Dusky Dolphins Lagenorhynchus Obscurus Research Articles

Predatory species left stranded following the collapse of the sardine Sardinops sagax (Pappe, 1854) stock off the northern Benguela upwelling system: A review

Sardine Sardinops sagax (Pappe, 1854) is an important forage species, in the northern Benguela Upwelling System (nBUS). Sardine was a key forage species of the pelagic component in the nBUS, but the population collapsed due to a combination of overfishing and ecosystem change and variability in the nBUS. Multiple predators depended on sardine as high-quality food at the time when it was abundant. This study reviewed the current knowledge of predators' diet pre- and post-collapse of the sardine population stock in the nBUS. Data were sourced from previous studies on the trophic interaction in the nBUS. The historical and contemporary diets of commercially exploited species that prey on sardine were found to be relatively well documented while there are data deficiencies for non-commercially exploited species including cetaceans, sharks and some non-commercially exploited fish species. Amongst the species most reliant on sardine as prey are African penguin Spheniscus demersus, Cape gannet Morus capensis, Cape cormorant Phalacrocorax capensis, Cape monkfish Lophius vomerinus, shallow-water hake Merluccius capensis, deep-water hake M. paradoxus, snoek Thyrsites atun, Albacore tuna Thunnus alalunga, Cape fur seal Arctocephalus pusillus, Common dolphins Delphinus delphis, Dusky dolphins Lagenorhynchus obscurus, Heaviside's dolphins Cephalorhynchus heavisidii, six gills shark Hexanchus griseus, copper sharks Carcharhinus brachyurus, school shark Galeorhinus galeus and pelagic sharks Prionace glauca. Some predatory species such as the African penguin, Cape cormorant, Cape gannet, and school shark, are considered endangered as per the International Union for the Conservation of Nature (IUCN) Red List criteria. Populations of Albacore tuna and Cape monkfish are near threatened, while Cape fur seals, common dolphins, and shallow-water hake are considered the least concerned on the IUCN list. Although the collapse of sardine has affected the food webs it has not resulted in collapse, rather there have been changes. Three prey species; bearded goby, Cape horse mackerel, and jellyfish, were identified as alternative prey for some of the predators that previously fed on sardine. This review showed how overexploitation of sardine could have had far-reaching effects on the nBUS through feeding linkages. Goby, although a low-quality prey, is a successful substitute for sardine probably mostly due to its high abundance, tolerance to low oxygen and ability to thrive in warm waters. However, further studies are needed to establish the strength of the ecological linkages of the prey species that replaced sardine in the diets of the predators.

Dietary plasticity of two coastal dolphin species in the Benguela upwelling ecosystem

Defining the trophic relationships of marine predators and their dietary preferences is essential in understanding their role and importance in ecosystems. Here we used stable isotope analysis of skin samples (δ15N values reflecting trophic level and δ13C values reflecting foraging habitat) to investigate resource partitioning and spatial differences of the feeding ecology of dusky dolphins Lagenorhynchus obscurus and Heaviside’s dolphins Cephalorhynchus heavisidii from 2 coastal study sites separated by 400 km along the coast of central (Walvis Bay) and southern (Lüderitz) Namibia in the Benguela upwelling ecosystem. Overall, isotopic niches of both predators were significantly different, indicating partitioning of resources and foraging habitats. Despite their smaller body size, Heaviside’s dolphins fed at a significantly higher trophic level than dusky dolphins. Stable isotope mixing models revealed that both species fed on high trophic level prey (i.e. large Merluccius spp., large Sufflogobius bibarbatus, and Trachurus t. capensis) at Walvis Bay. The diet of both dolphin species included smaller pelagic fish and squid at Lüderitz. Spatial differences highlight that Heaviside’s and dusky dolphins may exhibit dietary plasticity driven by prey availability, and that they likely form distinct population segments. Important prey for both dolphin species, specifically Merluccius spp. and T. t. capensis, are the main target of trawl fisheries in the Benguela upwelling ecosystem, highlighting potential resource overlap between dolphins and fisheries.

South Africa’s newly approved marine protected areas have increased the protected modelled habitat of nine odontocete species

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 633:1-21 (2020) - DOI: https://doi.org/10.3354/meps13190 FEATURE ARTICLE South Africa’s newly approved marine protected areas have increased the protected modelled habitat of nine odontocete species Jean Purdon1,*, Fannie Shabangu2, Marc Pienaar3, Michael J. Somers4, Ken P. Findlay5 1Whale Unit, Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa 2Fisheries Management Branch, Department of Environmental Affairs, Cape Town 8000, South Africa 3South African Environmental Observation Network, uLwazi Node, Pretoria 0083, South Africa 4Eugène Marais Chair of Wildlife Management, Centre for Invasion Biology, Mammal Research Institute, University of Pretoria, Pretoria 0002, South Africa 5CPUT Research Chair: Oceans Economy, Cape Peninsula University of Technology, Cape Town 8000, South Africa *Corresponding author: purdonjean@gmail.com ABSTRACT: Marine protected areas (MPAs) are important for the preservation of ecosystem functioning, ecosystem services, resilience and biodiversity around the world. In South Africa, the role of MPAs in the protection of cetaceans is poorly understood, a knowledge gap that may affect management decisions and future cetacean conservation. Here, we used presence data of 9 odontocete species (namely southern bottlenose whale Hyperoodon planifrons, common dolphin Delphinus delphis, dusky dolphin Lagenorhynchus obscurus, false killer whale Pseudorca crassidens, Indo-Pacific humpback dolphin Sousa chinensis, Heaviside’s dolphin Cephalorhynchus heavisidii, killer whale Orcinus orca, Risso’s dolphin Grampus griseus and Indo-Pacific bottlenose dolphin Tursiops aduncus) to predict their distribution in the South African exclusive economic zone (EEZ) using ensemble models. The data were collected from various opportunistic, historical and scientific records spanning the period 1957-2014. Up to 9 predictor variables (sea surface temperature, chlorophyll a concentration, salinity, bathymetry, distance to shore, bottom slope, eastward and northward sea water velocity and bioregion) were used in the ensemble model to predict the distributions for each odontocete species. Model results suggest that some of the species’ preferred habitats are partially (i.e. <5% of the distribution) protected by the established MPAs, but the protection area does increase with the recently approved MPAs. This study provides a baseline for the distribution of the 9 odontocete species in relation to the MPAs, which could facilitate the protection and management of these species in the region and help identify important marine mammal areas. KEY WORDS: Habitat modelling · Species distributions · Marine protected areas · Odontocetes · South Africa Full text in pdf format Information about this Feature Article Supplementary material NextCite this article as: Purdon J, Shabangu F, Pienaar M, Somers MJ, Findlay KP (2020) South Africa’s newly approved marine protected areas have increased the protected modelled habitat of nine odontocete species. Mar Ecol Prog Ser 633:1-21. https://doi.org/10.3354/meps13190 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 633. Online publication date: January 09, 2020 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2020 Inter-Research.

Northernmost record of dusky dolphin &lt;i&gt;Lagenorhynchus obscurus&lt;/i&gt; in coastal waters off northern Peru (4°S)

Dusky dolphin Lagenorhynchus obscurus is distributed primarily in cool coastal waters at several continental margins and island borders in the Southern Hemisphere. Off Peru, the northernmost record of this species has been in front of the coast of Salaverry (ca., 6°S). In this paper, we report for the first-time a pod of dusky dolphin at the coast of Los Órganos (4°9.517’S; 81°11.958’W) northern Peru, thus extending the potential distributional range ca., 350 km towards the equator. A group of between 10 to 20 adult individuals was sighted on 17 October 2017, during a whale-watching excursion. Digital photographs and film allowed us to confirm the species based on body morphology and coloration. The sighted group was moving around the area without heading to a given direction. This record constitutes the northernmost record of dusky dolphin in Peru and arguably in the Southern Hemisphere.

Birds and mammals off the northern coast of Argentina: first report of an association between birds and a feeding Pygmy Right Whale Caprea marginata

When the icebreaker Oden passed between 39°36'S, 57°46'W and 39°59'S, 58°11'W on 20 November 2007, an extraordinary observation was made. A feeding Pygmy Right Whale Caprea marginata, a species rarely seen, was attended by eight Grey Phalaropes Phalaropus fulicarius, two Slender-billed Prions Pachyptila belcheri, and four Wilson’s Storm Petrels Oceanites oceanicus. The birds returned to feed around the head of the whale every time it surfaced, presumably copepod plankton straining out between the baleen. The site is off Rio de la Plata estuary where nutrient rich freshwater meets cold water of the Malvinas (Falkland) Current, creating a hotspot with high levels of plankton food. The conditions were extraordinarily favourable for observation with a calm sea, no wind and only a very weak swell. Six multispecies feeding groups were seen with a total of 42 species of birds, eleven species of whales, dolphins and porpoises, and three species of seals. Dusky Dolphins Lagenorhynchus obscurus and Great Shearwaters Puffinus gravis were predominant in the groups.

Acoustic observations of dusky dolphins Lagenorhynchus obscurus hunting Cape horse mackerel Trachurus capensis off Namibia

Predator-prey interactions of mammals and their fish prey in marine ecosystems are rarely identified and recorded. We document for the first time the underwater behaviour of hunting dusky dolphins Lagenorhynchus obscurus and the responses of their prey, Cape horse mackerel Tra- churus capensis, observed in open ocean waters off northern Namibia. Predator-prey interactions were monitored acoustically during a continuous period of 2 h with a split-beam scientific echo sounder, and the surface behaviour of the dolphins was observed from the ship's deck. In total 54 predator-prey events were observed (mean, 0.45 events min -1 ). The maximum burst speed during attack was 9.9 m s -1 , while the average attack speed was 3.4 m s -1 (mean swimming speed: 1.4 m s -1 ). Dolphin traces were predominantly located underneath the fish aggregation (63% of the time), as the dolphins attacked the schools from underneath (mean depth: 120 m; maximum depth: 156 m). The dolphin target strength at 38 kHz was, on average, -31.5 dB (95% CI: -33.4 to -30.2 dB). The attacks caused immediate reactions in the Cape horse mackerel aggregations: subschools were forced towards the surface where they were herded into dense aggregations by the dolphins. Observed predator response patterns included 'Vacuole' (n = 21), 'Split' (n = 19), 'Bend' (n = 10) and 'Hourglass' (n = 4). Packing densities changed significantly before (0.4 fish m -3 ), during (2.0 fish m -3 ) and after (0.3 fish m -3 ) the dolphin attacks, and when predators burst into the fish aggregations, mean (±SD) intraschool packing densities of horse mackerel were significantly lower in front of the predators (0.33 ± 0.17 fish m -3 ) than behind (6.65 ± 1.76 fish m -3 ).

Modeling habitat use for dusky dolphin and Commerson’s dolphin in Patagonia

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 421:217-227 (2011) - DOI: https://doi.org/10.3354/meps08912 Modeling habitat use for dusky dolphin and Commerson’s dolphin in Patagonia Griselda V. Garaffo1,*, Silvana L. Dans2,3, Susana N. Pedraza2,3, Mariana Degrati2,3, Adrián Schiavini4,5, Raúl González6, Enrique A. Crespo2,3 1Universidad Nacional de Mar del Plata, Funes 3600, CP (7600) Mar del Plata, Argentina 2Centro Nacional Patagónico (CONICET), Boulevard Almirante Brown 2825, CP (9120) Puerto Madryn, Chubut, Argentina 3Universidad Nacional de la Patagonia, Boulevard Almirante Brown 3600, CP (9120) Puerto Madryn, Chubut, Argentina 4Centro Austral de Investigaciones científicas (CONICET), Houssay 200, CP (V9410) Ushuaia, Tierra del Fuego, Antártica e Islas del Atlántico Sur, Argentina 5Wildlife Conservation Society Representación, Amenabar 1595, Buenos Aires, Argentina 6Instituto de Biología Marina y Pesquera Almirante Storni, Güemes 1030, CP (8520) San Antonio Oeste, Río Negro, Argentina *Email: garaffo@mdp.edu.ar ABSTRACT: Several species of small cetaceans inhabit the coastal area of Patagonia (Argentina), but little is known about their distribution and the degree of overlap between them. The goal of the present study was to build habitat-selection models for small cetaceans in order to assess areas of particular importance for the different species. These models were constructed using physiographic and remotely sensed variables. From 1994 to 2007, 13 aerial surveys were conducted along the Patagonian coast (from Golfo San Matías: 40°40’–42°14’S, 65°00’–63°47’W to Bahía de los Nodales: 48°00’S, 65°35’W). A grid of 0.5° × 0.5° cells was constructed for the study area. Each cell was characterized by environmental variables and by the encounter rate (ER) for each cetacean species. The ER of each species was investigated in relation to environmental variables using generalized linear models, and model averaging (multimodel inference) was used to obtain a predicted ER for the different species. The correlation between the ER of different species was analyzed by Spearman rank correlation. The environmental variables that were found to be significant predictors of species distribution differed between species. The ERs of dusky dolphin Lagenorhynchus obscurus and Peale’s dolphin L. australis showed a positive relationship. Commerson’s dolphin Cephalorhynchus commersonii presented a more coastal distribution than the other species, and individuals were more often found feeding in estuarine zones. Knowledge of the patterns of distribution of small cetaceans along the Patagonian coast provides baseline knowledge of how these species interact with each other and their environment. Such information should be considered when managing potential areas of conflict between coastal small cetaceans and human activities. KEY WORDS: Distribution modeling · Dolphins · Generalized linear model · Habitat selection · Patagonia Full text in pdf format PreviousNextCite this article as: Garaffo GV, Dans SL, Pedraza SN, Degrati M, Schiavini A, González R, Crespo EA (2011) Modeling habitat use for dusky dolphin and Commerson’s dolphin in Patagonia. Mar Ecol Prog Ser 421:217-227. https://doi.org/10.3354/meps08912 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 421. Online publication date: January 17, 2011 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2011 Inter-Research.

Dusky dolphins Lagenorhynchus obscurus and Cape fur seals Arctocephalus pusillus pusillus: fatty acid composition of their blubber and prey species

The fatty acid composition of the blubber of five dusky dolphins Lagenorhynchus obscurus and five Cape fur seals Arctocephalus pusillus pusillus from the northern Benguela ecosystem (South-East Atlantic) and their main prey was determined. Differences in fatty acid composition of the inner and outer blubber layer of the dolphins were substantial, with higher relative amounts of monoenic fatty acids with 14, 16 and 18 carbons in the outer layer and higher relative amounts of saturated, long-chain monounsaturated and polyunsaturated fatty acids in the inner layer. This stratification is similar to the general pattern that has been observed in a variety of marine mammals, but the degree of stratification is the highest yet observed, with the long-chained (n3) fatty acids being more than 20 times more abundant in the inner than in the outer layer. On the other hand, the seals’ blubber consisted of only one uniform layer, densely supported by connective tissue. The whole-body fatty acid composition of the prey was species specific. The dolphins and seals had significantly different fatty acid composition of their blubber. In both species, the blubber fatty acid composition was different from the composition of the prey, indicating that a phylogenetic component is involved in the determination of the fatty acid composition of the blubber.

Using active acoustics to compare lunar effects on predator–prey behavior in two marine mammal species

Many delphinids feed on vertically migrating sound-scattering layers. The migration of micronektonic animals in these layers is strongly affected by light, both solar and lunar. Active acoustic approaches were used to observe lunar phase effects on the diel patterns of sound-scatter- ing layers in 2 habitats and to simultaneously observe the behavior of foraging spinner dolphins Stenella longirostris in Hawaii and dusky dolphins Lagenorhynchus obscurus in New Zealand. Lunar phase was important in structuring the behavior of diurnally migrating animals in scattering layers off both New Zealand and Hawaii. While the responses of these scattering layers to lunar phase dif- fered between locations, the layers were similar in continuing to migrate to surface waters during all moon phases, in contrast to results from other locations. In both dusky and spinner dolphins, dolphin relative abundance increased with increasing lunar illumination. The dolphin response to lunar phase is not clearly explained by the observed changes in prey. However, the results suggest that lunar phase is likely to be important in driving behavior of the many delphinid species that forage on vertically migrating prey. Active acoustics can be used to simultaneously study predator and prey, elucidating the foraging behavior of other dolphin species feeding on sound-scattering layers. Com- paring the observed patterns to the phylogeny of these diverse species could provide insights into the evolution of behavior in delphinids.

Epidemiological pattern of tattoo skin disease: a potential general health indicator for cetaceans

The presence of tattoo skin disease (TSD) was examined in 1392 free-ranging and dead odontocetes comprising 17 species from the Americas, Europe, South Africa, New Zealand and Greenland. We investigated whether TSD prevalence varied with sex, age and health status. TSD was encountered in cetaceans from the Pacific and Atlantic Oceans as well as in those from the North, Mediterranean and Tasman Seas. No clear patterns related to geography and host phylogeny were detected, except that prevalence of TSD in juveniles and, in 2 species (dusky dolphin Lagenorhynchus obscurus and Burmeister's porpoise Phocoena spinipinnis), in adults was remarkably high in samples from Peru. Environmental factors and virus properties may be responsible for this finding. Sex did not significantly influence TSD prevalence except in the case of Peruvian P. spinipinnis. Generally, there was a pattern of TSD increase in juveniles compared to calves, attributed to the loss of maternal immunity. Also, in most samples, juveniles seemed to have a higher probability of suffering TSD than adults, presumably because more adults had acquired active immunity following infection. This holo-endemic pattern was inverted in poor health short-beaked common dolphins Delphinus delphis and harbour porpoises Phocoena phocoena from the British Isles, and in Chilean dolphins Cephalorhynchus eutropia from Patagonia, where adults showed a higher TSD prevalence than juveniles. Very large tattoos were seen in some adult odontocetes from the SE Pacific, NE Atlantic and Portugal's Sado Estuary, which suggest impaired immune response. The epidemiological pattern of TSD may be an indicator of cetacean population health.

Prey occurrence in the stomach contents of four small cetacean species in Peru

The diets of long-beaked common dolphins Delphinus capensis (n=117), dusky dolphins Lagenorhynchus obscurus (n=72), Burmeister's porpoises Phocoena spinipinnis (n=69) and offshore common bottlenose dolphins Tursiops truncatus (n=22) were determined based on the analysis of the stomach contents collected from animals landed in ports along the Peruvian central coast and from Marcona, in southern Peru, during 1987-1993. The number of prey ingested was obtained by counting the number of fish otoliths and cephalopod mandibles (beaks). Only fish could be identified to species level. Long-beaked common dolphins fed mainly on Peruvian anchovy Engraulis ringens (70.0% by number), Panama lightfish Vincigerria lucetia (7.8%) and slimtail lanternfish Lampanyctus parvicauda (6.7%). Dusky dolphins consumed mainly anchovies (49.7%, 16.8%), slimtail lanternfish (23.6%, 0.1%), Inca scad Trachurus murphyi (17.1%, 0%) and mote sculpin Normanichthys crockeri (0%, 76.0%) off the central Peruvian coast and Marcona, respectively. In the same areas, Burmeister's porpoises fed mainly on anchovy (88.9%, 77.6%), silverside Odontesthes regia (6.5%, 0%), mote sculpin (0%, 8.1%) and South Pacific hake Merluccius gayi (0.6%, 7.9%). Offshore common bottlenose dolphins consumed mainly slimtail lanternfish (39.2%), barracuda Sphyraena sp. (13.5%) and Peruvian pilchard Sardinops sagax (13.3%). The diversity indices of the diet and temporal shifts in the main prey suggest an opportunistic feeding strategy for the four cetacean species studied, which take advantage of the locally most available epipelagic and mesopelagic schooling fish. Cluster analysis shows high similarity in their diets, with these four marine top predators being able to optimally exploit the high productivity of the Peruvian upwelling ecosystem.

Mortality of dolphins and porpoises in coastal fisheries off Peru and southern Ecuador in 1994

Of 722 cetaceans captured mostly in multi-filament gillnets and landed at Cerro Azul, central Peru, in 87 days during January–August 1994, 82·7% were dusky dolphin Lagenorhynchus obscurus, 12·6% Burmeister's porpoise Phocoena spinipinnis, 2·4% long-beaked common dolphin Delphinus capensis and 2·4% bottlenose dolphin Tursiops truncatus. The total kill estimate for a seven-month period, stratified by month, was 1567 ± 237 (SE) cetaceans. Data collected at 16 other ports showed that high levels of dolphin and porpoise mortality persisted in coastal Peru at least until August 1994 when an unimplemented 1990 ban on small cetacean exploitation was renewed. Circumstantial evidence suggests that, thereafter, increasing enforcement reduced direct takes and illegal trade in meat but also hampered monitoring. The absence of abundance data precludes any assessment of impact on populations. An interview study in October–December 1994 of the extensive multi-filament gillnet fishery from Puerto Bolívar in southern Ecuador indicated, despite a low catch rate per boat, an estimated annual take of 227 bottlenose dolphins in the inner estuary of the Gulf of Guayaquil. This represents some 9% of the resident bottlenose dolphin population, or more than twice its estimated birth rate. Two mono-filament gillnet boats did not report any entangled cetaceans.

Genital and lingual warts in small cetaceans from coastal Peru

We report on genital warts in dusky dolphins Lagenorhynchus obscurus, long-snouted common dolphins Delphinus capensis, bottlenose dolphins Tursiops truncatus and Burmeister's porpoises Phocoena spinipinnis caught in fisheries off central Peru. Lesions were observed inside the genital slit, on the skin adjacent to it, on the penis and on the vagina. Macroand microscopical features of the lesions resemble those of benign genital warts associated with papillomavirus infection in humans Genital warts from L, obscurus and P spinipinnis contained nuclei which stained positive for genus-specific papillomavirus structural antigens, though weakly in the latter species. These data suggest that papillomavirus(es) may be the etiological agent(s) of the disease. The prevalence of the lesions in 130 small cetaceans was high: 66.7% (confidence interval, CI, 57.0 to 74.0%) in L. obscurus (n = 78). 50% in D. capensis (n = 10), 33% in T truncatus (n = 9) and 48.5% (C1 33.0 to 64.0%) In P. spinipinnis (n = 33). This suggests a venereal transmission of the disease, as in humans. Sexual variation in wart prevalence was found in L. obscurus and P spinipinnis with males being 2 and 3 times more infected than females, respectively. No correlation was observed between body length (as a measure of age) and wart prevalence, suggesting that no strong and long-lasting immunity was induced in affected animals or that they may have been infected by different types of papillomaviruses. Lingual tumours were seen in 1 D. capensis.

The exploitation of small cetaceans in Coastal Peru

Several species of small cetaceans are captured by fishermen in Peruvian coastal waters and used for human consumption. A large directed fishery exists for one species, the dusky dolphin Lagenorhynchus obscurus. In addition, two other species, the Burmeister's porpoise Phocoena spinipinnis and bottlenose dolphin Tursiops truncatus, are commonly taken in both directed fisheries and incidentally to other fishing operations. To examine the exploitation of these species in detail, we monitored the catches at several small ports in central Peru during 1985 and 1986. The vast majority (over 90%) of small cetaceans landed at these ports were dusky dolphins captured in drift gill nets. A few animals were taken in demersal gill nets, purse seines, by hand-thrown harpoons and other methods, Artisanal fishermen captured small cetaceans when the animals were available and when other more lucrative fisheries were unavailable. Most dolphin and porpoise meat was consumed fresh, although a small amount was salted and dried. Published statistics of the weight of small cetaceans landed at Peruvian ports, in conjunction with species composition and mean species weight data collected during this study, allow us to estimate that approximately 10 000 dolphins and porpoises were landed in Peru during 1985.

On the identity ofProdelphinus petersiiLütken, 1889 and records of dusky dolphinLagenorhynchus obscurus(Gray, 1828) from the southern Indian and Atlantic oceans

Prodelphinus petersii Lutken. 1889 from Amsterdam Island is assigned as a junior synonym of the dusky dolphin Lagenorhynchus obscurus (Gray. 1828). This identification and three confirmed sightings from near the Prince Edward Islands represent the first records of the dusky dolphin from the Indian Ocean. L. obscurus is documented also for the first time from the mid-Atlantic near Gough Island, and its much disputed occurrence off the Falklands Islands is confirmed. Possible sightings of L. obscurus from both the southern Indian and Atlantic oceans are reviewed. Available evidence Supports a disjunct distribution for L. obscurus and the existence of discrete stocks confined to continental shelves and oceanic island groups. However, the taxonomic status of Lagenorhynchus species sighted in offshore tropical waters needs to be clarified.