’ll need to maintain frequent feedings in order for the newborns to do well. I’ve outlined the recommended fry feeding schedule for you below, which is based on Tracy Warland’s fry feeding regimen as a professional breeder. When looking over these recommendations, bear in mind that the home hobbyist almost always needs to be more concerned about underfeeding than overfeeding (it’s ordinarily only the pros that worry they might be feeding their fry too much). The humble home breeder will have his or her hands full just trying to keep up with the endless appetites of all those fry.

With that in mind, here are some suggestions and information to serve as guidelines when getting your rearing program started, Grant:

Fry Feeding Schedule

When feeding baby brine shrimp (bbs) or Artemia nauplii to seahorse fry, you want to avoid overfeeding (feeding them too much at a single feeding) as well as feeding them newly hatched bbs which have depleted their yolk supply and are nutritionally barren. The best way to do that is provide the fry with many small feedings throughout the course of the day, each of which they can clean up fairly quickly, rather than one or two massive feedings.

I suggest feeding the fry 3-5 times daily, at least 2-3 hours apart. When you are feeding the right amount, the fry should consume most of the nauplii within the first 20-30 minutes, but give them 3 hours to finish the rest and digest it fully before you feed them again. Ideally some brine shrimp will remain throughout each 3-hour feeding session, albeit at a greatly reduced feeding density after the first half-hour.

In other words, your ideal fry feeding schedule should go something like this: 8 AM feed, 11 AM feed, 2 PM feed, 5 PM feed, 8 PM feed, lights out at 11 PM. Harvest the baby brine shrimp for each feeding session in succession from each of the jars you started hatching at 3-hour intervals. This will assure that the Artemia nauplii you are feeding to the fry are no more than 3 hours old and thus at the peak of their nutritional value.

Like all babies, seahorse fry exist only to eat and poop. To say they are voracious is a gross understatement — at this stage of their development, the newborns have but one mission in life: to eat and thus to grow. Researchers have found that a single seahorse only a few weeks old can consume 3000-4000 newly hatched brine shrimp in a single day! Milligram for milligram, a great white sharks feeding habits appear downright dainty and positively anorexic compared to a baby seahorse on the prowl for live prey. And as you can imagine, when well-fed fry eat that much, defecation is amazingly rapid, with each newborn producing an average of one fecal pellet every 25-30 minutes.

One of the many quirks of seahorse anatomy is that they lack a true stomach like ours with the capacity to store food between meals (Bellomy, 1969). Rather, they are endowed with a rudimentary "stomach" that is little more than a pouchlike expansion of their intestine with no distinct separation between it and the rest of their digestive tract (Tamaru, Aug. 2001). Food passes continuously through this simple stomach instead of being stored therein. This is an adaptation to a sedentary lifestyle in which seahorses feed while at rest (as ambush predators that wait for their prey to come to them) more or less continuously throughout the daylight hours, rather than storing food or stockpiling energy in fat reserves (Tamaru, Aug. 2001). And like other carnivorous fishes, their intestinal tract is also relatively short (Tamaru, Aug. 2001).

Therefore, think of their digestive tract as a short continuous tube. When a seahorse is full, nothing more can be taken in at one end of its digestive tract without something being passed out of the other end. Seahorse fry don’t stop eating once they are full — the feeding instinct of these seagoing gluttons is so strong it compels them to keep eating as long as suitable prey is present. Baby seahorses, not sharks, are the ocean’s "remorseless eating machines!"

When they are overfed, particularly on hard-to-process Artemia nauplii, food passes through their system too fast to be digested properly. Because they swallow their prey whole and intact, this can actually reach the absurd point where they are passing live Artemia in their fecal pellets (Warland, 2003)! When that happens they are getting virtually no nourishment from their food and are literally starving in the midst of plenty. Here’s how Tracy Warland, a commercial seahorse farmer in Port Lincoln, Australia, describes this feeding dilemma and how to deal with it:

"We feed by looking closely at the ponies feces under a microscope, (a cheap dissecting microscope is ample); we breed 5 different species and all the ponies are the same, in as much as they are total gluttons. Baby seahorses (ponies) will eat so much instar 2 Artemia that they will pass out live Artemia in their feces, and they will of course not get any nutritional value from any feeds, so by over feeding you will starve them to death. We have done this. So if you feed them too much you will just love them to death as they will starve due to inability to digest. We look at the feces to determine the level of digestion and feed accordingly. Usually a feed is what the biomass of the tank can clean up in a 20-minute session, after which we leave them alone for about 2 hours and then feed them again. As soon as they defecate, we use a pipette to gather up the droppings and examine them under the microscope to check digestion levels and adjust our feeding accordingly. This is not necessary for every feed as you can soon learn the quantity required for each feeding; just make sure that the Artemia is digested fully (Warland, 2003)."

So if you have a microscope, you can easily verify that you are feeding enough but not too much at any given feeding by visual examination of the fry’s fecal pellets. Otherwise, you will eventually learn the right amount to feed and how often to feed from experience. The right feeding regimen varies according to species, the size of the brood and the size of your nursery tanks, as well as the type of food you are providing, so it is difficult to make generalizations in that regard. But Tracy Warland recommends the following:

"You need to add enough food for your fry to eat for about 15-20 minutes (75%
of the food should have been consumed within that time). If it is not, then you have added too much. The fry then should have some time to digest this food, about 2 – 3 hours is plenty. Provide at least 3-5 feedings daily. Only feed during daylight hours and turn off lights at night (Warland, 2003)."

As I said, Tracy’s feeding regimen may not be the best option for the home hobbyist, however. The average hobbyist has his hands full just trying to keep up with the demands of a brood of fry, doesn’t have access to a microscope to monitor the fecal pellets of the fry, and generally needs to be far more concerned about underfeeding than overfeeding. The salient point is that when rearing fry, many small feedings daily are vastly preferable to one or two large feedings. Most hobbyists are more successful at rearing when their goal is to assure that the fry have access to at least some food throughout the day. Many breeders accomplish this by adding small amounts of newly hatched Artemia to their nurseries whenever they walk by. For the sake of hygiene and water quality, its important to siphon off the bottom of the nursery tanks between feedings, whether or not you are able to do a microscopic examination of the fecal pellets.

It’s imperative that you work out the most efficient feeding regimen one way or another, since overfeeding is not only bad for the seahorse’s digestion, it also debilitates the fry because it is very energetically demanding for them to pursue prey and eat nonstop all day long (Warland, 2003). With a little experience, you will soon work out the feeding regimen that works best for you.

Many home hobbyists find an alternating 2-hour feeding schedule works well during the day. The fry are allowed to feed for 2 hours, then fasted for 2 hours, then given another feeding and fasted for 2 hours, and so on. The nursery is then darkened overnight and the seahorses are rested.

The general idea is to set up multiple hatching containers so that you can harvest the newly hatched brine shrimp nauplii from a different hatchery for each feeding. Thus, if you’re going to be feeding five times a day (i.e., every three hours throughout the day), then you would set up a battery of five separate brine shrimp hatcheries, and you would start the brine shrimp cysts hatching in each of them at three hour intervals.

The reason you stagger the hatching jars that way, adding the eggs to each at three hour intervals, is to assure that you are feeding the fry newly-hatched Artemia nauplii that have just emerged from their eggs, and therefore are at the peak of their nutritional value, for each of the feedings. Right after the first instar Artemia nauplii have emerged from their shells, their yolk supply is completely intact and they are more nutritious, since when the seahorse fry eat them, they get the benefit of all the nutrients in the rich yolk supply. Several hours after the Artemia nauplii have hatched out, they will have consumed much of their yolk supply and have relatively little nutritional value as a result. So it is very desirable to feed the newborns seahorse fry first-instar Artemia nauplii that have just emerged from their shells, because the nauplii are the smallest at that stage and therefore the easiest for even the undersized fry (i.e., runts) to swallow and more importantly because the newly emerged nauplii retain their maximum nutritional value at that point.

Once the Artemia nauplii undergo their first molt and becomes second-instar nauplii, they have exhausted their yolk supply and develop mouthparts so they can begin feeding on their own. Baby brine shrimp at this stage are larger and and may be too large for the smallest newborns to eat, and the second-instar bbs must be fed or enriched (i.e., gut-loaded) at this stage or they have very poor nutritional value. So the idea is to assure that you are always feeding the newborn seahorses first-instar Artemia nauplii that have just hatched and retain their full supply of yolk.

That’s why it’s important to stagger the start of the hatch in each of the hatcheries. If you started the brine shrimp hatching at the same time in all five of the hatcheries, by the time you did your second feeding of the day, some of the brine shrimp would be three hours old. Likewise, some of the brine shrimp you fed for the third feeding would be six hours old, and some of the brine shrimp you offered at the fourth feeding that day would already be nine hours old, and so on. The older brine shrimp nauplii would have used up more and more of their yolk supply, or already entered the second-instar phase before they were fed to your seahorses, and not have been nearly as nutritious as the brine shrimp you offered for the first feeding that day.

Staggering the start of the hatch in each of the hatching containers therefore allows you to offer primarily newly-hatched first-instar Artemia nauplii with complete yolk supplies at each of the feedings throughout the day. In other words, for the first feeding of the day, you harvest the Artemia nauplii from the hatchery you started first. You harvest the nauplii for your second feeding from the hatching jar you started hatching three hours later, and you harvest the nauplii for the third feeding from the hatchery you added the Artemia cysts to six hours later, and so on.

In short, if you will be feeding your seahorse fry five times a day, your ideal fry feeding schedule should go something like this: 8 AM feed, 11 AM feed, 2 PM feed, 5 PM feed, 8 PM feed, lights out at 11 PM. Harvest the baby brine shrimp for each feeding session in succession from each of the jars you started hatching at 3-hour intervals. This will assure that the Artemia nauplii you are feeding to the fry are no more than 3 hours old and thus at the peak of their nutritional value.

There are a couple of tip offs that indicate mating has occurred you should keep in mind so that you can tell when a male is pregnant, Grant.

First of all, when a female ripens a clutch of eggs in preparation for mating, her lower abdomen becomes noticeably swollen, particularly around the area of the vent. When she subsequently mates and passes her eggs along to the male, she may then lose up to 30% of her body weight as a result. So if you notice that one of your females has slimmed down dramatically at the same time one of the male’s pouches has become enlarged, that could be an indication of a successful egg transfer.

The other rule of thumb to keep in mind is that if a stallion’s pouch remains enlarged for more than three days in a row, there is a good chance that an egg transfer may have taken place rather than that the male is simply showing off for the females by pumping up his brood pouch.
Gravid males also 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 to feed and miss a meal or two or fail to show up at the feeding station now and then.

Here are some other indications to look for that indicate mating has occurred and that the pregnancy is progressing normally:

Indications of Pregnancy.

If you witness the copulatory rise and exchange of eggs there is no doubt that mating has occurred and, knowing the date of conception, you can confidently begin the countdown toward the maternal male’s delivery date. Knowing approximately how long the gestation period will be allows plenty of time to prepare nursery tanks, set up a battery of brine shrimp hatcheries, and culture rotifers and ‘pods for the insatiable fry.

But what if you missed the big moment? How do you proceed if you missed the actual mating and transfer of eggs, and you’re not sure if you will soon be dealing with a gravid male and hordes of hungry newborns?

There are no aquatic obstetricians, underwater ultrasounds, blood tests or over-the-counter pregnancy tests to perform, and I shudder to think how one might go about collecting a urine specimen to dip! No worries. Fortunately, there are subtle signs and suggestions that indicate a pregnancy is underway. There are number of changes in the parents’ appearance and behavior to look for. For instance, the male and female will still continue to flirt, but the nature a their displays will change from full-blown courtship to regular greeting rituals.

After mating, in subsequent days the couple will continue to change colors and brighten up when in close proximity and dance together in an abbreviated version of courtship known as the Morning Greeting or Daily Greeting. The pair exhibits the same basic behaviors and maneuvers as when they were courting with one big difference — the male never "pumps" and the female does not "point."

In addition, as the pregnancy progresses, the male’s pouch darkens due to the proliferation of epithelial and connective tissue and the placenta-like changes taking place in the wall of the marsupium, and the pouch gradually swells and expands according to the number of young developing within. The latter is not always a reliable indicator, however. Inexperienced couples often spill eggs during the exchange and a male’s first few broods are often inordinately small. The brood pouch of a male that is carrying only a few fetal fry is hardly any larger than normal, and hobbyists have often been surprised by unexpected births under such circumstances.

On the other hand, an experienced male carrying a large brood can be easily distinguished by his obviously expanding pouch. These mature breeders may carry broods numbering over 1600 fetal fry, depending of course on the species. A stallion incubating hundreds of fry will have an enormously distended pouch by the time his due date approaches.

Gravid males often become increasingly reclusive and secretive as their pregnancy advances. When the onset of labor and birth is imminent, the male will begin to shows signs of distress and his respiration rate will increase to 70-80 beats per minute. The fully developed young become very active and shake loose into the lumen of the pouch shortly before delivery. In some cases, the writhing of the young can be detected through the stretched membrane of the pouch, which causes the male considerable discomfort. He may become restless and agitated as a result, swimming slowly to and fro and pacing back and forth like, well — an expectant father. The fry are usually born in the early morning hours between midnight and dawn, arriving all at once or in multiple batches 24 hours apart.

So if you happen to miss the exchange of eggs, watch closely for the following indications that mating has occurred:

(1) A change in the physical appearance of the parents. The gravid male’s pouch will change from a light opaque color to a dark brown due to the elaboration of the internal structures and thickening of the walls of the pouch. It will enlarge steadily over the next few weeks as the young grow and develop, and the aperture will change from fully dilated to a tightly closed vertical slit. The female’s trunk will change from rotund, full with ripe eggs, to noticeably shrunken and pinched in immediately after the exchange of eggs.

(2) A change in the seahorses’ courtship displays. The pair will continue to flirt and dance and brighten in coloration as part of their Daily Greetings, but the male will no longer pump (no pouch displays) and neither the female nor the male will point. The pair will make no more copulatory rises.

(3) A change in the behavior of the male. He may become increasingly shy and reclusive. Gravid males may go off their feed as the delivery date approaches, missing meals or even going into hiding. When birth is imminent, he will become agitated and distressed and his respiration will increase markedly.

When you notice these telltale signs of pregnancy, it’s time to kick your brine shrimp hatchery into high gear and start some microalgae and rotifer cultures brewing.

Best of luck with your seahorses and their future progeny, Grant!

Happy Trails!
Pete Giwojna