seahorse fry

Dear hobbyist:

Congratulations on getting so many of your Mustang babies to the four-week mark. Well done!

The bright orange coloration you noticed in some of the fry is not unusual and is not symptomatic of a health problem. Because of the tremendous genetic diversity built into the current generation of Ocean Rider Mustangs as intraspecific hybrids, it is quite common for some of the offspring in a brood to develop different traits, including coloration. For example, although most Mustang babies will be dark in coloration like their parents, it is normal for some of the young to develop yellow or orange coloration at a certain stage of development. Likewise, whereas most of the Hippocampus erectus babies are plain or average in terms of their spinal development, some of them may develop extravagant cirri that give them a fancy, spiky appearance. (We’ll discuss the genetic diversity of the Mustangs a bit more later in this post.)

So I don’t think the fact that you are starting to lose some of your juveniles at this point has anything to do with the fact that some of them are brightening up and displaying orange coloration — rather, I suspect you are losing some of the month-old offspring because they have reached a transitional stage in their development in which their dietary needs are changing. It is customary to begin weaning the juveniles off of their steady diet of enriched brine shrimp, which is no longer adequate for all of the nutritional needs of the rapidly growing four-week olds at this point, and we often see a spike in the mortality rate of the juveniles and about this age as a result.

In order to get over this hurdle, I suggest that you do two things: begin adding a small dose of 37% formalin to your nursery tank(s) and begin adjusting the diet of the four-week old Mustang babies, as discussed below:

First of all, I recommend that you add two drops of 37% formalin per gallon to your nursery tank every other day. This will inhibit the growth of fungus and bacteria, helping to keep the nursery tanks more sanitary, as well as protecting the fry from protozoan parasites. Adding two drops of the formalin every 48 hours will not be harmful to the developing fry in any way, and should help improve your survivorship by minimizing some of the problems that typically plague the juveniles at this stage of development

Secondly, it’s time for you to wean the juveniles off of newly hatched Artemia nauplii onto a staple diet of frozen foods. Here are some suggestions that may help to make the tricky transition period a little easier:

Making the Transition to Frozen Foods:
Converting the Fry to Frozen Foods

The current thinking is that the fry can remain on a steady diet of newly hatched Artemia until you are ready to begin weaning them onto a diet of frozen foods (usually minced Mysids and/or Cyclop-eeze). Aquaculturists are now converting the fry to frozen foods earlier than ever, often beginning around 3-4 weeks old. Jeff Mitchell reports that the fry are healthier and grow faster the sooner they make the transition to enriched frozen foods, and he expects the young seahorses to have made the transition to frozen foods by the age of 4-1/2 weeks.

I generally have the best results using frozen Mysis. The best way to prepare the Mysis for the juvenile seahorses is to mince the frozen Mysis coarsely rather than putting it through a blender. How fine or coarse you need to chop it depends on the size of your fry, since you want to wind up with bite-size pieces of Mysis. Initially, many breeders prefer to shave small pieces of Mysis off of a cube while it’s still frozen.

The frozen Mysis that works best for most hobbyists is Hikari in frozen blocks rather than trays. The Hikari Mysis is much smaller than Piscine Energetics Mysis relicta and that makes it easier to shave off bite-sized pieces for the young seahorses. Some hobbyists report even better results using the new Mini Mysis offered by H2O Life, which is small enough that it often doesn’t need to be minced or shaved before offering it to the juveniles.

When it comes to shaving the Mysis, a technique that works well for many home hobbyists is to use a potato peeler to shave off bits of the Hikari Mysis from a frozen block, and then use a single edged razor blade to further mince the frozen bits the potato peeler has removed.

Try offering the minced Mysis exclusively for their first feeding of the day when the youngsters are the hungriest. Watch the juveniles closely to see if any of them begin to pick at the minced Mysis or pick it up from the bottom. If they still aren’t having any of it, siphon up the uneaten frozen Mysis after about half an hour and offer them newly hatched brine shrimp soaked in Mysis juice so that they have something to eat, and intermingle some freshly minced Hikari frozen Mysis or Cyclop-eeze in with the bbs.

When the fry have grown a little larger and can accommodate bigger pieces of Mysis, I find it convenient to carefully thaw whole Mysis individually and then carefully chop them into several pieces. Or the Mini Mysis by H2O Life can be fed to the larger juveniles whole and intact, if you can obtain it.

Either way, it is very important to be extra diligent about vacuuming up leftovers (and any fecal pellets) while the fry are making the transition to frozen Mysis. Otherwise, the minced Mysis that doesn’t get eaten right away while it’s still suspended in the water column or shortly after it has settled on the bottom will begin to degrade the water quality in your nursery tank. (Adding two drops of 30% formalin per gallon will help to keep the nursery tank more sanitary when using minced Mysis or converting the juveniles to a staple diet of frozen foods.)

It’s important to overlap the fry food when they are making the transition. Offer them shaved or minced Mysis along with the newly hatched brine shrimp they are accustomed to eating. (Many times it’s better to offer the minced Mysis first, while the fry is still the hungriest, and then add the baby brine shrimp.) Once they begin eating the bits of frozen Mysis well, gradually increase the amount of minced Mysis and decreased the amount of baby brine shrimp you offer at every feeding until they are finally eating the shaved Mysis almost entirely.

Overlapping the feedings this way, offering newly-hatched brine shrimp as usual along with just a little frozen Mysis at first, assures that there is familiar food available to the fry while they are making the transition and makes sure that the slow learners still get enough to eat.

Some hobbyists find it helpful to begin soaking the newly hatched brine shrimp in Mysis juice for a week or two before they actually began offering the bits of minced Mysis along with the bbs. That way, the juveniles get used to the scent of the frozen Mysis and associate it with food before you start to add the bits of frozen Mysis.

Here’s a previous post from Patti that describes how she weaned her erectus fry onto frozen to Hikari Mysis:

[open quote]
I’m wondering if nutrition is your problem.
Could you train them onto frozen mysis? My 4 week old erectus are
eating shaved Hikari frozen mysis already. They started not eating
much of the BBS and looking around the bottom of the bowl. I
enriched the shaved mysis w/Vibrance & put it in the bowl. It goes
to the bottom and they’re on the hunt. They’ll look at it a good
while and then snick. It only took 1 day to train them. I swish it
around a little at first to get them interested.

I think the mysis is better for them nutritionally and they don’t
have to spend so much energy eating all those tiny BBS. Give it a
try. It may take a few days. I gave mine the mysis 1st – before
adding the BBS. That way they were pretty hungry. Then I gave them
some BBS for desert to make sure each one got something to eat if
they weren’t eating enough mysis yet.
Patti [close quote]

Notice that Patti’s erectus fry were all hitching and beginning to look around on the bottom for things to eat, indicating that they were ready to give up their planktonic existence (i.e., the high-risk pelagic phase) and make the transition from live brine shrimp suspended in the water column to frozen foods.

Other breeders go a step further and begin adding a little of the minced Mysis to their nursery tanks with the newborns right from the start to help build up their intestinal flora and ultimately enable them to better digest the frozen Mysis when they start eating it. they feel that this helps the babies get them used to the scent of the Mysis and conditions them to associate it with food, which helps to make the transition from live food to frozen Mysis easier later on when they’re the right age.

For example, here’s how Neil Garrick-Maidment, a very successful breeder in the UK, describes this technique:

Hi Peter and all,

I tend to put in a very small amount of finely chopped mysis in with the fry
from day 1. The idea behind this is to create a bacterial soup in the fry
water to help load the fry gut with the right bacteria to break up the mysis
shrimp which tends to be quite hard.
It makes it easier to get them to switch to dead mysis later on BUT it is
crucial to clean the tank daily and water change to stop a problem with
disease..

Neil Garrick-Maidment
Director
The Seahorse Trust
36 Greatwood Terrace
Topsham
Devon
England
EX3 0EB

Cyclop-eeze is also worth considering when weaning the youngsters onto frozen fare. When the juveniles are the right age, don’t hesitate to try them on frozen Cyclop-eeze first if you aren’t having any luck with the frozen Mysis. Lelia Taylor is one hobbyist who has had good results using the Cyclop-eeze, as she described below:

<open quote>
I have had success placing BBS in Cyclop-eeze, then feeding the mixture to my babies. They readily take the Cyclop-eeze. As they get bigger I add frozen, enriched brine shrimp. they began eating the frozen food immediately. Using the same principle, I began adding Mysid shrimp, along with the brine shrimp and Cyclop-eeze. I have found, even very young babies, will pick the larger pieces of Mysid shrimp, into bite sized pieces. I have also had success culturing copepods in my baby and grow up tanks. The babies readily feed on these, as well. <close quote>

Hobbyists who have tried The Cyclop-eeze for their juveniles are unanimous in saying that the frozen Cyclop-eeze is far superior than the freeze dried product for this purpose. They report that the bars of frozen Cyclop-eeze in particular work well because they will shed copious amounts of the bite-size frozen cyclops into the water.

Bonus tip: adding one or two older juveniles that are already eating the frozen Mysis well to the nursery tank along with the inexperienced fry in order to act as their mentors can hasten the transition. Many hobbyists report that fry learn to take frozen minced mysids much faster and easier when they are provided with teachers to show them the way. These teachers are usually a few of the older fry from a previous brood, which have already become proficient at feeding on the frozen mysids (Liisa Coit, pers. com.). The younger fry are quick to copy them, learning from their example.

Okay, now that you’re up to speed regarding how to help the four-week olds make the transition to frozen foods to improve their nutrition, let’s take another look at the superior genes that are built right into your Mustangs and Sunbursts. To understand how the tremendous genetic diversity that’s built into Mustangs and Sunbursts is reflected in their offspring, let’s start with the basics. Essentially, when they begin working with a particular species, Ocean Rider’s approach is to obtain sufficient broodstock from throughout their range to completely eliminate any concerns about inbreeding, and then to pair males and females from different bloodlines in order to achieve intraspecific hybridization. That way, each pairing actually increases the genetic diversity of the offspring, and providing you avoid brother-sister crosses when you subsequently select your breeders for the next generation, each new generation will actually be strengthened (more genetically diverse than their parents) through the phenomenon of hybrid vigor.

This is especially true considering the primary traits Ocean Rider selects for are adaptability, disease resistance, vigor, aggressive feeding habits, good coloration, and rapid growth. Far from being recessive characteristics that could eventually result in inbreeding, these are all adaptive traits that increase the line’s fitness and improve survivorship. In fact, they are the same sort of traits Mother Nature herself selects seahorses for in the wild to assure survival of the fittest. When nature culls out the weakest and least fit, it is known as "natural selection." It is nature’s way of keeping a species strong, vigorous, and adaptive (i.e., evolving to better fit its niche). The only difference is that Mother Nature is selecting for suitability to their natural habitat, whereas aquaculturists are selecting seahorses for fitness to captive conditions. In both cases, the selection process assures that the specimens become ever stronger and better adapted to their environmental niche, whether that is the aquarium or the ocean itself.

Practiced in this manner, selective breeding actually strengthens and improves a strain generation by generation, producing seahorses that are progressively hardier and better suited for aquarium life. This level of domestication not only improves their general health but also eliminates much of the stress wild seahorses experience in captivity, allowing cultured seahorses not only to live longer but to live better.

Initially, the breeders’ goal is not to rear the maximum number of offspring from each brood, but to assure that the weaker offspring are weeded out at every stage, and that only the fittest fry are selected for further rearing. As a result, it typically takes Ocean Rider several generations to strengthen a new line of seahorses in this manner before it is ready to bring to market.

It’s a good system: a multigenerational approach to rearing which assures that farm-raised seahorses will only continue to get stronger, hardier, and more trouble free over time as they become ever better adapted to aquarium conditions

When you consider that Ocean Rider has been working with Hippocampus erectus since 1998, producing dozens of generations of Mustangs and Sunbursts, each more genetically diverse than its predecessors, it’s easy to understand why there is so much variation within a given brood of seahorse fry. It is very commonplace for brothers and sisters in the same brood to express differences in variable trait’s such as coloration, spininess, the size and shape of the coronet, the presence or absence of cirri, and so on.

In short, within the same brood of young, it is quite common to have some juveniles that are very spiny along with others that are very smooth skinned. In the same brood, there may be some fry with all well-developed coronets and others with only low, rounded bumps, and many whose crowns are somewhere in between those extremes. There may be a few fry with very elaborate cirri adorning their heads and necks, whereas most of their brothers and sisters have no cirri at all. The same variability in coloration holds true as well.

For example, Mustangs produce offspring that typically display the dark coloration and lined pattern so characteristic of wild H. erectus. But in a large brood of Mustang fry, there will typically be a few specimens which display yellow or orange as their background coloration.

Best of luck keeping up with the endless appetites of your voracious fry and weaning them onto frozen foods!

Happy Trails!
Pete Giwojna