Marine Wildlife Encyclopedia
Graysby Cephalopholis cruentata
Species ID: S.CC
Description: A stocky fish with rounded fins and a large mouth with obvious lips. Graysbys are light brown to grey in colour with many small brown or red spots, with three to five spots along the base of the dorsal fin. These spots are usually black during the day, but may become white at night. Sexes appear similar. Juveniles resemble adults but are often darker in colour and may have a white line running down the snout
Maximum Size: 40 cm (16 in)
Longevity: Approximately 12 years
Status: Not currently on the IUCN endangered species list
Graysby & People: An important species for local fisheries across the Caribbean. Often caught in fish traps, by hook and line and spearfishing
Geographical Range: Found throughout the Caribbean and Gulf of Mexico; north to the Carolinas and south to Brazil
Coral Reef Zone: Found in the back reef, fore reef and drop-off zones
Favourite Habitat: Graysbys are found in reef areas that contain caves, crevices, or hollow sponges where they hide during the day. Juvenile graysbys are often found in slightly deeper water than adults
Depth Range: 2–170 m (7– 561 ft)
A Day in the Life:
Dawn: Graysby activity declines after a busy night on the reef
Day: Graysbys rarely move more than a few metres. They are often found resting in sponges or in reef cracks and crevices
Dusk: Graysby activity increases
Night: Graysbys are most active during the night, patrolling large areas of the reef in repeated circuits
Who Eats Who
This species is a coral reef carnivore that consumes almost any organism that can fit in its mouth. Graysbys eat fishes such as chromis, squirrelfishes and gobies, as well as crustaceans such as crabs and shrimp. They have also been known to eat smaller groupers, such as coneys and even other graysbys. Graysbys are consumed only by larger reef carnivores, such as barracuda and sharks.
Scuba Diver & Snorkeler Best Practices
Participate in environmental initiatives. Participate in underwater cleanup projects and public education efforts whenever possible. These initiatives make a huge difference to the coral reef, and help spread word of eco-snorkeling best practices.
Graysbys are relatively bold fish, and as such are easy to approach, particularly during the day when they rest on the reef or in barrel or vase sponges. Regulate your breathing and approach slowly along the bottom in order to get the best view.
During the day, graysbys can be found resting in the shelter of a cave or sponge, from which they ambush passing fishes and crustaceans. This means that graysbys wait for prey to swim close by before striking, usually swallowing prey whole. Graysbys are most active during the night, when they search for food. During these hunting trips, they usually focus on hunting crustaceans which have left their shelters for the night. Some individuals hunt alongside moray eels at night; since eels can squeeze into tight spots in the reef as they hunt, they often flush out prey that would otherwise be inaccessible to the graysby. Whatever prey escapes the jaws of the eel is quickly snapped up by its hunting partner. As many as four graysbys have been seen hunting alongside a single moray eel, and they have even been seen nudging eels to encourage them to get to work!
Observe, record & share:
O S.CC-101 – Hunting crustaceans: During the night, graysbys actively hunt crustaceans
O S.CC-102 – Hunting with moray eels: Graysbys sometimes hunt alongside moray eels
O S.CC-103 – Ambushing prey: Graysby wait for their prey to swim close by before striking, sometimes swallowing them whole
Attack & Defense Behaviour
Graysbys are bold fish and usually hold their ground in the presence of potential threat. If the threat gets too close for comfort however, they will usually retreat into a cave or crevice. Smaller graysbys prefer to hide within vase, barrel or tube sponges. Large male graysbys defend a territory containing several females against neighbouring males. The size of a typical territory is believed to be only about 20 m2 (approximately 200 square feet), but individuals may patrol areas 100 times this size while they hunt at night. Aggressive fights can break out between territory holders, consisting of several rounds interrupted by short breaks. Fights often begin with a staring contest, where two fish size each other up from distance. If neither fish backs down, the opponents get physical and charge suddenly at each other with open mouths, often colliding with surprising force. Individuals may also swim closely back and forth while jostling and shoving each other. Finally, the two fish may lock jaws and wrestle in yet another test of strength.
Observe, record & share:
O S.CC-201 – Escape into reef: A threatened graysby will retreat into the reef and hide
O S.CC-202 – Hiding in a sponge: Smaller graysbys hide in hollow sponges
O S.CC-203 – Stare: Two opponents stare at each other from a distance
O S.CC-204 – Charge and collide: Graysbys charge each other and collide with surprising force
O S.CC-205 – Pushing: Graysbys complete circuits where they push and shove their opponent
O S.CC-206 – Mouth-fighting: Graysbys may lock jaws and engage in a shoving match
Graysbys are relatively bold fish, and as such are easy to approach, particularly during the day when they rest on the reef or in barrel or vase sponges. Regulate your breathing and approach slowly along the bottom in order to get the best view. Graysbys reproduce sexually by broadcast spawning and change sex from female to male as they age. Females become sexually mature at about three years of age (roughly 16 cm or 6.3 inches), and change into males around the age of five (roughly 20 cm or 8 in). Males establish harems of females which they defend vigorously against other males. Harems usually count three females per male, but under heavy fishing pressure which tends to remove large males, females may outnumber males six to one. Very little is known about graysby spawning behaviour, but it is believed to involve a classic spawning rush, where the male and his females swim rapidly towards the surface before releasing eggs and sperm into the water. Spawning occurs within the males’ small defended territories from May to September in the southern Caribbean, but its timing may vary depending on location.
Observe, record & share:
O S.CC-301 – Male with harem: Larger male graysbys may be surrounded by several smaller females during mating
O S.CC-302 – Spawning rush: The male graysby and his females rush torward the surface before releasing eggs and sperm into the water
Territorial dispute: Graysby fights occur in increasingly aggressive stages, broken up by minute-long time-outs. The first stage – the face-off – literally involves a staring match where the two foes size each other up from distance. In the next stage, the two fish suddenly dart towards each other with open mouths and collide. The third stage involves much pushing and shoving as the two fish swim back and forth alongside each other. The final stage of the encounter may involve the two fish locking jaws and wrestling in a final test of strength until either the sequence begins again or until one fish is finally overpowered and retreats.
Did You Know?
• Some circumstantial evidence suggests that graysbys have a pretty good memory. Individuals that are caught on a hook and line for sport and then returned to the sea are very hard to catch a second time, suggesting that they learn their lesson first time around.
• Graysby are protogynous hermaphrodites – organisms that switch sex from female to male as they mature. This is the most common kind of sex change in Caribbean reef fish. Protandrous hermaphrodites, which change sex from male to female, are much less common. The snook (Centropomus undecimalis) is one of only a handful of Caribbean reef fish species known to be a protoandrous hermaphrodite.
What to do?
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