The fish of Saint Brandon
The reef and lagoon system at Saint Brandon supports somewhere in the order of 175 recorded fish species across more than thirty families, with the true number almost certainly higher. Saint Brandon has never been comprehensively surveyed, and new species are still being described from its waters. The most recent, a small sand-dwelling wrasse, named from the atoll as recently as 2013.
What follows is not a complete inventory. The full species list belongs in a scientific report, and the 1998 World Bank Management Plan and the surveys since are the proper places to find it. What I have written about here are the fish I met with my own eyes, the fish I caught, the fish I photographed, and the fish I would have moved through during nineteen days of snorkelling, droning, and watching from a pirogue. These are the ones whose presence shaped the daily experience of being there. Some species are named because I saw them clearly. Others are named because they are so abundant in the habitats I visited that I cannot honestly leave them off.
Babonne St Cecilia — Epinephelus species (Comet grouper)
Locally called the Babonne. The first fish I caught at Saint Brandon, on a trolled lure on Day 1, and according to the captain, the best food fish you can pull from these waters. A slow-growing grouper, reaching sexual maturity at four to six years and changing sex from female to male at five to six years — a phenomenon known as protogynous hermaphroditism, common across the family Serranidae. Large individuals can carry ciguatera toxin, a natural marine biotoxin produced by Gambierdiscus dinoflagellates that bioaccumulates up the food chain. The Albion Fisheries Research Centre has been monitoring ciguatera at Saint Brandon, with inconclusive results.
Dame Berri — Lethrinus mahsena (Sky emperor)
The most commercially important fish at Saint Brandon, accounting for 82 to 88 percent of total catch by weight according to the 1996 MRAG report. Widespread across the western Indian Ocean, from the Red Sea to Sri Lanka. They forage on sandy patches near coral reefs, eating molluscs, crustaceans, sea urchins, polychaete worms, and small fish. They reach 65 centimetres in length, though they are commonly caught at 35 to 45. Like the Babonne, they are protogynous hermaphrodites, with females becoming males at around five to six years. I caught four on Day 6 between Chaloupe and Baleine.
Vieille Saint Sillac — Cephalopholis sonnerati (Tomato grouper)
A reddish grouper resembling the more famous coral hind but darker, larger, and less marked. I caught one off Île Raphael. Locally called the Vieille Grise. Reaches 50 centimetres.
Capitaine — Lethrinus nebulosus (Spangled emperor)
The second of the two main commercial emperor species. Larger than the Dame Berri, growing to 86 centimetres. Inhabits coral reefs, seagrass beds, mangroves, and sand-and-rock margins from very shallow water down to 75 metres. I caught Capitaine off the Raphael reef.
Barracuda (Baroi) — Sphyraena species
I caught four off the Raphael reef. Solitary, slow-cruising, mouth full of needle-like teeth. The fishermen are wary of larger individuals because of ciguatera. Smaller specimens are excellent eating.
Needlefish — Tylosurus species
A long, slender, silver fish that hovers near the surface in clear shallow water. I hooked one trawling and had to cut the hook out — they are bony, hard-mouthed, and difficult to release.
Parrotfish — Scarus ghobban (Cateaux) and other Scaridae
Parrotfish are the great sand-makers of the reef. They graze algal turf with fused, beak-like teeth, scraping reef limestone in the process, and excrete the limestone as the fine white sand that forms Saint Brandon’s beaches. A single large parrotfish produces hundreds of kilograms of sand a year. The archipelago is full of them. Scarus ghobban alone was documented in 79 individuals during the 1997 transect surveys, and the wider family includes Scarus atropectoralis, Scarus ovifrons, Scarus dimidiatus, Scarus strongylocephalus, Scarus tricolor, Scarus sordidus, Cetoscarus bicolor, and Hipposcarus longiceps. Beach sand at Saint Brandon is, in a quite literal sense, parrotfish-made.
Bluespine unicornfish — Naso unicornis
A surgeonfish with a single forward-projecting horn growing from its forehead. Drifts in small schools across the reef-flat in shallow water. One of fourteen surgeonfish species documented at Saint Brandon. Surgeonfish are named for the sharp scalpel-like spines on either side of their tail-base.
Orangespine unicornfish — Naso lituratus
Recognisable by the bright orange band along the dorsal fin and the two cream-yellow scalpels at the tail. Common across the reef-flat at depths of one to thirty metres.
Powder-blue surgeonfish — Acanthurus leucosternon
One of the most photogenic fish of the western Indian Ocean. A powder-blue body, a yellow dorsal fin, a black face mask, a white throat. Schools graze the algal turf on the reef-flat. Frequently photographed at Saint Brandon.
Convict surgeonfish — Acanthurus triostegus
The most schooling of the surgeonfish — silver with five black vertical bars, moving in clouds across the reef-flat at the eastern edges of the lagoon. So common at Saint Brandon that during transect counts they appeared in groups of twenty or more.
Sailfin tang — Zebrasoma desjardinii
A tall, oval-bodied surgeonfish with vertical orange-and-grey banding and a tall sail-shaped dorsal fin. One of the most striking reef fish in the archipelago.
Cordonnier — Siganus sutor (White-spotted rabbitfish)
A schooling rabbitfish of the shallows — silver with delicate white spots, found grazing on filamentous algae and seagrass. Toxic spines line the dorsal fin; rabbitfish handled carelessly cause painful stab wounds. Reaches 45 centimetres. An important food fish locally.
Cordonnier — Siganus sutor (White-spotted rabbitfish)
A schooling rabbitfish of the shallows — silver with delicate white spots, found grazing on filamentous algae and seagrass. Toxic spines line the dorsal fin; rabbitfish handled carelessly cause painful stab wounds. Reaches 45 centimetres. An important food fish locally.
Yellowstripe goatfish — Mulloidichthys flavolineatus
Pale, silvery, with a single yellow horizontal stripe along the side and two long sensory barbels under the chin used to probe the sand for invertebrates. Schools of dozens are common over sand-and-rubble lagoon floors. They are restless. They do not pose.
Cheeklined wrasse — Oxycheilinus digrammus
One of the larger wrasses on the reef, beautifully patterned in green and orange. The 1997 species list documents over forty wrasse species from Saint Brandon — the family Labridae is one of the most diverse on the reef.
Bird wrasse — Gomphosus caeruleus
A male bird wrasse is unmistakable: slim, electric green-and-blue body with an absurdly long, beak-like snout. Females are pale. They forage by inserting that beak into reef crevices for small invertebrates. Common on the reef-terrace.
Moon wrasse — Thalassoma lunare
Brilliant green with magenta head markings and a yellow crescent on the tail. Constantly in motion. One of the most-photographed wrasses on Indo-Pacific reefs.
Picasso triggerfish — Rhinecanthus aculeatus
Named for the abstract pattern of yellow, black, blue, and white slashes across its body, bold and unrepeatable. Common in shallow lagoon water. Aggressive in defence of its nest. Mauritian Creole sometimes calls it poisson picasso.
Titan triggerfish — Balistoides viridescens
The largest triggerfish on Indo-Pacific reefs, growing to 75 centimetres. Olive-green with a yellow throat. Famously aggressive around its sandy spawning bowl during the breeding season — divers and snorkellers are sometimes charged. Documented at Saint Brandon in the 1997 surveys.
Oriental sweetlips — Plectorhinchus vittatus
A large, slow, often-photographed reef fish with a yellow body with bold black-and-white horizontal stripes when adult. Dark-and-white spotted when juvenile. Hangs motionless under coral overhangs during the day, feeds at night.
Lined butterflyfish — Chaetodon lineolatus
One of the larger and more striking butterflyfish, pure white with delicate vertical black lines and a black-edged dorsal fin. The 1997 transect surveys documented thirteen species of butterflyfish at Saint Brandon, including Chaetodon auriga (threadfin), C. kleini (sunburst), C. lunula (raccoon), C. trifascialis, C. vagabundus (vagabond), Forcipiger flavissimus (longnose), and Heniochus acuminatus (longfin bannerfish).
Pennant coralfish — Heniochus acuminatus
The “longfin bannerfish.” Black-and-white vertical bands, with a dramatic streamer trailing from the dorsal fin. Often confused with the moorish idol but unrelated. Hangs in pairs over the reef.
Moorish idol — Zanclus cornutus
The iconic single-species genus — black, white, and yellow, with a long trailing dorsal pennant. Sometimes mistaken for the bannerfish above, but anatomically very different. Documented at Saint Brandon.
Bigeye trevally — Caranx sexfasciatus
Large, silver, fast-moving predators that patrol the reef edges in tight schools, often hundreds strong. Sometimes called carangue locally. The schools dazzle.
Bluefin trevally — Caranx melampygus
Smaller than the bigeye, electric metallic blue with scattered black-and-blue spots. The most beautiful of the trevallies.
Bonito — Sarda species
A pelagic predator of the open lagoon and offshore — torpedo-shaped, blue-striped, fast. I caught at least one off the reef south of Avocaré.
Yellowfin tuna — Thunnus albacares
The fishermen caught tuna in numbers off South Island during our visit, and shared a fillet with us. Yellowfin tuna grow to 200 kilograms and are the principal pelagic species of the wider Mauritian and Indian Ocean fishery.
Fusiliers — Caesio species (silver longies with blue stripes)
My field notes describes them as silver longies with horizontal blue stripes. These I am sure are Caesio caerulaurea or Caesio teres — schooling reef fish that hover in clouds above the reef edge, planktivorous, glittering in any light. One of the defining fish of the Indo-Pacific reef.
Trumpetfish — Aulostomus chinensis
A long, slim, elegant predator that drifts head-down through the water column, mimicking a stick of seagrass. Found on every reef habitat in the archipelago.
Cornetfish — Fistularia commersonii
Even longer and slimmer than the trumpetfish, with a whip-like extension to the tail. Difficult to see until you see it.
Saint Brandon sandy — Novaculops alvheimi
A new species of labrid (wrasse) described in May 2013 from specimens collected at Saint Brandon. A small sand-burrowing wrasse, given the species name alvheimi after the Norwegian marine scientist Oddgeir Alvheim. The discovery confirmed what scientists had long suspected — that the isolated atoll harbours species not yet known elsewhere. Further discoveries are considered likely.