The feeding index based on a predator’s preference for prey is expressed as:

Correct option is C

Correct Answer: (c) Ivlev’s electivity index
Explanation:
→ Ivlev’s electivity index measures the degree of preference a predator shows for particular prey types relative to their availability in the environment.
→ Value ranges from –1 (complete avoidance) to +1 (strong preference).
→ Widely used in feeding ecology studies.
Information Booster:
→ Helps identify key prey species for fisheries management.
→ Useful in understanding predator–prey interactions.
→ Important tool in aquaculture diet formulation.
Additional Information (Other Options):
(a) Index of preponderance – combines frequency & volume.
(b) Ponderal index – deals with weight proportions.
(d) Condition factor – measures health/robustness.