The majority of damselfishes engage in a range of ritualized behavior to attract mates and prepare nest sites. The male, and sometimes the female, begin to groom and tend a rocky surface several days before spawning. He removes invertebrates and algae with his mouth, sometimes allowing certain elements to remain, as is the case with Hypsypops rubicundus, a species that weeds out all but red algae from the site. Courtship activities accompany cultivation of the potential nest. Males may give auditory signals; depending on the stage of courtship, species of Eupomacentrus emit three different types of chirps and grunts. They may also display visual signals, with most damselfish males assuming distinct colors for courtship, and many executing various movements to entice the female to the nest site. Such movements have been described as “leading,” which may include quick bursts of swimming and intermittent hovering in front of the female, “signal-jumping,” or rapid up and down movements, and “dipping,” which is similar to signal-jumping and includes an abrupt descent.
One group of damselfishes, the anemonefishes (subfamily Amphiprioninae), enter into permanent monogamous pairings and as a rule display a simplified pattern of courtship. Fish in this subfamily are protandrous, a mating system in which male individuals can become female. Ambosexual (neither sperm- nor egg-producing tissues are active) juveniles live on an anemone with a sexually mature male and female pair. If the female dies, her male partner develops into a female to take her place. The largest juvenile grows rapidly and replaces him as the dominant male.
Mating System: monogamous ; polyandrous ; polygynous ; polygynandrous (promiscuous)
Damselfishes appear to spawn year-round, with many groups increasing spawning activity in early summer. In the subtropics spawning is usually limited to the warmer months of the year, but a few spawn in fall or winter. It is common for reef-dwelling damselfishes to spawn in accordance with lunar rhythms, with greatest activity occurring near the full and new moons. Spawning usually takes place in the morning. Synchronous spawning has been observed, and in some species, the higher the number of individuals in a group, the higher the degree of synchrony. Some damselfishes spawn within their permanent territory, while others (planktivorous damselfishes that live in the water column) must seek temporary territories for courtship and spawning. Location of a spawning site may involve solitary males or may be a communal activity in which schools of males, juveniles, and females travel until the males form a colony of territories on an acceptable site. Site choice varies according to species and may include rock ledges, cleaned coral branches, algal turf, empty shells, or the roofs of caves. Males typically prepare the site for spawning and then attract gravid (egg-bearing) females to the nest (see Reproduction: Mating Systems). The male guards the nest from predators and other males while the female lays her eggs in long rows, forming a solid, uniform mass of eggs in a single layer. The eggs are demersal (adhere to the substrate), and clutch size varies from 200 to 2500 eggs depending on the species.
Polygyny is common: one male may guard the eggs of several females, and damselfish harems have also been observed. Some damselfish are promiscuous, and still others are monogamous. Polyandry has been reported only in an anemonefish, although monogamy is the general rule for anemonefishes (Amphiprion and Premnas). These fish stay paired for at least a year and sometimes for their entire lifetime. They spawn year-round, usually near the full moon. Hypotheses suggest that lunar spawning occurs because of the increased light for nest tending, the greater currents for larvae dispersal, and the relative abundance of spawning invertebrates as a food source. Anemonefish most frequently live in single pairs, along with a group of sexually immature individuals, in association with an anemone (see Reproduction: Mating Systems). Groups containing several males and females may occasionally occur if the fish population density is extremely high. Spawning occurs at the base of the anemone, on a rock surface, or, if the anemone lives on sand, on a surface the fish drag near the anemone. The male clears the nest site by biting at the tentacles of the anemone until they withdraw, and then leads the female there for spawning, during which both fish quiver and bite the nest surface.
Key Reproductive Features: iteroparous ; seasonal breeding ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sequential hermaphrodite (Protandrous ); sexual ; fertilization (External ); oviparous
Male damselfishes (and in very few cases, females) guard their eggs until they hatch. They remove detritus, sand, and fungus-afflicted eggs, fan the eggs, and guard against predators. Most become more aggressive when egg-tending, but this is not the case with anemonefishes (Amphiprion and Premnas). In general fry are left to care for themselves after hatching, but in one Indo-Pacific species, Acanthochromis polyacanthus, parents guard their school of young near the spawning cave for three to six weeks.
Parental Investment: male parental care ; female parental care