Gobiesocidae

Background

Clingfishes are primarily found near the shore in the Atlantic, Indian and Pacific Oceans, including marginal seas such as the Mediterranean, Gulf of Mexico, Caribbean and Gulf of California. The greatest species richness is in tropical and warm temperate regions, but the range of a few extends into colder waters, like Diplecogaster bimaculata (north to Norway), Apletodon dentatus, Lepadogaster candolii and L. purpurea (all three north to Scotland), Gobiesox maeandricus (north to Alaska), Gobiesox marmoratus and Sicyases sanguineus (both to southernmost South America), and Gastrocymba quadriradiata (from New Zealand's subantarctic islands).

Clingfishes mainly inhabit shallow rocky reefs and shores, coral reefs, seagrass meadows and algae beds. They often live in places exposed to strong currents and wave action, and some are amphibious. As long as the strongly amphibious, intertidal-living species are kept moist by splashing waves, they can survive for up to three–four days on land, gaining oxygen from the air by the branchial surfaces (gills), skin and perhaps the mouth. At least a few species even tolerate a relatively high degree of water loss when on land.

A relatively small number of species shelter in sea urchins or crinoids. Whether this relationship is obligate or facultative varies with species. In some, only young clingfish are obligate and gradually move away as they become adult. Three clingfish species, the Australian Cochleoceps bicolor and C. orientalis, and the warm East Atlantic Diplecogaster tonstricula, are cleaner fish that will cling onto the bodies of larger fish.

Although several species can occur in brackish water, only seven Gobiesox species from warmer parts of the Americas are freshwater fish that live in fast-flowing rivers and streams. Most known clingfish species are from relatively shallow coastal waters, but several inhabit the mesophotic zone and a few even deeper, with Alabes bathys, Gobiesox lanceolatus, Gymnoscyphus ascitus, Kopua kuiteri, K. nuimata and Protogobiesox asymmetricus reported from depths of 300–560 m. Because of their small size and typical habitat, it is however suspected that still-undiscovered deep-water species remain.

Even in shallow coastal waters many clingfish are highly cryptic and easily overlooked, mostly staying under cover, although there are species that are active and will swim in the open. As a consequence their abundance is often not well known. Several species are only known from a single or a few specimens. Species that appear uncommon or rare based on standard methods can actually be common if using methods that are more suitable for detecting them.

Studies of better-known species have shown that they can be locally abundant. As many as 23 individuals of Lepadogaster lepadogaster have been documented from a single square metre. As of 2018, the IUCN has evaluated the conservation status of 84 clingfish species. The majority of these are considered least concern, 17 are considered data deficient, 8 considered vulnerable and a single endangered.

The vulnerable and endangered species all have small distributions, restricted to islands or a single bay. Three Gobiesox species that are restricted to fresh water in Mexico have not been rated by the IUCN, but are considered threatened by Mexican authorities.