|Document Type:||Journal Article|
|Title:||Factors influencing the orientation of migrating fishes|
|Author:||Gerald B. Collins|
The influence of certain physical and chemical characteristics of water upon the orientation of one type of anadromous fish was examined by presenting the migrating fish with a choice between two channels with different water characteristics. The orientative influence of the water properties was measured by the number of fish selecting each channel. The reactions of more than 8,000 fish of the genus Pomolobus--alewife, P. pseudoharengus (Wilson), and glut herring, P. aestivalis (Mitchill)--were tested as the fish migrated upstream through the Herring River at Bournedale, Mass., toward their spawning area.
Presented with a choice of waters having different temperatures, 77 percent of the fish entered the channel with the warmer water when the temperature difference continuously exceeded 0.5°C. The response of the fish to temperature differences near the threshold difference decreased as the temperature level of the water increased. Presented with a choice of waters having different amounts of free CO2, 72 percent of the fish entered the channel with the water having the lower CO2 content when the free CO2 difference exceeded 0.3 ppm. The sex of the fish appeared to have no influence on its response to differences in CO2 or temperature. Experiments indicated that velocity and turbulence can influence orientation. The relative or orientative influence of CO2 and temperature, when the two factors were in opposition, was shown to depend on their relative differences of magnitude.
Behavior of the fish during the experiments indicated that the orientation was accomplished by a method of "trial" involving both movement of the fish and a comparison of intensities of stimulations which were successive in time.