The Bluehead – one prolific little Wrasse

Bluehead wrasse life stages from juvenile to adult , harem spawning, group spawning and feeding

TL-BR: Initial phase male or female. Transition phase male or female. Terminal male. Harem feeding on yellowtail damsel nest. Initial males mass spawning with female. TR: Harem feeding on small sessile invertebrates hiding in seaweed.

If you ever snorkeled or dove on a reef in the Caribbean, Bahamas or Florida you likely saw groups of a small, colorful wrasse called bluehead (Thalassoma bifasciatum). This fish is probably the most common wrasse species in tropical western Atlantic. Why are blueheads so abundant? Well, for one, they breed every day.

Blueheads are protogynous hermaphrodites that mature at just 3-4 cm, which is when they begin to sow their oats. Mature adults have two dominant color phases. Females and small males (derived from juvenile sex change) share the same color phase (initial phase) and large dominant males display the distinct bright blue head for which the species is named (terminal phase). Terminal males defend territories and maintain harems of females. When a terminal male becomes absent, the most dominant female or initial male transitions to replace it.

Social groups in blueheads typically consist of one dominant terminal male and a female harem, plus a few or more initial (sneaker) males. Every day throughout the year whenever tides are favorable, terminal males pair spawn with 20-50 females in their harem. This, no doubt, keeps them really busy, and allows the initial males to sneak in a spawn or two. In fact, on larger reefs, initial males are so numerous that they form groups, often by the hundreds, to sneak spawn with willing and available females. Repeated spawnings of multiple large groups within the same area is not unusual.

Needless to say, there is no shortage of bluehead gametes on tropical coral reefs in the western Atlantic -:)