what is the meaning of sonar pit?

Answer 1

It is a tag that gets picked up by sonar. (You don't need batteries to run them.)

Identifying Lobsters using Passive Integrated Transponder (PIT) Tags
By Diane Cowan

Scientists at The Lobster Conservancy, a non-profit corporation dedicated to sustaining a thriving lobster fishery in the Gulf of Maine[1] (TLC, www.lobsters.org), have modified three tagging methods to mark individual lobsters. They use Passive Integrated Transponder (PIT) tags to investigate growth in adults; Coded Wire Tags (CWT) to study growth and movements of juveniles; and Sonar Tags to track the movements of egg-bearing females. This, the first in a series of three articles, describes the TLC’s use of PIT tags.



The two major challenges encountered when attempting to tag lobsters are molting, and the problem of adhesion of tags in the marine environment.