fry and salinity

Dear Nigel:

Whether or not hyposalinity may be beneficial for seahorse fry depends on whether they are pelagic or benthic in nature, which varies depending on the species. 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. Pelagic seahorse fry may benefit from lower than normal salinity (around 1.016) because it reduces their buoyancy and helps to keep them away from the surface.

Benthic seahorse fry, on the other hand, are bottom huggers and do not need reduced salinity in their nursery tanks. Zulus (Hippocampus capensis) and dwarf seahorses or Pixies (Hippocampus zosterae) produce benthic babies which do just fine at normal salinity. Since you are considering keeping Zulu-lulus (H. capensis), you won’t need to adjust the salinity at all in order to raise the babies.

Best of luck with your seahorses, Nigel!

Happy Trails!
Pete Giwojna

Dear Nigel:

Yes, sir, A newborn seahorse’s first instinct is to head to the surface to fill its swim bladder. Pelagic seahorse fry, which undergo a free-swimming or planktonic stage of development, tend to remain near the surface afterwards. Benthic seahorse fry, however, typically make a quick trip to the surface to inflate their swim bladders and then immediately settle down to a bottom-dwelling existence.

As in many other bony fishes, the seahorse’s gas bladder functions as a swim bladder, providing the lift needed to give them neutral buoyancy (Seahorse Anatomy, 2004). In essence, the swim bladder is a gas-filled bag used to regulate buoyancy. Because the seahorse’s armor-plated body is quite heavy, this organ is large in Hippocampus and extends well down into the body cavity along the dorsal boundary (Seahorse Anatomy, 2004). It will have a whitish to silvery appearance and is a simple, single-chambered sac that begins at the bend in the neck and extends to about 1/3 of the length of the coelomic cavity (Bull and Mitchell, 2002).

The gas bladder arises as a simple pouch or outgrowth from the foregut (Evans, 1998). In newborn seahorses, this connection with the gut is retained as an open tube (physosymotous), called the pneumatic duct, and seahorse fry gulp air at the surface to fill their gas bladder initially. There is only a short window of opportunity to do this, since the fry lose this open connection very early in life. As a result, the air bladder is often completely closed off (physoclistous) in fry that are more than a few days old, and they can no longer inflate their gas bladders this way. Consequently, fry that miss this early opportunity to gulp air — perhaps as the result of an oily or greasy film at the surface of the water — suffer from underdeveloped swim bladders. As they grow and become heavier, they sink to the bottom and are unable to swim or feed normally.

This is the case with most seahorse fry. If denied access to the surface to inflate their swim bladders, the fry behave normally while they are small and their weight is still negligible. But over the weeks, as they grow and put on weight, their underdeveloped swim bladders and inability to achieve neutral buoyancy increasingly handicap them. Once they gain a little weight, they sink like rocks. Unable to swim, they are reduced to slithering along the bottom on their bellies and are commonly referred to as sliders. This deficiency does not become apparent until the fry are several weeks old. Needless to say, this hinders their swimming ability and severely limits their feeding opportunities, delaying their growth and development, and rendering entire broods useless. In several cases, the problem was traced back to an oily film on the surface of the nursery tank, which prevented the newborns from filling their swim bladders with air (Silveira, 2000). A protein skimmer will prevent this by removing filmy surface layers and surfactants in general.

I have never reared Hippocampus capensis myself, so I cannot say for certain whether the newborns are physosymotous or physoclistous at birth. But the Zulu babies are as benthic as they come, which is what the phrase "drop like rocks" is meant to indicate. To play it safe, you should allow them an opportunity to inflate their swim bladders at the surface, as many other benthic seahorse fry do.

Yes, providing your in-tank refugium is large enough and is free of hydroids and Aiptasia rock anemones, it will make an acceptable nursery tank for seahorse fry. The abundant pods and microfauna that populate a refugium can supplement the daily feedings of newly-hatched brine shrimp (Artemia nauplii) you provide for the fry. Just allow the newborns an opportunity to fill the air bladders at the surface, and then transfer them to your in-tank refugium once they are a day or two old and they should be fine. How large is a refugium, Nigel?

When you order a mated pair of seahorses, they have been paired up for one or more breeding cycles. Beyond that, there’s no way of knowing for sure how experienced they are or how many broods they may have produced overall. In general, the seahorses you receive will be young adults that have recently become sexually mature and begun breeding.

It’s a misnomer to speak of a breeding pair as inexperienced or experienced parents, since the young are completely independent and left to their own resources from the moment of birth. So there’s really no such thing as parental care among seahorses…

Ocean Rider has been in existence since 1998, and to my knowledge, they have never had to deal with a hurricane. Unlike Florida, the Eastern Seaboard, and the Gulf of Mexico, which may face one severe storm after the other during hurricane season, such events are quite rare in Hawaii. The vast majority of hurricanes die well before they get that far West. The Ocean Rider aquaculture facility is uniquely situated at the National Energy Lab, which means they have unlimited access to ultra-pure natural seawater at any temperature they desire from deep beneath the ocean, which is completely unaffected by conditions at the surface. As long as they have power, the seafarm is assured of clean, recirculating ocean water, and with backup generators to assure an uninterrupted source of power, the facility is relatively weatherproof.

Best of luck with your Zulus, Nigel!

Happy Trails!
Pete Giwojna

Dear Nigel:

Setting up a separate nursery tank (I would make it at least 5 gallons) with a sponge filter is generally a good idea. However, I would not use the nursery as a paternity tank if you can avoid doing so.

Whether to allow the pregnant male to give birth in the main tank and then to transfer the fry to the waiting nursery, or to transfer the expectant father to the nursery tank ahead of time so he can delivery his brood there is a very important decision. There are two schools of thought on this issue. Some hobbyists feel it’s best to use the nursery tank as a paternity ward, since the delicate newborns never need to be handled if the male gives birth directly in the nursery. Other breeders feel it’s better to disturb the pregnant male as little as possible and prefer to have him deliver his brood right where he is, in the familiar surroundings in which he’s most comfortable.

That’s a no-brainer, Nigel. In my opinion, it’s ALWAYS better to assure the well being of the male and safeguard your broodstock. A pair-bonded couple will soon establish a regular breeding cycle in the aquarium, producing a new brood every two, four, or six weeks. (The gestation period varies with the species and is often correlated with the lunar cycle so that the fry are delivered during the highest tides, which helps disperse the young; Vincent, 1990.) A healthy pair-bonded male will deliver a new brood of young every month or so during the breeding season, producing countless offspring over the course of its life. But if you lose a breeding male, you lose all of his future progeny with him, as well as the superior genetic traits he carries. It is folly to jeopardize the health of a pregnant male for the sake of the brood he is carrying at the moment.

Handling a gravid male, especially when the pregnancy is well-advanced, should be avoided at all costs. At best, it will be stressful for the male to be captured, separated from its mate, and transferred to a strange new environment (Giwojna and Cozzi-Schmarr, Feb. 2002). At worst, rough handling and stress can trigger premature delivery or cause the pregnancy to be aborted altogether, adversely affecting the health of the male and his brood (Giwojna and Cozzi-Schmarr, Feb. 2002). Stressing a pregnant seahorse has many detrimental effects, including decreased appetite, adverse hormonal changes, impairing the immune response and lowering disease resistance.

Separating the expectant father from his mate at this crucial time can also prevent him from re-mating with his chosen partner and may even break up a pair-bonded couple (Giwojna and Cozzi-Schmarr, Feb. 2002). Throughout his pregnancy, the male maintains daily greeting rituals with his mate that serve to strengthen and reinforce their pair bonds and keep them physiologically attuned to one another. When the male gives birth, his mate is normally waiting nearby, ready to hydrate her clutch and rise for the exchange of eggs as soon as he has recovered. Many times they will resume their mating dance and re-mate scant hours after the male delivers his latest brood.

Isolating the male from his partner during the pregnancy effectively puts an end to all of that. They are preventing from conducting morning greetings, their carefully orchestrated breeding cycle may be disrupted as their hormonally regulated reproductive synchrony is lost, and the pair bond is weakened accordingly (Giwojna and Cozzi-Schmarr, Feb. 2002). Their bonding may even be broken as a result. That’s not what a successful breeder should strive for!

If you are concerned about the filtration in your main tank "eating" the newborns, modifying your filter to prevent this is a much better alternative than transferring the male to a paternity ward (Giwojna, Feb. 2002). Just screen off the intakes or cover them with sponge prefilters. Or you can simply switch off the skimmer and any supplemental filter(s) when his due date arrives and delivery is imminent. (Just don’t shut down your primary biofilter!) That way, the male can remain with his partner through the pregnancy and deliver his brood in a stress-free environment.

Here are Carol’s thoughts on the matter:

"As Pete Mentioned, probably the most stressful thing one could do to a pregnant (gravid) male that is close to giving birth would be to "handle" him by moving the male from his normal environment (home!!) to a new and unfamiliar environment like a different holding tank. (hotel room!!). This unnecessary "transfer" and " handling" will force him to adapt to a strange environment causing a general increase in his stress level causing many possible negative outcomes such as decrease in appetite, lowering of the immune system causing opportunistic pathogens currently present in the aquarium but not at high levels to take a hold on the sea horse causing health problems, and sadly may prevent him from re mating with his mate.

You see, the male will continue his bonding rituals (such as Pete has described) with his mate during the birthing process and immediately after giving birth. The pair will begin the treasured mating dance that will hopefully result in a successful egg transfer from the female to the male often within hours after giving birth!! Remember that with many sea horse types the older the male the larger the size of his pouch and therefore the greater the number of sea horse babies in the pouch!! For example, a 5 year old adult H.reidi male may give birth to as many as 2000 babies with each spawn!!!! A young 6 month old juvenile male may only give birth to 10 or 20 babies!!! It is also more likely that the older male has been mating with the same female all is life!! Imagine the stress of not being with his " beloved" during this time!

This unnecessary "handling" or "transfer" is, of course, extremely hard on wild caught males and may cause his death immediately after giving birth. One should avoid purchasing wild caught pregnant males at all costs. It is easy to feel sorry for him in the pet store, but his purchase only encourages the collectors to take additional pregnant males the next time causing further devastation to the already highly threatened wild sea horse populations.

Certainly this "handling" or "transfer" stress is greatly reduced with the farm raised pregnant males but the general concept still applies. If you purchase a farm raised pregnant male you should not expect a male that is almost ready to give birth but one that is within 2 weeks of giving birth. The normal gestation period averages at 30 days depending mostly on species and environmental parameters such as temperature and diet.

If these conditions are not optimum and the general stress level of the male is too high, the male will simply re-absorb the eggs or abort them. You will sadly think that he was never pregnant

If , however, you are able to keep these parameters optimum, you will have a much greater chance of being successful with your pregnant male so that you can enjoy this amazing phenomena of the pregnant male sea horse!! With a little more patience you will surely be rewarded with the great performance of the sea horse mating dance followed by the most precious site of all……the fat bellied pregnant male sea horse!!!"

Aloha, Carol Cozzi-Schmar

Generally, the only time a paternity tank is advisable is on those rare occasions when a pregnant male develops a health problem that requires treatment (Giwojna, Feb. 2002). In that case, it’s best to make the transfer early in his pregnancy (at least 2 weeks prior to his delivery date). Make sure the hospital tank/paternity ward has been prefilled with water from the main tank to reduce stress and ease the transition. If at all possible, transfer his mate along with him. And situate the paternity tank in a quiet, low traffic area, making certain it includes enough shelter so that the expectant father won’t feel vulnerable and exposed.

In your case, Nigel, since you are maintaining a therapeutic level of copper in your seahorse tank due to potential problems with ich (Cryptocaryon irritans), this could be one of those rare exceptions when it may make sense to consider using your nursery as a paternity tank. If you do so, transfer his mate along with your male Zulu. But if there are no health problems in your seahorse tank, then I would allow him to give birth their and transfer the fry to the nursery tank afterwards. (Don’t use the copper water from your seahorse tank for the nursery, however. Fill the nursery with freshly mixed saltwater that you have preadjusted to the same temperature, pH, and specific gravity as the main tank.)

Best of luck raising your Zulu fry, Nigel!

Happy Trails!
Pete Giwojna

Dear Nigel:

No, don’t move your great gravid male! As long as you are not having an outbreak of ich or any other disease problems in your seahorse tank, it’s best to leave the pregnant male and his mate in the main tank while he delivers. That way he can remain amid the familiar surroundings where he is most comfortable, surrounded by his tankmates, in a roomy, well-decorated aquarium with good filtration including a fully functional biofilter.

That is much preferable to transferring the pregnant male and his mate to a small 2 or 5 gallon nursery tank that is sparsely decorated as best and has only a sponge filter that has not yet been cycled. Two adult seahorses in such cramped accommodations would be very uncomfortable for more than a day or two, and it would be impossible to maintain adequate water quality in the nursery tank under those conditions without performing daily water changes. Nursery tanks are also relatively bare and sparsely decorated as a rule, which facilitates cleaning and maintenance, but which will leave your pregnant male feeling vulnerable and exposed. As long as you are not having any disease problems in your seahorse tank, there’s no need to subject him to such a stressful situation.

Just allow him to give birth in the main tank where he feels at home. Copper sulfate in therapeutic dosages is not harmful to seahorses, and even the newborns can tolerate exposure to Copper at the usual treatment levels without any problems. Leave your male Zulu and his mate in the seahorse tank, and then transfer his fry to your nursery tank after he delivers. As long as you adjust the saltwater in your nursery tank to match the specific gravity, pH, and temperature of your main tank, the fry can be transferred directly into the nursery tank with no acclimation whatsoever. That is by far your best option.

Best of luck with your pregnant male and as babies, Nigel!

Respectfully,
Pete Giwojna