Akthue. — On the Brown Trout introduced into Otago. 471 



have already assigned to my enquiries, have their sources in large in- 

 land lakes, and include the Waitaki, Clutha, and Waiau Elvers. At 

 the same time I think that the Pomahaka and Mataura Eivers may be said 

 to be partially snow-fed ; but the other rivers and streams from the Mataura 

 to the Waitaki may very properly be regarded as not coming within that 

 designation. The lakes also of the interior, lying at altitudes above sea- 

 level of 1,000 to 1,400 feet, and surrounded by steep snow-clad mountains 

 from 5,000 to 9,000 feet in height, in the spring and early summer become 

 charged with an excess of snow-water, which raises the rivers which are the 

 effluents of these lakes to the greatest height they attain during the year. 

 And warm rain, with a north-west wind under such conditions invariably 

 causes very heavy floods, sometimes disastrously so. Perhaps scarcely less 

 important in their bearings on trout are droughts with warm low water in 

 summer, and frosts in winter, but these latter I consider do not affect our 

 rivers much. The greater proportion of the Otago rivers are not affected 

 by snow during the spring, summer, and autumn months, and so are all 

 the better adapted for affording a food supply, as well as more suitable 

 water for the growth of the young trout fry. 



Added to the above considerations the winds, temperature of the water, 

 and atmospheric pressure also combine to exercise their influence on the 

 breeding, food- supply, growth, and habits of our trout. For example, a 

 clear rapid snow-fed river produces, with a light-coloured bottom, silvery 

 trout, while the food cannot be very abundant or varied, and the chances of 

 the ova hatching out are not great. Very cold water, with too rapid a 

 current and shifting shingle, is eminently unfavourable to the reproduction 

 of food and growth of fishes. Such a river is the Clutha in its upper 

 waters. On the other hand such trout as it could support would probably 

 escape fungoid growths. Of an opposite class is the Waiwera or Waipahi — 

 with an average flow of water, dark bottomed, good pools and reaches, with 

 plenty of shelter under the banks, and much vegetation on these banks, 

 abundance of food from the land, from aquatic plants, and from the gravel 

 and rocks, also at a certain season from the sea even — where we find trout 

 fairly plentiful, brown coloured, with golden bellies and scarlet spots, of 

 immense strength and most excellent flavour. 



At this point I might be asked to'explain more fully what on earth trout 

 have to do with gneiss and conglomerate, with the chemistry of water, with 

 the temperature of water, or with the particular compass-bearing of the 

 wind that may blow over the water ? And yet these things not only affect 

 them directly through their organs of breathing and secretion, but what is 

 even of greater importance, indirectly through their stomachs. Well 

 aerated water is very necessary to a trout's vitality, but that is of no use 



