Monday, April 14, 2014

Larval Rearing of the Purple Mask Angelfish

3 day old P. venusta larvae.  Photo credit: Karen Brittian.
Larval rearing trials began with the spawning of a Paracentropyge venusta pair in the summer of 2013. The first successful larval rearing trial started with a small spawn on November 13, 2013.  This was the fifth larval run with this species and the focus was on food density and consumption at different developmental phases.  The diet consisted of both cultured copepods and wild collected plankton with all food items being less than 100 microns in size.  To assess consumption rates, five random samples were taken for initial food counts at the start of each test period. All food items added to the larval tank during the test period were counted while maintaining a density of 1 to 2 food items per ml in the water column. At the end of the time period counts were again done to determine larval consumption. At this point a 75% water change was carried out. I was surprised at the amount of food these little larvae could put away and as an example, at day 28 post hatch the larvae consumed approximately 2,150 food items each over a 12 hour period, (5:00am to 5:00pm).

32 day old P. venusta larvae.  Photo credit: Leighton Lum.  
At one month of age the larvae started targeting larger prey items and ignored the food items less than 100 microns in size. At this point newly hatched and enriched Artemia were added to the diet along with adult cultured copepods.  The larvae also began to display benthic behavior by associating with the corners of the tank, the air stone and airline tubing.  A piece of dried coral rubble was added where the larvae took shelter. 

The larvae continued to grow and develop; they were moved into a growout tank at 57 days old.  At this point we had 17 larvae remaining which equates to 6% survival from hatch. The development of juvenile colors came slowly. On day 95 they had black pigment on parts of their fins and tail.  A month later at 130 days old they were the beautiful blue and yellow of the adults.

115 day old P. venusta juvenile.  Photo credit: Leighton Lum. 
Larval rearing of this species proved relatively “easy” in their first few weeks of the larval stage after which point larval development and growth seemed to slow. This could be attributed to the type and amount of wild plankton collected and fed out at that time. I feel that the larval phase could be shortened and improved upon in the area of diet. After metamorphosis the larvae were again slow to develop with a reluctance to accept non-living food items and this is also another area for improvement. The Reef Frenzy and Herbivore Frenzy frozen foods were the first choice of the juveniles when they began to accept non-living food. Currently these juveniles are fairly bold and are consuming frozen and dry foods with gusto.

Karen Brittain

Wednesday, March 26, 2014

Brood Stock Management, Spawning and Egg Collection of the Purple Masked Angelfish (Paracentropyge venusta)

Female P. venusta (note the light precaudal band). 
Photo credit: Leighton Lum.
Paracentropyge venusta were identified as a good candidate for captive breeding since they often do not adjust well to captive life after being collected in the wild. A juvenile pair from Japan was established for broodstock. The immature fish were introduced to each other during quarantine. Due to the timid nature of this species, quarantine was a dark blue barrel with black plastic pipe provided as hiding places.

Male P. venusta. Photo credit: Leighton Lum.
The pair is housed in a 440 liter tank with a foot print of 122cm by 46cm and a height of 76cm to provide room for a spawning rise. They are housed with a pair of Red Sea Regal Angelfish, Pygoplites diacanthus and a single Multibarred Angelfish Paracentropyge multifasciata.

Feeding occurs at least 3 times daily with a varied diet of frozen clams, table shrimp, Mysis shrimp, krill, Artemia, commercial frozen and dry food and nori. The mature male now measures 8.5cm total length; the female is slightly smaller at 7.5cm. The female has a 1-2mm, pale colored band at the precaudal region of the body. This band is present in small juveniles and may be a simple trait of sexual dimorphism for this species.

Spawning began when the pair was just over two years of age.  Initial spawns were small and infrequent.  During the summer of 2013, spawns became increasingly larger with a higher fertility rate although still on an irregular cycle.  Spawns are now more regular and vary 300 to approximately 1000 eggs.  Pre-spawning chasing activity generally begins around 7:00pm which is 2 hours before lights out.  Spawning normally happens within 30 minutes of lights out.

The eggs are approximately 700 microns in diameter with a single oil drop. They are positively buoyant and float at the water surface.  The eggs are then collected using a 500 to 600 micron mesh net. They are placed in a container with water from the broodstock tank and allowed to incubate over night without aeration.  Once the eggs begin to develop, the embryo becomes heavily pigmented appearing quite dark as compared to other angelfish eggs. This makes them easy to see and count. Fertile eggs hatch 16 hours after spawn at 27C.

Special thanks to DJ Linehan of Tropical Fish Emporium for broodstock acquisition and species information.

Karen Brittain

Tuesday, March 25, 2014

Yellow Tang… so close, yet so far… – Update from OI

Day 60 yellow tang larvae.  Photo credit: Dean Kline.
Since we last wrote at Day 50, we’ve observed a lot of interesting things with our yellow tang larvae. Probably the most important thing we observed is their very inefficient feeding capability. At their size (~1cm), newly hatched Artemia nauplii should have been easy prey, but time and time again we’d watch them strike and miss, or partially catch one only to spit it out. Artemia nauplii definitely don’t seem to be adequate to sustain yellow tang at this stage in development. Likewise enriched Artemia were all but rejected. Also, at this stage, the fish seem to rely on their large pectoral fins for propulsion and were very awkward moving around the tank.  We would frequently observe them floundering about and then suddenly right themselves and swim on quite normally. This seemed to require a lot of energy, which in their compromised nutritional state, likely lead to some additional stress. They also tended to gravitate to the tank walls, and appeared to sometimes be grazing or picking things from the walls.  Although we included live rock, macroalgae and other substrate in the tanks at this point, we did not observe any sign of the fish wanting to be near the bottom.  Settlement seemed to be a long way off.

Day 83 yellow tang larvae (Lucky).  Photo credit: Chad Callan.
From Day 50-60 we continued to lose fish daily; which seemed to be stuck in metamorphosis and were not advancing through this particular stage. We quickly realized that yellow tangs probably have some rather specific nutritional and/or environmental requirements that we were not meeting. We had only ~25 fish at day 60 and were down to 3 fish by Day 65. It seemed we were at the end of this run.  However, some hope remained as our sole surviving fish, “Lucky”, refused to succumb to the fate of his tank-mates. We were surprised daily to see him swimming each morning from Day 67 onward.  He seemed to be growing and his dorsal spine was definitely shrinking (a sign that this stage might be ending).  Unfortunately, this “lucky streak” ended on Day 83.

From the pictures you can certainly see that “Lucky’s” body was beginning to complete this stage of metamorphosis, with his dorsal spine nearly gone and head shape transforming.  If we had only had a few more days with him!  We learned a lot during this trial and will continue to work towards resolving these late-stage challenges in future attempts.  We already have more larvae in the hatchery and will work our way back to this point again!  In the meantime, Emma will continue to update you on her thesis research as she works to resolve some of their early mortality issues.  So much still to learn!




Monday, March 10, 2014

Building a Rising Tide in Hawaii

Dr. Clyde Tamaru and Ms. Karen Brittain of the University of Hawaii are important partners in Rising Tide Conservation. Karen has been focusing on looking at all things related to broodstock management, egg collecting and larval rearing for the Bandit Angelfish (Apolemichthys arcuatus). 

Back in December, Reed Morgan led his Boy Scout troop in building the first phase of our new microalgae culture area, which is part of Reed’s Eagle Scout project. The older boys built and painted a bench for the new algae cylinders. They constructed a wood frame and assembled and attached light fixtures to the frame. They made a PVC airline to the cylinders including drilling and tapping the air valves. The younger boys moved and spread gravel in the area fronting the hatchery that becomes slippery in the winter. I was very impressed with how hard they worked and how helpful they were towards each other!

We had to wait for backordered bulkhead fittings for the cylinders so did not get to fully complete the project that day. The fittings are here now and Reed completed the project in January. This project now allows us to grow five 100 liter cylinders of algae in the space we formerly had room for one 200 liter rectangular algae tank. This gives us many more options for growing what we need and is greatly appreciated. Also appreciated is the loan of the cylinders from the Dept. of Land and Natural Resources, Division of Aquatic Resources.

Dr. Judy St. Leger

Monday, March 3, 2014

Milletseed Butterflyfish Update: Good News / Bad News

Let’s get the bad news out of the way first. We lost our last remaining milletseed butterflyfish larvae at 44 dph (days post hatch).

The good news is we’ve gained ample insight into the larval stages of milletseed butterflyfish and can now identify where bottlenecks in development are occurring. With this knowledge we can address the parameters at these critical junctions. We currently have another batch of larvae at 25 dph and others coming up behind that. 

An accurately scaled comparison of larvae at 24 hours post hatch (inset;
2.32 mm NL) and 44 days post hatch (8.35 mm SL). Credit: J-M Degidio.
Additionally, two of our current populations are spawning twice weekly and data on fecundity, fertilization rates, hatching success, and survival are being gathered from each spawn. From information obtained in our last trial, we now know that larvae can feed on copepods throughout development and that we witnessed mortality events around 11, 20, 27, and 35 dph. Addressing these bottlenecks is our priority. It appears that swim bladder inflation is occurring approximately 11 dph and may be associated with our first mortalities. We also know that flexion is beginning around 27 dph with completion occurring by 30 dph. At this time, body depth increases dramatically. After approximately 38 dph, the tholichthys larval stage (a stage where large calcified head plates form) begins to recede however the preopercular spine and an opercular plate remain.

We hope to address these mortality issues through a variety of replicated studies investigating different parameters such as nutrition, light requirements, water flow, and settlement cues. Our goal is to understand the effect of each variable we test and optimize aquaculture techniques for the milletseed butterflyfish.

The Rising Tide Team at the Tropical Aquaculture Laboratory

Friday, February 28, 2014

Introducing Emma Forbes: OI / HPU Grad Student Focused On Yellow Tangs

Hello everyone!!

My name is Emma and I’m a graduate student at Hawai’i Pacific University (HPU) working toward my master’s in marine science. I’ve been one lucky girl these past few years! I graduated from Old Dominion University with a B.S. in Biology. I had such a wonderful time there and was given so many opportunities, but like everyone I had to grow up and leave my loving “nest”. After graduation I accepted an internship at Two Oceans Aquarium in Cape Town, South Africa and absolutely loved it. While there I got hands on experience with culturing systems, tag and release, commercial collections and husbandry. Then, because adventure calls, I moved to Hawai’i!

In Hawai’i I’m working towards my master’s degree under the direction of Dr. Chatham Callan at the Oceanic Institute (OI) and HPU. My research is centered on the successful culturing of yellow tang. I’ve been lucky enough to be accepted into a wonderful team here at OI who have taken the time to show me the ropes. My research focuses on the nutritional composition of live feeds, algae and copepods, as well as pathogenic bacteria within the culturing environment and possible use of probiotics. These two aspects are hypothesized to play a role in the mass mortality of larvae seen around 7 days post hatch. Everyone at OI spends countless hours in the lab making sure the algae, copepods, and our [adorable] broodstock have everything set as we prepare to start trials and take care of the thousands of larval fish we are hoping to have.

Rising Tide has generously donated money to help support this research and I am beyond thankful for all that they've done. It’s been such a wonderful experience so far.  Recently, on a strike of luck, we have successfully had a few yellow tang larvae survive up to 58 days post hatch (as of this posting). It has been an exciting experience for us as we watch their development progress and examine settlement cues for the first time.

Just a little bit about myself…I am originally from New York and get large amounts of pleasure out of rubbing in my geographic location to everyone back home. (Note: People getting over 10 inches of snow don’t like when you send them pictures of beaches and palm trees). I’ve been in love with the ocean and water since a young age. My parents typically had to plan vacations around bodies of water for me to spend hours in. It’s been a dream come true to spend the last year and a half in Cape Town and Hawai’i, especially since my time in both places has been surrounded by fish and people who love them as much as I do!

I will keep everyone updated on our progress with the yellow tang. Thank you again to Rising Tide, SeaWorld / Busch Gardens, HPU and OI. Also, a huge thanks to Dr. Callan and the entire OI “susTANGability team”, it’s been great coming in to work everyday! 


Emma Forbes 

Monday, February 24, 2014

Yellow Tang Research at the Oceanic Institute – Making Exciting Progress

Larval development of yellow tangs from 15 to 50 days post
hatch (dph).  Photo credit: Dean Kline and David Hoy.
Research on culturing yellow tangs began at the Oceanic Institute (OI) back in 2001 around the same time as initial, exciting breakthroughs were achieved with dwarf angelfish (by OI and others like Frank Baensch and Karen Brittain). It seemed, back then, that we were just around the corner from some major steps forward with the culture of previously thought “impossible to rear” species. Indeed, there has been incredible progress with the culture of marine ornamentals since that time. However, yellow tang have proven to be far more difficult to rear than many of the other targeted marine ornamental fish species under investigation.  More than a decade later, we are finally seeing some exciting progress with rearing this species and will share updates about our work on this site.

On Jan 1, 2014 we stocked a 1000L tank with about 40,000 yellow tang eggs. In this rearing attempt we experimented with very high water turn-over rates, and very clean (ultra UV dose) water. As in previous studies, we used the calanoid copepod, Parvocalanus crassirostris, as our feed. While this was only one tank (we are currently testing these methods again), we immediately noticed far more fish making it through the early larval period than ever before.  We were really excited to see 1000’s of fish survive past the first 2-3 weeks and ended up with more than 600 at day 35.  We have since moved the fish to smaller tanks and are investigating potential settlement cues, like photoperiod and substrate.

The fish recently crossed day 50 and appear to be looking very close to settlement. We’re observing fairly high mortality during this period of transition, but still have more than 150 fish distributed among our tanks.  We are hoping at least a few make it through, but regardless are very encouraged by this recent progress!

With newly obtained support from Rising Tide Conservation and the Hawaii Tourism Authority, we are looking forward to pushing this culture technology forward.  This work will be supported by an HPU graduate student (Emma Forbes) who will introduce herself in a separate post.  Stay tuned for updates from OI and Emma!


Chad Callan