224 The Life Story of the F.ish 



storm of gale intensity swept out across the sea and in its 

 wake dead tilefish were scattered at the surface over an area 

 170 miles long by twenty-five miles wide. It was estimated 

 by careful observers that they numbered no less than one 

 billion, four hundred million. Scientists believed that it was 

 not the storm which killed the fish, but a "straying" move- 

 ment of the Gulf Stream in which it shifted its course to the 

 eastward, and allowed the bottom where the tilefish had lived 

 in the warmth of its current to be invaded by chill waters. 

 This "cold wave" was lethal to the tilefish. Although com- 

 plete and total extinction was believed unlikely, no tilefish 

 were seen for years. Then gradually the Gulf Stream moved 

 back to its former course and they began to be found again. 

 By 1 9 1 5 they were considered to be as abundant as ever, and 

 in 1937, one of the last good pre-war years, three million 

 pounds were caught valued at one hundred thousand dollars. 



Other examples of "natural" destruction of a fish which 

 man looked upon as his property are not unknown, the most 

 recent being the Great Lakes smelt, which has almost dis- 

 appeared due to what is believed to be a virus disease. 

 However, in many cases not nature, but man, is the villain. 

 Over-exploitation by man, "over fishing," is believed to be 

 at least one of the factors in the extreme fluctuations of 

 the populations of such species as the menhaden, the halibut, 

 and the sardine. Whoever or whatever is to blame, severe 

 reduction in numbers of any important fish means that a 

 certain amount of the nourishing elements of the sea which 

 it formerly turned into food for human beings is no longer 

 being utilized, or is being utilized by forms which we can- 

 not catch or do not find edible. 



To study such problems and the methods whereby fish 

 populations can be maintained in a state of utility to the 

 human race is one of the fields of endeavor of a compara- 

 tively young science called fisheries biology. The "maximum 



