Population structure, mobility and conservation of common bottlenose dolphin off south-west England from photo-identification studies

2017 ◽  
Vol 98 (5) ◽  
pp. 1055-1063
Author(s):  
Tom Brereton ◽  
Duncan Jones ◽  
Keith Leeves ◽  
Kate Lewis ◽  
Rachel Davies ◽  
...  
Keyword(s):  
Population Structure ◽  
Coastal Waters ◽  
Bottlenose Dolphin ◽  
English Channel ◽  
Photo Identification ◽  
South West ◽  
Common Bottlenose Dolphin ◽  
Abundance Estimates ◽  
Yearly Maximum ◽  
South West England

In this study photo-identification data were used to better understand movements, population structure and abundance of common bottlenose dolphin (Tursiops truncatus) in south-west England and surrounding waters, to inform conservation efforts. A catalogue of 485 photographic sightings of 113 individuals was compiled from ~150 common bottlenose dolphin encounters made on 87 dates between March 2007 and January 2014. From these and other data, three likely sub-populations were identified in the western English Channel, demarcated by bathymetry and distance to land: (1) south-west England – inshore Cornwall to Devon, (2) offshore English/French waters and (3) inshore France from Brittany to Normandy. Maximum abundance estimates for south-west England coastal waters, using two methods, ranged between 102 and 113 (range 87–142, 95% CL) over the period 2008–2013, likely qualifying the region as nationally important, whilst the yearly maximum was 58 in 2013. The population was centred on Cornwall, where 19 well-marked animals were considered ‘probable’ residents. There were no ‘probable’ resident well-marked individuals found to be restricted to either Devon or Dorset, with animals moving freely within coastal areas across the three counties. Movements were also detected within offshore English waters and French waters (from other studies) of the western English Channel, but no interchange has as yet been detected between the three regions, highlighting the possible separation of the populations, though sample sizes are insufficient to confirm this. Given the findings, south-west England waters should be considered as a separate management unit requiring targeted conservation efforts.

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 The influence of fish farm activity on the social structure of the common bottlenose dolphin in Sardinia (Italy)

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e10960
Author(s):  
Serena Frau ◽  
Fabio Ronchetti ◽  
Francesco Perretti ◽  
Alberto Addis ◽  
Giulia Ceccherelli ◽  
...  
Keyword(s):  
Social Structure ◽  
Bottlenose Dolphin ◽  
Foraging Strategy ◽  
Important Change ◽  
Fish Farm ◽  
Photo Identification ◽  
Common Bottlenose Dolphin ◽  
The Social ◽  
Dolphin Population ◽  
The Common

In a wide variety of habitats, including some heavily urbanised areas, the adaptability of populations of common bottlenose dolphin (Tursiops truncatus) may depend on the social structure dynamics. Nonetheless, the way in which these adaptations take place is still poorly understood. In the present study we applied photo-identification techniques to investigate the social structure of the common bottlenose dolphin population inhabiting the Gulf of Alghero (Sardinia, Italy), analysing data recorded from 2008 to 2019. The social structure analysis showed a division of the entire population into five different communities and the presence of non-random associations, while there was no evidence of segregation between sexes. Furthermore, results highlighted an important change in social structure through time, likely due to a reduction in fish farm activity since 2015. The division of the population into different communities, the presence of segregation based on the foraging strategy (inside or outside the fish farm area) and the social network measures were evaluated by analysing independently the two datasets: the intense and low farm activity periods: 2008–2014 and 2015–2020, respectively. Segregation among individuals belonging to the same foraging strategy class was found only in the earlier period, and the composition of the four communities was consistent with this result. Our study improves the knowledge about bottlenose dolphin adaptation, as a lower complexity in social structure was linked to a reduction in anthropogenic food availability.

A robust baseline for bottlenose dolphin abundance in coastal Moreton Bay: a large carnivore living in a region of escalating anthropogenic impacts

2008 ◽  
Vol 35 (7) ◽  
pp. 593 ◽  
Author(s):  
Vimoksalehi Lukoschek ◽  
B. Louise Chilvers
Keyword(s):  
Bottlenose Dolphin ◽  
Anthropogenic Impacts ◽  
Bottlenose Dolphins ◽  
Estimation Methods ◽  
Line Transect ◽  
Mark Recapture ◽  
Abundance Estimate ◽  
Photo Identification ◽  
Moreton Bay ◽  
Abundance Estimates

Marine megafauna populations in coastal waters are increasingly threatened by anthropogenic impacts. Moreton Bay, a large embayment in south-east Queensland, lies adjacent to one of the fastest growing regions in Australia and has a resident population of bottlenose dolphins, Tursiops aduncus. Evaluation of the effectiveness of any proposed management strategy requires robust population abundance estimates. We estimated abundances of bottlenose dolphins in central eastern Moreton Bay (350 km2) using two commonly used abundance estimation methods for cetaceans: photo-identification mark–recapture and line-transect surveys. Mark–recapture data were analysed in CAPTURE using a model that allowed capture probabilities to vary between sampling events and between individuals. Based on an estimated 76% of the population identifiable photographically, total abundance estimates were 673 ± 130 s.e. (1997) and 818 ± 152 s.e. (1998). Line-transect data, analysed using DISTANCE, gave an abundance estimate of 407 ± 113.5 s.e. (2000). These abundance estimates are large compared with many other coastal bottlenose dolphin populations. The line-transect surveys comprised a pilot study, and the lower line-transect abundance estimate is probably best attributable to methodological issues. In particular, smaller mean group size was estimated for the line-transects surveys (2.85 ± 0.29 s.e.) than the mark–recapture surveys (4.87 ± 0.39 s.e., 1997; 5.78 ± 0.73 s.e., 1998), and line-transect group sizes were probably underestimated. In addition, the line-transect detection probability (g(o)) was assumed to be one but was almost certainly less than one. However, the possibility of an actual decline in population size cannot be ruled out. Coefficients of variation (CV) were lower for mark–recapture than for line-transect surveys, however, CVs of line-transect estimates could be lowered through improved survey design. We evaluated the power of these surveys to detect trends in potential population declines for bottlenose dolphins in Moreton Bay and make recommendations for ongoing monitoring strategies.

Occurrence of Atlantic humpback (Sousa teuszii) and bottlenose (Tursiops truncatus) dolphins in the coastal waters of Guinea-Bissau, with an updated cetacean species checklist

2015 ◽  
Vol 96 (4) ◽  
pp. 933-941 ◽  
Author(s):  
Ruth H. Leeney ◽  
Caroline R. Weir ◽  
Pierre Campredon ◽  
Aissa Regalla ◽  
Jeff Foster
Keyword(s):  
Coastal Waters ◽  
Bottlenose Dolphin ◽  
Tursiops Truncatus ◽  
Conservation Status ◽  
Temporal Distribution ◽  
Cetacean Species ◽  
Guinea Bissau ◽  
Common Bottlenose Dolphin ◽  
The Status ◽  
Spatio Temporal

There is a paucity of information on the cetacean fauna of Guinea-Bissau in West Africa. We compiled records published in the literature and novel unpublished sighting data (2008–2014) to examine the occurrence and distribution of cetacean species. At least 10 species were verified to occur in Guinea-Bissau waters, of which eight were documented from a small number of sightings, whaling captures or skeletal remains. By far the most frequently recorded species were the common bottlenose dolphin (Tursiops truncatus) (N = 146) and the Atlantic humpback dolphin (Sousa teuszii) (N = 110). These two species were sympatric in distribution, both being found throughout coastal waters from the northern regions of Canal de Jeta and Rio Mansôa south to the Rio Cacine and around the Arquipélago dos Bijagós. However, differences were apparent in their finer-scale distribution and in the distance of sightings from shore, with bottlenose dolphin sightings generally occurring further from shore (and especially in the region of the Canal do Gêba) than Atlantic humpback dolphins. Sightings indicate that both species likely inhabit Guinea-Bissau waters throughout the year. Dedicated systematic cetacean survey work is urgently needed in coastal Bissau-Guinean waters in order to ascertain the abundance, spatio-temporal distribution, population structure and causes of mortality of bottlenose and Atlantic humpback dolphins, particularly given the Vulnerable conservation status of the latter species. Clarification of the status of cetaceans in offshore waters requires survey effort throughout the Guinea-Bissau EEZ.

The dinoflagellae bloom on the coast of south west England, August-September 1978

1979 ◽  
Vol 59 (2) ◽  
pp. 515-517 ◽  
Author(s):  
G. T. Boalch
Keyword(s):  
Sea Water ◽  
Personal Communication ◽  
Coastal Areas ◽  
South Coast ◽  
English Channel ◽  
Fish Kills ◽  
Noctiluca Scintillans ◽  
Scuba Divers ◽  
South West ◽  
South West England

Towards the end of August 1978 SCUBA divers studying a rocky area in Mounts Bay noticed numbers of dead and dying fish and invertebrates in their study area. Their observations were passed on to Dr G. W. Potts (Griffiths, Dennis & Potts, see below, p. 520). Samples of the sea water, which appeared to be very rich in phytoplankton, were taken but unfortunately were too poorly fixed for the identification of naked dinoflagellates. At the same time a number of reports of‘red tides’ and ‘fish kills’ in Mounts Bay were being passed to Mrs Stella Turk of Camborne.During the first 2 weeks of September 1978, high mortalities of intertidal populations of several ‘bait’ species, notably lugworms, were reported to the Plymouth Laboratory by anglers along the south coast of Cornwall. In the same period, abnormally high numbers of the red-band fish, Cepola rubescens, were caught in the trawls of the Laboratory's research vessels (Dr A. J. Southward, personal communication). In addition, some 20–30 specimens of another burrowing species, Amalosoma eddystonense, were taken in several trawls on the Looe Grounds; this was rather surprising since this large echiuran was thought to be rare in the Plymouth area (Dr P. E. Gibbs, personal communication).The author also received reports indicating that the non-photosynthetic but luminescent dinoflagellate Noctiluca scintillans (Macartney) Ehrenb. was abundant in coastal areas of the western English Channel. This organism is well known for forming slicks varying in colour from orange to blood-red (Le Févre & Grail, 1970; Grail, Le FévreLehoerff & Le Févre, 1971).

Raja richardsoni from the continental slope off south-west England

1965 ◽  
Vol 45 (3) ◽  
pp. 773-777 ◽  
Author(s):  
G. R. Forster
Keyword(s):  
New Zealand ◽  
Continental Slope ◽  
Type Specimen ◽  
English Channel ◽  
Lateral Process ◽  
South West ◽  
Number Of Teeth ◽  
South West England

A pair of rays caught by line from 1300fm westward of the English Channel have been identified as Raja richardsoni Garrick known only from the type specimen also taken by line in New Zealand waters from about the same depth. The Plymouth rays agree well with the New Zealand fish in proportional measurements, in bearing denticles on both surfaces, and in the absence of spines but differ slightly in colour, in their smaller number of teeth, and in the greater development of a lateral process on the nasal flap.

scholarly journals Genetic divergence and fine scale population structure of the common bottlenose dolphin (Tursiops truncatus, Montagu) found in the Gulf of Guayaquil, Ecuador

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e4589 ◽  
Author(s):  
Rosa de los Ángeles Bayas-Rea ◽  
Fernando Félix ◽  
Rommel Montufar
Keyword(s):  
Population Structure ◽  
Bottlenose Dolphin ◽  
Tursiops Truncatus ◽  
Bottlenose Dolphins ◽  
Western Coast ◽  
Common Bottlenose Dolphin ◽  
Dolphin Population ◽  
The Common ◽  
Gulf Of Guayaquil ◽  
Outer Estuary

The common bottlenose dolphin, Tursiops truncatus, is widely distributed along the western coast of South America. In Ecuador, a resident population of bottlenose dolphins inhabits the inner estuarine area of the Gulf of Guayaquil located in the southwestern part of the country and is under threat from different human activities in the area. Only one genetic study on South American common bottlenose dolphins has been carried out to date, and understanding genetic variation of wildlife populations, especially species that are identified as threatened, is crucial for defining conservation units and developing appropriate conservation strategies. In order to evaluate the evolutionary link of this population, we assessed the phylogenetic relationships, phylogeographic patterns, and population structure using mitochondrial DNA (mtDNA). The sampling comprised: (i) 31 skin samples collected from free-ranging dolphins at three locations in the Gulf of Guayaquil inner estuary, (ii) 38 samples from stranded dolphins available at the collection of the “Museo de Ballenas de Salinas,” (iii) 549 mtDNA control region (mtDNA CR) sequences from GenBank, and (iv) 66 concatenated sequences from 7-mtDNA regions (12S rRNA, 16S rRNA, NADH dehydrogenase subunit I–II, cytochrome oxidase I and II, cytochrome b, and CR) obtained from mitogenomes available in GenBank. Our analyses indicated population structure between both inner and outer estuary dolphin populations as well as with distinct populations of T. truncatus using mtDNA CR. Moreover, the inner estuary bottlenose dolphin (estuarine bottlenose dolphin) population exhibited lower levels of genetic diversity than the outer estuary dolphin population according to the mtDNA CR. Finally, the estuarine bottlenose dolphin population was genetically distinct from other T. truncatus populations based on mtDNA CR and 7-mtDNA regions. From these results, we suggest that the estuarine bottlenose dolphin population should be considered a distinct lineage. This dolphin population faces a variety of anthropogenic threats in this area; thus, we highlight its fragility and urge authorities to issue prompt management and conservation measures.

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