scholarly journals Population Dynamics Reveal a Core Community of the Common Bottlenose Dolphin (Tursiops truncatus) in Open Waters of the South-Western Gulf of Mexico

2021 ◽  
Vol 8 ◽  
Author(s):  
Jaime Bolaños-Jiménez ◽  
Eduardo Morteo ◽  
Christian A. Delfín-Alfonso ◽  
Pedro F. Fruet ◽  
Eduardo R. Secchi ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Gulf Of Mexico ◽  
Bottlenose Dolphins ◽  
Closed Population ◽  
Quantitative Evidence ◽  
Photo Identification ◽  
The Core ◽  
Mobile Species ◽  
Common Bottlenose Dolphin ◽  
Main Driver

The presence of transient and temporary individuals in capture-mark-recapture studies may violate the assumption on equal catchability, and thus yield biased estimates. We investigated the effects of residency patterns on population parameters of bottlenose dolphins inhabiting the coastal waters off the Alvarado Lagoon System (ALS), Veracruz, Mexico. We hypothesized that this population is open but there exists a “core community” that behaves as a closed population. Between 2006 and 2010, we conducted 75 photo-identification surveys and recorded 263 dolphin group encounters, in which 231 dolphins were identified. Individuals present during only one season, classified as transients (n = 85), were excluded from the study, and a standardized residency index (IH4) was computed for each dolphin that remained in the sample (n = 146). We used the K-means clustering method to split the sample into groups based on individual (seasonal, annual) IH4 values. These clusters were named as regular residents (RR, n = 55), occasional residents (OR, n = 45), and occasional visitors (OV, n = 46). The cumulative frequency of newly identified individuals displayed an asymptotic trend for the whole sample and all clusters, indicating that most of the individuals present in the study area during the study period were identified. The assumption of demographic closure was tested to define the core community, and was rejected for the whole sample and the OV cluster (p < 0.001 in both cases), indicating that the population is open. The closure assumption was not rejected for RR and OR clusters (χ2 = 6.88, DF = 13, p = 0.91, and χ2 = 17.8, DF = 16, p = 0.33, respectively), indicating that these clusters were demographically closed over the 5-year period. Thus, we defined this aggregation of individuals as the “core community”. The closed population model Mth indicated that the total abundance of this core community was 123 individuals (95% CI: 114–133). Our results provide quantitative evidence of the existence of a core community in open waters of the Gulf of Mexico, and points toward residency pattern as a main driver of population dynamics. These results highlight the importance of considering residency patterns when dealing with heterogeneity in the sample of a highly mobile species.

scholarly journals Strong site-fidelity increases vulnerability of common bottlenose dolphins Tursiops truncatus in a mass tourism destination in the western Mediterranean Sea

2013 ◽  
Vol 94 (6) ◽  
pp. 1227-1235 ◽  
Author(s):  
Joan Gonzalvo ◽  
Jaume Forcada ◽  
Esteve Grau ◽  
Alex Aguilar
Keyword(s):  
Site Fidelity ◽  
Bottlenose Dolphins ◽  
Local Population ◽  
Western Mediterranean ◽  
Marine Biodiversity ◽  
Tourism Destination ◽  
Photo Identification ◽  
Mass Tourism ◽  
Management Actions ◽  
Common Bottlenose Dolphin

The local population of common bottlenose dolphin in the Balearic Islands coastal waters, a mass tourism destination in the western Mediterranean subject to increasing anthropogenic pressures, was monitored over a three-year period. Photo-identification surveys provided a relatively small population estimate, even though the islands are considered to be a hotspot for the species in the Mediterranean. Dolphins showed strong site-fidelity and relatively limited mobility across the archipelago, which makes them highly dependent on waters which are severely affected by overfishing, habitat degradation and boat disturbance resulting from a continuously-growing tourism and shipping industry. Ecosystem-based management actions are urgently needed to ensure the conservation of this fragile population of bottlenose dolphins. Conservation measures should be developed within the already-existing political and legal marine biodiversity conservation framework and in collaboration with local authorities and stakeholders.

scholarly journals The first record of a piebald common bottlenose dolphin (Tursiops truncatus) in offshore waters of the north-western Black Sea

2020 ◽  
Vol 2020 (19) ◽  
pp. 103-107
Author(s):  
Oksana Savenko ◽  
◽  
Keyword(s):  
Black Sea ◽  
Coastal Waters ◽  
Bottlenose Dolphin ◽  
Bottlenose Dolphins ◽  
The Black Sea ◽  
Photo Identification ◽  
Dorsal Fin ◽  
The North ◽  
Common Bottlenose Dolphin ◽  
North Western

Piebaldism is one of three types of hypopigmentation of animals, when some areas on the skin have no pigments. Anomalously white cetaceans are rare, although they have been reported in more than 20 different cetacean species, including the common bottlenose dolphin, which in the Black Sea is recognized as an endangered endemic subspecies — the Black Sea bottlenose dolphin (Tursiops truncatus ponticus Barabash-Nikiforov, 1940). Its main habitat in the north-western Black Sea region is the coastal waters, however, these dolphins also occur offshore. Thirty cases of anomalously white bottlenose dolphins have been reported from the Black Sea, which were unevenly distributed, and only a few sightings have been reported from the north-western Black Sea. Cetacean observations were conducted in the Ukrainian part of the north-western Black Sea waters in April 2017, onboard the research vessel "Auguste Piccard". All encountered cetaceans were photographed, and individual distinctiveness of dorsal fin images was used for their photo-identification. On 13 April 2017, four groups of up to four individuals of bottlenose dolphins were encountered in the same area at a distance of 61 km south of Odesa (34 km from the nearest coast). The depth at the observation site was about 20 m. The initially observed type of dolphins’ behavior was feeding. However, two groups changed their behavior and followed the vessel by 5–6 individuals for approximately 18 minutes. The joint group consisted of adults and one juvenile individual. Among the adults, there was one piebald specimen with white patches on its dorsal fin, peduncle, and tail fluke. The piebald dolphin was photographed and photo-identified. Our research has shown that piebald Black sea bottlenose dolphins occur not only in the coastal waters, but also in offshore waters of the north-western Black Sea. However, the frequency of such hypopigmentation in local populations remains unknown. Further intensive photo-identification and genetic sampling of local stocks of the Black Sea bottlenose dolphins are necessary for the assessment of their population genetic structure and its divergence.

scholarly journals Capitoline Dolphins: Residency Patterns and Abundance Estimate of Tursiops truncatus at the Tiber River Estuary (Mediterranean Sea)

Biology ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 275
Author(s):  
Daniela Silvia Pace ◽  
Chiara Di Marco ◽  
Giancarlo Giacomini ◽  
Sara Ferri ◽  
Margherita Silvestri ◽  
...  
Keyword(s):  
Population Size ◽  
Tursiops Truncatus ◽  
Site Fidelity ◽  
Bottlenose Dolphins ◽  
River Estuary ◽  
Suitable Habitat ◽  
Tyrrhenian Sea ◽  
Abundance Estimate ◽  
Photo Identification ◽  
Tiber River

Periodic assessments of population status and trends to detect natural influences and human effects on coastal dolphin are often limited by lack of baseline information. Here, we investigated for the first time the site-fidelity patterns and estimated the population size of bottlenose dolphins (Tursiops truncatus) at the Tiber River estuary (central Mediterranean, Tyrrhenian Sea, Rome, Italy) between 2017 and 2020. We used photo-identification data and site-fidelity metrics to study the tendency of dolphins to remain in, or return to, the study area, and capture–recapture models to estimate the population abundance. In all, 347 unique individuals were identified. The hierarchical cluster analysis highlighted 3 clusters, labeled resident (individuals encountered at least five times, in three different months, over three distinct years; n = 42), part-time (individuals encountered at least on two occasions in a month, in at least two different years; n = 73), and transient (individuals encountered on more than one occasion, in more than 1 month, none of them in more than 1 year; n = 232), each characterized by site-fidelity metrics. Open POPAN modeling estimated a population size of 529 individuals (95% CI: 456–614), showing that the Capitoline (Roman) coastal area and nearby regions surrounding the Tiber River estuary represent an important, suitable habitat for bottlenose dolphins, despite their proximity to one of the major urban centers in the world (the city of Rome). Given the high number of individuals in the area and the presence of resident individuals with strong site fidelity, we suggest that conservation plans should not be focused only close to the Tiber River mouths but extended to cover a broader scale of area.

scholarly journals AEROBIC MICROORGANISMS ASSOCIATED WITH FREE-RANGING BOTTLENOSE DOLPHINS IN COASTAL GULF OF MEXICO AND ATLANTIC OCEAN WATERS

2006 ◽  
Vol 42 (3) ◽  
pp. 536-544 ◽  
Author(s):  
John D. Buck ◽  
Randall S. Wells ◽  
Howard L. Rhinehart ◽  
Larry J. Hansen
Keyword(s):  
Atlantic Ocean ◽  
Gulf Of Mexico ◽  
Bottlenose Dolphins ◽  
Free Ranging

scholarly journals Occurrence of bottlenose dolphins (Tursiops truncatus) in the Río Negro Estuary, Argentina, and their mid-distance movements along the northeastern Patagonian coast

10.5597/00226 ◽  
2017 ◽  
Vol 11 (1-2) ◽  
pp. 170-177
Author(s):  
Mauricio Failla ◽  
Verónica A. Seijas ◽  
Els Vermeulen
Keyword(s):  
Tursiops Truncatus ◽  
Feeding Activity ◽  
Bottlenose Dolphins ◽  
Activity Patterns ◽  
Long Distance ◽  
Identification Rate ◽  
Photo Identification ◽  
Rio Negro ◽  
Patagonian Coast ◽  
Main Activity

A systematic study was carried out on bottlenose dolphins (Tursiops truncatus) in the Río Negro Estuary (RNE), Patagonia, Argentina, to analyze their occurrence and activity patterns in this region. The photo-identification data of this study was further compared to data from an adjacent region to gain information on the animals' movements along the northeastern Patagonian coast. Information was gathered through land-based observations between the months of March and July of 2008 up to 2011. Data on dolphin activity patterns were collected via an ad libitum focal-group sampling mode. At the same time, dorsal fin images were obtained from as many dolphins as possible for identification and subsequent re-identification of individuals. Total effort equaled 188h, resulting in 58h of observation of 124 dolphin groups [sightings per unit effort (SPUE) = 0.66 group/h]. Most of the groups observed contained between one and five individuals, and two main activity states could be determined, namely traveling (65%) and foraging (26%). The photo-identification effort, which started opportunistically in 2006, resulted in a catalogue of 17 individual dolphins, with a total mean re-identification rate of nine days (max. = 24 days). When comparing these pictures to the existing catalogue of Bahía San Antonio (BSA; approximately 200km west from the study area) dorsal fins of 15 individuals could be matched and most (n = 12) could be subsequently re-identified in both areas, indicating their long distance movements along the northeastern Patagonian coast during the austral autumn months. This season coincides with the lowest dolphin abundance and feeding activity in BSA. This study indicates that bottlenose dolphins enter the RNE to forage at least during autumn. It further suggests that the search for food resources is the main trigger for their movement patterns along the northeastern Patagonian coast during this season, at least for certain individuals. More research is needed to accurately confirm these hypotheses.

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