The gobies, family Gobiidae, are among the most speciose fish families, with more than 2000 species in 200 genera worldwide and a long taxonomic history (Van Tassell 1998). They are generally small- to mid-size fish that dwell mostly in shallow warm marine waters, although some inhabit brackish waters and estuaries and a few hundred species live in fresh water environments. Gobies have fused pelvic fins that they can use as a suction device to hold rocks and other objects in their environment. This sucker is functionally analogous (of separate evolutionary origin so not homologous) to suction-forming organs in in other fish, for example remoras and lump suckers. Most goby species eat small invertebrates and plankton, some eat other fish. Gobies are important prey for many larger fish. Few goby species are fished commercially as a human food source; some examples are: round goby, monkey goby, toad goby, and grass goby. Some species of salt-water gobies are popular in the aquarium trade.

(Van Tassell 1998; Wikipedia 2012)

Currently 212 genera and 1,875 species are recognized, making gobies the largest marine fish family and the most species-rich family of vertebrates. Gobies and blennies combined make up a dominant portion of the small fish inhabiting benthic tropical reefs around the world. Additionally, gobies are usually the most abundant freshwater fish on oceanic islands. This group is so poorly known due to their cryptic and secretive nature that 10 to 20 new species are described each year, making them the marine family with the greatest number of newly described species. The range of morphology, behavior, habitat and reproductive strategies within this family is undeniably impressive.

Gobies are found worldwide in fresh, brackish and saltwater. They are concentrated in the tropics and subtropics, mainly of the Indo-Pacific, but some marine species can be found in the subarctic streams of southern Siberia. Gobies have been transported beyond their natural range via the intake pipes or ballast water of large ships. One species, Neogobius melanostomus, a native of the Black and Caspian Seas, was introduced into one of the Great Lakes in North America around 1990 and has since spread into all five. Between 1960 and 1963 two marine gobies native to Japan, Korea, and China had established populations along the California coastline and by 1980 they were established in several parts of Australia.

Biogeographic Regions: nearctic (Introduced , Native ); palearctic (Native ); oriental (Native ); ethiopian (Native ); neotropical (Native ); australian (Introduced , Native ); oceanic islands (Native ); indian ocean (Native ); atlantic ocean (Native ); pacific ocean (Native ); mediterranean sea (Native )

Other Geographic Terms: island endemic

Most gobies are extremely small; in fact, the smallest known vertebrate is a goby from Japan, no longer than 10 mm at sexual maturity. The largest, Gobioides broussenetii from the Caribbean, may reach 50 cm TL. Gobies are usually recognized by their small size, the existence of two dorsal fins (the first with eight flexible spines and the second soft), and a blunt round head with large eyes. Some gobies have prominent head barbells as well. Most gobies, and all freshwater species, have pelvic fins united to form an adhesive or sucking disc. However, some reef species have separated pelvic fins although the degree of separation is highly variable. The   scales may be cycloid, ctenoid, or absent and the lateral line is absent. (Click here to see a   fish diagram).

Coloration in gobies ranges from vivid, especially in reef species like the brilliantly marked neon gobies, to drab, as in many estuarine species (Bathygobius). Still others may be pallid or translucent (Coryphopterus). Although most reef gobies are sexually monomorphic in terms of permanent coloration and gross morphology, temporary sexual dichromatism (color differences between the sexes) has been observed during courtship and spawning on reefs and other habitats. When permanent   sexual dimorphism does occur, it may vary even within a genus. For instance, males in some genera, Lythrypnus and Coryphopterus, have longer dorsal and/or anal spines than females, but other species within these genera lack any morphological differences. Permanent sexual dichromatism also exists in some species but investigators have been unable to explain why there is such variation within genera.

Many gobies have evolved unique physical adaptations for life in tidal or estuarine environments. For instance, mudskippers, which span the genera Boleophthalmus, Periophthalmus, Periophthalmadon, and Scartelaos, are essentially amphibious. The skin contains numerous blood vessels enabling them to take up atmospheric oxygen and a muscular tail helps them to skip over the mud. Additionally, their eyes are perched high on the head to allow them to forage effectively and avoid predation. Another goby, Gillichthys mirabilis, has evolved a highly vascularized buccopharynx, which allows it to gulp air from the surface when the waters it inhabits become depleted of oxygen.

Other Physical Features: ectothermic ; bilateral symmetry

Sexual Dimorphism: sexes alike; male larger; sexes colored or patterned differently; male more colorful; sexes shaped differently; ornamentation

Gobies are extremely successful in their ability to exploit microhabitats inaccessible to most other fishes; they are found from subarctic streams in Siberia to mountain streams at altitudes of 2,000 m on islands to ocean depths of 800 m. On coral reefs, they can be found in the numerous cracks and crevices or out in the open among corals (Gobiosoma). Others build burrows (Signigobius) or use the burrows of invertebrates, ranging from polychaete worms to clams. Members of the genera Boleophthalmus, Periophthalmus, Periophthalmadon, Scartelaos, and Bathygobius have uniquely adapted to tidepools, mudflats and mangrove swamps, where some even climb out of the water for extended periods to forage (discussed further in Food Habits). Still others build numerous holes along sandy beaches (Coryphopterus) or compose a large part of the fishes in estuaries, inland seas and continental shelf environments as deep as 800 m.

The approximately 200 species found in freshwater form a separate category of gobies. Gobies are extremely successful in freshwater habitats where few other fish are found, such as oceanic islands. Half of the freshwater species are part of the subfamily Sicydiinae. Members of this group exhibit a high degree of island endemism and some even reach the headwaters of high-elevation rivers (2,000 m) in mountains. Some species have a short marine life-stage while others have evolved to live completely within freshwater environments.

Habitat Regions: temperate ; tropical ; saltwater or marine ; freshwater

Aquatic Biomes: pelagic ; benthic ; reef ; lakes and ponds; rivers and streams; temporary pools; coastal ; abyssal ; brackish water

Other Habitat Features: estuarine ; intertidal or littoral

Gobies are classified as zooplanktivores, omnivores, and carnivores, as they feed on a wide variety of small organisms like crabs, shrimps, smaller crustaceans (such as copepods, amphipods, and ostracods), mollusks, annelids, polychaetes, formaninferans, sponges, small fishes, and eggs of various invertebrates and fishes. Many gobies are quite selective in their feeding habits, favoring an individual prey item, such as a minute algae or small invertebrate. Others have evolved unusual adaptations to allowing feeding in habitats formerly off-limits to fish. For instance, mudskippers (Boleophthalmus, Periophthalmus, Periophthalmadon, and Scartelaos) take on an amphibious character, actively foraging over mudflats and up mangrove roots for crustaceans and insects (see Physical Description for more information on this). Members of the genus Gobiosoma are well known for their brilliant colors used to distinguish them as cleaner fishes. These gobies feed on the parasites and dead skin of larger fish. Some freshwater species of the subfamily Sicydiinae are amphidromous: the larvae are carried downstream to the ocean where they feed and grow (they travel for feeding, not reproduction, unlike many other fishes) before migrating back to freshwater island habitats.

Primary Diet: carnivore (Piscivore , Eats eggs, Eats non-insect arthropods, Molluscivore ); herbivore ; omnivore ; planktivore

Gobies are extremely important in almost any ecosystem they occupy because their relative abundance makes them an essential part of the food chain. Gobies have the greatest impact on the benthic environment since most reside there. Gobies may be the keystone species (dominant in the food chain) in the freshwaters of small oceanic islands because they are often one of the few species of fish that exist in these areas.

Ecosystem Impact: keystone species ; parasite

Species Used as Host:

• Branched Corals
• Sponges
• Sea Urchins

Mutualist Species:

• Shrimps

Due to their small size, gobies must be wary of many different predators, such as sea snakes, shore birds and larger fishes. It’s no surprise that they have developed a wide range of behaviors to defend themselves. Perhaps the most characteristic feature of gobies is their secretive nature. They rarely leave their burrows and display a wide range of coloration for camouflage. Some gobies are translucent and have only a few colored spots to match their surroundings while others have formed symbiotic relationships with shrimp. In the latter case Crytocentrus steinitzni sits outside the burrow watching guard while the shrimp clears out the burrow they share. Cleaner fishes of the genus Gobiosoma enjoy relative freedom from predation due to their color pattern and cleaning behavior. Others live within sponges, sea urchins, the branches of corals, or the roofs of caves for protection. Some gobies even rely on chemical protection, producing a poison called tetrodotoxin, which also occurs in pufferfishes and species of salamander. Some morphological adaptations can be found in mudskippers (Boleophthalmus, Periophthalmus, Periophthalmadon, and Scartelaos). The eyes of mudskippers are located on the tops of their heads to detect and avoid shore birds as well as to locate prey, and their powerful tail allows them to move quickly along the mud.

Known Predators:

• larger fish (Actinopterygii)
• sea snakes (Hydrophiidae)
• shore birds (Charadriiformes)

Anti-predator Adaptations: aposematic ; cryptic

Gobiidae is prey of:
Actinopterygii
organic stuff
Hydrophiidae
Charadriiformes

Based on studies in:
Puerto Rico, Puerto Rico-Virgin Islands shelf (Reef)

This list may not be complete but is based on published studies.

Gobiidae preys on:
Isopoda
Amphipoda
Pycnogonidae
Tanaidae
non-insect arthropods

Based on studies in:
Puerto Rico, Puerto Rico-Virgin Islands shelf (Reef)

This list may not be complete but is based on published studies.

There is considerable evidence that gobies use visual, tactile, chemical, auditory, or olfactory cues in reproduction and territorial behavior (see Reproduction and Behavior). It is quite likely that investigators will find more evidence of different types of communication as research progresses.

Communication Channels: visual ; tactile ; chemical

Other Communication Modes: pheromones

Perception Channels: visual

In most gobies, eggs hatch in one to five days and grow rapidly within a few days. At hatching the larvae are quite advanced with pigmented eyes, well-developed jaws, digestive tracts, and vertical fin folds. The small transparent larvae (between 2 and 10 mm long) are usually dispersed in the water column where they swim for three to 20 days. Finally, the larvae settle into a suitable habitat and develop colors that allow them to blend in with the surroundings. They reach sexual maturity within a few months. However, in temperate climates development may take much longer, with sexual maturity occurring after one to two years.

A notable exception to this developmental pattern (and there are likely many others) can be found in burrowing gobies. In this species, the male remains in a burrow, which is sealed shut by the female, for up to five days. During this time, the burrow is periodically reopened and the eggs cleaned by both male and female before the male is again sealed in the burrow. The eggs develop entirely within the burrow and only one juvenile apparently exits the burrow, suggesting that juveniles receive nourishment through cannibalism, as well as food reserves and their surroundings. Upon exiting, the juvenile immediately begins a benthic existence.

Tropical gobies develop very quickly and probably live no longer than one year but in cooler areas some species may live between two and ten years.

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

Barcode of Life Data Systems (BOLD) Stats
                                        

Specimen Records:	5,804	Public Records:	1,916
Specimens with Sequences:	4,824	Public Species:	255
Specimens with Barcodes:	4,665	Public BINs:	317
Species:	629
Species With Barcodes:	562

Access Published & Released Data: Download FASTA File

Collection Sites: world map showing specimen collection locations for Gobiidae

Genomic DNA is available from 3 specimens with morphological vouchers housed at Research Collection of Slava Ivanenko

There are five critically endangered gobies, 18 listed as vulnerable, and 12 listed as low risk. Agricultural practices and the introduction of non-native species are some important causes for their decline. This is not surprising considering the diversity of this family and the fact that many are confined to a single lake or river system, or one or few islands. Some may go extinct before humans become aware of their existence.

No specific information was found concerning any negative impacts to humans.

In the Caribbean and Philippines amphidromous gobies (see Food Habits) form a large portion of the catch as they migrate upstream in freshwater creeks. A number of gobies have been successfully bred in captivity, and some are also popular in the aquarium trade.

Positive Impacts: pet trade ; food