Sunday, March 8

Gone fishing

Walking along Nikao beach one day in February we saw a large number of dead fish along the high waterline. They were small, up to about four centimetres, transparent or silver-coloured and flat (although this could have been the result of being dead and dried out). More washed up over the next few days.
They were probably maito (surgeonfish) juveniles. The fish develops from little more than an egg with a tail to a miniature adult during the larval stage out in the ocean. When they become juveniles they move onto the reef and lagoon. Transparency helps save them from being eaten by predators and the adult can look very different.
A few days later the lagoon was swarming with tiny black fish. There were shoals all along the shoreline but particularly around rocks and coral outcrops where they seemed to be grazing, sucking up food like a vacuum cleaner.
The Cook Islands Biodiversity Database lists 18 different sorts of maito. These ones looked like the dusky surgeonfish, however I have since been told they are striped bristletooth (at the moment there's no picture of them in the database).
If the numbers are similar all around Rarotonga, there must be several million of them in the lagoons and there are even more on the outer surfaces of the reef. That’s what the birds, probably brown noddys, are fishing for.
Apparently this mass swarming occurs every five or six years, for reasons unknown, although some of the video of the last time it happened was taken in 2006 and there were larger flocks of fishing noddys that time.
The surviving maito are now growing larger, and there are still plenty around so it’s surprising that there aren’t more birds after them. The birds wouldn’t even have to walk along the beach, just stand in the water and wait for dinner to come to them.
Maybe the noddys actually like the thrill of the chase. It could be fun dive-bombing the surf.
Anyone for avian extreme sports?