Technical Bulletin No. 0003: Factors Affecting the Migration of Fish

A review of the literature reveals that the behavior of migratory fish is influenced by several natural phenomena as well as by man-made influences. The object of fish migration is to arrive at a point in a stream suitable for spawning. Migratory fish generally go about attaining this objective with determination since the strongest biological impulse - that of reproduction – is  involved. This urge eclipses hunger in many species. The natural factors influencing migration are as follows; 1. Volume and Velocity of River Discharge. 2. Turbidity of Water. 3. Physical Barriers. 4. Water Temperature and General Weather Conditions. Those for which man are responsible are: 1. Over-fishing. 2.  Stream Pollution. The relative importance of each of these factors was determined since in the river under study all these influences were present.