Diversity and distribution of cetaceans off Mirissa in the southern coast of Sri Lanka II. Relationship with sea surface temperature, salinity and water density
E.P.D.N. Thilakarathne , P.B.T. Pradeep Kumara, R.M.G.N. Thilakarathna
Lack of proper scientific data on the behaviour of cetaceans is a major constraint in managing whale and dolphin watching activities without affecting cetacean populations in marine waters off Mirissa, where it has become a high income generating tourist activity. Therefore a shipboard surveys were conducted using a special whale watching boat for 43 days from January to April 2012 in an area of about 940 km2 in Mirissa, southern coast of Sri Lanka to identify the environmental parameters that affect the abundance of cetaceans.
During this study, 8 cetacean species including 6 toothed whale species (Physeter macrocephalus, Globicephala melas, Peponocephala electra, Orcinus orca, Tursiops truncates and Stenella longirostris) and two baleen whale species (Balaenoptera musculus and Balaenoptera physalus) were identified.
Results of the study revealed that relationship between species occurrence and the measured water quality parameters (temperature, salinity and density) was significant (p < 0.05). From the identified species blue whale and melon headed whale can tolerate high density (1.02±0.0) and salinity (blue whale-36.35±0.75; melon headed-35.55±0.51) range while blue whale (28.53±0.89), sperm whale (28.47±0.93) and spinner whale (28.66±1.04) can tolerate wide temperature range.
Keywords: marine mammals, southern Sri Lanka, temperature, salinity, density, whale watching