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Yellowfin Surgeonfish

Acanthurus xanthopterus

An underwater photograph of a vibrant, light blue Yellowfin Surgeonfish angled downward to pick algae off a rocky reef, displaying its bright yellow face markings and orange-striped dorsal fin.
A pristine side-profile underwater photograph of a large Yellowfin Surgeonfish swimming solo through clear, open blue water, showing its purplish-grey body, yellow-accented pectoral fins, and dark caudal spine.
A close-up macro underwater photograph focusing on the head of a Yellowfin Surgeonfish grazing on a rocky reef, capturing its gold-ringed eye, yellow facial band, and fine blue scribbled body lines.
A large school of light blue and grey Yellowfin Surgeonfish swimming closely together over a rocky reef floor in the Pacific Ocean.

Adult

Family: Surgeonfishes (Acanthuridae)
Size: Up to 70 cm (28 in) | Common: 40 cm
Depth: 5 – 90m (15 – 295ft)

Distribution: Widespread Indo-Pacific and Eastern Pacific (Baja California to Ecuador, including the Galapagos and Malpelo).

Identification: The giant of the surgeonfish family.

  • Coloration: The body is a beautiful purplish-blue to pale grey. The key identifying marks are the bright yellow pectoral fins and a distinct yellow mask or patch extending around the eyes.
  • Fins: If you look closely at the dorsal (top) and anal (bottom) fins, they feature striking, alternating horizontal stripes of neon blue and orange-yellow.
  • The Scalpel: Like all surgeonfishes, they have a sharp, retractable spine located in a small groove on either side of the tail base (caudal peduncle) for defense.

Behavior: A heavy-duty reef grazer.

  • Diet: They are herbivores and detritivores. You will constantly see them picking at the rocks to eat benthic algae and detritus. They often ingest sand to act as grit in their stomachs to help digest the tough plant matter.
  • Schooling Strategy: They frequently travel in large schools. This "mob" tactic allows them to overwhelm aggressive, territorial damselfish and freely graze on their carefully guarded algae farms.

You just learned about this fish...

NOW COME SEE IT!

Fun Dive Cover page in Bahia Solano
Fun Dive Cover page in Bahia Solano
Fun Dive Cover page in Bahia Solano

Behind the Lens

Jalvan

Underwater Photographer & Instructor

Documenting unique marine biodiversity from the Red Sea across the Pacific Ocean. Dedicated to creating a visual catalog of Bahia Solano's marine life for conservation and research.

Photography: Sony A7C II | Olympus EPL10
Video: Osmo Action 5 Pro | GoPro

Follow my work:

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REFERENCES & DATA SOURCES

  • Scientific ID: Verified via FishBase (Froese & Pauly).
  • Field Guide: Reef Fish Identification: Baja to Panama (Humann & DeLoach).
  • Regional Data: Ankla Azul Marine Observation Log (Bahia Solano).

More Than Kicking Your Fins

At Ankla Azul, diving is more than kicking your fins. It's patient teaching, sharp safety, and real care for the place we call home. As an SSI Instructor Training Center and an SSI Blue Oceans Center (2025 award), we blend skill-building with ocean awareness—Fish ID, coral nursery work, community education, and rescue support—so every dive grows confidence and respect for Bahía Solano's wild Pacific.