The genus Parioglossus comprises about 13 species found throughout the tropics of the Indo-West Pacific oceans. The recent discovery of a Parioglossus species on Great Barrier Island and in Northland is the first record of any fish from this genus in New Zealand waters. The species found here, the dart goby, is native to the east coast of Australia. How and when it arrived here is unknown, but ship ballast water is one possibility.
Superficially, the dart goby resembles a bully. However, there is no gap between the two dorsal fins, and the scales are very tiny, almost invisible. These features easily distinguish the dart goby from the bully species. The dart goby is also very small, with a maximum size of about 40 mm.
Generally, members of the Parioglossus genus inhabit marine and estuarine waters. The two known New Zealand locations of the dart goby are at least partly seawater. The Great Barrier site occurs in a low gradient wetland where the tidal wedge penetrates inland, and the Northland site is a small, brackish, coastal stream. However, laboratory tests showed that the dart goby could tolerate fully fresh water for at least a fortnight.
Very little is known about the life history or ecology of the dart goby, either here or in Australia. The extent of its distribution within New Zealand is also unknown. This makes it difficult to consider what impacts its introduction might have on the native flora and fauna. Such knowledge will only come after further surveys and studies on this little known fish.