Photo-identification and habitat use of Atlantic humpback dolphins Sousa teuszii around the Río Nuñez Estuary in Guinea, West Africa

Abstract

Ecological data for the Atlantic humpback dolphin Sousa teuszii are scant. Six on-effort Sousa teuszii sightings were recorded during 817.6 km of boat-based effort in the Río Nuñez region of Guinea during October and November 2013. Two incidental sightings were also reported. Groups comprised 1–25 animals. Photo-identification produced a minimum population estimate of 47 animals. Most sightings (n = 5) were located close (<1 km) to shore along a 5.7 km stretch of coast on the west side of Île de Taïdi, primarily over shallow, sand–mud habitat. Two very distinctive individuals were present in all four Taïdi photo-identification encounters, suggesting high site fidelity and stable associations. Two sightings occurred in the outer Río Nuñez Estuary much farther from the coast (5–12 km) but in relatively shallow water (≤15 m) over sand–mud sediment. Focal follows (n = 5: 0.2–3.8 h duration) produced 9.02 h of behavioural data. Travel (51%), foraging (39%) and feeding (9.2%) dominated, with Taïdi dolphins spending more time foraging and feeding than the outer estuary groups. Three individuals had linear-severed dorsal fins consistent with injuries from fishing line. Some management implications of variation in habitat, site fidelity and movements of Sousa teuszii groups are discussed.

Keywords: behaviour, human impacts, nearshore, population size, site fidelity