This time of the year is an interesting one for the Norfolk cardinalfish, Ostorhinchus norfolcensisas, as they are busily procreating.
Known as ‘big eyes’ on Norfolk Island, they are a quiet little fish, normally floating under ledges in schools, drifting quietly, noses into the current. These guys are mouth brooders. That is, the male nurtures the eggs in his mouth, closely guarded by the female who usually positions herself beside and just behind him. She releases the egg mass close to her male. He then takes them up in his mouth and there they stay until ready to hatch. In the photo (below) you can see his distended pouch beneath his jaw.
Every now and then he will open his mouth to aerate and rotate the eggs. It is a fleeting moment every few minutes or so. You see him extend his gills and then spit and gulp. It looks a little like he is blowing chewing gum bubbles.
While he is minding the babies, he’s unable to eat. This can be for as long as a couple of weeks. The closer he gets to releasing his babies, the more often he aerates and turns the eggs, and the more he does it, the more other fish take an interest, maybe hoping for a free meal! That is where she comes in, shooing away any potential egg stealers.
Bobbing around in a stiff current on the surface of the water in poor light, meant capturing that well on camera was beyond me; however, I was able to watch a pair for quite a while as the female shepherded and nudged him from behind.
I am looking forward to seeing all the juveniles in a few weeks.
