Akthue. — On the Brown Trout introduced into Otago. 



473 



Growth. 



It is of the first importance, at this stage, to be sure of the real species 

 of trout which has been introduced into Otago — the progeny of the original 

 lot got for us in Tasmania by Mr. G. P. Clifford, in 1868. Now, Mr. 

 Clifford has told me there could be no crossing with S. salar or S. trutta at 

 the breeding ponds on the Plenty, in Tasmania, as the trout there were 

 carefully kept separate, and in ponds by themselves. So far, good ; and as 

 I stated in my previous paper, the original ova from England were taken 

 from three rivers, the Weycombe, Buckinghamshire, and the Wey, by Mr. 

 Francis Francis ; and from the Itchen, by Mr. Frank Buckland. The 

 Salmon Commissioners of Tasmania, however, so far as I could find out, 

 have not placed on record the precautions taken, if any, to keep the lots 

 separate in the hatching-boxes, or to say what proportion of each were 

 reared and produced ova. All I have been able to learn is that many ova 

 died, and that it is impossible to determine which English river or rivers 

 may be represented by the progeny. However, taking Dr. Giinther's 

 arrangement of species as my guide, it determines the trout from any of the 

 above-named rivers to be S. fario ausonii, or the southern form, which I 

 take to be the same as the Thames trout. It is capable of growing to a 

 large size in its native streams, or may be called a large-framed trout, and 

 is believed by good authorities to drop down into brackish water sometimes, 

 or even as far as the sea itself. While it may be admitted readily that this 

 trout does sometimes migrate in this manner, I must remark that I have 

 never seen any absolute demonstration of the fact adduced by any author. 

 But I shall have occasion again to offer my own observations on this point, 

 and so shall leave it alone now. 



The period of hatching at our Opoho hatchery may be seen from the 

 following examples : — 



Year and Locality Trout Ova 



Last Ovum 



Time of Hatching 



Temp, of Water. 



got in. 



Hatched. 



in days. 



Fan. 



1868 Ponds at Plenty, Tasmania 



October 30th 



About 70 





1869 „ 



„ 14th 



„ 70 





1878 Otago Eivers 





„ 78 



42°— 52° 



1879 „ .. .. 



„ 23rd 



78—88 



41°— 50£° 



1880 



„ 30th 



80—95 



40°- 57° 



1881 „ .. 



„ 20th 



64—75—77 



41°— 53° 



1882 „ .... 



„ 30th 



70—80 



39°— 50° 



The Tasmanian ova may properly be omitted in determining the ordinary 

 time taken for hatching, as they were subjected to unusual vicissitudes 

 before reaching Otago. The mean time of the other lots taken from trout 

 in Otago waters is 78 days, or, leaving out the manifestly abnormal dura- 

 tions of 64 and 95 days, we get a range of 70 to 88 days, or, on an average, 



