272 Spawning. Chapt. xxi. 



known, we are apt to lose sight of in connection with sea-fisheries, 

 I think we are in a fair way to discover the causes which govern 

 the migrations of certain sea-fish. We are accustomed to look 

 upon the sea as one vast pond of still water, differing only from 

 other ponds in being salt, in having tides, and in being more 

 moved by winds than other ponds or lakes, by reason of its having 

 a larger surface exposed to their influence. We are not ignorant, 

 by the way, that there are currents also, and that there is one 

 mighty one called the Gulf-stream, and we can understand 

 mariners having to know something about them ; but that they 

 should affect fisheries is not, I think, commonly considered. So 

 many and various, however, are the sea currents, that it would be 

 a much more accurate starting point for thought, if we looked upon 

 the ocean as an agglomeration of vast salt-water rivers of varying 

 depths and velocity, of greatly varying temperatures, with banks 

 and courses as well defined as fresh-water rivers, with counter 

 currents or back sets along those watery banks, some of them 

 flowing on the surface, some at the bottom. From their widely 

 varying circumstances, these vast sea rivers naturally support 

 different sorts of insect life, or, in other words, different sorts of 

 food for fishes. These currents or sea rivers, their strength, their 

 length, their depth, their breadth, their course, their tempera- 

 ture, their saltness, have been laboriously ascertained; the mariner 

 has them all well laid down in charts, and studies them care- 

 fully. The sea pisciculturist should do likewise. I hold that he 

 can expect to make little progress in his science till he studies 

 it from this point of view. What should we know about the 

 salmon and its propagation if we had always watched it in one 

 particular pool, and not taken into consideration the flow of the 

 river, and its varying circumstances in different parts of its 

 course? The same remark applies equally to the Mahseer, which 

 is migratory only in fresh water. Similarly, how can we expect 

 to understand the migrations of herrings, mackerel, pilchard, etc., 

 unless we study them with special reference to their rivers, the 

 salt-water rivers of the sea. 



Having then floating spawn and flowing rivers in the sea, it is 

 easy to conceive that the former is earned great distances by the 

 latter, and frequently taken out of our ken. But if we identified 

 the sea rivers in which particular spawn was shed, we might, by 



