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.