New Zealand has around 40 native freshwater fish species and about half of them spend part of their lives at sea. Most NZ species, 25 according to some sources, belong to just one group known as the galaxiids. These fish have no scales and are so named because of the markings on their skin, which have been likened to a galaxy of stars. All but five galaxiid species do not migrate, but those that do develop as larvae in the ocean as part of the zooplankton, returning to rivers to spend all of their adult life in fresh water. The juveniles of these five galaxiid species are what make up New Zealand's whitebait catch.

During the months of August to November visitors to the streams around Pauatahanui Inlet will see the occasional person perched on the bank, eyes focussed on the water. What they are keenly hoping for is a large catch of small freshwater fish carried upstream in shoals on the incoming tide. These are the young of several species of fish which are treated as a delicacy by culinary afficionados and ordinary people alike. Known collectively as whitebait they are cooked in various recipes, the best known of these being fritters.

While the five species that make up whitebait are all found in New Zealand waters only three species have been recorded in Pauatahanui Inlet streams. The majority of the catch consists of the very widely distributed Galaxias maculatus or inanga, with a much smaller percentage of Galaxias argenteus (the endangered giant kōkopu) and Galaxias fasciatus (the banded kōkopu). Inanga are the smallest of the species, rarely exceeding 110mm in length, but the one whose life cycle is most fully understood. (Photo of adult Galaxias maculatus, left, by Stephen Moore.)

Found in places as far flung as Chile, Argentina and Australia, G maculatus is the most widely distributed native freshwater fish in the world. It is also the shortest lived of the whitebait species. Inanga, the New Zealand name, inhabit lowland slow-moving streams within a short distance of the sea and are poor climbers, avoiding waterfalls or steep gradients. Swimming together in shoals the adults feed on aquatic and terrestrial insects and crustaceans. Together they migrate downstream to the estuaries during the extra-high spring tides of autumn and spawn on overhanging fringing vegetation within the estuarine boundary. Many adults die after spawning and those that survive the first year will die after the second.

The eggs develop out of water, above the normal high tide limit, until the next spring tide occurs, two to four weeks later. On re-submersion the eggs hatch and the larvae are carried out to sea. Here they spend 5-6 months as plankton feeders before returning during spring, not always to the same river, as shoals of 50mm-long whitebait. The translucent juveniles swim against the river's flow, keeping near the edge where the current is weakest. The rest of their lives is spent maturing into adults higher up the river before the migration begins again the following autumn. (Photo of juvenile Galaxias maculatus, right, by Rob Suisted.)

Of the other two species adult banded kōkopu have numerous pale stripes across the body and can grow up to 26cm long. They are good climbers and make their way well upriver until they find small forest streams with plenty of cover and shade. Like other galaxiids, banded kōkopu have sensors on their heads to detect when and where something hits the water, enabling them to feed on insects that fall from overhanging plants. The giant kōkopu is a secretive species and loves having plenty of cover to hide under, preferring gently flowing overgrown streams, swampy lagoons and lake edges. It is a skulking predator, lurking under cover and making speedy dashes to nab its prey. Both banded kōkopu and giant kōkopu are also incorrectly called native or Māori trout.

Each species of whitebait has particular areas for spawning and inanga are no exception. A survey of all inanga spawning grounds by Wellington Regional Council in July 2001 identified, at that time, several such locations in the rivers and streams entering Pauatahanui Inlet. In Duck Creek it was an area of tall fescue, toetoe and flax overhanging the stream. At Pauatahanui a new bridge was being constructed over the stream and two nearby areas were identified with tall fescue, toetoe, blackberry and mint. The Horokiri stream was found to be an unlikely spawning area due to grazing and removal of riparian vegetation, and there was no likely area on the Kakaho stream due to mechanical grading of the riverbanks. So locations for spawning were seen to be limited and an education programme was set up to help improve the situation. A lot has happened since then in most locations, with the exception of Duck Creek, but we are not aware of any new surveys undertaken to establish the current condition of these spawning sites.

Whitebaiting in New Zealand is a seasonal activity with a fixed and limited, legally enforced, period of time when the whitebait normally migrate upriver. The strict control over net sizes and rules against blocking the river to channel the fish into the net aim to allow sufficient quantity of whitebait to reach the adult habitat and maintain stock levels.

'Whitebait' is not just a New Zealand term but one used in other parts of the world as a general name for the immature fry of many important food fish such as herring, sprat, sardines, mackerel, bass and others. In England whitebait is mostly fully marine Clupeidae fish, mainly herring.



This article first appeared in 'The Inlet', the newsletter of the Guardians of Pauatahanui Inlet, in August 2014.

Last Updated: 14/12/2015 12:01am