2023 Güney Denizi Keşif Gezisi

JBL Expedition South Seas I and II

Rare fish species

As a marine aquarist, you have an eye for when something rare swims in front of your diving goggles. These can include, let’s say, black surgeonfish with a body diameter of 30 cm. At first we thought it was a colour morph of the brown tang (Zebrasoma scopas). But their size alone eliminated them and they were later identified as Zebrasoma rostratum. We observed some strange behaviour in (only) this species: They apparently had no territory of their own and were aggressively chased away by all the other surgeonfish species when approaching the corals. Normally, strong aggressive behaviour is only seen within species or towards similarly coloured fish. But somehow nobody likes the big black ones.

Pygmy angelfish look like little jewels in the reef. The flame angelfish (Centropyge loricula) are particularly striking. They were much more sociable with each other than in aquariums. We counted up to 8 animals per 2 square metres and we didn’t see any aggressive behaviour at all.

The twospined angelfish (Centropyge bispinosa) is known for its variable body colouration. It was interesting that we were able to see 2 colour forms side by side.

A rarely seen pygmy angelfish was Paracentropyge multifaciata. It was only found singly and in pairs at depths of 30 m or more. As it is quite shy, photographing it was a real challenge.

On two of around 60 dives, we saw the beautiful chiseltooth wrasse (Pseudodax moluccanus). It can be found at depths of 20-plus metres, always singly and on steep slopes. Like all wrasses, it is extremely difficult to photograph due to its erratic swimming behaviour.

Among the triggerfish we saw, the halfmoon picassofish (Rinecanthus lunula) was the rarest. This species was first described in 1983. It tended to live at depths of between 10 and 30 m, while its relative, the Picasso triggerfish (Rhinecanthus aculineatus), was only ever found on sand in shallow water.

Among the many small damselfish, which were numerous and present everywhere, we also found some rare species here and there. Chromis nitida has so far only been described from the Great Barrier Reef and Lord Howe Island. We saw this species in the Tuamotus near Toau. This could be a first description from this region of the Pacific.

The small Pycnochromis acares were also only to be found on very few reef sections. These very pretty damselfish had previously only been described from other regions of the tropical Pacific. They had probably been overlooked because everyone only had eyes for the fascinating sharks and manta rays!

We even noticed a colour deviation among the well-known cleaner fish: Labroides dimidiatus is often described with a yellowish head area, but hardly ever with a red area under the stripe on the body. If you look on Google, you will only find one photo of this species with the red-orange bar among hundreds of others. Our photo seems to be the first really sharp photo of this variant.

In the open water, we discovered a species of fish at the Fakarava north passage that presumably belongs to the genus Genicanthus (lyretail angelfish). In the open water they feed on plankton. Our photo isn’t great, unfortunately, but this animal always kept a large distance from the divers. We were unable to find out which species it was.

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Water and light measurements, results

Güney Denizi Keşif Gezisi

JBL Expedition South Seas I and II

Rare fish species

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