Distribution & Abundance

How do we study the abundance of finless porpoise?

Finless porpoises seen in helicopter survey Finless porpoises seen in vessel survey

Since finless porpoise has no dorsal fin and it is grey in colour, the sighting efficiency during the survey is lower for it than for the Chinese White Dolphin. After taking all the biases in the abundance estimates into account and calculating the correction factor from acoustic data, line transect survey is still a very reliable method for studying the abundance of finless porpoise.