Article

NEW RESULTS ON A BOTTLENOSE DOLPHIN (TURSIOPS TRUNCATUS) COMMUNITY AT RANGIROA ISLAND (FRENCH POLYNESIA)

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INTRODUCTION By studying and comparing dolphin populations living in different habitats, we will be able to isolate the environmental factors shaping the range of behaviors this polymorphic species has developed. At Rangiroa Island (Tuamutu – French Polynesia), a population of bottlenose dolphins is described by the locals to be visiting the Tiputa pass almost every day, all year-round. A first study was conducted during four weeks from mid October to mid November 2001 in order to better understand the residency pattern, population size, habitat use, and social structure of this community. MATERIALS AND METHODS Study area The atoll of Rangiroa has two passes. Out-flowing and in-flowing currents strongly influence the sea state in passes by making the waves respectively appear and disappear for periods of nearly 6 hours.. One of the passes, the Tiputa pass, covers an area of roughly 0.2km 2 . Its depth ranges from 15 to 60 m. For the purpose of this study, the pass was divided into two zones (zone I and zone II) based on their characteristics. Zone I is from 25 to 60 m deep, coral covers the bottom, and the waves, if present, are stronger than in zone II. This second zone is less deep, and its bottom is sandy. A third zone, called "zone III", is the edge of the pass at the ocean side. Deeper than the two other zones, no current is observed. The waves, if present, are wind-induced and not a result of in and out-going currents. Shore-based surveys Day long surveys Five complete days of 11 hours and 40 minutes each were spent on the pass shore to record every 15 minutes dolphin absence/presence, their relative activity, the direction of the current, the force of the waves, the meteorological parameters and the absence/presence of boats. 4pm to 5pm surveys During 11 days, a one hour period from 4pm to 5pm was spent on the pass shore to record every 5 minutes dolphin absence/presence, their behavioral sequences, the direction of the current, the force of the waves, the meteorological parameters, and the absence/presence of boats.

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Whale-watching activities provide important socio-economic benefits for local communities and constitute powerful platforms incentive for marine mammals protection or more broadly marine environments. However, these activities can cause adverse effects on targeted populations, with considerable downside associated risks of injuries and fatality for whale-watchers during in-water interactions. France with its overseas territories has the second largest exclusive economic zone, in which more than half of existing cetacean species are encountered. In these territories, recreational and commercial whale-watching, including swim-with cetacean activities, have recently developed. Yet, few studies focused on these activities and their associated impacts across French territories, leading to an unclear assessment of the situation. To address this issue, we reviewed cetaceans occurrence within the French EEZ, whale-watching industry, targeted species, local management of marine mammal-based tourism activities and regulations in France Mainland and some overseas territories (Reunion Island, Mayotte and French Polynesia). Forty eight species are encountered in the French EEZ, and 15 are targeted by whale-watching activities. A total of 185 operators, including 34% offering swim-with cetaceans tours, offered trips in France and overseas in 2019. While several more or less restrictive regulations exist locally, our results indicate that French’s national legal framework for marine mammals protection remains inadequate and insufficient to cope with the recent development of this activity. As conservation biologists, managers and stakeholders from these French territories, we cooperated to provide general guidelines for a sustainable development of whale-watching at national scale. We urge (1) to legally acknowledge and regulate whale-watching commercial activities; (2) to create a national legal framework regarding whale-watching and swim-with marine mammals practices, while accounting for local distinctiveness and disparities across regions; (3) to conduct more research to evaluate local short and long-term impacts on targeted marine mammals populations as well as the socio-economic benefits ; 4) to reinforce synergetic relations between the different stakeholders.
Article
Small boat surveys were organised off the Society Islands (French Polynesia), with 2–3 active ob-servers on board. Sampling was done with Beaufort 4 sea state or less, cruising at 10 km/h mostly on engine power, from March 1996 to May 1999. The area of study extends over 400 km from Tahiti at the southeast, to Maupiti at the northwest, and was divided into 4 sectors: the lagoon area, the inshore stratum (<10 km from the barrier reef) of the Windward and Leeward Islands, and the offshore stratum. For a seasonal analysis the survey data were divided into a September–November period and a March–May period. A sighting rate and a relative abundance index (individual/km of effort) was estimated for delphinids, for each stratum and each period. Mean and variance estimates were computed with Distance 2.2 software. Some 134 sightings were obtained during a total effective effort of 6482 km, including 5222 km with sea state less than Beaufort 3. The humpback whale (Megaptera novaeangliae) was observed 35 times, the sperm whale (Physeter macrocephalus) and the dwarf sperm whale (Kogia simus) once, two species of beaked whale (Mesoplodon densirostris and Ziphius cavirostris) were observed 8 times, and seven species of delphinid were sighted 91 times, in order of decreasing frequency: Stenella longirostris, Steno bredanensis, Globicephala macrorhynchus, Peponocephala electra, Lagenodelphis hosei, Tursiops truncatus and Grampus griseus. The inshore strata had relative abundance indices of 0.258 delphinid/km (Windward Islands) and 0.219 delphinid/km (Leeward Islands), while only 0.021 delphinid/km were found in the offshore stratum. Cetaceans in general favour the inshore waters. An index of 0.123 delphinid/km was found during the March–May period, compared to 0.345 during the September–November period. Factors influencing the distribution of cetaceans are dis-cussed and comparisons given with results obtained in other archipelagos and the eastern tropical Pacific.
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