Abstract
Indo-Pacific humpback dolphins (Sousa chinensis) have attracted considerable attention due to their critically endangered status and related conservation issues, but their trophic relationships and ecological significance in coastal ecosystems are poorly understood. For instance, this species is noticeably more abundant in the Xin-Huwei River Estuary (Ex) of Western Taiwan than in the nearby Zhuoshui River Estuary (Ez), though it is unclear why the distribution shows such partitioning. To explore this topic, we conducted field surveys seasonally for two years from 2012 to 2013 and constructed Ecopath models of Ex, Ez, and an offshore site (Dm) to compare energy flow within the food webs. Model comparisons showed that the availability of food resources was the main factor influencing the biomass of Indo-Pacific humpback dolphins. Specifically, its more frequent occurrence in Ex can be attributed to greater phytoplankton production and greater biomasses of macroinvertebrates and prey fish than in the other two areas. An increase in fishing activity might decrease the food availability and, consequently, the biomass of the dolphins. Although the decline in the dolphin population would increase the biomass of some prey fish species, local fishermen might not necessarily benefit from the decline due to the concurrent decrease of highly valued crabs and shrimp. Collectively, our work suggests that the Indo-Pacific humpback dolphin is a keystone species in tropical coastal waters of Taiwan, and thereby exhibit a disproportional large ecological impact given their relatively low abundance.
Highlights
The Indo-Pacific humpback dolphin (Sousa chinensis), known as the Chinese white dolphin, is mostly observed within 400 m of shore throughout the Indian and Western Pacific oceans [1]
The food webs in the three study areas rely on two major food sources: autochthonous phytoplankton production within the system and allochthonous organic detritus transferred from other systems (Fig 2)
The input of organic detritus to the system from the catchment was increased to 10 g wet weight (WW) m-2 yr-1 and 35 g WW 274 m-2 yr-1 in Ez and Dm, respectively, to meet the need for the consumption of additional organic matter within the food web during the mass-balancing exercise
Summary
The Indo-Pacific humpback dolphin (Sousa chinensis), known as the Chinese white dolphin, is mostly observed within 400 m of shore throughout the Indian and Western Pacific oceans [1]. Trophic Significance of Indo-Pacific Humpback Dolphin estuarine habitats for feeding [2,3,4]. Estuarine habitats are known to be their preferred feeding grounds, the trophic relationships between the Indo-Pacific humpback dolphin and other organisms within coastal ecosystems remain virtually unknown. An understanding of these trophic relationships could potentially increase our ability to explain the abundance and distribution of the Indo-Pacific humpback dolphin, as well as to predict its population dynamics under periods of future environmental change. Trophic models have been constructed to explore the possible reasons for the population dynamics of Steller sea lions in Alaska [14]. A trophic model of a Galápagos rocky reef system comprising the Galápagos sea lion was constructed to explore trophic relationships within the system and potential solutions to overfishing [15]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
