Conservation of the Whitebait Fishery by Peter Ravenscroft The Five Species of Galaxias The whitebait catch is made up of the…
The whitebait catch is made up of the common smelt and five species of migratory indigenous ﬁsh. These fish come from the galaxiid group.
The largest of the galaxiids is the giant kokopu (Galaxias argenteus). This rare fish generally does not penetrate too far inland. It is found in a variety of habitats, but always where there is plenty of cover. It grows to a reasonable size. The largest I have seen was 350mm in length, but it has been recorded up to approximately 450mm.
Little is known of the spawning of the giant kokopu, except that it turns up occasionally in eel fishermen fyke nets in the winter months. When the juveniles of the giant kokopu return, they are approximately 120 days old and 40-50mm in length and run late in the season, around November.
The banded kokopu (Galaxias fasciatus), although quite common in places, especially on the Otago Peninsula, is still considered to be vulnerable. They like the brown stained waters and the overhead cover of our many small and unmodified streams.
The adult fish can obtain a length of 250mm and may live for 10 years. The banded kokopu, particularly the juveniles, are excellent climbers, being able to climb vertical, damp walls and waterfalls. There have only been a couple of recordings of spawning – one was in ﬂooded leaf litter and another occurred with inanga. The whitebait appears in our rivers around the month of October. They are approximately 120 days old and are 40 – 50mm in length.
Short-jawed kokopu (Galaxias postvectis) is one of New Zealand’s rarest and most vulnerable fish species. It is predominantly found on the South Island’s West Coast and several places in the North Island. Even where it is found, it is far from common. Little is known of this fish, but it is the focus of some research work by the Department of Conservation. It grows to a length of approximately 250mm and is generally found in unmodified native forest streams.
Koaro (Galaxias brevipinnis) is found throughout New Zealand. They avoid brown coloured waters, preferring clear, rapid-flowing streams. The koaro is also found in some Otago lakes, for example, Wanaka, Hawea and Mahinerangi, where they use the lakes like the sea. Life span is approximately 6 – 8 years and possibly longer. They have been known to reach a length of 270mm, but are m ore commonly found around 160 – 180mm. As juveniles, they are excellent climbers and have been referred to as “elephant ears” on account of their large pectoral fins, which assist their climbing. This climbing ability enables them to penetrate far inland. The whitebait appears in our rivers around September and October. They are approximately 130 days old and they are 45 – 50mm long.
Inanga (Galaxias maculatus), is probably the best understood of all the galaxiids. It also is very important to the whitebaiter, making up approximately 95 percent of the catch on the South Island’s East Coast. It is found in a wide variety of habitats. It does not have a strong climbing ability and generally does not penetrate too far inland. The whitebait appears in our rivers from July onwards. They are approximately 150 days old and are 50 – 55mm in length. The fish appear to have several spawnings that take place, mainly from January to May. Most spawn in their first year and die, but some fish may survive to three years.
Recently, the Department of Conservation has been identifying inanga spawning sites as part of a national programme. Several sites have been located in Otago. I have been involved in looking for and surveying these sites. What seems to happen is that the spawning inanga go to the top end of the tidal reach, generally during a new moon, but certainly not always. The extra high spring tides allow the inanga to wriggle their way further up and inland amongst the grasses on the stream bank, where they lay a large band of tiny eggs (1mm in diameter) along the stream edge.
Tall fescue (Festuca arundinacea), Chewing’s fescue (Festuca rubra) and creeping bent (Agrostis stolonifera) are three kinds of grass used by inanga spawning at the Otago sites. The reason these plants are used is that they generally have a moist and abundant root mat. This is important to stop the tiny eggs from drying out. Here the eggs lie and develop approximately 1 – 1.5 months until they are ﬂooded by the next spring high tide. When they hatch, the tiny 7mm long larvae are washed out to sea.
In Otago, we have located inanga spawning sites at Orokonui Stream, Waitati, Waikouaiti, Waianakarua and Shag Rivers and Waiareka Creek. The largest site of all, about 60 metres long, was on the Shag River. It had a band of eggs varying from 100mm to 190mm wide. A number of the sites we found were already protected from stock by natural barriers, such as a bluff, banks or gorse, but the Waiareka Creek spawning site, with its gentle, sloping banks was vulnerable to stock tramping. The landowner has agreed to fence off 150m of his land to protect the site. The support landowners have shown in the protection of these sites has been much appreciated and very encouraging.
There are a number of possible reasons for the decline in the whitebait fishery. They include the draining of most of our wetlands, deforestation of our river catchments, ﬂood gates and culverts that stop the progress of fish, and the destruction of spawning habitats. When inanga lay their eggs on a river bank, they remain for approximately a month and can be vulnerable to stock damage. All it takes is one cattle beast to trample or graze a stretch of river bank used for spawning, and that contribution to the next whitebait season is gone. To help sustain the fishery, we should protect these spawning sites. One way is by temporarily fencing them off, although locating the sites is not easy.
Although not a galaxiid, or even a whitebait at all, the common smelt – Retropinna retropinna is often caught in whitebait nets in the spring. These little fish are bigger than juvenile whitebait and have a strong cucumber smell. Although you can eat smelt most whitebaiters toss them back in the water.
Not just an old swamp! Here’s a great example of a quality whitebait habitat at the Hapuka Estuary Wildlife Sanctuary on the West Coast of the South Island.
This post was last modified on 13/07/2018 12:41 pm
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