PROPAGATION AND DISTRIBUTION OF FOOD FISHES, 1931 631 



OUTPUT 



The magnitude of fish-cultural operations depends largely upon the 

 availability of brood stock. Other factors are temperature and water 

 conditions, the amount of equipment used, the size of the operating 

 force, and the progress of science in the development of methods 

 and apparatus. Where a brood stock is held at a hatchery, as with 

 trout and bass, a fairly consistent production may be realized from 

 year to year. Where collections of eggs are made from traps and 

 racks intercepting spawning migrants, as with the salmon, the pro- 

 duction may be fairly uniform, though it depends largely on the 

 escapement from commercial fisheries. The collection of eggs from 

 purely lake forms, such as whitefish, lake trout, and cisco, and from 

 such salt water fishes as the cod, haddock, pollock, flounder, and 

 mackerel, depends upon the abundance of fish and upon weather 

 conditions in the vicinity of the spawning areas, as these conditions 

 regulate largely the use of fishing gear. Because by far the greater 

 proportion of the numerical output of the division consists of eggs 

 and fish of the third group, the total production is largely influenced 

 by conditions beyond the bureau's control. 



Adverse weather conditions do not often cause the suspension of 

 all activities in the collection of eggs of a species of fish. In 1931, 

 however, they were largely responsible for a decrease of 1,135,999,000 

 in the distribution of cod and pollock as compared with the output of 

 these two species during the preceding year. This decrease was more 

 than t-\vice the difference between the total distribution in 1931 and 

 the all-time record of 1930. 



The total distribution of the past year shows a 6 per cent decrease 

 when compared with the total for 1930. The output of the game 

 fishes, included in the total, decreased 3)2 per cent, due largely to a 

 considerable decline in the number of sunfish handled in the rescue 

 work; and the output of the marine species decreased 10 per cent, 

 owing to adverse weather conditions encountered during the collection 

 of cod and pollock eggs. On the other hand, the distribution of 

 anadromous fishes increased 98 per cent, owing to increased collections 

 of eggs of the shad, glut herring, and Pacific salmon; and the output 

 of commercial fishes of interior waters was increased 16 per cent, 

 due to the unusually large numbers of carp and buffalofish handled 

 and to larger numbers of eggs of the cisco, pike perch, and whitefish 

 obtained in the Great Lakes operations. 



Of the total distributions, 3.6 per cent were anadromous species 

 and 2.8 per cent game fishes. The marine species, which are planted 

 in the egg and fry stages, constituted 81.8 per cent; 11.4 per cent 

 consisted of the commercial species of interior w^aters, while the 

 miscellaneous fishes, mostly species of minor importance handled in 

 the rescue operations, amounted to two-fifths of 1 per cent. The 

 fingerlings distributed, numbering 320,040,700, showed a 28 per cent 

 increase over the corresponding figures for 1930. 



