Tursiops Truncatus Research Articles

Public knowledge and awareness of the conservation of the common bottlenose dolphin (Tursiops truncatus) along the central coast of Peru

Abstract Although the coastal common bottlenose dolphin Tursiops truncatus is under legal protection, this species is threatened by bycatch and direct hunting along the Peruvian coast. Species conservation can be better achieved if communities are empowered with knowledge and actions to mitigate negative impacts on vulnerable species. Thus, it is important to understand people's degree of knowledge about a species and its conservation issues. This study evaluated the knowledge and perception of aspects of the biology, ecology and conservation status of the common bottlenose dolphin in coastal communities along the central coast of Peru. Structured questionnaires were completed by 197 people, and seven people participated in open‐ended interviews in January 2022. Most respondents were knowledgeable of the distribution and ecology of common bottlenose dolphins. Seventy per cent of those surveyed were aware of some threats to this species. Some respondents were eager to take part in actions that would aid in the conservation of the species. However, 69.5% (n = 137) were unfamiliar with the word ‘bycatch’. Charismatic species can engage the public in conservation actions. This research shows that common bottlenose dolphin can be used as a flagship species for marine conservation. It is important to actively involve all stakeholders, particularly fishers, in conservation efforts and the measures that need to be taken to improve common bottlenose dolphin conservation.

Two Decades of Coastal Dolphin Population Surveys in Israel, Eastern Mediterranean

Along the Mediterranean coast of Israel, two near-shore dolphin species are prevalent; Tursiops truncatus (least concern, IUCN) and Delphinus delphis (endangered, IUCN). Ship-board surveys and sporadic sightings over the last two decades have shown that the two differ in distribution-T. truncatus is found along the entire coast and D. delphis only in the south. The environmental and anthropological factors affecting these species' spatial distribution and determining their habitat preferences in this area are largely unknown. This work is a first attempt at summarizing 20 years of observations and studying habitat preferences for both species, by use of Generalized Additive Models. T. truncatus was found to be present in all areas of the continental shelf where survey effort coverage was sufficient, with a high affinity towards bottom trawlers. Model results showed D. delphis distribution to be associated to (shallow) water depths, though the factors driving their limited latitudinal distribution currently remain unknown. It is evident that T. truncatus and D. delphis are present in segregated areas of the Israeli continental shelf and T. truncatus currently sustains a delicate balance with continuously shifting human activities, while the drivers of D. delphis distribution are more specified, yet still not fully understood.

A note on the use of dolphins as bait in the artisanal fisheries off Bahía Solano, Chocó, Colombia

Dolphin hunting for fishing bait in Bahía Solano, Chocó, Colombia, was evaluated during eight months, between July 2005 and April 2006. Interviews were conducted with 122 fishermen (18.2% of the registered fishermen in the zone), who cover at most 890km2 when fishing (approximately 2.3% of the Pacific Territorial Sea of Colombia), and data obtained from landings at a fishing company. Only fishermen using longlines (37.3%) confirmed using dolphins as bait. It was not possible to obtain additional information about date, specific location or dolphin species, but the most probable captured species were common bottlenose dolphin and pantropical spotted dolphin. Nine dolphins were killed during the study period (1.1 dolphins/month) and extrapolating these numbers to all fishermen using longlines in the region (250), 24 dolphins might have been taken during the study period (3 dolphins/month). Fish species caught using dolphin bait include Pacific bearded brotula, groupers and smooth-hound.

Seasonal abundance and distribution patterns of common bottlenose dolphins (Tursiops truncatus) near St. Joseph Bay, Florida, USA

Three unusual mortalities events involving bottlenose dolphins (Tursiops truncatus Montagu 1821) occurred along Florida’s northern Gulf of Mexico coast between 1999 and 2006. The causes of these events, in which over 300 bottlenose dolphins are known to have died, are still under investigation. The impact of these mortality events cannot be fully evaluated, because little prior information on bottlenose dolphin abundance and distribution patterns exist in this region. Thus, the goals of this study were to estimate seasonal abundance, develop site-fidelity indices, and describe distribution patterns of bottlenose dolphins in St. Joseph Bay, Gulf County, Florida, USA. This study site was chosen because it was impacted by all three unusual mortality events and was the geographic focus of the 2004 event. Mark-recapture photo-identification surveys were conducted across multiple seasons from February 2005 through July 2007. Site-fidelity indices were calculated for each identifiable dolphin based upon all photo-ID efforts undertaken in the area. Distribution patterns were investigated by short-term (12-94 days) radio-tracking of tagged individuals across seasons (April-July, n=9; July-October, n=15). Mark-recapture closed and robust abundance estimates, as well as site-fidelity indices suggest that St. Joseph Bay supports a resident community of 78-152 bottlenose dolphins. During spring and autumn, this region experiences an influx of dolphins, as demonstrated by closed and robust abundance estimates of 313-410 and 237-340, respectively. These results are supported by the distribution patterns of radio-tagged individuals. Individuals tagged in summer tended to stay within or near St. Joseph Bay, whereas two individuals tagged in spring ranged more than 40km from the study site. This study provides the first detailed examination of bottlenose dolphin abundance and distribution patterns for this region of the northern Gulf coast of Florida. These results suggest that unusual mortality events probably had, and will in the future have, seasonally variable effects on bottlenose dolphins in St. Joseph Bay. Future mortality events that occur during the summer and winter in St. Joseph Bay may predominantly affect resident individuals, while those that occur during the spring and autumn will probably affect both residents and seasonal visitors.

Mark-recapture estimates of seasonal abundance and survivorship for bottlenose dolphins (Tursiops truncatus) near Charleston, South Carolina, USA

The stock structure of western North Atlantic bottlenose dolphins (Tursiops truncatus) is complex, with seasonally migratory stocks often overlapping with year-round resident stocks. High rates of exchange between northernmost sites have been documented but movement and seasonal fluctuation in abundance among sites along the southern portion of the US Atlantic coast is not well understood. To better understand seasonal abundance, a three-year mark-recapture study of bottlenose dolphins in coastal and estuarine waters near Charleston, South Carolina, USA was conducted. A robust design was employed in order to minimise bias and more precisely determine seasonal estimates of abundance and concurrently examine temporary immigration/emigration and survivorship. Systematic boat-based surveys were carried out (n = 192) from January 2004 to December 2006. The entire study area was surveyed one week per month; an additional survey was conducted in the months in which seasonal abundance was estimated: January (winter), April (spring), July (summer) and October (autumn). Standard photo-identification techniques were used to accumulate sightings of 521 distinctively marked dolphins, 65% of which were sighted more than once. Pollock’s robust design was applied using MARK and the ensuing abundance estimates were adjusted for the seasonal proportion of unmarked dolphins (ranging from 0.27 to 0.40) in the population. Estimates ranged from 364 (95% CI = 305–442) in January 2004 to 910 (95% CI = 819–1018) in October 2006. Summer abundance estimates were consistently greater than those from winter months, although estimates varied considerably among years. The same model was used to calculate an annual survival rate estimate of 0.951 (95% CI = 0.882–1.00) for marked individuals within the population. A high degree of transience, demonstrated by seasonal influxes of single-sighted individuals, made it difficult to differentiate between mortality and permanent emigration. The results support the occurrence of three distinct dolphin groups found in Charleston waters: year-round residents; seasonal residents; and transients. Reporting abundance and survivorship estimates together is useful in explaining and validating results for populations in which transient individuals occur. These results provide important information for stock and viability assessment of coastal bottlenose dolphins in the western North Atlantic.

Odontocetes of the Southern Ocean Sanctuary

Twenty-eight odontocete species were identified as occupying sub-Antarctic and Antarctic habitat covered by the 1994 IWC-established Southern Ocean Sanctuary. Toothed whales evidently play an important part in the Antarctic polar ecosystem. Twenty-two species are autochthonous in showing a regular, apparently year-round, presence in the Sanctuary: Physeter macrocephalus, Kogia breviceps, Orcinus orca, Globicephala melas edwardii, Pseudorca crassidens, Lagenorhynchus cruciger, Lagenorhynchus obscurus, Lissodelphis peronii, Cephalorhynchus commersonii, Cephalorhynchus hectori, Tursiops truncatus, Delphinus delphis, Phocoena dioptrica, Hyperoodon planifrons, Berardius arnuxii, Ziphius cavirostris, Tasmacetus shepherdi, Mesoplodon layardii, Mesoplodon traversii, Mesoplodon grayi, Mesoplodon bowdoini and Mesoplodon hectori. Six species are considered vagrants into the Sanctuary: Kogia sima, Grampus griseus, Steno bredanensis, Mesoplodon peruvianus, Mesoplodon densirostris and Mesoplodon mirus. However, vagrant status of these three mesoplodonts is only provisionally assigned, considering that improved knowledge of diagnostic features of beaked whales should, as in recent years, continue to facilitate at-sea identification. Two species are considered as having a ‘contiguous’ range (records less than 2° north of Sanctuary boundaries): Mesoplodon ginkgodens (at 39°S) and Mesoplodon mirus (at 38°24’S). The habitual southern range of at least four odontocetes extends significantly farther poleward than expected. G. melas edwardii is regularly encountered south of the Antarctic Polar Front, much like M. grayi which is known to reach the Ross Sea ice edge (ca. 67°S). Z. cavirostris and L. obscurus cross the Polar Front occasionally. The distribution of M. peruvianus and M. traversii and their relation to SST are unclear. Their southernmost records, 42°31’S and 44°17’S respectively, may either be extralimital or, more likely, reflect ordinary austral range. Temporally non-aligned distribution patterns of Hyperoodon planifrons in Antarctic and South African waters may suggest stock segregation.

Cetacean strandings in San Diego County, California, USA: 1851–2008

There were 717 cetacean strandings recorded in San Diego County, California, USA between 1851 and 2008. These strandings comprised 18 odontocete and 6 mysticete species. Common dolphins (both the short-beaked (Delphinus delphis) and long-beaked common dolphin (D. capensis)) were the most commonly stranded cetacean species (43.2%), followed by bottlenose dolphins (Tursiops truncatus) (16.5%), gray whales (Eschrictius robustus) (11.0%), and Pacific white-sided dolphins (Lagenorhyncus obliquidens) (7.0%). A higher number of strandings was observed in the La Jolla and Coronado/Imperial Beach areas, which likely reflects the influence of coastal protrusions in those regions. Strandings of bottlenose dolphin neonates suggests their calving season extends from May to September. Strandings of common dolphin species peaked in the early- to mid-1970s and in the late-1990s to 2008, coincident with cool oceanographic regimes. In addition, extralimital strandings of harbour porpoises and temporal changes in stranding rates of Dall’s porpoises (Phocoenoides dalli) and short-finned pilot whales (Globicephala macrorhynchus) may have been associated with changes in oceanographic conditions. Evidence of human interaction in strandings included entanglements, boat strikes, shootings and harpooning. Overall, the stranding record largely reflected the species composition of the Southern California Bight and provided confirmation for presence of cryptic species not previously recorded by aerial and ship surveys.

Life in the Caribbean: age and growth of common bottlenose dolphins Tursiops truncatus in Cuban waters

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A note on long-distance matches of bottlenose dolphins (Tursiops truncatus) around the Irish coast using photo-identification

Images of 120 individual bottlenose dolphins from around the Irish coast were obtained from three photo-identification catalogues. Twenty three individuals were subsequently re-sighted, which is a re-sighting rate of 19%. The distance between re-sightings ranged from 130 to 650km and the duration from 26 to 760 days. Images were also compared to a catalogue of resident dolphins from the Shannon Estuary candidate Special Area of Conservation and from Wales but no matches were found. This short study provides strong evidence that bottlenose dolphins in Irish coastal waters are regularly undertaking large movements around the entire Irish coast and must be considered highly mobile and transient. These results have important implications for the conservation and management of this species.

Environmental variables and machine learning models to predict cetacean abundance in the Central-eastern Mediterranean Sea

Although the Mediterranean Sea is a crucial hotspot in marine biodiversity, it has been threatened by numerous anthropogenic pressures. As flagship species, Cetaceans are exposed to those anthropogenic impacts and global changes. Assessing their conservation status becomes strategic to set effective management plans. The aim of this paper is to understand the habitat requirements of cetaceans, exploiting the advantages of a machine-learning framework. To this end, 28 physical and biogeochemical variables were identified as environmental predictors related to the abundance of three odontocete species in the Northern Ionian Sea (Central-eastern Mediterranean Sea). In fact, habitat models were built using sighting data collected for striped dolphins Stenella coeruleoalba, common bottlenose dolphins Tursiops truncatus, and Risso’s dolphins Grampus griseus between July 2009 and October 2021. Random Forest was a suitable machine learning algorithm for the cetacean abundance estimation. Nitrate, phytoplankton carbon biomass, temperature, and salinity were the most common influential predictors, followed by latitude, 3D-chlorophyll and density. The habitat models proposed here were validated using sighting data acquired during 2022 in the study area, confirming the good performance of the strategy. This study provides valuable information to support management decisions and conservation measures in the EU marine spatial planning context.

Cetacean distribution and relative abundance in Colombia’s Pacific EEZ from survey cruises and platforms of opportunity

Cetacean sighting data collected under various programmes in Colombian Pacific waters were collated with the goal of assessing the distribution and abundance patterns of all species occurring in the exclusive economic zone (EEZ). Distribution maps are presented for 19 species and one genus based on 603 sightings collected between 1986 and 2008. Ordered by sighting frequency, these species were: humpback whale (Megaptera novaeangliae); striped dolphin (Stenella coeruleoalba); common bottlenose dolphin (Tursiops truncatus); pantropical spotted dolphin (Stenella attenuata); common dolphin (Delphinus delphis); Risso’s dolphin (Grampus griseus); sperm whale (Physeter macrocephalus); rough-toothed dolphin (Steno bredanensis); short-finned pilot whale (Globicephala macrorhynchus); mesoplodont whales (Mesoplodon spp.); Cuvier’s beaked whale (Ziphius cavirostris); melon-headed whale (Peponocephala electra); false killer whale (Pseudorca crassidens); killer whale (Orcinus orca); spinner dolphin (Stenella longirostris); dwarf sperm whale (Kogia sima); Bryde’s whale (Balaenoptera edeni); pygmy killer whale (Feresa attenuata); minke whale (Balaenoptera acutorostrata) and fin whale (Balaenoptera physalus). Concentrations of sightings were observed in three geographic areas: (1) the continental shelf (depths <200m) and the contiguous continental slope (200–2,000m); (2) over the Malpelo Ridge, an offshore bathymetric feature and (3) the northeast corner of the EEZ between Golfo de Cupica and the border with Panamá, although we do not rule out that these patterns could be an artefact of non-random effort. In inshore waters, the most frequently seen species were pantropical spotted dolphin, common bottlenose dolphin and humpback whale. For several of the data sets we provide encounter rates as indices of relative abundance, but urge caution in their interpretation because of methodological limitations and because several factors that affect sightability could not be accounted for in these estimates. Our results provide useful information for ongoing regional research and conservation initiatives aimed at determining occurrence, population status and connectivity within adjacent EEZs in the eastern tropical Pacific. Suggested research priorities include conducting dedicated surveys designed for estimating abundance and monitoring trends throughout the EEZ and focused studies in areas of special interest like the continental shelf, the Malpelo Ridge and the vicinity of Cupica and Cabo Marzo. More research is also needed in terms of quantifying the sources and impact of anthropogenic mortality on population size. Studies characterising genetic diversity and stock discreteness in coastal species (pantropical spotted dolphin and common bottlenose dolphin) would help inform local management strategies.

Genetic structure of common bottlenose dolphins (Tursiops truncatus) inhabiting adjacent South Florida estuaries – Biscayne Bay and Florida Bay

Coastal common bottlenose dolphins show a variety of migration and residency patterns adding to the difficulty of defining stocks for management purposes. Genetic structure plays an important role in identifying population stocks of dolphins. This study examines genetic differentiation in common bottlenose dolphins both between two social groups occurring in Biscayne Bay, Florida and between Biscayne Bay and an adjacent group of dolphins in Florida Bay. Skin biopsy samples were sequenced at the mitochondrial DNA (mtDNA) control region and genotyped at microsatellite loci. Significant genetic differentiation was found between bottlenose dolphins in Biscayne Bay and Florida Bay (mtDNA FST = 0.139, p ≤ 0.001; microsatellite FST = 0.042, p ≤ 0.001) supporting independent management stock status for these two populations. Within Biscayne Bay, evidence of weak but significant population differentiation was found between the two social groups using microsatellite markers (FST = 0.0149, p ≤ 0.009); however, differentiation was not evident from the mtDNA-based estimates of FST and φST. The lack of differentiation at mtDNA coupled with field observations indicating overlapping home ranges for these two groups suggests ongoing, though perhaps low, levels of interbreeding. These data are insufficient to warrant splitting the Biscayne Bay management stock at this time.

Long-term site fidelity and seasonal abundance estimates of common bottlenose dolphins (Tursiops truncatus) along the southwest coast of Florida and responses to natural perturbations

Information characterising site fidelity and abundance for common bottlenose dolphins (Tursiops truncatus) along the southwest coast of Florida is important for defining stock structure for management purposes. Long-term site fidelity and ranging patterns of bottlenose dolphins in Charlotte Harbor and Pine Island Sound, Florida were investigated using photo-ID data collected during 566 boat-based surveys from 1982 through 2007. Seasonal abundance estimates were generated from seven multi-week field seasons during 2001 through 2006, before and after a major hurricane and red tide event occurred in the area. In total, 1,154 distinctive dolphins were identified up to 34 times each with 84% of individuals resighted on more than one day. Multiple year residency rates were high with 81% of dolphins sighted in at least two years and 30% over ten or more years. Seventy-six percent of individuals with sightings on two or more days were observed in both summer and winter. Of 249 dolphins sighted on ten or more days in the study area, 83% were never observed outside the study area, indicating strong site-fidelity. Two years after a devastating Category 4 hurricane in 2004 and following two years of Karenia brevis harmful algal blooms, 94% of dolphins were observed in the same region within the study area and abundance estimates remained stable. Documenting range and site fidelity patterns of individuals over long periods of time is helpful for characterizing population structure and for examining changes attributable to environmental factors and perturbations such as hurricanes, harmful algal blooms and climate change.

Cetacean sightings and acoustic detections in the offshore waters of Sri Lanka: March–June 2003

The Indian Ocean Sanctuary was established in 1979 in an effort to allow exploited stocks of whales to recover from whaling and to facilitate benign research. Further information is required to establish comprehensive management and conservation measures for species within these waters. The current study took place in the offshore waters of Sri Lanka in early 2003. During three research cruises conducted between 29 March and 17 June 2003 the R/V Odyssey covered a total track line of 4,480km around the island resulting in 52 confirmed group sightings of 11 species from three cetacean families. As the tracklines were designed to locate sperm whales (Physeter macrocephalus) for tissue sampling, they accounted for the greatest number of sightings. Only two species of balaenopterids, the blue whale (Balaenoptera musculus) and the Bryde’s whale (Balaenoptera edeni), were recorded with the blue whale being the most frequently sighted species. Spinner dolphins (Stenella longirostris) were the most dominant species in terms of numbers. Some small odonotocetes such as the common bottlenose dolphin (Tursiops truncatus), striped dolphin (Stenella coeruleoalba) and Fraser’s dolphin (Lagenodelphis hosei) were observed in mixed-species groups, while one group of melon-headed whales (Peponocephala electra) was seen associating with a group of sperm whales. Risso’s dolphins (Grampus griseus) were frequently sighted throughout the research cruise, with one unusual record of a large mating group. Many sightings were made in the vicinity of the numerous submarine canyons around Sri Lanka’s coastline highlighting their potential role in enhancing productivity in the offshore waters. It is concluded that Sri Lankan offshore waters hold a rich, but little surveyed cetacean fauna that warrants further studies and implementation of conservation measures to protect these populations.

Discrete or not so discrete: long distance movements by coastal bottlenose dolphins in UK and Irish waters

The potential for long distance movements in common bottlenose dolphins (Tursiops truncatus) from six UK and Irish study sites was examined using photographs of natural markings. Here we provide the first evidence for long-term re-sightings between the Moray Firth, Inner Hebrides and across international borders to the Republic of Ireland as determined for eight individuals over a ten year period from 2001 to 2010. Minimum dispersal distances of up to 1,277km were resolved providing a new distance record for the species in European waters. Although none of the sightings were made within protected areas, several were made in waters used by animals from a Special Area of Conservation (SAC) revealing some evidence for connectivity between areas previously regarded as discrete. Our findings highlight the need to mitigate broader-scale anthropogenic impacts affecting these dolphins across multiple sites throughout their coastal range. Accordingly, we underline the importance of developing wider conservation measures for this species in UK and Irish waters, but particularly in prospective corridor areas potentially linking designated SACs in the Moray Firth, Cardigan Bay and Shannon Estuary.

Baseline data on abundance, site fidelity and association patterns of common bottlenose dolphins (Tursiops truncatus) off the northeastern Tunisian coast (Mediterranean Sea)

The common bottlenose dolphin has been studied intensively in numerous locations around the world but very little is known about this species along the South Mediterranean Basin. In this study, the temporal distribution of dolphins, group dynamics, site fidelity and association patterns of common bottlenose dolphins along the northeastern coastal waters of Tunisia was assessed through mark-recapture photo-identification techniques. Prior to this study, no research has focused on bottlenose dolphins within these waters, despite the potential for human impacts on this species. A total of 718h of boat-based observations, spanning 284 days, were spent at sea between August 2008 and July 2010. During this period, 253h were spent in direct observation of 317 groups of common bottlenose dolphins. Bottlenose dolphins were observed in all seasons, although seasonality was evident, with more encounters during the summer. Photo-identification studies show that 43 individuals used the northeastern coast of Tunisia on a regular basis, while others were present less often. Based on a social structure analysis it was possible to discriminate different communities related with the spatial distribution of the sightings (Zembra island, Hammamet, Kelibia and Galite island).

An analysis of historical bottlenose dolphin (Tursiops truncatus) strandings in the Mississippi Sound, USA using classification and regression trees (CART)

Trends in bottlenose dolphin (Tursiops truncatus) strandings can be used to examine several factors associated with mortality and life history and are essential for detecting unusual mortality events (UMEs). This study characterised stranding trends in the Mississippi Sound (MS) region of the northern Gulf of Mexico (GoM) from 1996–2009 using kernel density estimation (KDE) and classification and regression tree (CART) analysis. An annual mean of 26.1 strandings (n = 14), SD = 13.7, 95% CI [18.2, 34.0] and a peak in strandings during spring (March–May) were evident from our analyses. Neonates stranded almost exclusively in spring indicating that this is the dominant breeding and calving season in this area. Spatial distributions revealed that the majority of dolphins stranded along central and western portions of the MS Sound near Gulfport, MS and on Ship Island during the spring and summer months, but were more often found in the eastern MS Sound during winter and autumn. Our CART analyses indicated that 1996, which contained a declared UME, was anomalous from other years as the number of adult, sub-adult and juvenile strandings was relatively high during the autumn and winter. Further, our analyses showed that the location of those strandings on Ship Island in autumn and winter was unique from all other years in the historical record. These results represent historical conditions that can be used as a baseline for future studies of the effects of environmental disturbances, including UMEs, in MS. This research also demonstrates the versatility and usefulness of CART for describing historical trends, detecting departures from the norm and explaining UMEs within the framework of a single analysis. This approach represents an objective assessment tool that could be used to assist governmental agencies with determining the onset of a UME and could help support or refute the cause of these events.

Paternity patterns in a long-term resident bottlenose dolphin community

Genetic analyses, initiated in 1984, have played a major role in our understanding of the structure and social relationships of the long-term resident community of common bottlenose dolphins (Tursiops truncatus) in Sarasota Bay, Florida (SBDC). One component of our ongoing study of the community’s social system involves using blood samples from periodic catch-and-release sampling for life history and health assessment studies, as well as skin from biopsy dart sampling studies and strandings, to investigate paternity and mating strategies in this community. These analyses, covering a span of four generations of calves, were originally based on chromosomes and protein electrophoresis, but with the advent of microsatellite DNA technology, the latter has become our analysis of choice. We have performed paternity analyses on 204 known mother-calf pairs. For 151 of the calves (74%), sires were identified within the SBDC, but for the remaining 26% of the calves all sampled males associated with the community were excluded and it is likely that a substantial contribution of paternity to the SBDC comes from outside the community. Of the SBDC males, only 52 males of the more than 200 potential sires were sires. The age of sires at time of conception of a calf ranged from 10 to 43 years, averaging 24 years old. These males have sired 1-7 calves during a documented period of reproductive tenure of as much as 24 years (average = 21.4 years). Four males have sired 6-7 calves each, these males siring calves in the community for more than 20 years. Another 19 males have each sired 3-5 calves and the remaining 30 males were identified as sires of 1-2 calves. Paired males sired 75% of the calves while 25% of the calves were sired by unpaired males. Females with multiple offspring generally had multiple sires for these offspring. These paternity analyses support the hypothesis that a major avenue of gene flow in the SBDC is through the males given their greater ranges, with occasional exchangeviavisits from males from other areas, as well as the occasional brief movements of females from outside the community range into the community.

A characterisation of common bottlenose dolphin (Tursiops truncatus) interactions with the commercial shrimp trawl fishery of South Carolina, USA

In the United States, interactions between the shrimp trawl fishery and bottlenose dolphins are known to exist; however, the level of mortality is largely unknown, and has not been studied in South Carolina, USA. The current study attempted to determine if interactions between bottlenose dolphins and the South Carolina commercial shrimp trawl fishery pose a significant threat to dolphin populations and if fishery related mortality is underreported. Onboard observations were made during a 25 day (August–December 2010) field study. No dolphin takes occurred during the observational period. These observations focused on direct physical interactions with the gear and depredation behaviours. Additionally, a subsample of the shrimp fishery in South Carolina was asked to participate in a mailed survey. The survey included questions related to gear, dolphin observations, and the status of the shrimp fishery. This paper also examines historical dolphin stranding data from the NOAA/CCEHBR MMIS database for signs of shrimp fishery interactions. A three-tiered flow diagram was developed to characterise each stranding case according to the likelihood that mortality resulted from trawler interaction. Field results point to significant dolphin presence around commercial trawlers (x2 = 23.406, p < 0.001). Survey results showed 12 unreported incidents of shrimp trawl fishery mortality of dolphins. Finally, stranding records revealed several more cases with signs of possible trawler interaction. The current US National Marine Fisheries Service (NOAA) designation of the fishery as a Category II fishery is correct. Increased observer coverage and improved communication with the fishery on the importance of reporting takes is warranted.

Abundance and distribution of marine mammals in nearshore waters off New Jersey, USA

Marine mammal abundance and distribution in New Jersey’s nearshore waters are not well known due to limited dedicated studies. The first yearround systematic surveys were conducted to determine the spatial/temporal distribution and estimate the abundance of marine mammals in this region prior to wind power development. Eight marine mammal species were observed: North Atlantic right whale (Eubalaena glacialis), humpback whale (Megaptera novaeangliae), minke whale (Balaenoptera acutorostrata), fin whale (Balaenoptera physalus), bottlenose dolphin (Tursiops truncatus), common dolphin (Delphinus delphis), harbour porpoise (Phocoena phocoena) and harbour seal (Phoca vitulina). Results indicate clear seasonal patterns in distribution and abundance. The fin whale, humpback whale and bottlenose dolphin were sighted during all seasons. The abundance of large whales in the study area was relatively low while the abundance of dolphin and porpoise species was high and largely seasonal. The bottlenose dolphin was the most abundant species; however, abundance was high only during spring and summer. Common dolphins and harbour porpoises were common in the study area during winter and spring. These baseline data will be used to assess potential environmental impacts of the construction and operation of offshore wind power facilities in this region.