Behaviour of free-ranging short-beaked common dolphins (Delphinus delphis) in Gulf St Vincent, South Australia

2013 ◽  
Vol 61 (4) ◽  
pp. 291 ◽  
Author(s):  
Nicole E. Filby ◽  
Mike Bossley ◽  
Karen A. Stockin
Keyword(s):  
Group Size ◽  
Water Depth ◽  
Large Scale ◽  
South Australia ◽  
Population Level ◽  
Common Dolphin ◽  
Time Data ◽  
Fishing Activity ◽  
Delphinus Delphis ◽  
Common Dolphins

Common dolphins are subject to large-scale fishing activity and tourism operations in South Australia; however, there is a paucity of data on this species. Understanding the behaviour of a population can contribute greatly to our knowledge of a species and how to manage potential population-level threats. This paper describes the behaviour of short-beaked common dolphins (Delphinus delphis) in Australian waters for the first time. Data were collected from 109 independent dolphin groups during boat-based surveys conducted in Gulf St Vincent, South Australia, between September 2005 and May 2008. Activity budgets were used to assess behaviour of common dolphins in relation to diel patterns, season, water depth, sea surface temperature (SST), group size and composition. Foraging (33.9%) and resting (2.8%) were the most and least frequently observed behaviours, respectively. Travelling (33.0%), socialising (20.2%) and milling (10.1%) accounted for the remainder of the activity budget. Diurnal differences were detected, with foraging (59.5%) and socialising (31.8%) groups most frequently observed from 10.00 to 11.59 hours. Behaviour did not vary seasonally or with water depth, SST, group size or composition. Behaviour varied significantly between single- and multispecies aggregations. Foraging was more frequent in multispecies aggregations, as 78.4% of all foraging behaviour observed for common dolphins occurred in the presence of other species. Multispecies aggregations were most frequently observed with flesh-footed shearwaters (Puffinus carneipes), which were present during 29.4% of common dolphin encounters. Behaviour varied significantly during aggregations with shearwaters, as 62.2% of foraging groups occurred in the presence of shearwaters. Resting, milling or socialising was rarely observed in the presence of any other species, indicating that the primary mechanism for aggregations is likely prey-related.

Cadmium Accumulation and Toxicity in The Bottlenose Dolphin Tursiops truncatus, The Common Dolphin Delphinus delphis, and Some Dolphin Prey Species in South Australia.

1998 ◽  
Vol 20 (1) ◽  
pp. 25
Author(s):  
M. Long ◽  
R.J. Reid ◽  
C.M. Kemper
Keyword(s):  
Tursiops Truncatus ◽  
Tooth Development ◽  
South Australia ◽  
Cadmium Accumulation ◽  
Human Consumption ◽  
Common Dolphin ◽  
Delphinus Delphis ◽  
Wet Weight ◽  
The Common ◽  
The Relationship

Twenty Tursiops truncatus and 20 Delphinus delphis from South Australia were analysed for cadmium levels, as were some fish and squid species which form part of their diet. In the dolphins, cadmium was accumulated mainly in the kidneys (range 0-38 μg/g), with levels in many individuals exceeding 20 μg/g (wet weight). On average, levels in kidney were three-fold higher than in liver and 26-fold higher than in muscle. Cadmium concentrations related to dolphin body length, but the relationship with tooth development class was less clear. 80% of the prey fish species analysed from Spencer Gulf exceeded NH & MRC health recommendations of 0.2 μg/g (wet weight) for human consumption. Sepioteuthis australis from upper Spencer Gulf contained significantly higher cadmium levels than Ceduna samples (0.21 ± 0.01 μg/g versus 0.13 ± 0.01 μg/g, p<0.001) (wet weight). On histological examination, 32% of adult dolphin kidneys showed pathological changes, proteinuria being the most common abnormality. High levels of cadmium were found in dolphins from widely spaced locations in South Australia.

scholarly journals Cetaceans using the marine protected area of "Parque Estadual Marinho da Laje de Santos", Southeastern Brazil

2017 ◽  
Vol 65 (4) ◽  
pp. 605-613 ◽  
Author(s):  
Marcos Cesar de Oliveira Santos ◽  
Giovanna Corrêa e Figueiredo ◽  
Marie-Francoise Van Bressem
Keyword(s):  
Protected Area ◽  
Marine Protected Area ◽  
Unknown Origin ◽  
Mantel Test ◽  
Southeastern Brazil ◽  
Common Dolphin ◽  
Balaenoptera Acutorostrata ◽  
Stenella Frontalis ◽  
Delphinus Delphis ◽  
Common Dolphins

Abstract The aim of this study was to evaluate the presence of cetaceans in the waters surrounding the Marine Protected Area (MPA) known as “Parque Estadual Marinho da Laje de Santos (PEMLS)”, placed in coastal waters at the southeastern coast of Brazil. Boat-based surveys were conducted once a month from June 2013 to June 2015. A specific transect was followed to cover the area of the quoted MPA, as well as its borders. A total of 24 boat-surveys rendered 18 sightings of cetacean groups of the following species: Atlantic spotted dolphin (Stenella frontalis) (12), rough-toothed dolphin (Steno bredanensis) (2), common dolphin (Delphinus delphis) (1), Bryde’s whale (Balaenoptera edeni) (2) and common minke whale (Balaenoptera acutorostrata) (1). Sightings of S. frontalis, the commonest sighted species, was positively correlated with water depth (Mantel test; r = 0.8072; p < 0.05). Photoidentified individuals moved back and forth to inner and outer areas of the MPA, remaining in the area throughout the 2-year survey. “Paisley” cutaneous marks of unknown origin were reported in two common dolphins for the first time in local waters. As the PEMLS has been used as an important spot for SCUBA divers, it is recommended that cetacean sightings could still be gathered in a future partnership, as well as using the acoustics tool to detect their presence when researchers are not in the field.

scholarly journals Short-term effects of tourism on the behaviour of common dolphins (Delphinus delphis) in the Azores

2017 ◽  
Vol 98 (5) ◽  
pp. 1187-1196 ◽  
Author(s):  
Arianna Cecchetti ◽  
Karen A. Stockin ◽  
Jonathan Gordon ◽  
José M.N. Azevedo
Keyword(s):  
Transition Probabilities ◽  
High Energy ◽  
Tourism Industry ◽  
Common Dolphin ◽  
Short Term ◽  
Delphinus Delphis ◽  
Critical Activity ◽  
Time Required ◽  
Common Dolphins

Short-term measures of behavioural responses of cetaceans to tourism operations have been used in many studies to interpret and understand potential long-term impacts of biological importance. The short-beaked common dolphin (Delphinus delphis) is the species most frequently observed in the Azores and constitutes an important component of the marine mammal tourism industry in this region. This study investigated the potential effects of tour boats on the behaviour of common dolphins off São Miguel, Azores, with particular focus on the changes in activity budget and the time required to resume activities after a tour boat interaction. Behavioural data were collected from land using a group focal-follow methodology. Markov chains were applied to analyse control and interaction sequences and to assess behavioural transition probabilities in both scenarios. In the presence of tour boats, dolphins significantly reduced the time spent foraging and increased the time engaged in other high energy activities. Dolphins also took significantly longer to resume feeding after an interaction occurred. The average bout length varied significantly between control and interaction scenarios, with foraging bouts being shorter during tour boats interactions. The results presented have management implications since feeding is a biologically critical activity. Disruption of foraging behaviour could lead to a decrease in energy intake for this population. With cetacean tourism likely to increase in the future, a precautionary approach to issuing new licences is advisable and any expansion would warrant an appropriate monitoring programme.

Acoustic Assessment of Populations of Common Dolphin Delphinus Delphis In Conjunction With Seismic Surveying

1996 ◽  
Vol 76 (3) ◽  
pp. 811-820 ◽  
Author(s):  
John C. Goold
Keyword(s):  
Seismic Survey ◽  
Avoidance Reaction ◽  
Common Dolphin ◽  
Survey Area ◽  
Delphinus Delphis ◽  
Air Gun ◽  
Before And After ◽  
Seismic Surveying ◽  
Acoustic Contact ◽  
Common Dolphins

Common dolphin, Delphinus delphis (bairdi), were monitored acoustically across a survey area of 2747 km2 during a three month period before, during and after an oil industry two dimensional (2D) seismic reflection survey. Over 900 h of audio survey data were collected and analysed, along with GPS positional data, to reveal trends in presence and distribution of animals. The presence of dolphins was determined from vocalization events on the survey recordings. Dolphin presence was assessed by a system of percentage acoustic contact. This was highest before and after the seismic survey, with common dolphins showing a clear south-westerly skew within the survey area and a probable south-westerly migration of animals between September and December. Acoustic contact with dolphins during the seismic survey also showed a south-westerly skew within the survey area, although percentages were lower. Monitoring during the period of seismic activity was restricted to the immediate vicinity (1–2 km) of the seismic vessel, so percentage contact most likely reflects the response of dolphins to such immediate activity. The overall result suggests an avoidance reaction by common dolphins to air gun emissions, although certain observations suggest tolerance to these sounds outside a 1 km radius of the guns.

Distribution and Population Demographics of Common Dolphins (Delphinus delphis) in the Gulf St. Vincent, South Australia

2010 ◽  
Vol 36 (1) ◽  
pp. 33-45 ◽  
Author(s):  
Nicole E. Filby ◽  
Mike Bossley ◽  
Ken J. Sanderson ◽  
Emmanuelle Martinez ◽  
Karen A. Stockin
Keyword(s):  
South Australia ◽  
Population Demographics ◽  
Delphinus Delphis ◽  
Common Dolphins

scholarly journals Quantification of interactions between the Portuguese sardine purse-seine fishery and cetaceans

2015 ◽  
Vol 72 (8) ◽  
pp. 2438-2449 ◽  
Author(s):  
Ana Marçalo ◽  
Isidora Katara ◽  
Diana Feijó ◽  
Helder Araújo ◽  
Isabel Oliveira ◽  
...  
Keyword(s):  
Total Mortality ◽  
Purse Seine ◽  
Annual Number ◽  
Common Dolphin ◽  
The South ◽  
Delphinus Delphis ◽  
The North ◽  
Common Dolphins ◽  
Purse Seine Fishery ◽  
Purse Seining

Abstract Interactions between cetaceans and the purse-seine fishery operating along the whole Portuguese continental coast were studied based on on-board observations from 2010 to 2011. Cetacean presence and mortality were estimated and characteristics under which interactions were most likely to occur were identified. Observations were made on 163 fishing trips (0.7% of the average annual number of fishing trips) and 302 fishing operations/hauls. Cetaceans were present during 16.9% of fishing events; common dolphins (Delphinus delphis) accounted for 96% of occurrences, mostly overnight in summer and early autumn. Regression models showed that cetacean presence during a fishing set was significantly (p &lt; 0.05) associated with sardine catches, effort, and latitude/longitude. Encirclement and mortality occurred in 2.3 and 1.0% of fishing events, respectively. Encircled species were the common dolphin, bottlenose dolphin (Tursiops truncatus), and harbour porpoise (Phocoena phocoena), but only common dolphin showed mortality (three individuals); raised to fleet level, estimated total mortality rates of common dolphins were 69 (95% CI 37–110) in the north and 91 (95% CI 55–165) in the south for 2010 and 78 (95% CI 47–140) in the south only for 2011. The estimated annual mortality rate due to purse seining is 113 (95% CI 3–264) common dolphins, which is ∼0.63% of the current most optimistic estimate of population size for the Portuguese fishing area (SCANS II). The wide confidence limits, as well as variation between years, reflect low observer coverage, emphasizing the need for increased monitoring to cover gaps in the spatial and seasonal distribution of observer effort and provide reliable estimates of bycatch.

Temperature-based summer habitat partitioning between white-beaked and common dolphins around the United Kingdom and Republic of Ireland

2008 ◽  
Vol 88 (6) ◽  
pp. 1193-1198 ◽  
Author(s):  
Colin D. MacLeod ◽  
Caroline R. Weir ◽  
M. Begoña Santos ◽  
Timothy E. Dunn
Keyword(s):  
United Kingdom ◽  
Water Depth ◽  
Classification Tree ◽  
Niche Partitioning ◽  
Summer Season ◽  
Relative Distribution ◽  
Common Dolphin ◽  
Republic Of Ireland ◽  
The United Kingdom ◽  
Common Dolphins

The white-beaked dolphin (Lagenorhynchus albirostris) and short-beaked common dolphin (Delphinus delphis) are two of the most abundant delphinid species in shelf waters around the United Kingdom (UK) and Republic of Ireland (ROI) in the summer season (May–October). As these two species have similar habitat preferences and diets, it might be expected that they would partition their otherwise shared niche to reduce the potential for competition at this time of year. This study used 569 sightings of the two species, collected from shelf waters (<200 m water depth) in the summer season between 1983 and 1998, to investigate whether there is evidence of widespread niche partitioning based on water temperature in this area. Below 13°C, white-beaked dolphins were dominant with 96% of sightings comprising this species. In contrast, above 14°C, 86% of sightings comprised common dolphins. A classification tree analysis found that of the four eco-geographical variables analysed (water depth, seabed slope, seabed aspect and sea surface temperature), temperature was the most important variable for separating the occurrence of the two species. These results are consistent with widespread temperature-based niche partitioning between white-beaked and common dolphins in shelf waters around the UK and ROI. As temperature is important in determining the relative distribution of these species, the range of the white-beaked dolphin might be expected to contract in response to increasing sea temperature resulting from global climate change, while that of the common dolphin may expand.

scholarly journals First records of the pantropical spotted dolphin Stenella attenuata, within groups of common dolphins Delphinus delphis in northern Peru

2021 ◽  
Vol 56 (1) ◽  
pp. 78
Author(s):  
Lara Martínez ◽  
Sebastián Silva ◽  
Belén Alcorta ◽  
Aldo S. Pacheco
Keyword(s):  
Single Species ◽  
Northern Coast ◽  
Common Dolphin ◽  
Mixed Species ◽  
Delphinus Delphis ◽  
Spotted Dolphin ◽  
Northern Peru ◽  
Species Groups ◽  
Stenella Attenuata ◽  
Common Dolphins

Although dolphins are mostly known to form single species groups of varying size, occasionally they aggregate in mixed-species groups. The presence of mixed-species delphinid groups along the Peruvian coast is unknown. Herein, we report the presence of a single pantropical spotted dolphin (Stenella attenuata) within large groups of the common dolphin (Delphinus delphis) at Los Organos in the northern coast of Peru. Sightings occurred on October 10th, 2016, January 7th, 2018 and September 21st, 2019. In one sighting the mixed group was feeding, while during the other two sightings the group was travelling. These records add new evidence about mixed-species delphinid groups in coastal waters of Peru. 

Cetacean captures, strandings and mortalities in South Australia 1881-2000, with special reference to human interactions.

2005 ◽  
Vol 27 (1) ◽  
pp. 37 ◽  
Author(s):  
CM Kemper ◽  
A Flaherty ◽  
SE Gibbs ◽  
M Hill ◽  
M Long ◽  
...  
Keyword(s):  
Human Impacts ◽  
South Australia ◽  
Common Species ◽  
Human Interaction ◽  
Common Dolphin ◽  
Data Set ◽  
Neonatal Deaths ◽  
Delphinus Delphis ◽  
Human Interactions ◽  
Shark Attacks

This study summarizes 660 events involving captured, live-stranded and dead cetaceans in South Australia between 1881 and 2000. Emphasis is placed on records (n = 361) during 1985-2000 when an active necropsy programme was underway. Average number of events per year was 30.4 and the most common species were the short-beaked common dolphin (Delphinus delphis) and Indo-Pacific bottlenose dolphin (Tursiops aduncus). Records were assigned to nine categories of circumstance/cause of death. Summarizing the total database, 60% were unknown circumstance, 22% not obviously anthropogenic, 13% unintentional human-related and 5% intentional human-related. In the data set of records for 1985-2000, 50% were unknown, 25% were not obviously anthropogenic, 20% were unintentional humanrelated and 5% were intentional killings. Non-anthropogenic circumstances included neonatal deaths, live strandings, significant diseases, shark attacks and choking. Cornynebacterium ulcerans is recorded for the first time in a cetacean. Unintentional circumstances included entanglement in fishing and aquaculture equipment (17% of necropsied carcasses from 1985-2000) and boat strikes. Intentional human-related circumstances were captures for live display and illegal killing. Five percent of the necropsied carcasses during 1985-2000 were attributed to shootings or stabbings/spearings. There is need for a formal reporting procedure for marine mammal deaths and human interaction involving injury and for steps to be taken to reduce human impacts.

Growth and reproduction of female short-beaked common dolphins, Delphinus delphis, in the eastern tropical Pacific

2007 ◽  
Vol 85 (1) ◽  
pp. 108-121 ◽  
Author(s):  
K. Danil ◽  
S.J. Chivers
Keyword(s):  
Life History ◽  
Sexual Maturity ◽  
Large Scale ◽  
Life History Strategy ◽  
Maximum Size ◽  
Tropical Pacific ◽  
Lactation Period ◽  
Eastern Tropical Pacific ◽  
Delphinus Delphis ◽  
Common Dolphins

We characterize the life-history strategy of female short-beaked common dolphins ( Delphinus delphis L., 1758) inhabiting the eastern tropical Pacific by estimating several growth and reproductive parameters. Reproductive condition (n = 700) and age (n = 405) were determined for animals sampled from those incidentally killed in the yellowfin tuna ( Thunnus albacares (Bonnaterre, 1788)) purse-seine fishery between 1975 and 1993. Females averaged 160.4 cm at age 2 years, 186.5 cm at attainment of sexual maturity, and 197.2 cm at asymptotic length. The estimated age at attainment of sexual maturity was 7.9 years and the oldest animal in the study was 25 years. Calving occurred throughout the year, with females producing a calf approximately every 2.1 years after a gestation period of approximately 11.4 months, an average lactation period of 16.5 months, and an average resting period of 2.8 months. A relatively high percentage (30.4%) of lactating females were simultaneously pregnant, which effectively shortens the average calving interval. No clear evidence of senescence was found. Estimated lengths at birth, 2 years of age, attainment of sexual maturity, and maximum size were greater than those reported for the temperate North Pacific population, indicating that large-scale geographic variation in life history occurs for this species, which likely reflects population-specific adaptations to the tropical and temperate habitats that they occupy.

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