Latin American Journal of Aquatic Mammals (LAJAM)
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Study and conservation of the Guiana Dolphin (Sotalia guianensis) (Van Bénéden, 1864) in French Guiana
No full textThe Guiana dolphin (Sotalia guianensis) occurs in warm and shallow waters of the Atlantic Ocean and the Caribbean Sea, from southern Brazil to Honduras, including estuarine and freshwater habitats such as Maracaibo Lake (Venezuela), and the Orinoco River. In 2018, the Guiana dolphin was reclassified from Data Deficient to Near Threatened on the global IUCN Red List. Nevertheless, the conservation status identified by national and regional Red Lists is even more alarming. In French Guiana, for example, the species is classified as Endangered based on strong pressures such as bycatch. In this region, the Guiana dolphin inhabits river mouths and coastal waters where most anthropogenic activities occur. Better knowledge of the biology and ecology is needed in French Guiana to help inform effective conservation actions. Here, we present ongoing studies to map the distribution of Guiana dolphins along the French Guiana coast and estimate abundance in a hotspot area. Aerial survey campaigns were conducted during the dry season in 2013, 2014, 2015, and 2019. Eight flights were conducted and 146 dolphins belonging to 39 groups were observed. Boat-based line-transect surveys were also conducted in the coastal waters of Cayenne in 2017 and 2018. Twenty-one survey trips were conducted covering 999.06 km. Three hundred and eighty-two dolphins belonging to 63 groups were observed. The total abundance in the Cayenne area was estimated at 128 dolphins (% CV = 30.92; CI (95%) = 70-235) with a density of 0.80 ind./km² (% CV = 30.92; CI (95%) = 0.44-1.47). Additionally, a descriptive analysis was performed on stranding data collected in French Guiana between 2014 and 2020 to identify the major cause of death and seasonality in the stranding events. In total, 43 dolphins were found, especially on the beaches of Rémire-Montjoly, Cayenne, and Kourou: bycatch was the major identifiable cause of death. We recommend a local conservation strategy and actions to be undertaken in the short- and medium-term to address different issues: knowledge, threats, conservation, and cooperation
First record of orca predation on franciscana dolphins (Pontoporia blainvillei) in Argentina
No full textInsights on the residency status and inter-island movement patterns of pantropical spotted dolphins Stenella attenuata in the Agoa Sanctuary, Eastern Caribbean
No full textThe pantropical spotted dolphin (PSD, Stenella attenuata) is the most common cetacean species observed within the Agoa Sanctuary, located in the Lesser Antilles, Eastern Caribbean. These dolphins are easily observable and are the main target of whale-watching activities along the leeward coasts of Guadeloupe and Martinique islands. Because PSD is common within the sanctuary it is considered a resident species, however, no research has been carried out to estimate its population status and movement patterns between islands. Previous unpublished work found the sighting of an individual in Martinique and Guadeloupe, suggesting potential exchange of individuals between these islands. To test this hypothesis a photo-ID survey in 2018 and 2019 was conducted, resulting in 54,298 photographs. With no matches of individuals between islands, our findings do not support regular exchange of PSD individuals between Martinique and Guadeloupe. However, given previous re-sighting data, it is possible that movement of individuals between islands exists but at lower frequencies than expected, which can only be detected through long-term surveys. Additionally, populations from both islands showed relatively high site fidelity. We found that in Guadeloupe the PSD population is homogeneously distributed along the coast. In contrast, in Martinique the PSD population was composed of two resident groups concentrated in one area. Moreover, 70 new individuals were identified in Guadeloupe and 54 in Martinique while POPAN modelling estimated the number of marked individuals in the study area during 2018 and 2019 at 89 in Guadeloupe and 90 in Martinique. This research provides the first insights on the residency and movement patterns of S. attenuata in the Agoa Sanctuary and can inform future efforts in management and conservation
Guidelines to merge stranding databases: the case of franciscana (Pontoporia blainvillei) in the extreme South of Brazil
No full textStrandings of several species of marine mammals have been monitored over the years off the south coast of Rio Grande do Sul State, southern Brazil. A long time series of records implies extensive databases on strandings. In the region, these databases are maintained by two institutions: (i) Núcleo de Educação e Monitoramento Ambiental (NEMA) [Environmental Education and Monitoring Nucleus] and (ii) Laboratório de Ecologia e Conservação da Megafauna Marinha (ECOMEGA) [Ecology and Conservation of Marine Mefagauna Laboratory] at the Federal University of Rio Grande – FURG. In order to make the time series as complete as possible and to make it a reliable source for research related to a particular species and region, the present work proposes a methodology for unifying both databases for franciscana (Pontoporia blainvillei) for the period 2000 - 2020 (NEMA, n = 3,029; FURG, n = 4,629). To build the unified database, specific metrics were outlined for the species and region, in order to confirm a ‘match’ of a record. The ‘match’ variable is a subjective value that classifies the resighting of a stranded animal as excellent (1), good (2), or regular (3). With the implementation of guidelines to merge stranding databases 1,812 ‘excellent’ and 97 ‘good’ combinations were recorded. Sixty records classified as 30 ‘regular’ matches were kept in the database, as they are possibly not recounts due to large differences in our primary and secondary metrics. To characterize a reliable match between distinct databases, the general guidelines outlined here need to be adapted according to the species of interest and the specificities of each monitoring program. The methodology developed to unify the databases had as its main objective the identification of matches
Easy food in the jungle: evaluating presence and relationships of Amazon River dolphin (Inia geoffrensis) at a provisioning site in the Amazon, Brazil
No full textProvisioning food to wildlife is a strategy used to habituate animals to human proximity during tourism activities, but it can contribute to changes in individual behavior and social structure and impacts on the nutritional health status. This article evaluates the presence and relationships of Amazon River dolphins (Inia geoffrensis) in feeding sessions at a floating house in Anavilhanas National Park, Brazil. The Amazon River dolphins most frequently observed during the study period also presented higher constancy in the feeding sessions. Food provisioning had a variable impact on Amazon River dolphins, making it possible to identify regular, occasional, and rare visitors. The most frequently observed Amazon River dolphins showed strong connectivity, with some individuals playing an important role in the network, acting as a bridge, connecting the set of nodes. These results provide important information about the level of conditioning and social relationships of Amazon River dolphins, which can assist in the development of strategies aimed at reducing the negative population health consequences of supplying food
Passive acoustic monitoring of river dolphin (Inia geoffrensis and Sotalia fluviatilis) presence: A comparison between waters near the city of Iquitos and within the Pacaya-Samiria National Reserve
No full textAll river dolphin species are in decline as a direct result of intensified anthropogenic activity along river systems. In South America, the size and geographical complexity of their range pose a challenge to status assessment. Passive acoustic monitoring offers a cost-effective, scalable, and readily standardized method for determining species distribution and can augment the spatiotemporal coverage of visual survey efforts currently underway. A passive acoustic survey of dolphin presence was conducted in two areas of the Amazon River subject to different degrees of human use; the inland port city Iquitos and the Pacaya-Samiria National Reserve, in Peru. Surveys were based on acoustic detection of biosonar activity. Recorders were distributed at 17 sites along 61 linear km of river habitat for durations of 46 to 148 h. Dolphin presence was 45% lower near the city than in the reserve. This study demonstrates the efficacy of acoustic monitoring as a method for testing dolphin redistribution and/or decline hypotheses in the context of anthropogenic development. The methods are applicable to continuous future monitoring and status assessment of river dolphins in South America as well as in Asia
Cetacean community off French Guiana
No full textAlthough human activities are developing in French Guiana Exclusive Economic Zone (EEZ) and surrounding countries, knowledge on diversity and ecology of cetaceans in the region is scarce. This study aimed to collect new information on the cetacean species occurring year-round in the entire French Guiana EEZ by combining visual and acoustic data obtained from three boat-based campaigns conducted by local NGOs. The GEPOG campaign was conducted from July 2011 to June 2012, four days every two months; the COHABYS campaign was performed five days per month from January to May 2018; the OSL campaign consisted in four 10-day surveys conducted in June, July, September and October 2018. The visual observation effort conducted when Beaufort sea state < 5 was 1,961 km, 1,491 km and 3,243 km respectively. Acoustic records were done when Beaufort sea state < 5 during daylight and/or nighttime, depending on the survey. A total of 132 cetacean sightings were done. Five cetacean families and 15 species were identified. Delphinidae was the family most frequently sighted (91% to 100% of groups and 99% to 100% of individuals per campaign). The most frequent species in the area were identified, along with their distribution and phenology: Guiana dolphin (Sotalia guianensis) was found in the coastal area (0-20 m), the long-beaked common dolphin (Delphinus delphis) was sighted on the shelf (20-100 m), along with the bottlenose dolphin (Tursiops truncatus) and the Atlantic spotted dolphin (Stenella frontalis) that were also common on the upper slope (100-1,500 m). Finally, the spinner dolphin (Stenella longirostris), the melon-headed whale (Peponocephala electra) and the pantropical spotted dolphin (Stenella attenuata) were frequent on the slope (100-3,500 m). The results suggest these species may be found in French Guiana waters all year round and mother and calf pairs, as indicator of reproduction, were observed for all of them except the long-beaked common dolphin and the Guiana dolphin. Mother and calf pairs of humpback whales (Megaptera novaeangliae), that potentially belong to the “A” stock, were also sighted twice, as well as two groups of sperm whales (Physeter macrocephalus) with calves. Hence, these results showed that French Guiana bears a particular responsibility for the conservation of cetacean biodiversity, but a lot remains to be done to strengthen knowledge and conservation of these species in the territory