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Monotaxis grandoculis, commonly known as the Humpnose bigeye bream, is a species of marine ray-finned fish belonging to the family Lethrinidae, the emperor and emperor bream family. It is characterized by its relatively deep body, large eyes, and a distinctive hump on the snout of larger adults. This species is a nocturnal predator, primarily feeding on benthic invertebrates and small fishes.
Physical Characteristics
- Body shape
- compressed
- Coloration
- Adults are typically silvery-grey to brownish-grey dorsally, fading to white or silvery ventrally. They often have a dark blotch at the base of the pectoral fin. Juveniles may exhibit dark bars or spots on their flanks, which fade with age. The fins are generally translucent or dusky.
- Scale type
- ctenoid
- Mouth position
- terminal
- Distinctive features
- Large, prominent eyes, especially in juveniles., A distinct hump on the snout, particularly pronounced in larger adults, giving it the 'humpnose' appellation., A relatively deep body, compressed laterally., A single, continuous dorsal fin., Small, conical teeth in the jaws, with no canines or molars, distinguishing it from many other Lethrinids.
- Dorsal fin
- Single dorsal fin with X spines and 10 soft rays.
- Tail fin
- Moderately forked caudal fin.
- Pectoral fin
- Long and pointed pectoral fins, typically with 13-14 rays.
- Distinctive fins
- Pelvic fins are thoracic, with 1 spine and 5 soft rays. Anal fin has III spines and 9-10 soft rays.
Identification Tips
Snout profile
Look for the characteristic hump on the snout, especially in larger individuals. This feature becomes more pronounced with age.
Eye size
The eyes are notably large relative to the head size, a key identifier for 'bigeye' breams.
Teeth
Observe the teeth if possible; Monotaxis grandoculis has small, conical teeth, lacking the canines or molars found in many other emperor species.
Pectoral fin base
A dark blotch at the base of the pectoral fin is often present and can aid in identification.
Habitat
- Water type
- saltwater
- Depth
- Typically found in depths ranging from 1 to 100 meters, though most commonly observed between 5 and 60 meters.
- Environment
- Inhabits coral reefs, rocky bottoms, sandy areas adjacent to reefs, and seagrass beds. Juveniles are often found in shallower, protected areas, while adults prefer deeper reef slopes and offshore banks.
- Geographic range
- Widespread in the Indo-Pacific region, from the Red Sea and East Africa eastward to the Hawaiian Islands and French Polynesia, northward to southern Japan, and southward to Australia.
Aquarium Information
- Care level: advanced
- Temperament: semi-aggressive
- Diet: carnivore
- Minimum tank size: 500 gallons
- Temperature: 23-28°C (73-82°F)
- pH level: 8.1-8.4
- Hardness: 8-12 dKH
- Compatibility: Best kept in a large, species-specific tank or with other robust, similarly sized fish. Avoid keeping with smaller, docile species.
- Special requirements: Requires a large tank with plenty of open swimming space and rockwork for shelter. Excellent filtration is essential due to its carnivorous diet. May be sensitive to poor water quality.
Wild Information
- Conservation status: least concern
- Seasonality: No specific seasonal patterns for availability; caught year-round in its range.
- Market price: Variable, often moderate to high depending on region and size.
- Commercial importance: medium
- Taste: Mild, white flesh
- Texture: Firm, flaky
- Cooking methods: Grilled, Baked, Fried, Steamed
- Nutritional value: Good source of protein and omega-3 fatty acids.
Key Facts
Nocturnal Hunterbehavior
The Humpnose bigeye bream is primarily active at night, using its large eyes to hunt for prey in low light conditions.
Dietary Shiftbehavior
While adults are mainly piscivorous and carcinivorous, juveniles often feed on smaller crustaceans and worms.
Hump Developmentinteresting
The distinctive hump on the snout of Monotaxis grandoculis becomes more prominent as the fish matures, particularly in larger males.
Solitary or Small Groupsbehavior
Adult Humpnose bigeye bream are typically solitary or found in small aggregations, especially during feeding.
Safety Information
Safe- Safety level: safe
- Venomous: No
- Edibility: edible
- Handling notes: No specific handling precautions beyond standard fish handling practices to avoid fin spines. The dorsal and anal fin spines can be sharp, so care should be taken to avoid punctures.
Similar Species
Yellowfin emperor
Lethrinus erythracanthus
Lethrinus erythracanthus has a more pointed snout, smaller eyes, and typically reddish or yellowish fins. Its teeth structure includes canines and molars, unlike Monotaxis grandoculis.
Spangled emperor
Lethrinus nebulosus
Lethrinus nebulosus has distinct blue spots on its scales and a more elongated body shape. It also possesses canine and molariform teeth.
Longface emperor
Lethrinus olivaceus
Lethrinus olivaceus has a much more elongated snout and body, and its coloration is generally more uniform olive-brown. Its teeth also differ significantly.
Scientific Classification
- Kingdom
- Animalia
- Phylum
- Chordata
- Class
- Actinopterygii
- Order
- Spariformes
- Family
- Lethrinidae
- Genus
- Monotaxis
- Species
- grandoculis
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