Observation of whale shark, Rhincodon typus (Smith, 1828) off Goa, northern Arabian sea

Abstract

The present observation illustrates about the incidental sighting of the whale shark, <em>Rhincodon typus</em> (Smith, 1828) on 16^th January 2018 in the coastal waters of Goa (15°47.086΄ N; 073°05.120΄ E) at a depth zone of about 74 m onboard the research vessel FORV Sagar Sampada during the cruise No. 370. The sightings were confirmed by visuals in real-time and photographs. This individual was characterized by pale yellow or white rounded to elongated spots on a dark grey background. Satellite-derived oceanographic parameters such as Sea Surface Temperature (SST), Sea Surface Salinity (SSS) and Chlorophyll ‘<em>a</em>’, (Chl-<em>a</em>) for the location where the animal was recorded, have shown different patterns from rest of the area and thus provided an insight into the preferred environmental conditions and foraging behavior of this species. The sighting location, off the Goa coast, was characterized by high Chlorophyll-<em>a</em> (1.2-1.8 mg/m^-3), dissolved oxygen (4 ml/l) in the 50 m depth and high concentrations of phytoplankton dominated by green <em>Noctiluca scintillans</em>. Present sighting merit the record of <em>R. typus</em> with the probability of foraging on the high abundance of phytoplankton in the coastal waters of the Arabian Sea. Therefore, the animal appeared to move along the gradient zones for its seasonal aggregations.