592 HOW DOES MAN CONSERVE HIS RESOURCES? 



ideal conditions until they are shipped, sometimes thousands of 

 miles, to their new homes. 



It has been found that if trout are kept in breeding ponds until 

 they are 3 or 4 inches long that their chance of survival is very 

 much better than if very young fish are planted. 



Practical Exercise 7. What laws does your state have for the protection of 

 fish ? Is there a chapter of the Isaak Walton League in your community ? If 

 so, what is this organization doing for the conservation of wild life? Is there 

 any work in conservation being done by other organizations ? 



Practical Exercise 8. Why is stream pollution an important factor in con- 

 servation ? Why do fish migrations play an important part in their conserva- 

 tion or destruction ? 



The conservation of shellfish. The problem of conserving 

 shellfish is concerned in part with the extermination of their 

 natural enemies. If we could kill off all starfish and boring 

 mollusks, the oysters and clams would be much more plentiful. 

 But over-fishing is the most important danger. The oysters of 

 Chesapeake Bay were thought inexhaustible until they were 

 almost fished out. Then the state of Maryland discovered that 

 oyster culture was necessary if this great asset was to be 

 preserved. 



Oysters pass the first few days of their existence as free-swimming 

 larvae. Then they settle on the bottom, and if they do not find 

 some solid object which raises them above the mud of the bottom, 

 they will die. Oysters are now protected by cultivation. On the 

 bottom, in certain areas of water, are placed bunches of twigs, 

 broken rocks, or old oyster shells to which the young oysters 

 attach themselves. The depth of the water in which oysters grow 

 varies. It may be ten feet or it may be as much as eighty feet. 

 After they have grown to approximately the size of a quarter or 

 half dollar these " seed " oysters are spread over the bottom of 

 the oyster beds. They are usually ready for the market in three 

 or four years. 



Clams and scallops have been nearly depleted in some areas, and 

 it has become necessary to conserve the supply by having closed 

 seasons and by transplanting the " soft clam " of the east to the 

 Pacific Coast, where it thrives. 



About 1894 it was discovered that the shell of the fresh- water 



