|Male (terminal phase)|
The stoplight parrotfish (Sparisoma viride) is a species of parrotfish inhabiting coral reefs in Florida, Caribbean Sea, Gulf of Mexico, Bermuda and as far south as Brazil. Like most of its relatives, it is able to change sex. Its typical length is between 1 and 1.5 ft (30 and 46 cm), but it can reach 2 ft (61 cm) at times. It is normally found during the day at depths between 15 and 80 ft (4.6 and 24.4 m).
Habitat: Stoplight parrotfish live on reefs, depending on the shelter, protection, and nutrition that densely packed coral provides. In particular, the 1-2 cm wide tubes of branched finger coral (Porites porites) provide shelter and protection as well as a food source (algae) to juveniles. Young may also be found in seagrass beds. Adults often reside in shallower waters, usually over reef bases. These fish are most commonly found in clear waters at depths of 3-50 m. These habitats are characterized by coral species such as staghorn coral (Acropora cervicornis), elkhorn coral (Acropora palmata), and boulder star coral (Montastrea annularis). Population density tends to be greater in offshore reefs than inshore reefs, possibly due to increased fishing pressures inshore.
Sex Change and Reproduction: The colors of the stoplight parrotfish in the initial phase, when it could be either a male or a female, are dramatically different from those in the terminal phase, when it is definitely a male. In the initial phase, the stoplight parrotfish can rapidly change the color of the scales on its underside from red to white. Juveniles of both sexes are not dimorphic; following a post-settlement period, they enter their initial phase. The majority of juveniles are female. Once reaching sexual maturity, some individuals may enter terminal phase; these fish are always male (sometimes known as secondary males or super males) and exhibit the blue-green coloration described above. Individuals that were born as males (known as primary males) will remain males into their terminal stage. Sex changes often occur when population numbers are low, and only involve females becoming males.
Stoplight parrotfish reach sexual maturity by the age of four. Secondary males may reproduce as females before changing sex. Primary males will often mate in groups with one female, while secondary males will reserve females as their own to mate with. Secondary males maintain and defend a harem of multiple (usually 3-7) females, mating with them daily. Breeding occurs year round, more often during summer months. Fish travel from shallower reef waters to deeper areas to release eggs, where they are subject to less mechanical stress from water currents. After hatching, juvenile fish return to shallower reef areas.
Eggs are released and fertilized externally during spawning, in deep water reef areas. Eggs are approximately 1 mm in diameter and are negatively buoyant. Larvae, typically 1.4 mm long, hatch 25 hours after fertilization. Upon hatching, larvae have no eyes, coloring, or mouths. Within three days of hatching, a mouth appears; little else is known regarding development at this stage. 
Behavior: Stoplight parrotfish inhabit all portions of a reef, but they are most abundant at shallow reef bases and slopes. Most parrotfish live alone or in small groups. The majority of observed aggressive behaviors have been with other spotlight parrotfish, rather than with other species. These fish use their pectoral fins for vertical locomotion and their caudal fins for quick bursts of speed. Foraging occurs throughout the day, year-round, for an average of 12 hours a day; the most activity occurs at the height of the afternoon during the summer months (up to 14 hours a day), while activity during winter months decreases (to about 10 hours a day). Stoplight parrotfish sleep on the bottom at night. They also appear to not be phased by human divers and snorkelers until approached too closely or suddenly, making for great viewing on the many reefs and sea grass beds they inhabit.
The common name, stoplight, comes from the marked yellow spot near the pectoral fin, which is clearly visible only in specimens in the terminal phase.
- Humann, DeLoach (2002). Reef Fish Identification - Florida Caribbean Bahamas. New World Publications, Inc. ISBN 1-878348-30-2.
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