32 H. C. DANNEVIG. 



after several unsuccessful attempts that what would seem 

 a highly satisfactory result has been attained. 



It is obvious that before the action of the fishermen 

 through the capture of too great quantities, or by excessive 

 destruction of young fish can be held directly responsible, 

 it is necessary to find in the changes of men's numbers or 

 methods, a fluctuation corresponding in some way with the 

 "ups and downs " in the abundance offish, as demonstrated 

 in Table IV., and as such a correspondence is not apparent, 

 it becomes necessary to look for the explanation in other 

 directions. 



As to the influence of physical conditions upon the abund- 

 ance of fish, I first of all made search for periodicity in 

 changes, and herein I received most valuable assistance 

 from the present Commonwealth Meteorologist Mr. Hunt, 

 who until recently was in charge of the local sub-depart- 

 ment. I examined large quantities of records having 

 reference to temperature, rainfall and winds, and this study 

 was I think in itself of some value owing to the disclosure 

 of certain meteorological phenomena that resulted, but 

 before referring to these and their bearing upon the abund- 

 ance of estuarine food-fishes in our waters, it is desirable 

 to shortly mention such principal features in the life of 

 these fishes as are likely to be seriously affected by pro- 

 longed climatic changes. 



Two principal features in the life-history of most of our 

 food-fishes have been fully demonstrated through some of 

 my earlier investigations, they are in short : — 



1. That the shoals of full grown fish that at certain 

 seasons of the year are seen to enter our estuaries or leave 

 them, are natives of this coast, they do not come from 

 "foreign parts " nor do they leave for such places. They 

 are our all own, and travel periodically northwards, mainly 

 in connection with their reproduction. 



