Salmonidae of Norway. 63 



are those of the Solway rivers about the end of October, 

 and from my own experience I should say that the 

 average date of spawning in Norwegian rivers is from a 

 month to six weeks earlier than the average of Great 

 Britain. 



The angling season closes generally upon September 

 15, and the spawning operations commence within a few 

 weeks' time, so the fish can reckon upon a full month at 

 least during which the ova and milt can be deposited 

 ere the surface of those rivers which freeze over will become 

 ice-covered. 



Some rivers in the south of Norway, and many further 

 north which flow out of lakes, are free of ice throughout 

 winter, but upon others the water running over thin 

 shallows is often frozen in patches right through, and 

 some situations which have been selected as redds may 

 be left high and dry as the river falls in, and the per- 

 centage of ova lost from these causes is far greater than 

 in a less rigorous climate, while the voracious bull-trout 

 ever exacts toll. There is also a considerable formation 

 of ground-ice in many rivers which is undesirable in a 

 hatchery, and the open ones run extremely dry. - 



In consequence of the low temperature of these rivers, 

 the regulation period of ninety days required for hatching 

 the ova is probably often exceeded, except where the rivers 

 are fed by warm springs. 



