VPP 322: Aquatic Animal Diseases, Health Care and Management (1+1)

INDICATORS OF FLUCTUATION POPULATIONS

Various criteria such as changes in age composition in the catches, shifts in areas of fishing, changes in catches etc. The following act as good indicators:

• Sustained decrease in age and size of the individuals indicate that the population is regressing.
• Sustained stunting of the individuals is a sign of expanding population.
• Sustained changes in the species composition of the catches is regarded as indication of fluctuating populations. The relative numbers of the different species in the catches by the change in proportion indicate which population is regressing.
• Sustained decline in the catch per unit effort is a reliable indication of regressing population
• The necessity to shift the fishing grounds in view of the falling numbers in catches is an indicator of the declining abundance in the population.
• For schooling pelagic species contraction of the area in which the buoyant eggs and larvae are collected i.e., shrinkage of the spawning areas is an indication of the declining adult abundance.