"You don't want to forget," the fish culturist replied, "that Nature is very exact. Everything has to balance. The whitefish born are ten times as many as those that mature, but the number that matures is just precisely enough to keep the supply going."
"I see that, all right," the boy answered.
"Well, then, if you disturb this balance by extensive fishing, isn't it easy to see that you've got to make up for it somewhere? We don't have to worry over keeping up the supply of catfish, for example, because Nature is being left alone, and she has worked the problem out. But if suddenly a big catfish market developed—as it easily might, because, in spite of popular opinion, catfish is good eating—and if thousands of them were caught, it would be necessary to find some way to help Nature in keeping up the supply.
"Now, the whitefish," he continued, "isn't like the salmon, which spawns carefully. The lake fish does that in a sort of hit-or-miss manner, with the result that only a small percentage of the eggs get a fair start. It is not difficult for us to put hundreds of millions of young fish into the lakes every year, and the proportion of these that survive will not merely keep the supply constant, but will even increase it."
"Then that will disturb the balance in another way?"
"Yes," was the reply, "but it will be at the expense of other species which are of no use to man. Nature is like the proverbial Irishman, she can't be drove, but she's mighty easy to lead. When
you return to the university, get hold of some books on the means by which all the various kinds of living creatures in the world are kept on an even balance, how they all get their food, and how every tiny speck fits into the whole world scheme. You'll find that sort of reading has more grip to it than any novel—except, perhaps, those of a few of the really great writers, of whom there are some in every age."
