THE LIFE OF THE WHITEBAIT.
MARINE I)KPAKTM IvNT’S
I? K PORT.
)N CAPTAIN HAYES’ INVRS-
TKIATION
The Marine Department’s report presented to Government last week coneeirning the investigations at presold being carried out into the life history of the whitebait (Galaxiiis allenuatus states): /Until the gups in our knowledge of the life history ol this species could he tilled up we were not in a position to tackle the framing of- regala lions for its conservation with due insight into the fundamental facts of the situation. In particular, it was recognised that light should he thrown on the spawning of the species. Resides the 'well-known fact that whitebait, which are inanga, at a juvenile stage, enter the 'months of rivers from the sea, there existed convincing evidence that the adults when about to .-pawn migrated in shoals from fresh water down to tidal water. The Maoris believed that the inanga spawned in the sea, and this view has been accepted iby European and New Zealand writers oil I In l subject.
“The exact, location and identification of the naturally deposited spawn and the distribution of the larval (pre-whitebait) stages were unknown until the Department's investigations were made. Some preliminary light was thrown on the subject, when, in May, 11)21), ripe inanga of .both sexes were obtained from the Whakaipimi drain, near Foxtail, and the ova. artificially lcitiliscd by (Captain L. Hayes. Different lots of these ova were kepi during the incubation stage in water of four different grades of saLaity—(1) 'Sea-water from Wellington harbour, (2) a mixture of .two parts of sea-water and one part-fresh water, (3) a .mixture of one part sea-water and two parts fresh wider, (4) fresh 'Wellington lap water (derived front tin' Wninnioniata). “The somewhat, surprising outcome of this was that healthy larval lushes hutched out from each lot, indicating that both eggs (embryos) and larvae were tolerant to lillier fresh, brackish, or! suit water, which is in itself , a very exceptional phenomenon. It suggested that Hu 1 natural incubation of this species took place under very variable conditions with regard to the salinity of the surrounding water, such its would be found, for insL-meV, near the mouth of a tidal riiver. ✓!! .was also found that the eggs preserved [bein’ vitality when kept packed in damp moss for several days. By this experiment also the character of the egg I ml. of the newly hatched larva was determined —a neecfisnry star-ting-point for the idenfideation of the same when found naturally occurring. The number of eggs produced by a single female inanga has been found to vary from 1500 in the smallest (2 5-Bin) (isli to over .13,1)00 in n very large (s{in) specimen. A* lIK I'l l TIDE HOM A N,OK.
"A further step now to In* recorded is the actual observation of the act of spawning, the location of the spawn, the incubation period, the emergence of (lie newlyhatched young (isli, and their natural distribution. These observations were carried out by Captain Hayes on (lie Maiiawatu Fiver between about three and a-half and eight miles from its mouth, on a visit made about the middle of .March, 11)30, and on subsequent ■ \isils. The main facts which lie brought to light are as follows: The ripe lisii migrate to the tidal water in shoals, arriving at the time of spring tides. These migrations were observed to lake place in the Manawa.lu Fiver this year in March (once), April (twice), and Mnv (twice). There was evidence to support the supposition Unit a spawning bad also taken place in February. Details of spawning in the grass <m the margin of the river as preciously published in these eolumus, were given and tile report further ■staled that at tho ..time when the eggs were hatching out considerable quantities of the larvae were •taken by tow-netting in the estuary just above the bar. It lias been demonstrated that if the spring tides .succeeding the one on which spa,wiling took place are not so •high, and therefore do not reach the zone where the spawn is deposited, the embryos remain unharmed while hutching is deferred. “The period between spawning and hutching may thus be about fourteen days, or it may be extended to much as forty-eight days (states the report). This provision by which, the parent tish deposit their spawn at places, which are only covered with water at the highest tides practically ensured immunity from enemies linden - the original natural conditions which •held previous to the colonisation of New Zealand. Under present-day conditions, however, adverse factors come into play which were not contemplated, so to speak, in the original natural state of affairs. in the locality investigated it. was found that horses, cattle, and even human beings, by trampling over the ground on which the whitebait eggs were deposited in hundreds of thousands, wrought a considerable amount of destruction. A full account of these observations and other points connected with the natural history of the whitebait will appear in a late report.
The light which .these successful investigations will throw upon the spawning habits of whitebait, when used as a basis for further research, will no doubt open up other discoveries. Quite recently, on a
visit to (lie Manawatu area, Captain Hayes found inanga ripe for spawning, from-four and a half indies to two and a half inches long, and early next month he will make another visit to ascertain the spawning conditions of October, which may vary considerably from -those of the earlier months of the veatr. lit April and May the high tides occurred at the full moon, whereas at this time of the year they come with the new moon. As occasionally spawn-ripe adults and new whitebait from the sea have been taken in the same net, it is obvious that much remains to be learnt of the spawning season.
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Manawatu Herald, Volume LI, Issue 4520, 21 October 1930, Page 2
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973THE LIFE OF THE WHITEBAIT. Manawatu Herald, Volume LI, Issue 4520, 21 October 1930, Page 2
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