SPENTFISH. 71 



sea after spawning, return into fresh water 

 bright and silvery before others get a taste of 

 salt water, the necessary time they remain in the 

 sea before returning is a problem as yet unsolved. 

 It has been proved that some fish return to fresh 

 water within four months from the time they 

 were marked, and therefore we may suppose 

 that spent fish can acquire the condition of clean 

 fish within that time. If all the spent fish re- 

 appeared in fresh water as soon as they had re- 

 covered their condition, the run of clean fish into 

 our rivers would last only for four months or 

 thereabouts ; but we all know that at the very 

 time the spent fish go seawards, clean fish pass 

 them to take up their quarters in fresh water, 

 which must have spawned during a previous year. 

 For example, clean fish that are running up in 

 February and March, must at the latest have 

 gone to sea as spent fish in May of the previous 

 year, and calculating that they would acquire the 

 condition of clean fish in about four months, they 



