BY R. J. TILLYAKD. 211 



between the iiitradiiced tntnt mid the fnod f^itpidii, the fislierief: are sooner or later 

 doomed to failure. 



With regai'il to the improvement of tlie food supply, the position is at pre- 

 sent a very serious one, in so far that the balance has been so greatly upset, that 

 no measures for the introduction of fresh types of food can be expected to suc- 

 ceed, unless such food is most carefully protected until it becomes well established. 

 It is, therefore, necessary to adopt at once measures which will not only help to 

 conserve the remnant of the food supply still existing, but will also give the 

 afiuatic fauna a chance of multiplying and approximating towards its original 

 abundance. To bring this about I would make the following recommendations: — 

 1. A badly impoverished stream should be selected, and should be completely 

 blocked by means of specially designed trap-nets, so as to prevent any trout jtass- 

 ing up it to spawn; also any trout at present in it should be taken out. Aquatic 

 insects should then be introduced from neighbouring small streams where no 

 trout exist (e.g., such parts of streams as lie above high waterfalls), and a 

 ■:-areful record kept by means of annual or biennial visits, upon the progi'ess of 

 the aquatic insect life in the stream. I estimate that it will take at least three 

 years, possibly five, for such an impoverished stream to return to its original con- 

 dition. If, at the end of two or three years, it becomes evident that the aquatic 

 fauna is increasing, steps should then be taken to block off in the same way each 

 spawning stream in turn; so that, in any given year, there will only be certain 

 streams open to the trout for spawning, wliile the rest will be given a chance 

 cf recuperation. 



For this purpose I would recommend either of the following two streams : — 

 (a) The Te TTairoa stream, from the waterful to the outlet of Lake Tarawera. 

 (There is an abundant supply of aquatic insects in the small creek on the left- 

 hand side of the road leading down to the wharf, about a mile from the Te Wniroa 

 stream) . 



(6) The Tokaanu stream. (Aquatic insects are abundant in the small streams 

 around Wahi, two miles away.) 



In both cases, the nature of the river-bed (pumice) and frequency of flood 

 water make it impossible to block the stream by means of stake or pile-nets. I 

 would, therefore, recommend that the nets be strung on strong supports driven 

 into the banks, and that their lower ends should hang freely into the stream, and 

 cari-y lead weights at short intervals. The accompanying diagrams (p. 212). show 

 the type of net to be used. 



If at the end of three years there is no sign of the native aquatic insect 

 fauna reasserting itself, I would i-ecommend that an attempt be made to intro- 

 duce the English "Oreen Drake" Mayfly. Ephemera daiiiea, or such other species 

 as are known to be of great value as food ior trout. These could be set fi'ee in 

 the larval condition in the streams selected as a sanctuary under recommenda- 

 tion (2) following this below. 



2. It is of the gTeatest importance that one lake, together with the streams 

 flowing into it, should be set aside as a sanctuary for the natural food-supply. 

 Most unfortunately, this aspect of the f|uestion was not considered when the 

 stocking of the streams with trout was undertaken. The result is that there is at 

 present no lake in the Rotorua District which does not contain trout. In the 

 Taupo District, an undertaking was given by the Government to the Maoris that 

 Lake Roto-Aira should be kept free from trout. Unfortunately, trout were sur- 

 reptitiously introduced into this lake two years or more ago, and have grown to a 



