H.—ls.

Toheroa. As a result of the economic depression no toheroas were packed at the canneries adjacent to the Ninety-mile Beach and the North Kaipara Beach beds this year. There has been a certain amount of commercial exploitation by persons holding selling licenses for the two areas on the North Kaipara beach that are available for commercial digging. The quantities thus utilized are not known, but they probably do not amount to very much. There is no doubt but that the greatest abstractions are due to visitors by motor-car and to holiday campers, as evidenced by the depleted condition of the beds in the more accessible parts of the beaches and in the vicinity of holiday camps. The regulations gazetted in September, 1931, have had a good result in checking the taking of excessive quantities, but there is still need for a more effective supervision on most of the toheroa beaches. It is also desirable that more attention should be paid to the matter of investigating the quantitative distribution of these bivalves, and especially the occurrence of the different year-groups in order that exploitation and conservation may be based on comprehensive knowledge and in accordance with rational considerations. With regard to the present well-stocked beds on the coast in the vicinity of Levin it is disquieting to find that there is an apparent shortage of the younger year groups, and a more thorough knowledge of the constitution of the stock would place us in a better position to shape our present and future policy in connection with measures of conservation. The same general consideration governs all problems of fishery conservation, but while in the cases of most species of fish and shellfish the practical difficulties of obtaining the required statistical and biometrical data are considerable, in the case of toheroas the task, given adequate time, is comparatively easy, since all the beds are accessible for about half a tide and can be sampled by digging and to a certain extent appraised by visual observation. In connection with the question of the renewal of the cannery lease on the Ninety-mile Beach an effort was made in February, 1933, to carry out a survey of the toheroa-beds between the Waipapakauri Road and the Maungonui Bluff on the Ninety-mile Beach by means of sampling unit areas over several miles of the beach. Thanks to the invaluable assistance of Mr. W. K. McLean, manager of the Northland Canneries, Ltd. factory, it was possible to cover a good deal of ground in a ten days' stay and to get an approximate idea of the toheroa population in terms of real numbers as against the unsatisfactorily vague reference to various degrees of plenitude or such terms as " countless millions " or " inexhaustible abundance," which have for too long been used in connection with natural assets of all kinds. This survey was by no means exhaustive, and it is desirable that more time should be given to extending, amplifying, and confirming the data thus far obtained. The aim of this undertaking was to get information as to (1) the part of the beach occupied by toheroa-beds, and (2) the population of the toheroa-beds expressed in terms of approximate average density per yard of bed or per mile of beach. Since it was obviously impossible in a short time to survey the 50-odd miles of beach over which the beds are distributed, the method adopted was to make a rapid and superficial survey by inspection over the greater part of the beach and to work intensively and by quantitative sampling on limited portions which should be fairly representative of the whole. Actually the stretch of approximately thirty miles between Waipapakauri Road and Maungonui Bluff was the only portion of the beach that came under examination on this visit, though there are about seven miles of toheroa beach to the south and, I understand, a longer stretch of beach northward of the Maungonui Bluff that carry stocks of toheroas which are regularly utilized by local settlers and Maoris. The conclusions from this survey regarding the present condition of the thirty miles of beach above mentioned may be summarized as follows: The first five miles proceeding northward from Waipapakauri Road contain beds at frequent intervals occupying not less than half the total length of the beach. The part nearest the road appears to be less densely stocked than farther north (probably on account of its being regularly dug by Maoris and settlers), but this portion was not sampled. The best beds are in the neighbourhood of the Karaka Stream, where digging for the cannery has principally taken place. The next five miles contain a series of good beds with only short intervals between, those to the south being practically continuous. The extreme south of this area is worked by the cannery diggers. The part of the beach between the eleventh and fifteenth mile from the road contains the best beds of toheroas of the largest size, more especially at the southern end in the neighbourhood of the Hukatere Stream. Between the sixteenth and twentieth mile from the road fairly good beds occur at the southern end, but the northern part is not so well populated. The ten miles of coast between here and the Maungonui Bluff are at present practically unproductive of toheroas of commerical size. Young stages were found (yearlings and two-year-olds), but it was not possible to ascertain the extent of their distribution or to get an idea of their real abundance. There can be no doubt, however, that at present this particular portion of the coast may be considered as barren compared with any part of the twenty miles to the southward or with its own condition a few years ago. As to the cause of the present condition of toheroa shortage here, one can only speculate. It is not due to human exploitation. Twice in the last four years there have been occasions when mortality on a considerable scale has taken place among the toheroas on this part of the coast —namely, in April, 1930, and in February, 1932. On the first occasion after a visit to the beach soon after the deaths took place I came to the conclusion that the effects of easterly gales in driving considerable quantities of dry sand from the sandhills on to the toheroa-beds had probably been the cause of the mortality. I was not able to make any direct inquiries regarding the 1932 case. Mr. Powell, conchologist to the Auckland Museum, was reported by the press to ascribe the probable cause to starvation brought about by an absence of plankton in the sea-water at the time. There is one outstanding physical fact that may be correlated with the disappearance of toheroas from this part of the beach and possibly with these two incidences of general mortality —that is, the shrinkage in the volume of fresh water in the lagoons occurring inland immediately behind the toheroa-beds. It seems possible, if not probable, that the diminution in the amount of fresh water that finds its way by seepage through the sandhills

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