Seahorse fry survival rate

[myfavoritereef]

Just curious. I have been successfully raising H. Erectus for several months now and I was wondering what others have experienced as survival rate. My August batch is down to 17 from 86 and my September batch is down to 42 from 85. Also, I seem to lose a large number of fry during the third week. Anyone else experience such loss? Fry are fed 3-4 times daily with the droppings siphoned twice per day. Any suggestions would be appreciated. Thanks!

 

[DanU]

Success rates are all over the place. Sometimes even for the same breeder. We have had over 95% and also have lost entire batches. Generally we expect to get over 80% on average.

Losing them at 3 weeks with this species would lend me to think you need to beef up mechanical filtration to remove organics and take a hard look at your live foods in terms of potential bacteria. Organic loading of the tank leads to increased microbial growth, both bacteria and protozoans can do the fry in. Artemia is a notorious source of pathogen growth.

Dan

 

[myfavoritereef]

Hi Dan, thanks for the response. I am using artemia hatched every 12-18 hours in clean containers for food and then larger artemia (purchased from the FS) and then converting to frozen mysis. I will beef up the mechanical filtration to see how it goes. Do you have a better recommendation for feeding?

 

[JLynn]

Well, I have no experience with breeding seahorses, but from what I have heard of others' experiences, larger artemia have next to no nutritional value. Their nutritional value can be greatly improved by gut loading them with selcon/Dan's feed/etc. I suspect the lack of nutrition in the larger artemia is why you are losing so many fry. If you have the time/space, it would be ideal to culture some copepods in lieu of the larger artemia, if not also the artemia naupli. Seahorse Source sells several species of copepods and has excellent information describing the use, size, life cycle, and culture of each species they sell; you should definitely check those out.

If you don't have space to culture copepods, you might try out greenwater tanks. If you don't already know, greenwater tanks can be used to raise fry; a sufficient level of phytoplankton is maintained in the water of the nursury tank to sustain the growth and reproduction of copepods/rotifers necessary to feed the fry. This is how Jim Welsh rears his pipefish, and I am sure it would be similarly effective with seahorse fry. It is a relatively tricky ecological balancing act, but it is a good option if you don't have the space to keep separate cultures of algae and copepods. I suggest you give Jim's breeding journals on MBI Site a look, if you haven't already.

Lastly, I have heard that probiotics are very useful in captive breeding efforts in general; you should consider that as well. I think Seahorse Source also offers probiotics, but if not them, I am sure other places offer them, too.

 

[vlangel]

Yes seahorse source does offer probiotics as I recently purchased some from them.

 

[DanU]

Tank cleanliness is big. Keep in mind what most are trying to do with fry is overstock a tank, over feed it and have very little flow. This is a recipe for disaster but it is what most folks rearing fry have to deal with. Beefing up the filtration plays a role, siphoning twice a day as you are already doing helps and I would also recommend scrubbing the inner tank surfaces with a non abrasive scrub pad daily to knock of the biofilm that develops quickly on these types of tanks.

The artemia can be tricky. It may or may not be a source of contamination. I have done consulting work with hatcheries that were having issues with artemia and they thought they were cleaning everything well. After a little investigating I proved they weren't despite the fact they were cleaning everything. The hatching vessel needs to be cleaned between each use. I actually use dishwashing detergent to cut the film with a non abrasive scrub pad. You want to make sure you use non abrasive as scratches make a perfect home for bacteria that you just can't get to without soaking for a period of time in bleach or using acid to clean it. I follow the soap with a very good rinse and then peroxide to cut any remaining soap residue. Airlines and nets/sieves need to be cleaned as well. Same goes for the enrichment containers.

You don't mention enriching the artemia. Both the nauplii and adult artemia need to be enriched with a product that has a high DHA/EPA ratio. Artemia rapidly catabolize the DHA component to EPA. Enrichment for nauplii needs to be a minimum of 12 hours and ideally 24 for max nutrition. Even newborn erectus fry can take 24 to 36 hour enriched artemia nauplii. Adult artemia should be enriched for a minimum of 2 hours or 4 hours for max nutrition.

There are also some things you can add to the enrichment to help boost your odds. These help but do not replace any necessary husbandry already mentioned. Ascorbyl Palmitate (Vitamin C) can be added to the enrichment process. Vitamin C is a very good immunostimulant and to some extent helps fight bacterial issues. Artemia catabolize this to Ascorbic Acid. Beta Glucan is also a known immunostimulant. Stabilized Allicin is a very powerful immunostimulant that also has antibacterial, antifungal, antiviral and antiparasitic properties. As mention, probiotics can be helpful as well at both helping combat disease as well as improving feed conversion ratios.

Another simple trick to help with cleanliness is to add some live mysid to the fry culture. Live mysids serve a dual role. First they help keep the tank cleaner as they will act as a cleanup crew. They will eat the same things as the fry. Secondly, they become a food source. They will naturally reproduce and their nauplii become food for the fry and as the fry get older they will start eating the adult mysids. When this happens, it is time to introduce frozen mysis as another food.

Probiotics can also be used in the tank as well as gutloading in the artemia. As an additive to the tank, it helps cut back on the organic loading which causes the high microbial populations.

Since I don't have a complete picture of the setup or what is actually happening, it is hard to correctly diagnose what is going on. Another thing to consider, is erectus fry can have high mortality if you have a lot of protozoans in the tank. This is easily recognized by the fry trying to scratch or pick at their heads with their tails. Formalin long term bath dose is very effective at knocking this back and preventing losses.

I can go on and on but this should give you some stuff to think about and try.

Dan

 

[myfavoritereef]

All of the suggestions are a huge help, thanks!

I have placed an order with Seahorse Source for the probiotics and the bare bottom brush tool. ( I was going to try and come up with something similar myself but this seems like the easier option).

Dan, you are correct in that a better cleaning on the artemia hatcheries is in order. I have not been using any soap or bleach when cleaning them and just rinsing with hot water. This sounds like a good place to start.

I have been enriching the BBS and adult artemia but the directions say 20-40 minutes. I will definitely increase the enrichment time.

How does a formalin long term bath dose work? Do I take the fry out and put them into a formalin bath or medicate the entire tank? I have the fry in our "fish condo" which is a commercial size tank with four levels and about 200 gallons.

Thanks for your continued support!

 

[DanU]

BBS take approximately 12 hours to fully pack the gut. By changing the water and enriching for another 12 hours they will assimilate what they have eaten into their tissues and repack the gut. Almost twice as nutritious at 24 hours of enriching over 12. Adult artemia can pack their gut in 2 hours and going 4 hours with them is like going 24 with BBS.

The Plankton Culture Manual would be a great reference book to have on hand. It has become a bit dated but it has a lot of good pertinent information. The FAO also has a great culture manual but it is a lot more technical. An online copy can be found here: http://www.fao.org/docrep/003/W3732E/W3732E00.HTM

Formalin long term bath is dosed every other day for 3 doses. Most fry tanks are stand alone bare bottom systems that can be dosed. If the system is tied into other tanks, then I do not recommend dosing it.

Dan