Black Axil Chromis Chromis atripectoralis

The Black Axil Chromis is nearly identical to the closely-related Blue-green Chromis but doesn't have the small, light-bordered, black spot where the pectoral fins join the body (see page below); the Blue-green sometimes has a dusky patch, making differentiation more difficult.

The two have an overlapping range of the reefs of the Indian Ocean from East Africa and western Pacific to Japan and New Zealand (but excluding the Red Sea and Eastern Pacific for the Black Axil). It grows to 10-11cm long. They retreat to branched coral to hide or sleep. Fish aggregate in shoals when not breeding.

Males will turn a little yellower green when ready to breed. He will build a nest, tend and aerate the eggs and guard them until they hatch.