This family is diverse and so each genus is treated as a separate file above.

The gobies are a world-wide family found mostly in warmer marine waters although some species enter fresh water and others live there permanently (see also Marine List). The number of species is high and this may be the most speciose fish family in the world with about 210 genera and an estimated 2000 species, perhaps more. A diversity of gobies occurs in the Caspian Sea basin. Not all Caspian gobies have valid Iranian records but most will probably be found there. Several gobies penetrate southern waters of Iran from the Persian Gulf and Sea of Oman and are described here. Others will probably be discovered when more detailed surveys are made.

Gobies are easily distinguished by their pelvic fins being united as an adhesive or sucking disk or cup. Body form and coloration are diverse. The pattern of head canals, canal pores and neuromasts is distinctive and used in identifying and relating species (except in Neogobius (Pinchuk, 1991)). However the neuromasts may be sunken in narrow furrows or pits and completely covered by epithelium so they do not preserve well and this can lead to confusion in identifications (Zambriborshch, 1968). There is usually a short spiny dorsal fin (2-8 flexible spines) separated from, but close to, a soft dorsal fin. The soft dorsal fin and anal fin are longer than the caudal peduncle. Scales may be cycloid, ctenoid or rarely absent. No obvious lateral line. There are 5 branchiostegal rays. Gill membranes are connected to the isthmus and gill openings are moderate to wide, or very restricted in the mudskippers. The head is usually blunt and the mouth is usually large. Teeth are usually small and conical in one to several rows in both jaws. Miller in Miller (2003) gives a suite of osteological characters defining the family.

Most gobies are quite small (5-10 cm) and they are often very abundant. Maximum size is about 50 cm. Some of the world's smallest vertebrates are gobies from the Indian Ocean, mature at 8 mm. Others, however, are large and form part of fisheries in both the Caspian Sea and the Indian Ocean. They are not significant food fishes in Iran. Gobies tend to rest on the bottom and move in sudden, characteristic dashes. The male goby guards a nest. Food is crustaceans, worms, molluscs and small fishes. Many gobies are important in the aquarium trade since they are beautifully coloured, small and tough.

They are known generally as gav mahi (= cow fish) or sag mahi (= dog fish) or contain the word gel (= mud) in Iran. A general review in Farsi of the Caspian gobies is given by Aslaanparviz (1991).

The males of some Caspian species become black during the spawning season, their fins elongate, head shape alters and some even become naked. Loss of tubercles in adult male gobies of the genus Benthophilus makes it possible to identify only juveniles and females. The males build nests and guard the eggs. Life span of certain Caspian species is said to be as short as one year, e.g. some species of Benthophilus, Knipowitschia, and Proterorhinus. Neogobius fluviatilis, N. melanostomus and N. gorlap consume the invasive ctenophore, Mnemiopsis leidyi, as much as 10-15% of total biomass in some areas (Mamedov, 2006).

The Black and Caspian Sea basins contain an endemic Sarmatian fauna of gobies. There are two main clades, the gobiine-benthophilines (or transverse gobiids) and the pomatoschistines (or sand gobies), that have probably been distinct for at least 40 million years. Miller (2001) and Miller in Miller (2003) reviews the evolutionary history of these two clades and their anatomical differences based on head papillae and osteology. The transverse gobiids include Mesogobius, Neogobius, Proterorhinus, Chasar, Anatirostrum, Benthophiloides, Benthophilus and Caspiosoma while the sand gobies include Knipowitschia and Hyrcanogobius. The Sarmatian fauna was separated from the Atlantic-Mediterranean fauna with the isolation of the Paratethys during the late Miocene Messinian salinity crisis as the Mediterranean dried. Partial flooding of the Mediterranean from the Paratethys in the early Pliocene allowed Sarmatian gobies to spread westwards. Within the Ponto-Caspian basin, evolution of species flocks was favoured by basin sub-divisions and rejoinings. The benthophilines may be a monophyletic group from these events.

Ahnelt and Duchkowitsch (2004) give information on the neogobiine stock. About 12-13 million years ago in the Middle Miocene, the Ponto-Caspian endemic and ancestral neogobiine stock may have differentiated from an Atlantic-Mediterranean gobiine stock. At this time the Paratethys was a sea with reduced salinity and a high level of endemism. The Neogobius-Proterorhinus stock developed independently from the recent Gobius stock that invaded the Mediterranean basin after that sea was restored about 5 million years ago in the Late Miocene.

The principal recent works on the systematics of Caspian gobies are by V. I. Pinchuk, D. B. Ragimov, Ye. D. Vasil'yeva, H. Ahnelt and P. J. Miller. Earlier works are by B. S. Il'in (also spelled Iljin or Ilyin).

Other gobies in Iran are the familiar tropical mudskippers which can move quickly over land, using the muscular-based paired fins to row across mud, and some can even clasp and climb mangroves. They can live out of water because the gill openings are small to prevent desiccation of the gills, oxygen can be taken into the chamber and absorbed through the gills and chamber wall, and they can also absorb oxygen through their skin. They often rest with the tail immersed in water for this purpose or roll around in shallow water to moisten themselves. They may live entirely in water, or will come onto land even when there is enough oxygen in the water. Their eyes are high on the head, protruding and able to revolve independently, and have a movable lower lid. The eyes are retracted periodically into small cups below the head to moisten them. Such eyes are very effective as a means to watch for potential enemies on land but their vision under water is blurred. Mudskippers have elaborate reproductive behaviour which involves tail standing, flip-flops, and fin displays. They are very territorial and defend their territory against other mudskippers and crabs. They can deliver a skin-breaking bite to humans even though they are only about 15 cm long!

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