Area utilization patterns of humpback dolphins (Sousa plumbea) in Richards Bay, KwaZulu-Natal, South Africa

Keith, Mark; Atkins, Shanan; Johnson, Alice; Karczmarski, Leszek

doi:10.1007/s10164-013-0375-z

Cited by 20 publications

(14 citation statements)

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“…Furthermore the effective sighting distance of 550 m for the 20 m elevated apartment complex "Cascades" was considerably lower than the effective sighting distance for the 10.5 m elevated Oceanarium, whereas the effective sighting distance for the Pier was undetermined as the rate of detection remained constant up to a distance of 600 m. These findings suggest that the dolphin preference for inshore shallow waters was due to their habitat use pattern and not a distance related bias (De Boer et al 2014). The predominantly inshore distribution as well as the animals' preference for shallow waters has previously been indicated for humpback dolphins in Algoa Bay as well as elsewhere in South Africa (Saayman et al 1972, Saayman and Tayler 1979, Findlay et al 1992, Atkins et al 2004, Keith et al 2013, Mozambique (Guissamulo 2008), Zanzibar (Stensland et al 2006), Australia (Corkeron 1990, Parra et al 2006, Taiwan (Wang et al 2007 and China (Parsons 1998, Jefferson 2000, Hung 2008, with water depth representing the main factor limiting their long-range as well as offshore distribution (e.g., Karczmarski et al 2000, Parra et al 2006, Guissamulo 2008, Hung 2008). Furthermore, a boat-based study conducted in Algoa Bay between 2008 and 2011 confirmed a mean water depth of 6.6 m (range = 2.5-12.5 m, SD = 2.24) for 50 sightings of this species (SP, unpublished data), supporting their preference for shallow-water in Algoa Bay.…”

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confidence: 68%

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Sixteen years later: Occurrence, group size, and habitat use of humpback dolphins (Sousa plumbea) in Algoa Bay, South Africa

Koper

Karczmarski

Preez

et al. 2015

Marine Mammal Science

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Coastal dolphins are more prone to cumulative impacts of environmental and anthropogenic changes than pelagic species. However, few studies use historical comparisons to evaluate those impacts across a temporal scale. The study presented here describes the pattern of occurrence, group size, behavior, and habitat use of humpback dolphins in Algoa Bay and compares these to a similar study conducted in the early 1990s. Results indicate a considerable change in the frequency of occurrence. Furthermore, the mean group size has decreased from six to three individuals, mainly due to an increase in occurrence of solitary individuals (36.3% vs. 15.4%). Foraging, which was previously the predominant activity (64%), has now been replaced by traveling (49%). Moreover, dolphins showed a negative reaction towards a variety of watercrafts and swimmers. These observed differences could be due to a change in prey abundance, direct anthropogenic disturbance, and/or population decline. We emphasize the need for long-term environmental and biological data series and long-term monitoring of the demographics of this population to accurately assess any changes observed in future.

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confidence: 68%

“…, Keith et al . ), Mozambique (Guissamulo ), Zanzibar (Stensland et al . ), Australia (Corkeron , Parra et al .…”

Section: Discussionmentioning

confidence: 99%

Sixteen years later: Occurrence, group size, and habitat use of humpback dolphins (Sousa plumbea) in Algoa Bay, South Africa

Koper

Karczmarski

Preez

et al. 2015

Marine Mammal Science

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“…This near-shore distribution places them in the marine waters most heavily utilized by humans (Keith, Atkins, Johnson, & Karczmarski, 2013;Stensland, Carlen, Sarnblad, Bignert, & Berggren, 2006). This near-shore distribution places them in the marine waters most heavily utilized by humans (Keith, Atkins, Johnson, & Karczmarski, 2013;Stensland, Carlen, Sarnblad, Bignert, & Berggren, 2006).…”

Section: Conservation Priorities For Cetaceans In Tanzaniamentioning

confidence: 86%

Cetacean rapid assessment: An approach to fill knowledge gaps and target conservation across large data deficient areas

Braulik

Kasuga²,

Wittich³

et al. 2017

Aquatic Conservation

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1. Many species and populations of marine megafauna are undergoing substantial declines, while many are also very poorly understood. Even basic information on species presence is unknown for tens of thousands of kilometres of coastline, particularly in the developing world, which is a major hurdle to their conservation.2. Rapid ecological assessment is a valuable tool used to identify and prioritize areas for conservation; however, this approach has never been clearly applied to marine cetaceans. Here a rapid assessment protocol is outlined that will generate broad-scale, quantitative, baseline data on cetacean communities and potential threats, that can be conducted rapidly and costeffectively across whole countries, or regions.3. The rapid assessment was conducted in Tanzania, East Africa, and integrated collection of data on cetaceans from visual, acoustic, and interview surveys with existing information from multiple sources, to provide low resolution data on cetacean community relative abundance, diversity, and threats. Four principal threats were evaluated and compared spatially using a qualitative scale: cetacean mortality in fishing gear (particularly gillnets); cetacean hunting, consumption or use by humans; shipping related collision risk and noise disturbance; and dynamite fishing.4. Ninety-one groups of 11 species of marine mammal were detected during field surveys. Potentially the most important area for cetaceans was the Pemba Channel, a deep, high-current waterway between Pemba Island and mainland Africa, where by far the highest relative cetacean diversity and high relative abundance were recorded, but which is also subject to threats from fishing. 5. A rapid assessment approach can be applied in data deficient areas to quickly provide information on cetaceans that can be used by governments and managers for marine spatial planning, management of developments, and to target research activities into the most important locations.

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“…Implementation of systematically-designed census exercise can provide quantitative baselines in an integrative way. The implementation of transect survey, with the information of GPS and animal-sighting records at each sampling sites, does not only estimate the population abundance inside the survey area but also figures the extent of occurrence by minimum convex polygon (MCP) and core/critical distribution site (such as 50% kernel density estimate), information essential for sound protected area design [13,16,[50][51][52][53][54]. Database from individual photo-ID histories can be used to estimate population size, apparent survival rate and, dependent on the temporal scale of database, life history parameters including Am, RI and Ax.…”

Section: Systematic Demographic Analysis: An Integrative Perspectivementioning

confidence: 99%

Assessing Population Trend and Risk of Extinction for Cetaceans Lacking Long- Term Census Baselines

Huang¹

2013

J Biodivers Endanger Species

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Assessment of population trend and risk of extinction, essential for informed conservation, needs baselines including percentage of population decline, extent of occurrence, population size, population structure and probabilities of extinction. Construction of these baselines usually claims long-term census efforts that are often insufficient or even lacking for many cetaceans, especially for those nearby rapidly developing countries. Restricted to variation from current census techniques, however, the approach based on long-term census database is unlikely to detect early or recent sign of population decline. Here, I propose an integrative perspective, the systematic demographic analysis, to solve life history and demographic parameters essential for status and risk assessment for the cetacean populations. Transect technique with the aid of GPS records and environmental characteristics can be used to estimate population abundance and figure the extent of occurrence and critical habitat, information essential for sound habitat protection. Capturemark-recapture technique based on the database from individual photo-ID histories can be used to estimate population size, apparent survival rate and life history parameters. Collections of stranded and by caught carcasses can be used to solve life history parameters, age-specific survivorships or mortality rates and population genetic diversity indirectly relating to population size. Applications of population viability analysis to above parameters such as VORTEX model or other individual-based stage/age matrix model that factors the stochasticity and uncertainty can be used to solve the likely range of rate of decline and extinction risk of threatened population. Finally, I emphasize the need to integrate the histories of long-term land use and landscape change when formulating habitat management programme for the rare and/or endangered populations to avoid skipping the low-sighting habitat from intense anthropogenic impacts.

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Area utilization patterns of humpback dolphins (Sousa plumbea) in Richards Bay, KwaZulu-Natal, South Africa

Cited by 20 publications

References 60 publications

Sixteen years later: Occurrence, group size, and habitat use of humpback dolphins (Sousa plumbea) in Algoa Bay, South Africa

Sixteen years later: Occurrence, group size, and habitat use of humpback dolphins (Sousa plumbea) in Algoa Bay, South Africa

Cetacean rapid assessment: An approach to fill knowledge gaps and target conservation across large data deficient areas

Assessing Population Trend and Risk of Extinction for Cetaceans Lacking Long- Term Census Baselines

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