By Susan L. Williams, Ph.D.
East of Flores cardinalfishes were documented during a dive trip aboard the M/V Seven Seas from 10–22 August 2017. I identified 27 species of cardinalfishes (Family Apogonidae), with a few still unclassified. Unlike the dozen species typically seen on Caribbean reefs, the diversity here in the Coral Triangle is remarkable. Often motionless, these small reddish fish subtly shift or hide behind coral when approached. My colleagues Sonia and Christina spent entire dives observing multiple species interact among Acropora corals using magnifying glasses. Below is a partial list of the species observed.
| Apogon sealei | bargill cardinal |
| Apogon crassiceps | ? ruby cardinalfish |
| Apogon compressus | splitbanded cardinalfish |
| Cheilodipterus artus | wolf cardinalfish |
| Cheilodipterus intermedius | intermediate cardinalfish |
| Cheilodipterus isostigmata | toothy cardinalfish |
| Cheilodipterus macrodon | tiger cardinafish |
| Nectamia luxuria | multi-barred cardinalfish |
| Nectamia viria | ? bracelet cardinalfish |
| Ostorhinchus aureus | ringtailed cardinalfish |
| Ostorhinchus bryx | bryx cardinalfish |
| Ostorhinchys cyanosoma | yellowstriped cardinalfish |
| Ostorhinchuys dispar | whitespot cardinalfish |
| Ostorhinchus fleurieu | flower cardinalfish |
| Ostorhinchus hartzfeldii | silverlined cardinalfish |
| Ostorhinchus hoevenii | frostfin cardinalfish |
| Ostorhinchus jenkinsi | spotnape cardinalfish |
| Ostorhinchus molucensis | Moluccan cardinalfish |
| Ostorhinchus multilineatus | manylined cardinalfish |
| Ostorhinchus neotes | larval cardinalfish |
| Ostorhinchus nigrofasciatus | blackstripe cardinalfish |
| Ostorhinchuys parvulus | redspot cardinalfish |
| Ostorhinchus rubrimacula | orangespot cardinalfish |
| Pristiapogomn kallopterus | iridescent cardinalfish |
| Rhabdamis gracilis | slender cardinalfish |
| Sphaeramia nematoptera | pajama cardinalfish |
| Taeniamia fucata | orangelined cardinalfish |
| Taeniamia zosterophora | girdled cardinalfish |
| Zoramia leptacantha | threadfin cardinalfish |
AMAZING tally for one single trip, only East of Flores!
East of Flores Cardinalfishes – Species List from Seven Seas Cruise
By Susan L. Williams, Ph.D.
During a dive expedition from August 10–22, 2017, aboard the M/V Seven Seas, I documented 27 species of East of Flores cardinalfishes (Family Apogonidae). The East of Flores region, part of the Coral Triangle, offers an extraordinary opportunity to study these often-overlooked reef inhabitants. Unlike the Caribbean, where you might encounter a dozen species, the cardinalfishes in this part of Indonesia showcase incredible diversity and subtle, fascinating behaviors.
Why East of Flores Cardinalfishes Matter
Cardinalfishes are small, often red-hued reef fishes known for their large eyes, nocturnal habits, and tendency to hover near coral heads. They are usually shy, remaining still or slowly moving between coral branches. Many divers miss them entirely — but with patience and attention, a stunning variety of East of Flores cardinalfishes becomes visible.
During this trip, my colleagues Sonia and Christina used underwater magnifiers and torches to observe how different species interacted around shallow branching Acropora corals. Some hovered in groups, while others stayed solitary, shifting position with the slightest movement around them.
What Makes East of Flores Special?
The East of Flores region is part of Indonesia’s lesser-explored dive zones. Strong currents, vibrant coral structures, and nutrient-rich waters create an ideal environment for reef biodiversity. Because it’s less impacted by tourism and fishing than other locations, it provides a pristine setting to observe cryptic species like cardinalfishes in their natural habitat.
This trip proved just how significant East of Flores is for marine documentation — especially for families like Apogonidae, where new species are still being described.
Observing East of Flores Cardinalfishes
To properly identify species, we spent dives scanning coral structures slowly, often spending 10–15 minutes in one small area. The East of Flores cardinalfishes showed subtle but distinct characteristics — split-banded markings, fin spot patterns, and jaw shapes visible only up close. Some species revealed themselves only at night, emerging under red light to feed in the water column.
Partial Species List
Here are some of the species I recorded:
| Scientific Name | Common Name |
|---|---|
| Apogon sealeyi | bargill cardinal |
| Apogon crassiceps | ? ruby cardinalfish |
| Apogon compressus | splitbanded cardinalfish |
| Cheilodipterus artus | wolf cardinalfish |
| Cheilodipterus intermedius | intermediate cardinalfish |
| Cheilodipterus isostigmata | toothy cardinalfish |
During a dive expedition from August 10–22, 2017, aboard the M/V Seven Seas, I documented 27 species of East of Flores cardinalfishes (Family Apogonidae).
For more on our previous species list from Raja Ampat, see our Raja Ampat cruise report
For more insights on the biodiversity of East of Flores cardinalfishes, check out this detailed species overview from FishBase.
Susan L. Williams, Ph.D.
Professor, Evolution & Ecology
University of California at Davis
Bodega Marine Laboratory
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