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2006/ Day 16
Claire Johnson, NOAA National Marine Sanctuary Program
Thick finger coral (Porites
duerdeni) provides shelter for a wide variety of reef fish.
Photo: Claire Johnson/NOAA
Swim by any number of small coral heads in the middle of a sandy flat and you will see an entire underwater
village. At the end of our last snorkel site and after putting away my underwater camera housing and my
REEF fish count slate, I swam over to a small head of cauliflower coral (Pocillopora
meandrina). Before I got close enough to scare them all away, there were approximately
45 Hawaiian domino damselfish (Dascyllus albisella) in sizes ranging from the size of a dime
to larger ones about 2 inches across making their distinctive purring noises. There was also a small
endemic saddle wrasse (Thalassoma duperrey), and a miniature oval butterflyfish
(Chaetodon lunulatus). As I swam closer to get a better look a tiny, endemic bluestripe
butterflyfish (Chaetodon fremblii) the size of a quarter, every single fish darted into a
hiding place or tiny crevice in the coral head, leaving the coral condominium appearing empty.
A small head of cauliflower coral (Pocillopora
meandrina) acts as a coral
condominium for fish like the Hawaiian domina damselfish pictured. Photo: Ellyn Tong
As Ellyn Tong and I explored this underwater village further, we continued to find little critters tucked
away. The small saddle wrasse had wedged itself in between two fingers of the coral. On every dive down
we discovered additional species tucked away, such as a miniscule Hawaiian turkeyfish (Pterois
sphex) the size of a half dollar buying time until it will be large enough to recruit to the
main reef and find a domain. Most of these juvenile fish will spend their young life zooming in and
out of the coral crevices. Exploring the outside world in search of food and tucking in to avoid
predation. Once these fish are big enough, most of them will recruit to the reef and spend the rest
of their lives there.
This is the time of year that juveniles are in abundance, generally living symbiotically with the coral.
In some cases, using the coral for protection, such as the Hawaiian domino damselfish, as it flutters
above feeding on tiny plankton floating by. The damselfish may inadvertently share part of its meal
with the coral polyps, making it a relatively fair arrangement. Reef fish are primarily driven by the
desire to feed, avoid danger and eventually reproduce. The relationships formed on the reef, such as
this small coral head are truly a matter of life and death.
Three juvenile amberjack (Seriola dumerili) taking up residence under the legs
of a dead Laysan Albatross chick. Photo: Ellyn Tong
Not all fish find protection in a small coral head while growing up. On a snorkel another day, we found
three juvenile amberjack (Seriola dumerili) taking up residence under the legs of a dead Laysan
Albatross chick. Until something larger decides to devour the free meal floating at the surface, these
small amberjack will find sufficient shelter and protection under the bird until they are big enough to
embark on their own pelagic adventures in the sea. They were quick-witted indeed. Any time we swam
close by, they nearly darted away, weighing the consequences of leaving their protection for the great
Although this coral head was a little larger than a basketball, this goes to show the significance of it
for the life of nearly a hundred juvenile fish. If this branching head of cauliflower coral had been
ruined by an anchor or a careless fisherman’s net an entire underwater community would have been impacted.
The small fish would scatter to quickly find a new home and in the meantime likely become a meal for a
larger, opportunistic fish. You can begin to imagine what the impact would be if several small coral
condominiums were inadvertently destroyed at a near-shore reef. The consequences could easily compound
over time and have long-term effects on the reef ecosystem. Think twice about your actions when you are
near any coral, no matter how small. You may be impacting an entire little underwater village.