the detriment of reproduction. What is needed is a successful 

 method of scanning the water without using extensive underwater 

 structures. 



Our scientists have solved the physical problem of passing adult 

 salmon upriver and young salmon down over low dams, and we 

 think high dams can be conquered in a reasonable length of time. A 

 difficult problem that still has to be solved, however, is to find a 

 sure method to attract adult salmon to the entrance of a fishway. 

 There also remains the problem of guiding fish without undue delay 

 through the unfamiliar environment of the reservoir at a reasonable 

 cost. One method might be to create a turbulent path from end to 

 end, or in some other way to simulate the river that they seek. 

 Some success has been achieved with electrical guiding, but more 

 needs to be done, and other methods perhaps should be tried. 



Another important series of problems exists in PLANKTON 

 RESEARCH. These microscopic plants and animals are the basis 

 of all organic production in the sea. Many fishes spend a part 

 of their lives in this drifting world as eggs and tiny larvae. 

 Plankton is also important food for many fishes. In collecting 

 plankton for study and for estimation of abundance, fine-meshed 

 nets usually are employed, but this is a cumibersome and awk- 

 ward method. Many plankton organisms are so tiny that they can 

 escape through finest mesh; others are sufficiently active so that 

 they can escape the net mouth. Thus, nets of any kind give a 

 biased sample at best. Somiething close to a complete sample can be 

 obtained by bringing aboard a quantity of water by pump, or in a 

 container, and separating the living organisms from the water by 

 centrifuge. But plankton is relatively sparse, and large amounts 

 of water must be handled to obtain a sufficient sample. 



Although plankton samples taken with nets are biased, they 

 still give useful information. One of the most successful ways 

 of studying the distribution of plankton over large areas of ocean 

 has been with the Hardy Continuous Plankton Recorder, which pre- 

 serves a sample on a moving belt of fine-meshed silk. Later ex- 

 amination of this strip under a microscope permits reconstruction 

 of the numbers and kinds of organisms along the path of the ship. 

 This method is successful only in waters where plankton is rela- 

 tively abundant, for the amount of water strained per unit area of 

 sea surface is small. Moreover, the net fishes at only one level, 

 and we know that the vertical distribution of plankton varies in time 



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