250 SALMON FISHING 



the salmon were first driven away by the gradual 

 canalisation of the river following the Thames 

 Navigation Acts of 1788, 1789, and 1812. These 

 enactments led to the continual erection of weirs and 

 pound locks, which, unprovided with passes, eventu- 

 ally barred the upper reaches to the fish. Mr. Spencer 

 Walpole, an Inspector of Salmon Fisheries in 1869, 

 was clearly of this opinion. In his report for that year 

 he wrote : ' The chief cause which has destroyed our 

 rivers in a salmon sense is the existence of weirs . . . 

 the invention of the pound lock seems to me to 

 explain very clearly the exclusion of salmon from 

 many rivers, including the Thames, which has taken 

 place during the last century.' The pound lock had 

 been substituted for the old open shoot, up which 

 barges were wound with winches ; the shoot had pre- 

 sented no obstacle to the fish. Immediately follow- 

 ing the complete canalisation of the river, in itself 

 sufficient to account for the disappearance of the 

 salmon, came pollution during the middle years of 

 the nineteenth century, which effectually completed 

 the work of destruction begun by the locks and 

 weirs. 



"The efforts of the London County Counoil and 

 the Thames Conservancy have resulted in a great 

 improvement in the state of the river. Those of 

 the Thames Salmon Association have been directed 

 towards showing that this improvement as regards 

 the lower waters has proceeded far enough to 

 allow of the passage up and down of migratory fish. 

 The canalisation difficulty is avoided by rearing the 



