Where do baby fish come from?

We have found evidence of fish breeding in the Giant Ocean Tank for decades. But until now we haven't focused any efforts on raising these fish. Thanks to a recent partnership with Dr. Andy Rhyne at Roger Williams University we are now actively collecting fish eggs and larvae and sending them off to a lab to be reared.

Our main focus currently is on damselfish. Unlike most fish that are pelagic spawners (spawn in open water), damselfish lay sessile eggs (meaning eggs that are attached to a surface). This makes it easy to find and remove them. In addition, the damselfish are very prolific in their egg laying – so much so that we are able to collect eggs on an almost daily basis! So far, we have collected eggs from sergeant majors, yellow-tail damselfish, dusky damselfish, bi-color damselfish, and blue and brown chromis.

Note the dark, gray/brown eggs attached to the top piece of coral. These are dusky damsel eggs.

For damselfish, the breeding cycle begins with the male picking a spawning site, which he then cleans and prepares. Most damselfishes lay their eggs on a piece of coral, but blue chromis lay their eggs in gravel. Once the site is prepared, the male tries to attract a female by changing colors and swimming excitedly. Some males evens emit clicking sounds. If these tactics work, then the female will deposit up to 20,000 adhesive eggs at the site and the male will then quickly fertilize them.

Bicolor damselfish

Once fertilized, it is up to the male to defend the eggs and, in some cases, to tend to the eggs. He tends to them by fanning water across them and by picking out dead eggs to prevent a fungus from developing. To defend the eggs the male attacks all intruders that get too close. This includes pulling the divers' hair!

The gestation period for damselfish is relatively short – about 3 to 7 days. The eggs change color as they mature. The yellowtail damsels’ eggs start off pink/yellow and become darker as they mature to brown/black. Sergeant majors’ eggs start off purple and lighten as they mature to yellow/clear. Hatched larvae feed on very small zooplankton like copepods and can take up to three years to mature.

Keep your eye right here on the GOT blog, we'll be posting about how the eggs are collected in an upcoming blog!

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