Humpback dolphins in South China Sea gulf synchronized with seasonal and tidal, suggesting conservation solutions

Researchers at Nanjing Normal University in China have concluded that Indo-Pacific humpback dolphins (Sousa chinensis) in the Beibu Gulf, China, travel between deep, gulf water and shallow, estuary zones based on season and tide. The scientists believe that they do this to follow prey with the same migration pattern.

The Beibu Gulf, located in the northwestern South China Sea, is supplied by water from two rivers, and the area leading into the saltwater gulf is an estuary. During the wet season (May-September), the estuary becomes less shallow and more accessible to the dolphins. It has been reported that most fish species, including those humpback dolphins prey on, follow the same pattern, which lead authors of the report to conclude that the dolphins migrate to follow a food source.An Indo-Pacific humpback dolphin (Sousa chinensis) in the Beibu Gulf

During the wet season, the estuary is also a good habitat for the humpback dolphins. It accommodates their sensitivity to water salinity and the deeper water that comes with the wet season decreases their risk of stranding. Fury and Harrison (2011) reported that bottlenose dolphins in an Australian estuary have the same pattern.

This study hopes to influence conservation strategies for Indo-Pacific humpback dolphins. “The management and protection of the marine nature reserve has always been difficult. Due to its open character, anthropogenic activities cannot be restricted like in land nature reserves,” said Dr. Bingyao Chen, one of the study’s authors. “This paper determines the seasonal and tidal core area of distribution of this species, which means we can better protect them seasonally.”      

However, human influence remains a problem for conservation. “Some anthropogenic activities, especially fishing, are the mainstays of the local economy. It is impossible to forbidden all fishing activities on the reserve. Therefore, we must work to transform the jobs of local fishermen to promote a win-win situation between dolphins and fishermen.”

Read the full article, published by Zoological Studies, here:
http://zoolstud.sinica.edu.tw/Journals/57/57-01.html

Follow Zoological Studies on Twitter @ZooStudies.

References:
Fury CA, Harrison PL. 2011. Seasonal variation and tidal influences on estuarine use by bottlenose dolphins (Tursiops aduncus). Estuar Coast Shelf S 93(4):389-395.

Media contact: Noah Last: lastn@gate.sinica.edu.tw