Re:Refugium setup and seahorse fry

Pete Giwojna

Dear Cheryl:

Yes, you’re quite right — if you can possibly provide them in suitable amounts, copepods are by far the best first foods for seahorse fry. Research shows that they are a natural prey item that constitutes a large proportion of the diet of pelagic seahorse fry in the wild. As such, the copepods are much easier for newborns to digest than newly-hatched brine shrimp, which have been removed from the marine environment by several million years of evolution. In addition, the copepods are much more nutritious with higher levels of highly unsaturated fatty acids and other lipids. Several studies demonstrate that seahorse fry grow faster and have improve survivorship when they are fed on copepods versus Artemia nauplii.

Best of all, research indicates that the newborns only need to be provided with copepods for about the first week of life (4-7 days) in order to achieve these benefits (Todd Gardner, pers. com.). After that, the newborns have grown enough and their digestive tracts have matured enough to be able to handle newly-hatched brine shrimp without difficulty and Artemia nauplii can serve as the staple diet for the fry thereafter.

In short, Cheryl, there is now considerable evidence that indicates copepods are a superior food source for newborn seahorses. In a nutshell, the copepods are simply far more nourishing and easier for the fry to digest than Artemia or rotifers.

For example, here are the abstracts from a couple of the recent studies on rearing seahorse fry with copepods that will give you a better idea of what I’m talking about (I would be happy to e-mail you copies of the complete studies off list if you’re interested):

Rearing West Australian seahorse, Hippocampus subelongatus, juveniles on copepod nauplii and enriched Artemia
M.F. Payne), R.J. Rippingale
School of EnÍironmental Biology Curtin University of Technology, GPO Box U1987,
Perth 6845, Western Australia
Received 3 November 1999; received in revised form 31 January 2000; accepted 31 January 2000

Improved captive breeding techniques are required for seahorses. Artemia nauplii are generally considered a poor first feeding diet for many seahorse species. This study compared growth and survival of newborn Hippocampus subelongatus reared on cultured copepod nauplii and Artemia nauplii enriched with Super Selcow. Early growth and survival of seahorses were significantly greater when fed copepod nauplii. Copepod nauplii were well digested by juvenile seahorses whereas Artemia nauplii were not. Fatty acid requirements of seahorses could not be determined.

The addition of UV water sterilization improved seahorse survival. When offered copepod nauplii of different sizes, 5-day-old seahorses preferentially selected the largest nauplii. Maximum predation rate in these juveniles was 214 copepod nauplii/seahorse. Provision of copepod nauplii to juveniles improves the prospects of establishing captive breeding populations of H. subelongatus. q2000 Elsevier Science B.V. All rights reserved.
Keywords: Seahorse; Copepod; Artemia; First feeding; HUFA; Prey selection

And from Robin James, Weymouth Bioservices

Effect of copepod diet on growth rate of juvenile Hippocampus abdominalis.

Artemia is commonly fed to juvenile sea-horses as it is cheap and easy to culture. However, it is known to have a low nutritional value and is thought to be unsuitable for the delicate digestive systems of the juveniles. Copepods are smaller, more nutritious and less abrasive, but difficult to culture and more expensive than Artemia. This trial aims to asses whether a copepod enriched diet produces an improved growth rate of newborn H. abdominalis when compared to the growth rate produced by a standard Artemia diet.

This study produce much the same results — copepods proved to be more nutritious and resulted in faster growth and lower mortalities than newly-hatched brine shrimp. A number of other studies have since demonstrated the same thing.

So by all means, continue to provide a highly nutritious copepods for your newborn seahorse fry for the first several days of their lives if you can manage it. Once they make it past the first week of life, you can then switch them on to newly-hatched Artemia nauplii as their staple diet without any ill effects.

For best results, use only the freshly hatched Artemia nauplii which still have their yolk sacs largely intact. Such newly hatched brine shrimp will have good nutritional value and be small enough for the week old seahorse fry to easily swallow and digest. Here is a copy of Neil Garrick-Maidment’s article that describes one way of assuring the newly hatched brine shrimp you provide for the babies will have maximum nutritional value. (Neil is a very successful breeder in the UK and the author of two guidebooks on the care and keeping of seahorses.)

Rearing Seahorse Fry on Artemia.

Neil Garrick-Maidment


The Seahorse Trust.

It has long been thought that rearing Seahorse fry on Artemia is impossible because they do not hold enough nutritional value. This is partially true but if dealt with in the correct way then artemia can be used very successfully.

Artemia is highly nutritious when it is first hatched out but the nutritional value drops very quickly to virtually nothing within 3 hours; added to this the carapace (shell) hardens during this 3 hour period and makes it very difficult to digest by all but the most harden fish fry.

The traditional way of cultivating artemia is to put the eggs into a pot of seawater, aerated at 80’ and wait for them to hatch 24 hours later. This one pot of artemia is usually used for a 24 hour period and quite often is stored in a refrigerator until it is used; this is where the nutritional problems occur unless the artemia is enriched. Once enriched (often for another 24 hours as the mouth parts do not form until 10 hours old) it often proves to be a poor source of food as it is by this point either too large or the carapace (shell ) of the artemia is too hard. By being too large or having too hard a carapace it means that fish fry like Seahorses cannot digest it as they have an extremely poor digestive system; which is not long enough to allow it to digest the hard carapace and derive enough nutrition from the naupilli. .

By changing the protocol of hatching the artemia it is possible to use it as a highly successful form of food especially for Seahorses; the only draw back with this system is that it is labour intensive.

The set up:

We use a 5 pot system for the hatchery, each one labelled 1 to 5; all five pots sit in a glass fish tank with 4 inches of water in it. This water is heated by heater/thermostat to 80’ and each of the pots is heated in turn by this hot water. Each pot also has an airline with an airstone into it.

The protocol:

Start with pot 1 and fill it with saltwater and add your artemia eggs (you can use unshelled eggs to increase the nutritional value higher.). 2 hours later repeat the process with pot 2 and then each 2 hours after repeat with the rest of the pots; it is possible to use more pots if your needs require it.

If you have set up pot 1 at 8am then 24 hours later at 8am the artemia should have just hatched out, this is then the time to feed pot one to your fry; it is crucial that the time between hatching out and feeding is kept to a minimum.

Harvest the artemia by letting the pot stand and the artemia will sink to the bottom and the egg shells will rise to the surface. Use a siphon through a very fine mesh trap to siphon them out of the pot, once you have enough artemia then give them a quick wash under a freshwater tap and then feed the artemia to your Seahorse fry.

It is crucial that you only feed a small amount of artemia to the Seahorse fry; enough to be eaten by the time the next pot is fed to the fry (2 hours later).

Once you have fed this pot of artemia to the fry do not be tempted to keep what’s left over, use it for some other fish species but don’t be tempted to feed it later on to the Seahorse fry.

Once you have harvested pot 1 immediately set it up again ready for the next 24 hour period.

Every time you go to feed the next pot of artemia be sure to siphon the tank of any debris from the bottom of the tank and crucially remove any left over artemia from the tank. This can be done by putting a light to the side of the tank to attract the artemia to it then siphon them from the tank. This is important as you do not want the Seahorse fry to be eating older hardened and nutritionally low value artemia.

After feeding the artemia remember to top up the water you have removed from the fry tank, this way you will be changing water throughout the day lessening the build up of harmful nitrites and ammonia in the water which is better for the Seahorse fry.

As a side note we usually use water from the adult’s tank to replace and indeed start up the fry tank; this is already filtered and as we use natural seawater it is a better source of water for the fry; they appear to do better in natural seawater than artificial.

These steps should be repeated every 2 hours with pots 2 then 3 then 4 then 5 and any others you add to the system.

This process should be repeated on time every 2 hours as the age of the artemia naupilli is important for its nutritional value and carapace hardness. <Close quote>

In short, Cheryl, I would suggest that you concentrate on feeding your newborns larval copepods for the first 4-7 days, and then switch them over unto newly hatched 1st instar Artemia nauplii, just as described by Neil above.

Best of luck with your prolific ponies and their offspring, Cheryl! Keep up the great work!

Happy Trails!
Pete Giwojna

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