Development of Captive Culture Technology for the Yellow Tang (Zebraso

[CFOh]

Some write up by Reefbuilders...

http://reefbuilders.com/2011/04/05/captive-bred-yellow-tangs/

Below articles from CTSA

The development of captive culture technology for yellow tang and other high-value reef species is imperative to protect our increasingly threatened coral reef ecosystem. Not only will captive production technologies help take pressure off wild fish populations, they will also provide new economic opportunities associated with the worldwide trade in marine ornamental species.

The first major hurdle encountered was the establishment of an egg supply. We were successful obtaining tank spawns from yellow tang early on in the project, but most eggs produced by captive stocks were either infertile, or failed to properly complete development (non-viable). Through a combination of better broodstock selection, improved broodstock holding systems and protocols, and superior broodstock diets we have slowly increased egg output, and most importantly, greatly improved egg quality. In particular, this last year we saw major gains with current yellow tang egg production, attaining levels of over one million eggs per month with a mean fertility rate of 84% with an egg viability rate of 51% (Fig. 1).

Figure 1. Picture of yellow tang broodstock tank (left photo) and overall egg production from captive broodstock population showing lunar pattern in egg production over time.

The second major hurdle was developing a suitable larval rearing system for newly hatched larvae. Yellow tang eggs demonstrate a typical developmental sequence to many pelagic spawning reef fishes with hatching occurring 21 to 22 hrs after fertilization. The resulting larvae are much smaller than other fish species cultured to date (including the pygmy angelfishes), which makes them highly sensitive to the physical attributes of the larval rearing system. Following hatch, larvae spend the first day at the tank surface and then move into the water column on day two while they complete mouth and eye development in preparation for feeding. Even light aeration (which facilitated hatching) was shown to be highly destructive to these fragile pre-feeding larvae. The use of static conditions helped improve early survival, however the deterioration in water quality precluded its practical application. In response we developed an upwelling water delivery system to maintain water quality while providing a less turbulent larval environment. These system improvements now support excellent early (pre-feeding) larval survival, enabling us to generate large numbers of larvae through the first-feeding period

Figure 2. Pictures of yellow tang larvae as they begin to feed on available prey items including algae and early stage copepod eggs and nauplii and begin to develop into characteristic pelagic larvae with notable growth in dorsal and pectoral spines.

The next challenge was identifying a suitable feed for yellow tang larvae as they develop functional mouths and eyes and begin to feed on day three. Limited efforts to feed yellow tang larvae using a similar copepod nauplii feeding regimen (based on success with flame angelfish, red snapper and bluefin trevally) proved unsuccessful for the yellow tang, with larvae failing to feed and dying of starvation. However, with a combination of improved broodstock egg supplies, use of copepod eggs and smaller nauplii, and an improved larval rearing system we were able to stimulate larvae to feed on eggs and nauplii of both Parvocalanus and Bestiolina copepods. However, only Parvocalanus appears amenable to stable production and large-scale culture.

Initial trials with early developing yellow tang larvae yielded feeding rates that were quite low and highly variable. Subsequent research revealed that larval feeding rates were highly affected by tank lighting and coloration. Thus the adoption of dark (black) colored experimental tanks along with use of a gentle upwelling water delivery best supported yellow tang larvae as they initiate feeding, with over 80% of the observed larvae exhibiting full guts upon microscopic examination at days 4 and 5 post-hatch (Fig 2). Associated with the initiation of feeding, we began to see significant changes in size and appearance of larvae as they continue to actively feed (Fig. 2). Notable changes include changes in shape, a deepening in the head and body musculature, growth and development of the brain and internal organs, along with rapid growth of protective spines from dorsal and pectoral fins.