Spatiotemporal heterogeneity in densities of the Taiwanese humpback dolphin (Sousa chinensis taiwanensis)

Dares, Lauren E.; Araújo‐Wang, Claryana; Yang, Shih Chu; Wang, John Y.

doi:10.1016/j.ecss.2016.12.020

Cited by 6 publications

(6 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The other plausible explanation for different abundance estimates between this study and Chen et al () may arise from increasing use of the Dafengjiang River Estuary habitat in the past decades that is highly associated with the coastal development histories (Wu et al, ). It is our concern that this difference implies a dolphin aggregation from disturbing/disturbed habitats to a lightly disturbed habitat, which has been reported in western Taiwan (Dares, Araújo‐Wang, Yang, & Wang, ; Karczmarski et al, ) and Xiamen (Wang, Wu, Zhu, & Huang, ).…”

Section: Discussionmentioning

confidence: 85%

Abundance and residency dynamics of the Indo‐Pacific humpback dolphin, Sousa chinensis, in the Dafengjiang River Estuary, China

Peng

Qing

et al. 2019

Marine Mammal Science

View full text Add to dashboard Cite

Robust population size estimates are essential for informing population conservation status. Residency dynamics show population habitat use through time. Population size of Indo‐Pacific humpback dolphins (Sousa chinensis) has been extensively investigated in Chinese waters, but their residency dynamics are rarely known. Mark‐recapture analysis based on photo‐identification records was applied to humpback dolphins in the Dafengjiang River Estuary habitat, one of the key habitats in the northern Beibu Gulf, China. Movement analyses based on lagged identification rate indicated the humpback dolphins spent, on average, 78.5 days inside and 46.9 days outside the survey area. Within the study area, the humpback dolphin abundance was 83 identifiable dolphins. A total of 353–430 humpback dolphins, estimated by POPAN modeling, were involved in this fluid habitat‐use dynamic. Robust Design analysis showed strong seasonality in humpback dolphin abundance and emigration probability, implying a movement‐ and habitat‐use pattern likely associated with spatiotemporal distribution of oceanographic characteristics and prey occurrences. Population surveys and conservation measures currently conducted in Chinese waters seldom consider seasonality in movements between habitat patches, which can be addressed by genetic analyses across habitats and cross‐matching photo‐identification records among neighboring habitats.

show abstract

Section: Discussionmentioning

confidence: 85%

Abundance and residency dynamics of the Indo‐Pacific humpback dolphin, Sousa chinensis, in the Dafengjiang River Estuary, China

Peng

Qing

et al. 2019

Marine Mammal Science

View full text Add to dashboard Cite

show abstract

“…Protection of these LCHs thus provides greater prospects for preserving regional ecosystem services in addition to facilitating population viability for humpback dolphins. In this context, anthropogenic activities that likely change oceanographic characteristics, such as coastal alterations with land reclamation, embankment and construction of harbours, may compromise regional ecosystem integrity (França et al, ; Huang et al, ; Karczmarski et al, ), which, in turn, shifts habitat‐use patterns of the Indo‐Pacific humpback dolphin around those disturbed habitats (Dares, Araújo‐Wang, Yang, & Wang, ; Karczmarski et al, ; Wang et al, ). This concern is not exclusive to the northern Beibu Gulf (Wu, Xu, et al, ), but may apply across the species' range.…”

Section: Discussionmentioning

confidence: 99%

Habitat configuration for an obligate shallow‐water delphinid: The Indo‐Pacific humpback dolphin, Sousa chinensis, in the Beibu Gulf (Gulf of Tonkin)

Huang

Peng

Chen

et al. 2019

Aquatic Conservation

View full text Add to dashboard Cite

1. Habitat configuration is an important baseline to delineate protected area design, refine impact mitigation measures and define habitat protection plans for threatened species. For coastal delphinids, outlining their habitat configuration becomes a real challenge when faced with large distribution ranges that straddle international borders, leaving broad information gaps in uninvestigated areas.2. This study projected likely habitats of Indo-Pacific humpback dolphins, Sousa chinensis, in the Beibu Gulf (Gulf of Tonkin) based on occurrence data and remotely sensed oceanographic characteristics. Net primary productivity was derived to measure the ecosystem service of humpback dolphin habitats.3. Bathymetry and chlorophyll-a concentration are major variables contributing to humpback dolphin habitat configuration, which is characterized by shallow water depth and high primary productivity. Three major, likely habitats were identified in the northern Beibu Gulf from western Leizhou Peninsula to the China-Vietnam border, western Gulf of Tonkin from the Red River estuary to the central coast of Vietnam, and south-western Hainan Island. Less than 9% of likely habitats are currently protected by marine protected areas.4. Affinity to high primary productivity and shallow depths implies that prey abundance and foraging efficiency influence habitat selection by Indo-Pacific humpback dolphins. Anthropogenic activities potentially altering oceanographic characteristics may impact regional marine ecosystem functions, and hence habitat configuration. Habitat protection actions for Indo-Pacific humpback dolphins includeimplementing coordinated and systematic surveys in major habitats, associating core habitat protection with protected area networks and maritime function zoning, ensuring ecosystem function integrity within major habitats, and reducing both explicit lethal impacts and implicit anthropogenic impacts from activities that change oceanographic features. The habitat protection plan should not only consider marine habitats, but also adjacent coastal landscapes and river catchments.

show abstract

“…For the TWD, spatial heterogeneity in density was shown to be significant (Dares et al, 2017). Therefore, it was not surprising that occurrence probabilities in this study were also not uniform.…”

Section: Discussionmentioning

confidence: 99%

“…The most obvious common feature shared across these blocks was the presence of still‐functioning estuaries (i.e. estuaries that still receive a considerable amount of freshwater input), which has been suggested as an important factor for the presence of TWDs (Dares et al, 2017). For example, the large Dadu River estuary is located within block 4, whereas the Luen Wei Channel, now functioning as an artificial river created by multiple sources of freshwater outflow, including sewage (industrial, residential, and agricultural) and other natural sources, empties into block 5.…”

Section: Discussionmentioning

confidence: 99%

“…The modelling followed the general structure of an MSRD framework (Nichols & Coffman, 1999) in which the yearly survey seasons (June–August) were treated as primary periods and the surveys within each year as secondary occasions. States in the model represented the location of the dolphins within equally sized areas created by dividing the study area into 14 blocks (Figure 1), each covering 10 km of latitudinal distance (in a similar manner to Dares et al (2017)). Basic assumptions of the MSRD for the model were that the population was closed within primary periods (i.e.…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

New abundance and survival estimates for the critically endangered Taiwanese white dolphin indicate no signs of recovery

Araújo‐Wang

Wang

Draghici

et al. 2022

Aquatic Conservation

Self Cite

View full text Add to dashboard Cite

1. Small populations of cetaceans with restricted ranges are particularly vulnerable to anthropogenic disturbances. The assessment of demographic parameters for these populations can provide meaningful insight into the ways in which they are being impacted by different threats. The Taiwanese white dolphin (TWD), Sousa chinensis taiwanensis, is a subspecies endemic to Taiwan and is classified as Critically Endangered.2. Multistate robust design mark-recapture models were fitted under a Bayesian framework to estimate demographic parameters and trends for the population from 2010 to 2018. Differences in these parameters by age category and the dolphins' use of their habitat were also explored. Abundance estimates varied from a maximum of 72 in 2010 (95% credible interval (CI) [65, 78]) to a minimum of 61 (95% CI [58, 64]) in 2017. In the oldest age category, abundance estimates varied from 10 (95% CI [10, 11]) in 2013 to 13 (95% CI [10, 13]) in 2016.3. Modelling showed that, over time, the abundance of dolphins in the oldest age group remained stable, while the remainder of the population, which includes reproductive individuals, experienced a steady decline. This decline is bound to affect the demographic recovery of TWD. 4. Spatial heterogeneity indicated that some areas (i.e. with consistent high occurrences) likely represent important areas for biological functions of the TWD. This suggests that the recovery of the population may be enhanced with immediate and focused actions (such as the ban of gillnet fisheries) in these areas.However, with a small and declining population, reducing threats throughout their entire range is needed, including the new offshore windfarm development being constructed in and adjacent to the dolphin's range.5. Concerted actions to address known threats, continued monitoring of the population, and education of stakeholders are needed to prevent the extinction of the TWDs.

show abstract

Spatiotemporal heterogeneity in densities of the Taiwanese humpback dolphin (Sousa chinensis taiwanensis)

Cited by 6 publications

References 33 publications

Abundance and residency dynamics of the Indo‐Pacific humpback dolphin, Sousa chinensis, in the Dafengjiang River Estuary, China

Abundance and residency dynamics of the Indo‐Pacific humpback dolphin, Sousa chinensis, in the Dafengjiang River Estuary, China

Habitat configuration for an obligate shallow‐water delphinid: The Indo‐Pacific humpback dolphin, Sousa chinensis, in the Beibu Gulf (Gulf of Tonkin)

New abundance and survival estimates for the critically endangered Taiwanese white dolphin indicate no signs of recovery

Contact Info

Product

Resources

About