Gobies exhibit a wide variety of mating systems but most seem to be promiscuous, either organized into a hierarchical social system, such as Coryphopterus personatus, or small territories maintained by individuals, such as Coryphopterus glaucofrenum and Lythrypnus dalli. A typical mating sequence begins with nest preparation by the male, which involves clearing and cleaning the area where eggs will be deposited. In response, the ventral area of the female swells and the male proceeds to swim back and forth between the female and nest site and in some cases the male will nudge the female with its snout. The male may also make exaggerated swimming motions in place by anchoring himself with the sucking disc.
There is evidence of monogamy in some gobies (Ioglossus spp., Gobiodon spp., Valencienna spp., Gobiosoma spp., and Paragobiodon spp., among others) but some of these pairings are the result of fierce territorialism toward other members of the same sex, which confines mating to that individual. However, there is evidence that some gobies recognize mates as individuals (Elacatinus lobeli), possibly through olfactory cues. In fact, extensive research on frillfin gobies has revealed a complex suite of visual, chemical, auditory, and olfactory cues used in courting behavior. For instance, an ovarian pheromone produce by female frillfin gobies has been shown to elicit courtship in males, even if the female is not present. Male frillfin gobies have also been observed making a knocking sound to initiate courtship. An example of visual cues is well illustrated by the alamo’o, which is found in the Hawaiian Islands. In this species, the male attracts females by perching on a rock and waving its rear end, which is bright yellow, back and forth in the current. Although there are very few studies as extensive as these for all gobies it is likely that a mixture of visual, tactile, chemical, auditory, or olfactory cues will be found in other gobies as well.
Mating System: monogamous ; polygynous ; polygynandrous (promiscuous)
Most gobies have extended spawning seasons with peak spawning depending on the species, but in colder regions breeding may only occur once or twice a year. Females may deposit from five to several hundred eggs, which the male then fertilizes. Some gobies exhibit protogynous hermaphroditism, such as members of the genus Paragobiodon. Individuals may be found in pairs, trios, or male-dominated harems depending on the species. In Paragobiodon harems the largest individual is always the dominant male and the second largest the functional female, and sex change is socially controlled. Most likely, similar hermaphroditism will be found in other territorial and pair-forming gobies. In estuarine species the lunar cycle is thought to play a role in spawning behavior as well as larval recruitment.
Key Reproductive Features: iteroparous ; seasonal breeding ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sequential hermaphrodite (Protogynous ); sexual ; fertilization (External ); oviparous
In most cases, male gobies guard the eggs after they are fertilized. The young probably stay close to adults for a period of time after hatching. Even if females are permanently paired, they rarely take part in parental care. In some freshwater island species parental care is not practiced at all. For instance, in the subfamily Sicydiinae the larvae are carried downstream to the ocean where they feed and grow before ascending the freshwater streams.
Parental Investment: male parental care