Abstract
At the request of Dr. H. M. Smith, commissioner of fisheries, certain studies have been made at the Woods Hole Laboratory of the Bureau of Fisheries on the factors influencing fish migration.
In testing reactions to various salts a simple apparatus was devised that seems to eliminate some of the drawbacks of the well-known Shelford apparatus.
It consists (Fig. 1) of two troughs running almost parallel into a large trough which has a movable partition permitting the water to escape at its sides. By a simple arrangement of stopcocks it is possible to change the inflow of any substance from one trough to the other very quickly. It is also possible to secure conditions similar to those in the Shelford apparatus by using an intake at the end of the large trough, thus furnishing three intakes, two of them parallel to each other. In this case the movable partition is not used, the outflow being in the middle of the larger trough.
The apparatus used during the summers of 1919 and 1920 is 20 feet long. The dimensions of the receiving trough are 10 feet in length, 83/4 inches in depth and 8% inches in width. The two tributary troughs are each 10 feet in length, 4 inches in depth and 41/2 inches in width. The tributary troughs have been elevated varying degrees so as to cause the water to flow downwards into the receiving pool. In addition to the use of barrels as containers for the solutions used, in some experiments the inflow has been directly from the circulation pipes of the laboratory.
The fish used in the experiments included Fundulus heteroclitus, Funddulus mnjalis, and Clupea harengus. They were tested with sea water of various dilution, and concentrations, m/10 solutions of NaC1, KCl, MgCl2, CaCI2, MgSO4, various combinations of those salts and also with sewage polluted water.
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