Abthur. — On the Brown Trout introduced into Otago. 469 



Hill. From this line, southwards to the coast, the rivers rise among older 

 or trap formation, and flow more or less through a wooded country. Among 

 the former, as a rule, the higher parts of the rivers are rock-bouud, while 

 the lower reaches and mid portions pass over alluvial flats, the shingle and 

 gravel in their channels being the debris of their parent rocks with more or 

 less quartz pebbles and fine sand. Among the latter class the gravel is 

 almost wholly trap with a little quartz, while very few streams among either 

 have beds entirely of clay or loam. A great number, especially of our 

 smaller rivers, are rock-bound in their entire course, and so, having a scanty 

 supply of gravel, are deficient in breeding capabilities ; but perhaps- two- 

 thirds of all the rivers are well adapted for spawning, so far as gravel and 

 sand can contribute to that end. One curious exception, however, must not 

 be overlooked here, viz., the Water of Leith, which, possessing a rocky 

 channel full of volcanic boulders, particularly in its lower course, and a 

 scanty supply of gravel, yet for several years subsequent to 1874, when it 

 was opened to anglers, produced an astonishing number of trout. It has 

 not maintained this character, but that is due to excessive fishing and 

 poaching. Eivers to the west of the Mataura are not included in the above 

 references, as the stocking of these has not been kept up ; and I have only 

 examined one trout taken there, viz., from the Oreti, a snow-fed water. 



The banks of the rivers are very much yet in their natural state, covered 

 by native grasses, and in some cases, bush ; but cultivation has overtaken 

 all the lower plains of the main streams to within a few yards of the water. 

 Cultivation no doubt affects the character of the food-supply, and quantity 

 also ; so do grass fires around the upper waters, while both lower the mean 

 flow of water in the rivers, directly and indirectly, also causing floods to 

 become much more violent, high and mischievous, although shorter in 

 duration than they used to be. During a residence of twenty years in Otago 

 I have seen quite enough evidence of the latter of these facts, as for example 

 in Shag Valley. 



The mouths of the principal rivers which enter the sea directly have 

 estuaries, protected by sandy bars. In the case of the Kakanui, Shag, and 

 Waikouaiti Eivers the tide has a course of a mile and a half or more, 

 upwards from the sea ; while the tidal way of the Mataura may be estimated 

 at five miles at the very least. Some of our best trout streams do not 

 discharge directly into the sea, but are feeders of larger rivers, having tidal 

 estuaries. So much then for a general definition of the geological conditions 

 of our trout rivers that relate to distribution. 



It only remains in this connection to mention that the lakes into which 

 trout have been placed are the Wakatipu, Wanaka, Hayes Lake, Waihola, 

 and Tuakitoto. The surroundings of the three former of these lakes are 



