Resting and roosting requirements of the near - threatened spot-billed pelican Pelecanus philippensis Gmelin 1789, in Pulicat Lake, Andhra Pradesh, India
The growing need for fish extraction for livelihood is resulting in the by-catch mortality and injury of the aquatic mammals through fishing gear entanglement. It is one of the most significant issue of conservation of Ganges dolphin. The inability of Ganges dolphins to identify the presence of monofilament gill nets results in entanglement and death due to suffocation. In this study, we have studied the interactions of Ganges dolphin with fishing gear (gill net) by attaching Pingers. It was assumed that the proximity zone around the fishing gaer is the risk zone for the Ganges dolphin. A visual observation was made in an experimental setup of: Control net (without reflectors or Pingers), net with reflectors (used locally to attract fish), Pinger with frequency and source level lower than what is used by Ganges dolphins (10 KHz and 132 decibel) and Pingers with Ganges dolphin frequency (70 KHz and 145 decibel). We have estimated that significant difference in mean sighting distance of Ganges dolphins from different experimental set ups. Nearest proximity in Control net was <1m with a sighting rate of 1.41 sightings/hr whereas for Dolphin Pingers it was 5 to 10m with a sighting rate of 0.12 sightings/hr. Dolphins seem to avoid fishing gear with active Pingers and hence the experiment should be carried forward to the next level of estimating if there is any attraction or change in catch per unit effort (CPUE) of fish or habituation of Dolphin. Popularising the efficiency of Pingers among stakeholders and introducing it to the fisher communities can be the next significant step to conserve the species.
Ganges dolphin, echolocation, entanglement, Pingers, Reflectors.
( 2020), Resting and roosting requirements of the near - threatened spot-billed pelican Pelecanus philippensis Gmelin 1789, in Pulicat Lake, Andhra Pradesh, India. Scientific Transactions in Environment and Technovation, 13(4): 145-155
Correspondence: Vaithianathan Kannan