This cool looking Hawaiian reef fish get up to 20 inches long and divers are use to seeing the females that are white with black stripes. Even the babies are the same color and they frequent shallow water usually just by themselves. The Coris are in the wrasse family and are always darting around looking for food so they are difficult to get pictures of.
As a biologist I have always known that most of the wrasse are all hatched out as females and grow to adulthood as females.
Then due to the needs of the colony in any given part of the reef one or two of the females will change colors and convert into males! With the wrasse the adult breeding males are very colorful and do not look at all like the adult females.
But for over 20 years shooting video of hilu I never saw what looked like a male Blackstriped Coris while I have seen dozens of the black stripped females? This did not make any sense to me but I did notice that the females all seemed to disappear from time to time and I always wondered where they went to.
Then one day I read an article about some DNA testing on these fish and it turns out that the males just live in deep water down below were were we can safely scuba dive.
So the females will leave the shallow reef and dive down into deep water where some then convert to males and breed. Then the females come back up to the shallow reef and lay their eggs. What an amazing journey.
Then in 2018 I was scuba diving in a cave in Kauai at about 50 feet deep and saw a two foot long fish I have never seen in over 20 years of diving in Hawaii.
This really caught me by surprise because I thought I had seen just about every known shallow water Hawaiian fish species.
This new fish was bright green, gold and blue! So I took a good video clip of the beautiful creature and sure enough got it identified and it was a male Blackstripe Coris! Not sure why this one decided to come up into shallow water but in the last two years I have seen dozens of deep water fish now living in shallow water here in Kauai.
At least now I know what both the male and female hilu look like! Hilu in old Hawaiian times were eaten by pregnant woman as they though the fish would cause them to have a ”well behaved” child and that is how the fish got its name. Out on the reef these fish are anything but “well behaved” as they zoom around non stop and steal small invertebrates from other fish that find their meal first.
You can see hilu in action in my video The Worlds Guide to Hawaiian Reef Fish up on my underwater educational web page at www.underwater2web.com. If you like marine life I have a daily marine life educational post I do on my Instagram at terry.lilley
Aloha from under the surf,
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Terry Lilley, a marine biologist, lives in Hanalei. His websites include underwater-2web.com and www.gofundme.com/5urrm4zw. All Photographs © 2016 Terry Lilly
