Surprise! Rainfordia opercularis, the Flathead Perch – Found in Indonesia

Rainfordia opercularis, Flathead Perch, by Ned DeLoach
Rainfordia opercularis, Flathead Perch, found in Raja Ampat, Indonesia

Raja Ampat, Indonesia. February 2019.  Ned bursts into our cabin, “Yan and I shot a fish we’ve never seen before!”  It must be good – he hasn’t bothered to dry off before rushing down to download his camera’s memory card into his laptop. Now I regret skipping the morning dive. Tapping with one finger to avoid dripping into the laptop keys, Ned describes how he and Yan spent 40 minutes in a small cavern, patiently waiting for the 6-inch fish to make a pass across the far back wall – every 7 or 8 minutes. Ok, not much chance that I would have been able to wedge myself in there too, so missing the dive wasn’t as bad as I thought.

After seeing Ned’s photo, Janet Eyre, who is diving with us and surveying fish for REEF, thinks it’s a Liopropoma and I agree, but Ned and Yan aren’t so sure. “It is way too big for that family,” cautions Ned. Janet and I counter, “It has a seabass eye…and the anal and rear dorsal fins look like a basslet’s.” Yan Alfian, our guide of eight years, has also guided for both Dr. Gerry Allen and Janet. He is very much in tune to Indonesian fish species and because we’ve dived together so much, realized as soon as he spotted it, that it was something rare that we hadn’t seen before. “It has a funny head,” says Yan, and re-emphasizes that it is a big fish compared to other basslets.

We’re on a 12-day cruise aboard Dewi Nusantara, well out of Internet range, so a positive identification will have to wait. Throughout the rest of the day, there is much buzz about “the fish” and everyone is excited when Stephen Laikun, another guide aboard Dewi, finds another individual on a different island during the third dive of the day. David Dempsey gets photos, including a good shot of its “funny head”.

Rainfordia opercularis, Flathead Perch by Dave Dempsey
You can see how the Flathead Perch got its common name

A week later, off the boat and on our way to our next destination, Ned hears back from Dr. Gerry Allen, who informs us that this is a range extension for Rainfordia opercularis, a fish that, until now, was thought to be an Australian endemic species. This is exciting news but isn’t too surprising, given the extraordinary species richness of the Bird’s Head Seascape.

Online searches reveal a little more about this interesting fish. The common name, Flathead Perch, certainly fits the fish. Described in 1923 by A. McCulloch, Rainfordia opercularis was named for Mr. E.H. Rainford, who collected the first specimen from the coast of Queensland, Australia. That original description aligned it with Grammistes. In 1983, Rainfordia  was placed in the epinepheline-serranid tribe, Liopropomini. In 2006, Drs. Carole Baldwin and Jeffrey Leis corroborated that placement in their description of two settlement-stage larvae. In 2011, the species took the aquarium industry by storm when a breeding pair sold for about $5,000. Then considered one of the rarest fish in the trade, the species has now been successfully bred and reared in captivity.

It will be interesting to see where else this fish is found. It seems once our Indonesian dive guides are in tune to a species, they start finding it in more places. At any rate, it’s one more exciting species for our life lists – this is certainly what keeps us diving! ~ Anna DeLoach


McCulloch, Allan R., 1923. Fishes from Australia and Lord Howe Island. No. 2. Records of the Australian Museum 14(2): 113–125, plates xiv–xvi. [10 December 1923]. 

Baldwin, Carole C. and Leis, J. M. 2007. “Rainfordia opercularis, a liopropomin serranid (Teleostei: Serranidae: Epinephelinae): corroborative evidence from settlement-stage larvae.” Ichthyological Research. 2007 (54):193–197.