Rearing G. personatus article

[KMB]

Here is an article I wrote in early 2002 regarding rearing G. personatus while working at the Waikiki Aquarium. It's a bit rough but maybe it'll trigger a new idea from someone here towards better rearing methods.

Karen



Captive Rearing of the Masked Angelfish, Genicanthus personatus at the Waikiki Aquarium

By: Karen Brittain
Aquarium Biologist
Waikiki Aquarium

Larval rearing research on the masked angelfish, Genicanthus personatus started in March of 1999 when the Genicanthus in one of our exhibits began spawning. Early rearing trials revealed that the G. personatus larvae were able to consume rotifers and copepods as a first food but could not survive through metamorphosis. In November of 2000 we discovered a new live first food and were able to get the angelfish larvae to survive to day 38. 2001 was spent trying different techniques on larval rearing trials using the new cultured food organism and on developing consistent culture methods for this organism. The successful rearing trial of the Genicanthus through metamorphosis started in November of 2001. The first Genicanthus took 72 days to completely settle out with the full color and behavior of a juvenile. The rearing of this angelfish is noteworthy in that o my knowledge it is the first to be reared on cultured foods as compared to wild plankton. In this article you will find some of the history behind the methods used to raise the masked angelfish as well as the “recipe” for taking this species and hopefully many other species of fish from egg to adult.

Some History:

At the 1999 Marine Ornamentals conference in Kona, Hawaii I presented a poster titled Early Larval Rearing of the Masked Angelfish Genicanthus personatus. In the poster I stated that I felt that food quality, rather than size was the bottleneck to getting marine angelfish through the larval phase. The following paragraph is taken from that poster.

“Food size has been considered to be a constraint to the first feeding of many larval fish under aquaculture conditions. Eggs of the masked angelfish, Genicanthus personatus, were collected from an exhibit tank at the Waikiki Aquarium in Honolulu, Hawaii. Development of the egg and early larvae to day 8 was recorded using a computer-based microscopic video capture system. Larval rearing trials testing first food items were run concurrently with the egg and larval development observations. Images were obtained of food items including copepods (Euterpina acutifrons) and rotifers (Brachionus plicatilis) in the guts of the larval angelfish. Thus, food quality, rather than size, appears to be the next challenge to closing the life cycle of this rare angelfish.”

Rotifers are microscopic planktonic animals often used as a first food item in the culture of marine ornamental fish and invertebrates. The average rotifer used in our larval rearing runs is 100 x 300 microns in size. Rotifers are easily cultured and can be nutritionally enhanced or enriched. We enrich the rotifers with the live algae Tetraselmis chuii or with Algamac 2000, a commercially available spray dried algae. When viewed under a microscope, the remnant mastax of the rotifers can be clearly seen in the gut of the larval fish demonstrating that rotifers can be consumed and digested by Genicanthus personatus. In our rearing trials we found that rotifers were consumed as early as day 4 after hatch in G. personatus, Centropyge loriculus and Centropyge flavisimus.


Copepods, Euterpina acutifrons are another cultured planktonic animal and were tried as a first and second food item during larval rearing trials. Genicanthus personatus larvae seemed to select newly hatched copepod nauplii over rotifers when offered a choice. Larvae fed rotifers as a first food switched to copepod nauplii when nauplii were added to the rearing tank. This may be due to the method of locomotion of the copepods. Rotifers have a smooth rolling form of locomotion whereas the copepods have a jerky hopping motion. Some researchers believe that larvae fish are attracted to the motion or swimming pattern of certain species of plankton. Although G. personatus larvae seemed to prefer copepod nauplii as a first food, the nauplii appeared to be incompletely digested in the digestive tract of the larval fish.

Now, three years and many larval runs later, I think that it is not so much food quality, but gut flora conditioning that was the breakthrough in closing the life cycle of the masked angelfish. Using a species of ciliate as a new first food may have had more of an effect as a “digestive conditioner” than as a food source. It may be that this ciliate provided a species or several species of bacteria that kick started the gut flora of the larvae and allowed them to better digest the rotifers offered on day 9. This theory has not been proven or even tested, it’s just my “gut feeling” J.

The Broodstock:

The broodstock Genicanthus personatus have been on exhibit in the “Northwestern Hawaiian Islands” tank since their arrival to the Waikiki Aquarium. The first of the G. personatus was collected from Midway Island in June of 1992. The other two were also collected from Midway in June of the following year. All three fish were collected as juveniles and have matured together in this exhibit. This display tank is a 325 gallon rectangular fiberglass tank with a front window. An undergravel filter plate is used as the primary form of biological filtration. This is an open system so there is always a slow trickle, approximately 5 liters per minute, of new seawater entering the tank. The bottom is covered with calcareous gravel and there are larger calcareous rocks attached to fibergrate to form a simulated reef area. Lighting is provided by two four foot 40 watt fluorescent bulbs (URI actinic and a CoraLife 50/50). The masked angelfish share this exhibit with several other fish also native to the Northwest Hawaiian Islands. These fish include one Pseudanthias thompsoni, one Chaetodon multicinctus, one Monotaxis grandoculis and two Centropyge interruptus.

Spawning in the tank was first noticed by aquarium intern Naoaki Kawahara on the morning of March 21, 1999. “Nao” noticed a small mass of what he thought were fish eggs floating in the tank. The mass was being picked at by the other fish in the tank. He immediately notified research associate Jerry Crow and they scooped the mass out of the water. Upon inspection the mass appeared to be infertile fish eggs stuck together in a clump. This was quite strange because the only pairs of fish in the tank were the Centropyge and the Genicanthus both of which are pelagic spawners that do not produce clumps of eggs. Since then the Genicanthus have spawned normal pelagic eggs. The clumping of the initial eggs may have had something to do with that instance being a first spawning for that female.

Larval Research:
The larval research area is outdoors on a wooden deck open on all sides and covered by semi transparent roofing materials. The larval rearing trials are conducted in a 4000 liter fiberglass tank located in the research area. This circular tank is eight feet in diameter and approximately three feet deep with a slightly conical bottom. The tank is prepared for a larval run by cleaning with a 50% solution of muriatic acid. A center standpipe covered with 60 micron nitex screen is used at the drain. Incoming water is added at a rate of 0.5 liters per minute. Aeration is provided at the center standpipe through two airstones. Aeration is not measured but is kept high enough to see the water at the surface being pushed from the center to the outer edges of the tank. The tank is covered by 50% shade cloth.

Genicanthus personatus eggs are spherical and positively buoyant with a diameter between 0.74 and 0.78mm. Most spawns from the Genicanthus exhibit at the Waikiki Aquarium contain between 20 and 200 eggs with a few collections containing over 300 eggs. The eggs are collected in the morning by skimming the surface of the tank with a plastic two liter beaker. Eggs are then acclimated and released into the larval rearing tank.

Eggs are collected daily from Sunday through Saturday. Because tank space is limited, eggs are collected for a full week and reared together in one tank. We then use the middle day of the collection week as the hatch date for that batch of larvae. For this reason the age of the larvae is seen as plus or minus 3 days. If the larval age is entered as d7 it is known to be between 4 and 10 days old.

Background/Trial and error:

Although much has been learned about the reproductive behavior and spawning of Pomacanthids in the wild and in captive environments, relatively little is known about their larval development and rearing requirements pertaining to aquaculture. When we are deciding which direction to take with each rearing run we not only base our decisions on past experiences rearing other species of fish, but also have to be open minded with new ideas. Often we are following our intuition and making changes through the rearing run rather than setting up a strict protocol for each trial.

Following are some examples taken from the notes of a few of the larval rearing runs that were conducted to show the direction we took in trying different tactics for larval rearing. In May of 1999 the larval rearing tank was used as a water bath to keep temperatures constant. Rubbermaid containers with 10 to 15 larvae in each were floated in the tank. Foods were added and small water changed were done. All of the larvae were dead at day 6.

In November of 2000 We conducted a rearing run of Genicanthus and Priolepis larvae together starting with a large batch of priolepis eggs and 50 G. personatus eggs. Water temperature was 75.4 F. Kent Phytoplex and Zoecon were used as the enrichments in the larval tank as well as the algae Tetraselmis chuii. Salinity was kept at 33ppt, which is a little lower than usual. Rotifers were maintained at 5 to 10 per ml. Copepods were added on day 21. Sanfrancisco strain Artemia was added on day 24. On days 27 through 38 we could only see one or two larvae at a time but they looked healthy. We siphoned the bottom of the tank hoping that we would find settlers and that would explain why we couldn’t see many larvae in the water column but found nothing. On day 38 the tank was drained through a 100 micron screen. One larva was collected on the screen. This larva looked much more like an angelfish than a goby, which surprised me after starting with such a small number of angel eggs. Although spending this much time and effort to get one deformed and not quite metamorphosed fish might be disconcerting and frustrating to the average person, it served to fuel our fire! Getting an angelfish to 38 days was a record for us even if it was deformed. We were closer than ever to being on the right track.

In December of 2000 we start with rotifers, Tetraselmis (TE) and Zoecon. Temp. = 75.6. In the first week the rotifer count goes up to 14R/ml. Zoecon and TE are added daily. At day 15 there are 20R/ml. Start adding phytoplex as well as TE. On day 21 we hadn’t seen any larvae for four days and we had a new batch of eggs from the broodstock tank, so the center standpipe was replaced with a screened standpipe and a slow water flow was started. The new eggs were added without draining or cleaning the tank. On day 8 for the second batch of eggs the “Artemia from the hatchery next to this tank must have been accidently introduced into the larval tank because there is quite a bit of growout Artemia in the larval tank. The Artemia is the same length as the larvae and makes searching for larvae more challenging! I’m going cross eyed! Ciliates have bloomed as well and they were not added intentionally either! What’s going on here?” By day 13 the Artemia are adult size and starting to reproduce. There are tons of Artemia feces in the water column. The larvae I see don’t look good. Some are actually rolling and tumbling.

In February of 2001 We tried a run stocking rotifers and ciliates together at the start on day 3. This was a static run, not using flow through water. During this run I couldn’t wear my contact lenses. Can’t see as well wearing my glasses so the comparison of how the larvae looked without using the scope is not consistent in this run. Observations were often made by other aquarists. Tried using Zoecon as the oil based enrichment along with Phytoplex and TE. The ciliates in this run were the larger and slower moving 40u x 50u barrel shaped critters as well as the smaller, faster 12u x 20u ciliates. “I can’t imagine that a larval fish could see the small ciliates.” At day 18 I can still see some larvae. They look healthy and active, darting in all directions. Head looks more defined. Temp.=75.9. beaker check for food shows no rotifers and plenty ciliates. On day 22 I could not find any larvae. On day 26 the tank was slowly drained through a 100 micron screen and no larvae were found.


In April of 2001 We started a run using 20 gallon glass tank with blackened sides. Add ciliates on day 2. Use fluorescent light on 24 hours. Day 4 shows the tank is loaded with ciliates. On day 6 many of the larger ciliates are present and about 90% of the smaller ciliates are gone. I see some dead larvae floating on the surface. On day 7 the larvae seem healthy but small. Temp = 78.1. Day 13 has larvae with large heads and skinny bodies. Scope check for food shows no larger ciliates and small ciliates only in the surface layer. No larvae seen the next day.


The successful rearing run:

A dense starter culture of ciliates and 20 liters of the algae Tetraselmis chuii (TE) are added to the tank on Tuesday morning, (which is recorded as day 0 of the larval run). On Thursday (day 2) morning 100ml of Algamac 2000 is added to the tank. From d2 through d8 100ml of Algamac is added each morning and 20 liters of TE is added each afternoon. During this time, at d5, the aeration is reduced slightly. The first Algamac enriched rotifers are added on d9 and the Algamac addition to the tank is increased to 150ml. Enriched rotifers are added every other day or as needed to keep the numbers in the tank at 1 rotifer/ml. On d13 the Algamac is again increased to 200ml/day. On d16 the incoming water is increased to 1.2 liters per minute and enriched Artemia nauplii are added. The addition of TE is increased to 30 liters/day. On d20 Algamac is increased to 300ml/day. On day 23 the nitex screen clogged. The aeration and incoming water were turned off while the screen was removed and cleaned. During this time the larvae could be more easily observed. They are deeper bodied now. Day 26 was the last day we added rotifers. The screen clogged again on day 27 and this time with the air and water off we saw ten larvae, one of which had a shiney silver abdominal area. The larvae are difficult to see because the tank is so large and not a clear water system, so each count is an estimate to the number left. Algae, Algamac, and Artemia were added on a daily basis for the rest of the run. On day 30 we had to clean the screen again. On day 32 Aquarium Director Bruce Carlson took some underwater video footage of the larvae. I put my hand into the tank to gently direct a fish towards the camera and the little fish began pecking at my hand as if picking algae off a rock! On day 27 with the air and water off we counted 12 larvae. The run continued on with the same protocol until day 48.

On day 48 we could count only 4 larvae at each try. My Christmas vacation was to start the next day and due to the fact that the aquarium was going to be very short staffed over the holidays and I have a clownfish hatchery at home, the decision was made that the young fish would go home with me. I felt very privileged to be trusted with these potentially valuable fish but it sure didn’t make for the relaxing Christmas vacation I had been looking forward to! The four fish were moved to a bare 29 gallon tank with one airstone and a few small bleached rocks. The two smaller fish died in the first week after being transported. On day 56 the larger Genicanthus had the behavior of a settled fish but was still silver in color. This larger fish stayed at one rock and swam in and out of the holes. On day 60 live copepods and powdered weaning feeds were added to the tank. Both fish were observed picking food off the bottom of the tank. On days 70 and 71 the larger Genicanthus was really hiding in a hole in the rock. I was determined not to bother the fish too much, but on day 72 I couldn’t take it anymore. I had to use a flashlight and move the rock to peer into the hole and check on the fish. And there she was, a beautiful glowing white opalescent Genicanthus with a clear tail and a black streak through the eye. My husband took a couple of not very good photos to email to Bruce Carlson who was in Florida at the time. I believe that the larger Genicanthus completely settled on day 69. Although she had the behavior of a settled fish at day 56, she did not have all of her color.


I had returned to work after my vacation on Dec. 30 (day 60 of the larval run) but we did not move the fish back to the Waikiki Aquarium until Jan. 15, 2002 (day 76). At this point the smaller of the two Genicanthus was behaving as a settled fish but had still not completely metamorphosed with the color change. On day 94 the smaller Genicanthus died after never fully metamorphosing. The larger Genicanthus now called “Geni” grew rapidly and at about 4 months old was approximately an inch in length.

The ciliates:

There are two species of ciliates that we have used in larval rearing trials. We have not yet had the species identified. The larger of the two is a barrel shaped slower moving ciliate measuring 40 x 50 microns. The smaller ciliate is approximately 12 x 20 microns and moves relatively fast with a spiral swimming pattern. Our first small steps at success came while using the larger ciliate, but the successful rearing run was accomplished using the smaller of the two ciliates. The smaller ciliate reproduces much more quickly than the larger one and its density in the rearing tanks can be brought up quite high.

Culture methods for the ciliates are still being perfected. We have been able to culture both species and find that the smaller is slightly easier to manipulate in terms of density. They can be cultured using Tetraselmis or Cheatocerus as a maintenance food. Due to their small size they are difficult to screen during harvesting. Therefore the rearing tank is inoculated with the culture and the ciliates are brought up to the preferred density within the rearing tank itself several days before the larval fish begin feeding. These ciliates are so small that actual counts are not taken. Beaker samples using a 100ml glass beaker are taken to get a feel for the ciliate density within the tank.

In rearing the masked angelfish from egg to juvenile we made a major breakthrough in the practice of aquaculture, but there is still much work to be done. I hope to continue conducting larval rearing runs with small “difficult to rear” marine ornamental fish and I hope that the information presented here will help others take this work farther so that successfully rearing difficult ornamental and food fish in captivity will become a common practice.

[Clownfish75]

Very interesting read, you certianly experimented with many different things.

Did you ever move back to copepods for later efforts?

Thanks

Christian

[KMB]

Christian, At the time I was using harpacticoids. The only calanoids I had were from wild plankton and I was paranoid about bringing undesirables in with the wild plankton. Now I have cultured calanoids which I think are promising. Unfortunately I don't have any fertile eggs to work with now. It's always something!

Karen

[KMB]

Christian, I realized I didn't exactly answer your question, so I'll try to clarify. After the successful larval run I had 5 or 6 chances to try and repeat the "good run". I tried doing the same thing and was not successful. So for G. personatus I did not try copepods again. I no longer work at the Aquarium but I do have my own angels (not Genicanthus-wish they were though ). I have tried cultured calanoid copepods with my angel larvae (mostly flames) and find them promising but it seems that something is still missing. I have only reached 30 days post hatch. Lately I have only one pair of angels (bandits) spawning and the eggs are infertile.

Hope that helps, Karen

[Clownfish75]

So you firmliy believe that you had more success due to the ciliates?

Do you think this could yield a greater survival with greater efforts?

as for lighting, was your lighting extremely high? i assume it was due to being outdoors and only under some plastic type clear/opaic roofing.
Christian

[Peter Schmiedel]

Very interesting to read ! So one should start ciliates research - a pitty that there are so many

[KathyL]

And on Day 60, what happened? You have no idea what a cliff hanger this is for me!

Thanks for the article. Fascinating!

[aomont]

And on Day 60, what happened? You have no idea what a cliff hanger this is for me!

I also DO need to know !!!!!!
Just awesome ! It was vibrating to read it went home with you.
Do you know which ciliate species you had offered ?
Do you have any pics besides this

http://www.breedersregistry.org/images/waikikibaby.gif
Anderson.

[KMB]

OOPS! Sorry everyone about that cliff hanger. Thanks for pointing it out Kathy. Looks like I didn't get the last page in there. Here it is. Maybe someone who knows how can attach this text to the first part.

Christian, I do believe I had success because of the ciliates. I think now that a combo of ciliates and calanoid naups is something worth trying. It is also something my coworkers enjoy teasing me about. At work ciliates are considered pests. As Peter said there are many of them and I think I got lucky with the ones I stumbled upon for the G. personatus. They were easy to culture. I often bring home the pests from work but don't have much luck culturing them.

Sorry Anderson, I don't know which ciliate species I had. I only know the ones I have tried by the common names that I give them. I do have some pics of the G. personatus but you'll have to give me another computer lesson on how to get them here.

So here's the rest of the story...

On day 60 live copepods and powdered weaning feeds were added to the tank. Both fish were observed picking food off the bottom of the tank. On days 70 and 71 the larger Genicanthus was really hiding in a hole in the rock. I was determined not to bother the fish too much, but on day 72 I couldn’t take it anymore. I had to use a flashlight and move the rock to peer into the hole and check on the fish. And there she was, a beautiful glowing white opalescent Genicanthus with a clear tail and a black streak through the eye. My husband took a couple of not very good photos to email to Bruce Carlson who was in Florida at the time. I believe that the larger Genicanthus completely settled on day 69. Although she had the behavior of a settled fish at day 56, she did not have all of her color.


I had returned to work after my vacation on Dec. 30 (day 60 of the larval run) but we did not move the fish back to the Waikiki Aquarium until Jan. 15, 2002 (day 76). At this point the smaller of the two Genicanthus was behaving as a settled fish but had still not completely metamorphosed with the color change. On day 94 the smaller Genicanthus died after never fully metamorphosing. The larger Genicanthus now called “Geni” grew rapidly and at about 4 months old was approximately an inch in length.

The ciliates:

There are two species of ciliates that we have used in larval rearing trials. We have not yet had the species identified. The larger of the two is a barrel shaped slower moving ciliate measuring 40 x 50 microns. The smaller ciliate is approximately 12 x 20 microns and moves relatively fast with a spiral swimming pattern. Our first small steps at success came while using the larger ciliate, but the successful rearing run was accomplished using the smaller of the two ciliates. The smaller ciliate reproduces much more quickly than the larger one and its density in the rearing tanks can be brought up quite high.

Culture methods for the ciliates are still being perfected. We have been able to culture both species and find that the smaller is slightly easier to manipulate in terms of density. They can be cultured using Tetraselmis or Cheatocerus as a maintenance food. Due to their small size they are difficult to screen during harvesting. Therefore the rearing tank is inoculated with the culture and the ciliates are brought up to the preferred density within the rearing tank itself several days before the larval fish begin feeding. These ciliates are so small that actual counts are not taken. Beaker samples using a 100ml glass beaker are taken to get a feel for the ciliate density within the tank.

In rearing the masked angelfish from egg to juvenile we made a major breakthrough in the practice of aquaculture, but there is still much work to be done. I hope to continue conducting larval rearing runs with small “difficult to rear” marine ornamental fish and I hope that the information presented here will help others take this work farther so that successfully rearing difficult ornamental and food fish in captivity will become a common practice.

["Umm, fish?"]

moves relatively fast with a spiral swimming pattern

I have a ciliate like that contaminating my copepod culture. I'll try to get some photos.

Karen, if you want to email me the photos (I don't have a file size limit on my email), I would be happy to host and post them for you.

[aomont]

Sorry Anderson, I don't know which ciliate species I had. I only know the ones I have tried by the common names that I give them. I do have some pics of the G. personatus but you'll have to give me another computer lesson on how to get them here.

No problem ! You have to host it to a internet site. No matter if it´s a personal HP like Andy´s suggestion or something like http://photobucket.com/ . Then you copy the image link and paste it inside your post like this

Code: Select all

[img] http://www.whatever.com [/img]

[/quote]

And there she was, a beautiful glowing white opalescent Genicanthus with a clear tail and a black streak through the eye.

This description makes me want to be there !

Thank you very much for the description of this run. When I first read about this on the web I thougth it would be long since I could read a description like that.

Anderson.

[KathyL]

At your service, I added the last bit to the first part.

Again, fascinating...

Thanks for posting that here!