Cephalorhynchus Commersonii Research Articles

Living in an estuary: Commersons dolphin (Cephalorhynchus commersonii (Lacepede, 1804)), habitat use and behavioural pattern at the Santa Cruz River, Patagonia, Argentina

Commerson's dolphins, Cephalorhynchus commersonii, suffer bycatch in fisheries and are target of dolphin-watching activities along Patagonia. Here we described dolphins' habitat use and behavioural pattern at the estuary of Santa Cruz River. Behavioural observations were made from vantage points using a spotting scope. Boat surveys were conducted randomly from Puerto Santa Cruz to the mouth of the river to analyze the habitat use. The survey area was divided into 1 km 2 cells and characterized with depth and benthic slope. The described behaviours for the Commerson's dolphin were: travelling, slow travelling, milling, resting, socializing, stationary swimming and diving. A new behavioural context was assigned to diving, a behaviour that showed a high frequency during downing tide, suggesting a benthic foraging strategy. Additionally, we found a strong influence of the tide on Commerson's dolphin behaviour. Habitat use models indicated that dolphins prefer shallow water inside the estuary. The knowledge of the behavioural patterns and the habitat use of these endemic species, in this unexplored area, provide tools for management and conservation purposes.

Mother–calf interactions and social behavior development in Commerson’s dolphins (Cephalorhynchus commersonii)

Abstract Mother–calf interactions and the behaviors of mothers during separation from their calves were examined in four Commerson’s dolphin (Cephalorhynchus commersonii) mother–calf pairs. Four infants were observed: 56.8 h over 30 days from birth to 263 days of age, 36.9 h over 20 days from birth to 149 days of age, 10.4 h over 3 days from birth to 2 days of age, and 15.0 h over 3 days from birth to 2 days of age. All four pairs shared common characteristics in the rate and frequencies of mother–calf interactions and the behaviors of mothers during the first week of life. After the first week, individual differences in changes in the frequency of each behavior were observed. The three behaviors considered representative of maternal care (parallel swimming, synchronous breathing, and body-to-body contact) were frequently performed in the first week; thereafter, the frequencies declined. Separate behaviors of mothers were infrequent during the first week and increased with an increase in infants’ age. Bumping by infants increased with time, suggesting an increase in soliciting by calves and conflict between mothers and calves. The frequency of flipper-to-body rubbing also changed but in a complex manner, probably because the calves needed to learn how to perform this behavior from their mothers and because initiator and recipient of this behavior can be changed quickly.

Abundance and Spatial Distribution of Commerson’s Dolphin (Cephalorhynchus commersonii) at a Breeding Site: Ría Deseado, Patagonia, Argentina

Abundance and spatial distribution of the Commerson’s dolphin (Cephalorhynchus commersonii) during spring and summer 2002-2004 and fall/winter 2003 were estimated in the estuary Ria Deseado, Patagonia, Argentina. To estimate the abundance, photo-identification and mark-recapture (positive method) were combined. Distribution of dolphins within the estuary was studied, and their locations were recorded using a GPS to perform a Kernel Density Analysis. Adult abundance was higher during spring (34 and 35 individuals in 2002 and 2003, respectively) and decreased during fall (7 individuals) and winter (16 individuals). Sightings of 132 adults during winter, spring, and summer (n = 12, n = 76, and n = 44, respectively) and 14 calves during spring and summer (n = 4 and n = 10, respectively) were recorded; mean school size was 2.0 ± 1.2. Distribution and abundance varied seasonally. During spring, dolphins were more equally distributed through the estuary than during summer when calves and adults remained mainly inside the estuary. The presence of dolphins year-round suggested that the inhabitants are residents of the estuary. This study offers new information on the ecology of the Commerson’s dolphin and confirms Ria Deseado as a breeding site for this species.

Influence of body size and ranging patterns on delphinid sociality: Associations among Commerson's dolphins

We investigated the association patterns of 48 identifiable Commerson's dolphins (Cephalorhynchus commersonii) photographed 2 or more times over a 2-year period in Baho´a Engano, Chubut, Argentina. The associations among them were not different from random for short time periods (7 days) but were significantly different from random for longer periods. Lagged identification rate and lagged association rate models show that dolphins remained in the area on average 15 days and then moved away as the original groups dissolved. Commerson's dolphins appear to have a fission-fusion society, and the observed strength of their associations is in concordance with the predictions regarding their body size and ranging patterns. The dolphins seem to rely on Baho ´a Engano as a core area for most of their activities, but the aggregations are labile and some individuals remain associated in a more stable manner with only a few other individuals.

Estimating dyad association probability under imperfect and heterogeneous detection

In animal behaviour studies, association indices estimate the proportion of time two individuals (i.e. a dyad) spend in association. In terms of dyads, all association indices can be interpreted as estimators of the probability that a dyad is associated. However, traditional indices rely on the assumptions that the probability to detect a particular individual ( p) is either approximately one and/or homogeneous between associated and not associated individuals. Based on marked individuals we develop a likelihood based model to estimate the probability a dyad is associated ( ψ) accounting for p < 1 and possibly varying between associated and not associated individuals. The proposed likelihood based model allows for both individual and dyadic missing observations. In addition, the model can easily be extended to incorporate covariate information for modeling p and ψ. A simulation study showed that the likelihood based model approach yield reasonably unbiased estimates, even for low and heterogeneous individual detection probabilities, while, in contrast, traditional indices showed moderate to strong biases. The application of the proposed approach is illustrated using a real data set collected from a population of Commerson's dolphin ( Cephalorhynchus commersonii) in Patagonia Argentina. Finally, we discuss possible extensions of the proposed model and its applicability in animal behaviour and ecological studies.

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.

Genetic divergence over small geographic scales and conservation implications for Commerson's dolphins (Cephalorhynchus commersonii) in southern Argentina

Cephalorhynchus commersonii is distributed in the nearshore coastal waters of South America, and thus is particularly vulnerable to bycatch in coastal nets and trawls. Our study documents genetic structure in presumed Commerson's dolphin subpopulations along the southern Argentina coastline, from the Ría Deseado in the north to Ría Gallegos in the south, and focuses on the potential for depletion in the apparently more heavily impacted Ría Gallegos area. Only two control region (423 bp) haplotypes were shared among all these locations (out of 11 identified), and striking differences in haplotype frequencies between areas are apparent. AMOVA analysis, using mitochondrial sequence data, indicates significant population subdivision (overall FST= 0.21, P < 0.001) between Ría Deseado (n= 8), Bahía San Julián (n= 11), Ría Gallegos (n= 31), and a small sample of dolphins from the captive colony at San Diego Seaworld (n= 7) derived from animals originally captured in the Strait of Magellan. Comparisons based on haplotypic distances indicated relatively strong differences between regions (ΦST= 0.30, P < 0.001). This research provides the first indication of reduced gene flow and genetic differentiation within local subpopulations of Commerson's dolphins, along a relatively small stretch of coastline.

Isotopic assessment of prey and habitat preferences of a cetacean community in the southwestern South Atlantic Ocean

We used stable carbon (δ 13 C) and nitrogen (δ 15 N) isotope analysis to investigate the trophic ecology of 8 small cetacean species of the southwestern South Atlantic Ocean: 6 delphinids (Grampus griseus, Lagenorhynchus cruciger, L. australis, Lissodelphis peronii, Pseudorca crassidens, and Cephalorhynchus commersonii) and 2 phocoenids (Phocoena dioptrica and P. spinipinnis). We also analyzed samples of possible prey collected from oceanic and coastal habitats adjacent to Tierra del Fuego. Cetacean bone-collagen δ 13 C and δ 15 N data revealed information on both habitat and prey preferences. We observed an isotopic continuum in which coastal species had the highest values of δ 13 C and δ 15 N (L. australis), while oceanic and southern species had the lowest values (L. cruciger and P. dioptrica), indicative of offshore foraging in cold oceanic waters near the Antarctic Conver- gence. Overlap in mean isotope values between C. commersonii and P. spinipinnis suggests that these species may have similar habitat and/or prey preferences. Isotope results for L. peronii, P. cras- sidens, and G. griseus suggest that at these latitudes (~54° S) they forage on the outer continental shelf. G. griseus show bimodal isotopic patterns, suggesting that 2 ecotypes that forage in different habitats and/or consume different prey items occur in this region of the southwestern Atlantic Ocean. The isotopic data presented here provide insight into the ecology of these cetaceans, with relevant implications for their successful management and conservation.

Mitochondrial DNA variation and population structure of Commerson’s dolphins (Cephalorhynchus commersonii) in their southernmost distribution

The Commerson’s dolphin, Cephalorhynchus commersonii, is found in shallow waters of the continental shelf off the eastern coast of South America between 40°S and 56°S. This species is taken incidentally in artisanal gillnet fisheries, especially along the shallow coastline of northern Tierra del Fuego and southern Patagonia. The biological importance of by-catch is likely to be underestimated if the boundaries of subpopulations are not properly defined. Here, we report on the sequence variation of the mitochondrial DNA control region of the Commerson’s dolphin from five areas defined in Tierra del Fuego, Argentina and Chile, to provide a preliminary assessment of population structure where conservation efforts are most needed. A 466 bp fragment of the mitochondrial DNA control region was sequenced from 196 samples of skin, teeth and bone, defining 20 haplotypes from 17 polymorphic sites. Nucleotide (π = 0.40%) and haplotype (h = 0.807) diversity were low compared to some other odontocete populations, but similar to that of other species of this genus. Genetic differentiation evaluated through analyses of molecular variance (AMOVA) showed significant overall differences among areas within Tierra del Fuego (Φ ST = 0.059, P < 0.01). An analysis of sex-specific population structure suggested that the dispersal rates of both females and males are low, indicative of females displaying greater site fidelity. The results from mtDNA control region sequences alone revealed significant differentiation among studied areas, which should be considered as independent management units. We recommend that the impact of localized gillnet mortalities should be managed on a local scale in these areas of Tierra del Fuego.

Echolocation in sympatric Peale's dolphins (Lagenorhynchus australis) and Commerson's dolphins (Cephalorhynchus commersonii) producing narrow-band high-frequency clicks

An increasing number of smaller odontocetes have recently been shown to produce stereotyped narrow-band high-frequency (NBHF) echolocation clicks. Click source parameters of NBHF clicks are very similar, and it is unclear whether the sonars of individual NBHF species are adapted to specific habitats or the presence of other NBHF species. Here, we test whether sympatric NBHF species sharing the same habitat show similar adaptations in their echolocation clicks and whether their clicks display signs of character displacement. Wide-band sound recordings were obtained with a six-element hydrophone array from wild Peale's (Lagenorhynchus australis) and Commerson's (Cephalorhynchus commersonii) dolphins off the Falkland Islands. The centroid frequency was different between Commerson's (133+/-2 kHz) and Peale's (129+/-3 kHz) dolphins. The r.m.s. bandwidth was 12+/-3 kHz for both species. The source level was higher for Peale's dolphin (185+/-6 dB re 1 muPa p.-p.) than for Commerson's (177+/-5 dB re 1 muPa p.-p.). The mean directivity indexes were 25 dB for both species. The relatively low source levels in combination with the high directivity index may be an adaptation to reduce clutter when foraging in a coastal environment. We conclude that the small species-specific shifts in distribution of centroid frequencies around 130 kHz may reflect character displacement in otherwise-stereotyped NBHF clicks.

Behavior and seasonal variation in the relative abundance of Commerson’s dolphin (Cephalorhynchus commersonii) in northern Patagonia, Argentina

Commerson’s dolphins (Cephalorhynchus commersonii) along the Patagonian coast of South America suffer incidental mortality in fisheries and are the target of a dolphin-watching industry. We describe the daily activity patterns and assess the variation in the relative abundance of the species near the northern boundary of its range. Information was gathered with a spotting scope from a cliff-top vantage point applying the method of scan sampling. Behaviors were categorized as individual feeding, cooperative feeding, directional swimming, socializing, and resting. These behaviors are similar to those observed in other species of small cetacean, but differences were found regarding the patterns of directional swimming and feeding techniques. Hunting tactics favored the association of terns with dolphin groups. No clear dial behavioral pattern was observed, but seasonal changes in the frequency of behaviors were recorded. Group and school sizes were larger during periods with colder sea surface temperature (SST). Seasonal abundance was correlated with SST, suggesting that at higher SST the species forsakes the area, probably in favor of coastal areas to the south with lower SST.

Teeth and Bones as Sources of DNA for Genetic Diversity and Sex Identification of Commerson's Dolphins (&lt;I&gt;Cephalorhynchus commersonii&lt;/I&gt;) from Tierra del Fuego, Argentina

Teeth and Bones as Sources of DNA for Genetic Diversity and Sex Identification of Commerson's Dolphins (&lt;I&gt;Cephalorhynchus commersonii&lt;/I&gt;) from Tierra del Fuego, Argentina

Feeding aggregation and aggressive interaction between bottlenose (Tursiops truncatus) and Commerson’s dolphins (Cephalorhynchus commersonii) in Patagonia, Argentina

We report the first recorded interactions between bottlenose dolphin (Tursiops truncatus) and Commerson’s dolphins (Cephalorhynchus commersonii). The diurnal behavioral patterns of bottlenose dolphins in Bahia Engano, Argentina, were similar to those described for other coastal populations around the world. The majority of the feeding bouts were recorded near the mouth the Chubut River. When not feeding near the river, bottlenose dolphins generally swam along the coast, and interactions with Commerson’s dolphins were recorded very close to the shore on two occasions during a 3-year period. In the first event, both species were feeding on a fish school. The second interaction was aggressive in nature, involving one juvenile and three adult bottlenose dolphins with several Commerson’s dolphins. Two of the adult bottlenose dolphins attacked the Commerson’s dolphins. We propose that the observed behavior represented defense of the juvenile bottlenose dolphin.

Commerson's Dolphins (&lt;I&gt;Cephalorhynchus commersonii&lt;/I&gt;) off Ría Deseado, Patagonia, Argentina

Studies of the biology and ecology of Commerson’s dolphins (Cephalorhynchus commersonii) in the Ria Deseado estuary (47o 46' S, 65o 58' W) were carried out during January-February 1986 to 1991 and 1994 to 1997, August 1987 and 1988, September 1995, and May 2003. Commerson’s dolphins were consistently located along a 24-km stretch of the Ria Deseado. Twenty-six dolphins were identified using marks, scars, and differences in the black and white pigmentation of the head, back, and sides. Two adult dolphins with the typical grey colour pattern of the calves of this species have been observed since 1994. Behavioural observations were recorded and fell into four general categories: (1) traveling (51%), (2) resting (21%), (3) feeding (19%), or (4) socialising (9%). Feeding behaviours included dolphins feeding at the surface, near anchor lines, and around piers. Commerson’s dolphins were directly observed feeding on silversides (Odontesthes). Calves were observed between mid-September and midMarch, which suggests that calves are born in the austral spring and early summer. Interactions between dolphins and seabirds/marine mammals were recorded. Killer whales (Orcinus orca) may prey on Commerson’s dolphins in this area.

Description of a new subspecies of Commerson's dolphin, Cephalorhynchus commersonii (Lacépède, 1804), inhabiting the coastal waters of the Kerguelen Islands

A small population of Commerson's dolphin ( Cephalorhynchus commersonii ), widely separated from the South American main population, inhabits the coastal waters of the Kerguelen Islands (Indian sector of the Antarctic or Southern Ocean). The dolphins of this population differ from those of South America by their pigmentation and morphology. Several arguments, including geographic isolation, morphological difference and genetic data (absence of genetic flow between populations and haplotype differences) lead to formally distinguishing a new subspecies, Cephalorhynchus commersonii kerguelenensis , from a nominate subspecies, Cephalorhynchus commersonii commersonii .

First record of a vagrant Commerson’s dolphin, Cephalorhynchus commersonii, at the southern African continental shelf

Commerson’s Dolphins Cephalorhynchus commersonii are distributed in two disjunct populations, one around southern South America and the other around the sub-Antarctic Kerguelen Islands. These populations have been shown to be morphologically and genetically distinct and movement between the two populations is unlikely. We report on the sighting of a single specimen over the South African continental shelf on 13 November 2004. To our knowledge this is the first record of this species in South African waters and such a vast distance (over 4000 km) from the known distribution limits.

First record of a vagrant Commerson's dolphin, Cephalorhynchus commersonii, at the southern African continental shelf

Commerson's Dolphins Cephalorhynchus commersonii are distributed in two disjunct populations, one around southern South America and the other around the sub-Antarctic Kerguelen Islands. These populations have been shown to be morphologically and genetically distinct and movement between the two populations is unlikely. We report on the sighting of a single specimen over the South African continental shelf on 13 November 2004. To our knowledge this is the first record of this species in South African waters and such a vast distance (over 4000 km) from the known distribution limits.

Nouvelles données sur les cétacés des îles Kerguelen / New data on cetaceans of the Kerguelen Islands

RésuméDes observations nouvelles et quelques échouages complètent le premier bilan faunistique établi en 1989 pour les îles Kerguelen. Aux neuf espèces identifiées précédemment ( Eubalaena glacialis , Balaenoptera acutorostrata , Megaptera novaeangliae , Physeter macrocephalus , Mesoplodon layardii , Cephalorhynchus commersonii , Lagenorhynchus cruciger , Orcinus orca , et Globicephala melas ) s'ajoutent, grâce à des échouages, deux nouvelles espèces: Ziphius cavirostris et Hyperoodon planifrons . En outre, la présence occasionnelle de Phocoena dioptrica est confirmée. L'événement le plus marquant est cependant le grand nombre d'observations (n=1649) de cachalots ( Physeter macrocephalus ) faites depuis 1989 au delà du plateau des îles, dans une zone peu fréquentée autrefois par les bateaux de pêche. Pour le dauphin de Commerson ( Cephalorhynchus commersonii ), espèce la plus commune, des données biologiques et écologiques s'ajoutent aux données faunistiques. Nous faisons également état, pour trois espèces ( Physeter macrocephalus , Orcinus orca , et Globicephala melas ), d'interactions avec la pêcherie à la palangre de la légine australe ( Dissostichus eleginoides ).

Preliminary estimate of incidental mortality of Commerson's dolphins (Cephalorhynchus commersonii) in an artisanal setnet fishery in La Angelina Beach and Ría Gallegos, Santa Cruz, Argentina

The Commerson's dolphin, Cephalorhynchus commersonii, is perhaps the cetacean species most impacted by fisheries in the coastal waters of southern South America, south of 41°S. Between January 1999 and February 2000, 66 Commerson's dolphins were found dead on the coasts of La Angelina and Ría Gallegos, and at least 37 of the ones at La Angelina beach (51°20'S, 069°02'W) were caught incidentally. These captures occurred in gill nets that were set in waters shallower than 15m and mainly for Patagonian blenny (Eleginops maclovinus), silversides (Odonthestes nigricans) and parona leatherjack (Parona signata). The season for set net fishing, extending from the end of August to mid February, overlaps with the breeding season (November-February) of Commerson's dolphins, which is also when this species moves inshore. The estimated catch per unit of effort (CPUE) for gillnets in the area of La Angelina was 0.229 dolphins x (1,000m of net x set)-1. By extrapolation, the estimated total by-catch during the 1999/2000 fishing season in the region of La Angelina and Ría Gallegos was 179 dolphins (SD = 18.8; CI = 141 - 212). Although no abundance estimation of Commerson's dolphins in this region is available, the estimated level of bycatch is concerning. Recommendations for action to mitigate and further document the impact of set gillnets are presented.

Direct and Indirect Effects of the Highseas Fisheries on the Marine Mammal Populations in the Northern and Central Patagonian Coast

Since 1989, interactions between marine mammals and fisheries have been monitored along the Atlantic Patagonian coast. The Argentinian national fishing fleet in the area is composed of approximately 208 vessels (75% trawlers; 16% jiggins; 9% longliners). The fleet operates the year-round from eight harbours between Escondida Island and San Jorge Gulf (80 000 naut. miles2). The important target species are: hake (Merluccius hubbsi), shortfin squid (IIlex argentinus) and shrimp (Pleoticus muelleri), while several tons of other fish are discarded. The dusky dolphin (Lagenorhynchus obscurus), the Commerson's dolphin (Cephalorhynchus commersonii) and the southern sea lion (Otaria flavescens) are incidentally caught. The dolphins become entangled mainly in mid-water trawls at night, while the sea lions become entangled in any kind of trawl. Annual mortality rates obtained are 170-480 sea lions (mostly males; figure estimated to be 1–2% of the population size in the area), 70–200 dusky dolphins (70% females) and 25–170 Commerson's dolphins. Feeding habits of top predators, fish catch and bycatch of the fishery were also studied. Dusky dolphins in the area prey mainly on anchovy and squid, while hake was the most important food item for Commerson's dolphins and male southern sea lions. Squid is also important prey for sea lions and overlaps in size with the fish taken by the commercial fishery. Fishing areas for squid taken by jigging vessels overlap in part with those of foraging sea lions. Even though the commercial size for hake is 30 cm or larger, smaller hakes are largely discarded by the fishery. A combination of operational and specific interactions have been detected. At present, mortality rates seem to be low and there is insufficient evidence of competition for prey species. However, there is concern about the large amounts of fish (particularly hake) discarded by the fishery.