There are a few fish species in the bays that are easily mixed up. Here’s four commonly confused pairs.

The banded sergeant and the blackspot sergeant

These are two different fish species, but it would be easy to not realise. Which is probably why the banded sergeant (Abudefduf septemfasciatus) was only identified as a new species for Norfolk Island in April 2022. When I first noticed it, I did a double take. I couldn’t work out what was different until I looked closely at the photos on my computer screen and compared it with its cousin, the blackspot sergeant (Abudefduf sordidus). Then I was quite easily able to tell the two apart. In common with some of the other doubles that I’ve listed here, these two fish often share the same niche on the reef – living in the sandy shallows, although there are many more blackspots than there are banded sergeants.

The scissortail sergeant and the Indo-Pacific sergeant

These species both inhabit very similar niches in the reef ecosystem, and even like to hang out together. They are both about the same size, although I think the mature Indo-Pacific sergeant (Abudefduf vaigiensis) will get just a smidgeon larger when it is mature, and they both have the five vertical black stripes against a white background. The scissortail sergeant (Abudefduf sexfasciatus) has two distinctive horizontal black stripes on its tail reminiscent of scissor blades, which is what gives it its name. As it matures, the scissortail doesn’t sport such an intense yellow blush when compared to the Indo-Pacific sergeant, as can be seen in the two images, below.

You’ll often see a school of one of these species, like the scissortails, with a lone random interloper, like the Indo-Pacific, swimming among them (see the image at the top of this story).

The surge wrasse and the Christmas wrasse

We all know our beautiful surge wrasse (aka the Rainbow Warrior, Thalassoma purpureum). Well, we have another very similar looking fish, particularly when it is compared to a younger female surge wrasse. It’s the Christmas wrasse (Thalassoma trilobatum). The Christmas wrasse is much harder to spot and even harder to photograph. Unlike its show-stopping cousin, it is shy and flighty. It skims around just beneath the surface of the shallow rock ledges at great speed, often where it’s too shallow follow.

I find the easiest way to tell them apart is by looking at the face markings. The female surge wrasse tends to have little dots whereas the colour on the Christmas wrasse is a more solid, rusty tan colour.

The banded snake eel and the convict snake eel

Both these snake eels share a similar body shape, and are quite different to that of many moray eels, which are thicker and have a more obvious dorsal fin. Both these snake eels have black and white bands, but the convict snake eel (Leiuranus versicolor) looks like a cookie cutter has taken bites out of the bands leaving a white spot in each one. The number of black bands with the white spots ‘cut out’ increases as the eel matures. When they are very young it can be difficult to tell the banded snake eel (Leiuranus semicinctus) and the convict snake eel apart. They both like living in the same sandy reaches of the bay and will burrow under the sand to get away from danger.