WHITEBAIT NURSERIES

Evening Post, Volume CXII, Issue 84, 6 October 1931, Page 5

WHITEBAIT NURSERIES

NATURE'S BOUNTY

PREVENTABLE LOSSES

CAUSE AND CURE

A considerable amount of mystery exists with regard to tlio life history of the whitebait, a delicacy now available in the fish shops and ono steadily increasing in popularity, though decreasing in abundance. The investigations of Captain Hayes, of tho Fisheries Branch of tho Marine Department, have thrown a good deal of light on the subject. While much still remains unknown the practical significance of what has already been revealed cannot be too greatly emphasised. Tho spawning habits of Gnlaxias attenuatus, tho young of which are known as whitebait, are unique in fish life. y The light thrown by the investigations of the Marino Department on the problems of how, where, and when this species spawns has indicated the necessity of taking steps to assist natural propagation. It has also pointed out tho way. It appears that the advantages originally bestowed by Nature have been largely nullified by the conditions brought about by civilisation and settlement. UNIQUE SPAWNING HABITS. The spawning habits of whitebait, states Captain Hayes, are unique. The adult fish (the inanga) migrate in shoals to the tidal water of rivers and streams for spawning. The shoal approaches the margin of the river at the time of high water of a spring tide. The rninuto eggs ax-e deposited among rush, grass, clover, or other vegetation which affords concealment for the spawning fishes and cover for the eggs, which adhere in small clusters on the ground about the bases of the stems of rushes or grasses. Spawning does not take place until tho highest of the spring tides has passed. The ova are thus loft ."high and dry" when the tide redeees, and since they are deposited as near tho water's edge as the fish can get and tho tides which follow are- of. diminishing size, there can be no further contact with the water until occurancc of next spring tidos —at the earliest a fortnight later. The spawn is thus assured complete protection from any aquatic enemy for practically the wholo of the incubation, period.. When the eggs are once more submerged on tho next spring tide reaching them, hatching takes place, and the larvae are carried down by the ebb tide to the sea. It bas been found that if the spring tides succeeding those during which the spawning took place are not so high and therefore do not reach the zono where the spawn is deposited, the eggs remain unhatched until a tide sufficiently high to reach them occurs. The young.then hatch out and are none the worse for the delay. The spawning may take place at any time between August and June, but the most considerable movements of the spawning shoals occur between January and May. : A NATIONAL ASSET. Captain Hayes's observations appear to indicate that Nature has provided this species with an instinctive knowledge of tho right moment to choose for tho deposit of their spawn, for.it has been found that when abnormally high tides have occurred the level of which would probably not be reached by subsequent spring tides, the fish have put off spawning until tho tides have receded somewhat. The egg stago may last about 14 days, or it may be extended to as much as nearly four times that period. This unique adaptation undoubtedly confers a great advantage upon this species in securing immunity from egg-devouring fishes or othor aquatic creatures. But European settlement has introduced an element of danger not, so to speak, anticipated by Nature. The. eggs are deposited on river banks in 'hundreds of thousands. Horses and cattle j^rampling over tho ground have been shown to bo responsible for the destruction of. vast numbers of the CggS.A" Photographs taken by Captain HayCs, which are reproduced to-day, indicate how this comes about. He stresses the necessity of taking steps to prevent this destruction by creating and maintaining spawning sanctuaries by fencing off known spawning areas' to prevent the access of cattle. The result of such action would be not only to prevent the destruction of eggs by trampling but also to permit the growth of herbage which is necessary to servo as cover for the spawn. In view of tho considerable value of the whitebait fisheries it is highly important that something in this direction should be done.