Spawning Mandarinfish! | JONATHAN BIRD’S BLUE WORLD


Coming up next on Jonathan Bird’s Blue World,
Jonathan searches for a rare and elusive reef fish. The ocean is full of amazing fish, like this
school of surgeonfish feeding on algae on the reef, colorful anemonefish, or this school
of sweepers hiding in the coral for protection. One of the most beautiful but rarely seen
fish is the Mandarinfish, found on coral reefs of the Pacific. Hi, I’m Jonathan Bird and welcome to my
world! Mandarinfish are extremely shy and only come
out of the reef at dusk to mate. I’m here in Micronesia on an island called
Yap, one of the best places in the world to find mandarinfish. And this evening, I am going on a dive to
see if I can find a few! I enter the water right at sunset. As the light levels get lower on the reef,
the daytime fish feed before they must hide for the night. A lot of changes take place on the reef at
dusk. Just before the sun sets, I have my best chance
of finding a mandarinfish. In the dim light, I search the reef carefully. I can’t use a flashlight because it would
scare the tiny fish. Mandarinfish are very shy…they rarely leave
the protection offered by the nooks and crannies in the reef. There…a small mount of movement catches
my eye. A mandarinfish! If I didn’t know it where and when to look,
I would never find it! As the sun sinks lower in the sky, the light
levels drop, and something magical happens. The Mandarinfish peeks out to see if the coast
is clear. These reclusive fish only venture from the
safety of their coral home to mate, and they only do it in a narrow window of time at dusk. A male wanders from female to female, courting
each one. His goal is to spawn as many times as he can,
with as many females as possible. He’s not particularly choosy about a partner. The females size him up—they are a little
more selective about a mate than he is. He’s not worried–if one female gets cold
fins, another one will jump in at the last minute. Then the male and female pair up and begin
to make practice runs, rising up off the reef, cheek to cheek. At last the pair spawns for real. Rising well above the reef to keep the eggs
from being eaten by the coral, the male and the female release their spawn at the same
time. The eggs are fertilized in the water column. Over and over, the male spawns as many times
as he can, perhaps as many as ten times in half an hour. The fertilized eggs then drift off into open
water to develop into tiny baby mandarinfish. Most will not survive to adulthood. Once darkness comes, the spawning ends. The mandarinfish seek protection in the reef,
safe for another day. Well, it’s after sunset and the mandarinfish
have finished mating for the night, and gone back into the reef. They won’t come back out of the reef until
tomorrow night, so for now, it’s time for me to go to bed.

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