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Centrolabrus exoletus, commonly known as the Rock Cook, is a small, slender wrasse species belonging to the family Labridae. It is characterized by its vibrant coloration, particularly during breeding season, and its distinctive small mouth. This species plays an important ecological role in its rocky reef habitats, primarily as a cleaner fish, removing parasites from larger fish.
Physical Characteristics
- Body shape
- elongated
- Coloration
- Highly variable. Males are typically more brightly colored, especially during breeding, displaying shades of green, blue, and orange, often with iridescent spots and lines. Females and juveniles are generally duller, often brownish or greenish with darker mottling. A prominent dark spot is usually present at the base of the caudal fin. The dorsal fin often has a dark blotch anteriorly.
- Scale type
- cycloid
- Mouth position
- terminal
- Distinctive features
- Small, protractile mouth with small, conical teeth., Relatively slender body compared to other wrasses., Dark spot at the base of the caudal fin., Often a dark blotch on the anterior part of the dorsal fin.
- Dorsal fin
- Single, long dorsal fin with 18-20 spines and 6-8 soft rays. The spiny portion is longer than the soft-rayed portion.
- Tail fin
- Rounded to slightly emarginate caudal fin.
- Pectoral fin
- Well-developed, rounded pectoral fins.
- Distinctive fins
- Pelvic fins are thoracic, located beneath the pectoral fins.
Identification Tips
Size and Shape
Small, slender body, typically not exceeding 12-15 cm in length.
Mouth
Distinguishably small mouth, which is a key feature compared to other wrasse species.
Coloration
Look for the variable but often vibrant green, blue, and orange hues, especially in males. The dark spot at the caudal fin base is a consistent marker.
Dorsal Fin
Observe the long dorsal fin with a prominent spiny section and often a dark blotch anteriorly.
Habitat
Its presence in rocky, algal-rich shallow coastal waters is a strong indicator.
Habitat
- Water type
- saltwater
- Depth
- Typically found in shallow coastal waters, from the intertidal zone down to about 25 meters (82 feet), occasionally deeper.
- Environment
- Prefers rocky reefs, kelp beds, and areas with dense algal growth, providing ample hiding places and foraging opportunities. Often found in crevices and among boulders.
- Geographic range
- Northeastern Atlantic Ocean, ranging from Norway and the British Isles south to the Iberian Peninsula, including the Bay of Biscay. Also found around the Azores and Madeira.
Aquarium Information
- Care level: advanced
- Temperament: peaceful
- Diet: carnivore
- Minimum tank size: 75 gallons
- Temperature: 10-20°C (50-68°F)
- pH level: 8.1-8.4
- Hardness: 8-12 dKH
- Compatibility: Generally peaceful with other non-aggressive, similarly sized temperate marine fish. Avoid housing with very aggressive or much larger species that might prey on it. Can be kept in small groups if sufficient space and hiding spots are provided.
- Special requirements: Requires a well-established temperate marine aquarium with plenty of live rock for hiding and foraging. A sand bed is beneficial for burrowing at night. Excellent water quality and stable parameters are crucial. A varied diet of small meaty foods is essential. May act as a cleaner fish in the aquarium, which can be beneficial for tank mates.
Wild Information
- Conservation status: least concern
- Seasonality: Breeding occurs primarily in spring and early summer (April to July), during which males exhibit more intense coloration and territorial behavior.
- Market price: N/A
- Commercial importance: none
- Taste: Not typically consumed due to small size and bony nature.
- Texture: N/A
- Nutritional value: N/A
Key Facts
Cleaner Fishbehavior
The Rock Cook is known to act as a cleaner fish, removing parasites from the skin of larger fish species, a behavior that is beneficial for the health of the reef ecosystem.
Sex Changebehavior
Like many wrasses, Centrolabrus exoletus is a protogynous hermaphrodite, meaning individuals are born female and can later change sex to male.
Nest Buildingbehavior
Males construct nests from algae, often in crevices or under rocks, where females deposit their eggs. The male then guards the nest until the eggs hatch.
Smallest Wrasseinteresting
It is one of the smaller wrasse species found in its range, rarely exceeding 15 cm in total length.
Safety Information
Safe- Safety level: safe
- Venomous: No
- Edibility: not recommended
- Handling notes: No specific handling precautions are required beyond standard care for live fish. They are not venomous and do not possess sharp spines that pose a significant threat. Handle gently to avoid stress or injury to the fish.
Similar Species
Cuckoo Wrasse
Labrus mixtus
Much larger, more robust body, and distinct sexual dimorphism with males being bright blue and orange, and females reddish-orange with black spots. The Rock Cook is significantly smaller and more slender.
Ballan Wrasse
Labrus bergylta
Larger and deeper-bodied than the Rock Cook, with a more variable but generally mottled brown, green, or reddish coloration. The Ballan Wrasse has a larger mouth and lacks the distinct caudal spot of the Rock Cook.
Goldsinny Wrasse
Ctenolabrus rupestris
Similar in size and habitat, but the Goldsinny Wrasse typically has a more golden-brown coloration, a prominent black spot at the anterior base of the dorsal fin, and often a smaller, less distinct caudal spot than the Rock Cook. The mouth of the Goldsinny is also slightly larger.
Scientific Classification
- Kingdom
- Animalia
- Phylum
- Chordata
- Class
- Actinopterygii
- Order
- Perciformes
- Family
- Labridae
- Genus
- Centrolabrus
- Species
- exoletus
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