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Caesio teres, commonly known as the Blue and Yellow Fusilier, is a vibrant and schooling marine fish belonging to the family Caesionidae. It is characterized by its striking bicolored pattern, with a bright blue anterior body transitioning to a distinct yellow posterior, including the caudal fin. These fish are pelagic-neritic, meaning they inhabit open water near the coast, and are often found in large, active schools over coral reefs and rocky substrates. They play a significant ecological role as planktivores and are an important component of reef ecosystems.
Physical Characteristics
- Body shape
- torpedo
- Coloration
- The anterior two-thirds of the body is brilliant blue, transitioning abruptly to a bright yellow on the posterior third, including the caudal peduncle and caudal fin. The dorsal fin is typically blue with a yellow margin, and the pectoral fins are often yellowish. Juveniles may exhibit a more uniform blue coloration with less pronounced yellow.
- Scale type
- ctenoid
- Mouth position
- terminal
- Distinctive features
- Abrupt bicolored pattern (blue anterior, yellow posterior), Deeply forked caudal fin, Small, protractile mouth, Elongated, fusiform body
- Dorsal fin
- X-XI spines, 14-16 soft rays; continuous with a slight notch.
- Tail fin
- Deeply forked, bright yellow.
- Pectoral fin
- 19-22 rays; relatively long and pointed.
- Distinctive fins
- Pelvic fins are small and located abdominally. Anal fin has III spines and 11-13 soft rays.
Identification Tips
Coloration
The most distinguishing feature is the sharp demarcation between the blue anterior body and the yellow posterior body and caudal fin. This pattern is consistent in adults.
Body Shape
Its elongated, torpedo-shaped body is characteristic of fusiliers, adapted for fast swimming in open water.
Schooling Behavior
Always observed in large, active schools, often numbering in the hundreds or thousands, making them easily identifiable in their natural habitat.
Mouth
The small, highly protractile mouth is indicative of its planktivorous diet, used for sifting small organisms from the water column.
Habitat
- Water type
- saltwater
- Depth
- Typically found in depths ranging from 1 to 60 meters (3 to 200 feet), occasionally deeper.
- Environment
- Coral reefs, rocky reefs, and adjacent sandy or rubble areas. They are pelagic-neritic, forming large schools in mid-water columns, often near drop-offs or outer reef slopes. They seek shelter within the reef structure at night.
- Geographic range
- Indo-Pacific region, from the Red Sea and East Africa eastward to Samoa, north to southern Japan, and south to Australia. Absent from the Persian Gulf and Oman.
Aquarium Information
- Care level: advanced
- Temperament: peaceful
- Diet: carnivore
- Minimum tank size: 250 gallons
- Temperature: 72-78°F (22-26°C)
- pH level: 8.1-8.4
- Hardness: 8-12 dKH
- Compatibility: Generally compatible with other peaceful, similarly sized fish. Avoid aggressive tank mates or those that might outcompete them for food. Best kept in schools of 5 or more.
- Special requirements: Requires a large tank with ample swimming space due to its active schooling nature. Excellent water quality and strong filtration are essential. A varied diet of high-quality planktonic foods is crucial for their health and coloration. They are prone to stress if not kept in a school.
Wild Information
- Conservation status: least concern
- Seasonality: No specific seasonal patterns for availability; present year-round in their natural range.
- Market price: Variable, often sold as food fish in local markets; occasionally in the aquarium trade.
- Commercial importance: medium
- Taste: Mild, slightly sweet
- Texture: Firm, white flesh
- Cooking methods: Grilled, Fried, Steamed, Baked
- Nutritional value: Good source of lean protein and omega-3 fatty acids.
Key Facts
Color Changebehavior
The vibrant blue and yellow coloration of Caesio teres can intensify or fade depending on the fish's mood, stress levels, or during spawning.
Schooling Mastersbehavior
Blue and Yellow Fusiliers form some of the largest and most dynamic schools on coral reefs, often moving in synchronized patterns to feed on zooplankton.
Ecological Roleinteresting
As primary planktivores, they play a crucial role in transferring energy from the planktonic food web to larger reef predators, making them a vital link in the reef ecosystem.
Nocturnal Retreatbehavior
While active planktivores during the day, at night, schools of Caesio teres often retreat into crevices or under ledges within the reef for protection from nocturnal predators.
Safety Information
Safe- Safety level: safe
- Venomous: No
- Edibility: edible
- Handling notes: No specific handling precautions are required beyond standard fish handling practices. They are not venomous and do not possess sharp spines that pose a significant threat.
Similar Species
Yellowback Fusilier
Caesio xanthonota
C. xanthonota has a yellow dorsal surface extending from the snout to the caudal fin, with the lower body being blue or white. The yellow coloration is more extensive dorsally, whereas C. teres has a distinct blue anterior and yellow posterior.
Red Sea Fusilier
Caesio suevica
C. suevica has a more uniform blue-green body with a yellow caudal fin, but lacks the sharp blue-to-yellow transition on the body itself. Its body is generally more slender.
Robust Fusilier
Caesio cuning
C. cuning typically has a more robust body, a yellow caudal fin, and often a yellowish tinge on the dorsal part of the body, but the blue-yellow transition is not as abrupt or as clearly defined as in C. teres.
Scientific Classification
- Kingdom
- Animalia
- Phylum
- Chordata
- Class
- Actinopterygii
- Order
- Perciformes
- Family
- Caesionidae
- Genus
- Caesio
- Species
- teres
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