70 MARKETABLE BRITISH MARINE FISHES CHAP. 



enormous destruction of eggs and young, either by the action of 

 enemies or by surrounding conditions or from scarcity of the 

 natural food. Thus in the case of the herring, which feeds both 

 in the young and the adult state chiefly on the swarming minute 

 creatures in the sea, an abundance of food is usually everywhere 

 available, while only those young turbot or ling can survive which 

 happen to find smaller fishes than themselves to feed upon, and 

 their prey is not to be found in every part of the sea, so that a 

 large proportion are starved to death. On the other hand if the 

 number of the young of the predaceous fishes were smaller, then 

 the chances of some of them finding prey would be fewer, and 

 consequently the abundance of the species would diminish. 

 Careful consideration shows that the production of large numbers 

 of eggs and young leads to the same result as the protection and 

 nourishment by the parents of a smaller number. There are 

 plenty of instances in which on both systems the abundance of 

 the adults neither increases nor diminishes greatly ; for example, 

 the spiny dog-fish which produces only six or seven young at a birth 

 is as abundant as ling or turbot. The one system may be com- 

 pared to the starting of a vast number of small boats of which 

 only a small percentage escape the perils of the sea and reach 

 port, the other to the equipment of a few large steamers which 

 are nearly certain to accomplish their voyage safely and 

 punctually. 



The eggs of different fishes are of different sizes. Those of 

 the trout and salmon are much larger than those of the most 

 familiar sea-fishes, and partly in consequence of this, but chiefly 

 because they are deposited in rivers and streams, they were well 

 known to sportsmen and naturalists long before the buoyant 

 eggs of sea-fishes were discovered. The egg of the salmon is 

 about $ inch in diameter. One of the largest among the eggs 

 of sea-fishes, namely that of the plaice, is only T V inch across, 

 and the majority are little more than Tr 1 .- inch. 



In the spawning season a certain proportion of the female 

 fish captured are ripe, and when they are handled or gently 

 squeezed the spawn escapes freely from them. The spawn if 

 taken on the hand forms a transparent mass which is easily seen 

 to be composed of a large number of round grains, similar in 

 appearance to glass beads. When the roc is opened before the 

 spawning season the eggs are seen to be minute white grains, 



