Re:Seahorse Fry

Pete Giwojna

Dear Nick:

The Brazilian seahorse (Hippocampus reidi) is one of my all-time favorites but they can indeed be very challenging to rear. Hippocampus reidi are famous among seahorse keepers for two things: brilliant colors and making babies. The Brazilian breeding machine is the most prolific of all the seahorses (Abbott 2003). They have a well-deserved reputation for churning out brood after brood every two weeks with relentless regularity, and hold the world record for delivering ~1600 young in a single brood (anecdotal reports of broods up to 2000 fry are not uncommon)! Not bad for a livebearer. But with that many fetal fry crammed into one incubator pouch, the inevitable tradeoff is that the young are born at a considerably smaller size than most seahorses (Abbott 2003). They also go through a lengthy pelagic phase, drifting freely with the plankton for up to 1-2 months, which makes H. reidi fry notoriously difficult to raise (Abbott 2003).

1. Is is wise to move the pregnant male away from the habitat until he gives birth?

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, sir. 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 (gestation is typically 14-21 days for H. reidi, Dave — closer to two weeks at water temperatures in the upper 70s), 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.

2. Is it true that seahorses will only give birth at night or with moon-light?

Many tropical and subtropical fishes have lunar or semilunar spawning seasons and Hippocampus is no exception (Vincent, 1990). Seahorse species that undergo a prolonged pelagic phase often coordinate their breeding activity with the lunar cycle, so that gravid males are due to deliver during the highest (spring) tides (Vincent 1990, Kuiter 1994a). The strong tidal currents at such times are believed to aid in the dispersal of their huge broods of pelagic fry.

So in the wild, parturition in seahorses with pelagic fry like your H. reidi is often coordinated with the moon phases and hence the tides. And indeed, under these circumstances, parturition very often takes place in the early morning hours.

In captivity, however, that’s not necessarily the case all. I have had seahorses give birth in the aquarium at all hours of the day and night. Sometimes, a large brood is delivered over the course of two or three days, with birth spasms and the ejection of fry punctuated periodically by periods of rest. Often times broods are delivered overnight, but captive-bred-and-raised seahorses are just as likely to give birth shortly after dawn, and many times I’ve arrived home from work only to find that a gravid male has delivered in my absence.

In short, with cultured seahorses, it’s not true that gravid males only give birth during the night or when provided with moonlights. When it comes to H. reidi, the breeding cycle is amazingly consistent. As long as you maintain the same water temperature and aquarium conditions, you will eventually be able to time their gestation period quite precisely, as they turn out brood after brood with machine-like regularity. This will allow you to anticipate parturition and maintain a vigil when the due date arrives, so you can safely retrieve the newborns before they run afoul of the filtration in your reef system.

3. WHEN should we start feeding the fry once they are born?

Seahorse fry are typically born with a limited yolk supply that is adequate to sustain for the first 6-12 hours of life, so the newborns do not need to be fed immediately. Food can be offered within the first few hours of life, but is not essential until after they have exhausted their yolk supply (Giwojna, Jan. 1997). The digestive tract of the newborns is very immature since they have been nourished entirely by yolk up until this point, and it can take several days for them to begin eating at their full capacity (Warland, 2003).

Even so, they are natural born hunters and will begin stalking prey almost the moment they are ejected from the male’s incubator pouch. Do not let their delicate appearance deceive you — newborn seahorses are formidable predators in their own right!

In the case of your H. reidi fry, you should begin providing them with copepod nauplii and rotifers within 6-12 hours of birth, and gradually increase the amount you feed as discussed below.

4. WHAT should we feed the fry once they are born? We have had some moderate sucess with live rotifers, and have heard that a mixed culture (harpact icoids) could also be used. The culture contains animals that will be between 250 – 500 microns in size. Is this too big for fry? What do you suggest we feed?

Larval copepods are more nutritious than rotifers and will make a better first food for your newborn H. reidi. I find that if I strain the copepod culture water through a 125-micron screen in order to separate out the larger copepods and adults (which are returned to the cultures to produce more nauplii) and then use a 35 µ screen to harvest larval copepods, it will produce copepod nauplii in a range of sizes that most pelagic seahorse fry can handle. But providing the fry with a varied diet consisting of different types of live microcrustaceans in a range of sizes as the fry grow will produce the best results.

For example, Jorge Gomezjurado recommends the following feeding regimen for H. reidi fry:

As with all seahorse fry, Gomezjurado finds that providing H. reidi fry with proper nutrition during the crucial first weeks of life is one of the greatest challenges in seahorse husbandry. He meets that challenge by providing the developing fry with a natural food chain of living prey (Bull and Mitchell, 2002, p51). This live food chain consists of phytoplankton (species such as Nannochloropsis aculata and Isocchrysis galvana), brine shrimp nauplii (Artemia franciscana), copepods (Acartia tonsa), and juvenile Mysis shrimp (Americomysis bahia) (Bull and Mitchell, 2002, p51). The microalgae (phytoplankton) serve as a source of food and nutrition for the various zooplankton in the chain, and the progressively larger prey items are introduced to the fry and juveniles as they grow (Bull and Mitchell, 2002, p51).

The feeding levels provided at NAIB depend on the stocking densities of the nurseries and rearing tanks, which Jorge cautions should not exceed 80 fry per gallon or 20 fry per liter in the case of H. reidi (Bull and Mitchell, 2002, p51). Recommended feeding densities for reidi and ingens fry are 10 rotifers/ml, 15 nauplii/ml, and 3 copepods/ml to start with, with the amounts increased accordingly as the fry grow to keep up with demand (Bull and Mitchell, 2002, p51). The water intakes in the rearing tanks are closed or markedly reduced during feeding times. Jorge finds that the gradual transfer from one live food organism to another is easily achieved simply by overlapping feedings at the different weaning stages (Bull and Mitchell, 2002, p51).

The zooplankton that comprise the live food chain at NAIB are enriched with essential vitamins, commercial Highly Unsaturated Fatty Acids (HUFA) rich in docosahexaenoic acid (DHA), and carotenoids such as Astaxanthene biological pigment Natu-Rose (Bull and Mitchell, 2002, p51). Special precautions are taken at NAIB in order to assure that the enriched brine shrimp nauplii (platinum-grade Artemia franciscana cysts) the Aquarium uses are germ free. The decapsulated brine nauplii are kept at high salinity (55-60 ppt) after hatching and the culture water is changed every day in order to prevent bacterial proliferation (Bull and Mitchell, 2002, p51).

Ocean Rider considers their specific rearing protocols to be proprietary information, but I have a lot of other information on the care and breeding of H. reidi that I will be happy to share with you off list, Nick.

Best wishes with all your fishes at the South Florida Science Museum, sir!

Happy Trails!
Pete Giwojna

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