Whitebait in need of a protection society

Press, 2 December 1978, Page 13

Whitebait in need of a protection society

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RUSSELL KING

As the season ends keen whitebaiters (many people) and successful whitebaiters (fewer people) notice that the type of whitebait caught changes. And they are equally sure that the total catch gets less each year.

Should a chain of natural disasters cause few eggs to be laid, or develop, Or hatch, then the few late developers further up the rivers that will not breed until the next year or two have obvious survival value for the species. The next year they will come down river in autumn to catch the high tides, breed, and continue the species.

Some mutter about overfishing. Will there be, they ask. whitebait for their children to catch in the future? It was only 20 years ago, in 1958, that experiments began in the south branch of the Waimakariri River to establish the life cycle of the whitebait. Sampling of the national catch was undertaken to find what is caught. The life cycle is still only vaguely known by most people. Mass spawning in autumn is the start of the cvcie. The eggs are small and are laid, at the top of spring high tides, among the grass. The eggs develop over the nex: two weeks and those not lost by dessication hatch on the next spring tide. The young, about 7mm long, are carried out to sea. Next spring, in their countless thousands, the slender, transparent, 50mm long whitebait swim back up the rivers. Most stay in the lower reaches within 16km of the river mouth and reach maturity their first year in fresh water. The few that swim “’urther inland mature in their second or third years. When mature they begin their spawnin'? migration in cyclic fashion to catch the spring tide, irrespective of whether it is at full moon or new moon Hundreds of fish may be involved in the spawning.

The fish are five of the native Galaxias species; fish that have no scales make superior whitebait. Three of these need treecovered streams to live in so they are very rare or non-existent in Canterbury, although commonly caught on the West Coast

early in the season. Milling on the coast will probably need to leave strips of forest along stream verges to ensure plentiful whitebait supplies of these species. The fifth, Galaxias argenteus or giant kokopu, grows to 58cm and weighs 2.7 kg. Its juvenile whitebait stage is caught along with young butlys and smelt at the end of tfwseason. It is rare because o! destruction by draining for agriculture of its coastal swampv habitat Canterbury whilebait. *5 per cent of New Zealand's whitebait, and a fair pro portion of Tasmanian aid South American whitebait, are lhe juvenile of the tnanga, Galaxias maculatuThis is tar superio. to the whitebait of Europe and Japan which are the soung of bonej sea fish, such as sprats, shad, herrings, shrimp, or sea perch. Preservation of our whitebait fishery depends, primarily, on maintaining a belt of trees along naturally forested streams. If the trees 'are felled and light penetration increases, the number of trout increases. And whitebait are trout food. Trees along the stream verge also help ensure water flow, while temperature patterns are more likely to remain as they always were so that the adult Galaxias can grow to maturity. Stream bed sediments and algae in the water will also vary less and remain, as the fish n»-ed them for optimum survival.