Authored by De Montgolfier B
The Caribbean coast of Martinique has a great wealth of marine mammals, with almost twenty species observed, including the short-finned pilot whale Globicephala Macrorhynchus. Little is known about this specie in Martinique. Boat surveys between “le rocher du Diamant” and “l’îlet la Perle” allow gathering data and pictures. Statistical analysis, SIG and photo identification provide first information on the pilot-whale population. Results indicate there is a rather small but healthy population of G. macrorhynchus in Martinique. It is composed of both resident and migrant groups and no seasonality was observed. Correlation between the percentage of teenagers and the number of boats might imply an effect of whale-watching on individuals.
Martinique Island, located in the Lesser Antilles, is surrounded to the east by the Atlantic Ocean and to the west by the Caribbean Sea. It is located in the middle of Agoa sanctuary, an MPA established in October 2010 by the French Government, that includes all Exclusive Economic Zones (EEZs) of French Antilles (143 256 km² [1]. This sanctuary, currently managed by the “Agence des aires marines protégées”, implements measures for the protection of cetaceans. Over the last few years, coastal regions of Martinique were exposed to demographic growth and tourism [2,3]. Whalewatching is booming on the Caribbean coast of Martinique [4]. Tourism can bring some advantages such as revenue for local communities or an improvement of people’s attitude toward the environment [5]. However, anthropogenic activities can impact marine mammals through environmental pollution, prey depletion or physical disturbances, especially in coastal areas [6].
In Martinique, whale-watching has been rapidly increasing over the past decade due to a stronger demand. Almost twenty species of marine mammals have been recorded in the Caribbean Sea [1]. For example, humpbacks whales (Megaptera novaeangliae), Bryde’s whales (Balaenoptera bryde), toothed whales such as sperm whales (Physeter macrocephalus) and various species of dolphins (Stenella attenuata, Lagenodelphis hosei, Tursiops truncatus) are observed. Many of them, like the pantropical spotted dolphin (Lange et al., in prep) or the sperm whale [7], are increasingly studied.
Amongst all cetaceans of the Caribbean French Antilles, the short-finned pilot whale (Globicephala Macrorhynchus, Gray 1846) is one of the less studied. This specie is found in all oceans and primarily distributed in warm waters [8-11], such as the Caribbean coast of Martinique. It is a highly gregarious species, travelling in socially cohesive groups from 10 to 50 individuals, but also encountered in large herds of several hundred [12,13]. Based on several studies, Globicephala sp. appear to live in relatively stable pods and not in fluid groups [10,14]. Pods generally contain individuals with close matrilineal associations [15,16]. Despite this, information on G. macrorhynchus is scarce in literature and its population trend is not well known [17].
Even if its northern Japan population is considered at risk, there is not enough data to evaluate its status elsewhere [11]. Due to this lack of data, the IUCN Red List of Threatened Species categorized the conservation status of this species as “data deficient” (IUCN). Moreover, this specie was principally studied in Japan [6,18,19], in the archipelago of Madeira [17,20], in the east coast of United States [21,22], in Canary Islands [9,23,24] and in Faroe Islands [12,13] but has never been studied in Martinique nor in the Caribbean.
Agoa sanctuary is committed to the sustainable management of cetacean populations of this area [1], because they play an important role in marine ecosystem as top predators and affect the entire food-chain through trophic linkages [19]. Detailed knowledge on marine mammals’ population, especially their movements, their survival rate or the pressures they are subjected to [6,25], are crucial to effectively manage and preserve the entire marine ecosystem. Since G. macrorhynchus is more observed and often exposed, as demonstrated by Bordes [26], this study focuses on this specie for the first time in Martinique. Our aim is to characterize its population to enhance our knowledge about it.
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