A netizen posted photos on Saturday showing a shark being pulled out of the sea off Beihai City in South China's Guangxi Zhuang Autonomous Region and transported away, prompting a police probe.
A spokesperson with Beihai's public security bureau said that a suspect surnamed Liao bought the shark for two yuan (USD 0.3) per kg on Saturday and sold it to another person surnamed Huang for five yuan per kg.
Whale shark is considered "vulnerable" by the International Union for Conservation of Nature and is a Class-B protected species in China.
They are spotted in waters off the Guangxi and Guangdong regions every May and June, state-run Xinhua news agency reported.