ABUNDANCE, RESIDENCY PATTERNS AND HOME-RANGE OF BOTTLENOSE DOLPHINS (Tursiops aduncus) INHABITING MALINDI-WATAMU MARINE PROTECTED AREA, KENYA.

Abstract

The Indo-Pacific bottlenose dolphin Tursiops aduncus is globally distributed in the Indo-West pacific region. Along the Kenyan coast, the species has been recorded in the Malindi-Watamu Marine Protected Area (MPA) and the Lamu archipelago in the north coast, while in the south coast this species has been sighted in Kisite Mpunguti MPA. However, data and information on the abundance, residence patterns and home-range of this important species has clearly been lacking. The present study assessed the abundance, residence patterns, and home range of T. aduncus in Malindi-Watamu MPA. Vessel-based surveys were conducted to collect images of the dorsal fin of the species for photo-identification data, as well as the coordinates of species sightings. The data was used to estimate species abundance using the virtual mark-recapture approach using the closed population two-sample Chapman-modified Petersen (CMP) method. Residency patterns were analysed using the individual re-sighting patterns while the home-range area was calculated in Arc GIS® (ESRI, Ver. 10.1) using the home-range add-in tool Kernel Density Estimator (KDE), and Minimum Convex Polygon (MCP) methods. Results showed an abundance estimate of 91 individuals (CI= 94-88, =0.05) with residence level of 94.3%. Results of the MCP (100%) showed a home-range of 40km2 with a core-use area of 13.1km2 (50% utilization distribution). The results reveal a small resident population of T. aduncus inhabiting Malindi-Watamu MPA, utilizing only a small proportion of the entire study area.The area utilized lies on the nearshore waters that are home to various anthropogenic activities which expose the species to numerous threats. Therefore, continuous monitoring of the anthropogenic activities within the identified dolphins home-range area is key to enhance conservation of this important marine species as well as avoid any incidences of bycatch from fishing related activities.