216 THE FISHER Y LA WS. 



to the sea, and the rest of their existence is spent in passing 

 every year to and fro between the sea and the upper fresh 

 streams. At all times of the year the fish are either 

 passing up or passing down the river. It is true the 

 greater numbers pass up in the summer months, but there 

 are generally some passing up or going down at other times 

 also. They are not bred at all, and cannot be bred, in 

 the tidal parts of rivers, though there they are caught 

 plentifully. 



" To enable the fish to inhabit a river, that is to say, to be 

 found not only in the fresh but the tidal parts of rivers, it is 

 thus essential that the parent fish should have an open 

 passage from the sea to the source, or at least to the upper 

 shallows of the river. The old fish require to go up the river 

 to breed, and the young fish require to come down the river 

 to grow; and after they are grown they still require to 

 alternate between the fresh waters and the sea. If at any 

 point between the tidal limit and the upper breeding- 

 grounds a barrier is made which obstructs this passage, 

 the stock of fish is necessarily diminished and gradually 

 annihilated. It thus follows that at the place where the 

 salt water meets the fresh, the whole stock of fish of the 

 river and estuary must pass at least once in their lives, 

 either coming or going. This is so in a state of nature, 

 irrespective of all laws. If all the fish must pass a par- 

 ticular spot, it equally follows that they may all with 

 certainty be caught at that spot if certain obvious means 

 for that end are used. 



" A weir is, in general terms, a kind of fixed structure 

 stretching across a river, the sole object of which is to make 

 a barrier to the progress of the fish, and so to compel 

 them into certain places or apertures, in which traps, 

 boxes, cruives, or coops are set, which confine and catch 



