Lamprey (Geotria australis)

The lamprey spends most of its life in the sea, where it uses a circular sucker (below) to attach itself to other animals and feeds by rasping a hole in their flesh. The adults, which are over 400 mm long, spawn in fresh water, and thus we find them in our waterways. The adults do not feed while in fresh water, however, and so are not parasitic on other freshwater fish.

Lampreys can be distinguished from eels by the presence of the circular sucker instead of a mouth and seven holes along their sides just behind the head. These are the gill openings. Male adult lampreys also have large pouches just behind their mouths. When they first come in from the sea, lampreys are bright silvery-blue (as in the photo above), but soon change to a drab dark grey colour.

We believe juvenile lampreys spend up to four years in fresh water before migrating to the sea. At first they are a muddy brown colour and look like small eels. They appear different from eels by having seven gill openings and no eyes. As they approach migration, juvenile lampreys develop eyes and change to a bright silvery-blue, just like the adults. However, they are only about 100 mm long at this stage.

Lampreys are found throughout New Zealand, and also in Australia and South America. Despite their wide distribution, they have not been reported from Stewart or Chatham islands.

Generally they occur close to the coast at low altitudes, but can use their circular sucker to surmount obstacles such as small waterfalls during their migration to spawning sites. Little is known about their breeding habits.

Lampreys were an important food resource for Maori, and elaborate weirs were constructed to catch them. This traditional fishery still occurs on a small scale in the Wanganui River near Pipiriki.