The Yangtze finless porpoise, Neophocaena asiaeorientalis, is a unique freshwater cetacean found exclusively in China’s Yangtze River and its connected lakes. This species is recognized by its distinctive “smile” and the absence of a dorsal fin, replaced by a low ridge along its back. The porpoise is currently classified as critically endangered, facing significant threats. Its presence serves as an indicator of the overall health of the Yangtze River ecosystem.
The Yangtze Finless Porpoise’s Main Prey
Yangtze finless porpoises are primarily piscivores, meaning they mainly eat fish. Their specific prey varies depending on the season and what is most available in their riverine environment. Studies have identified at least 20 fish species in their diet.
Common fish species consumed include Coilia brachygnathus, Pseudobrama simoni, Pelteobagrus nitidus, and Hemiculter bleekeri. They also prey on various minnow species, anchovies, and bottom-dwelling fish like carp, catfish, and loach. Their diet also includes crustaceans like shrimp, prawn, small crabs, and lobsters.
They also eat cephalopods like squid, octopus, and cuttlefish. This diverse diet highlights their adaptability. The porpoises possess 15-21 pairs of spade-shaped teeth in both jaws, which they use to capture and crush the shells of their prey.
Hunting Strategies and Habitat
Yangtze finless porpoises use sophisticated hunting strategies in the murky Yangtze River. They rely heavily on echolocation, emitting high-frequency ultrasonic pulses to navigate and locate prey. These biosonar signals adjust to detect different targets and adapt to varying environmental conditions.
During prey capture, porpoises increase their echolocation activity and produce specific “buzz signals,” which are rapid click trains indicating active feeding. Their agile swimming allows them to chase fish at high speeds, making sharp turns and quick accelerations. They can dive to the riverbeds, using their teeth to grasp and process their catch.
Their hunting behaviors are closely linked to their habitat, which includes the main Yangtze River channel and connected lakes such as Poyang and Dongting. These areas offer varied depths and currents, influencing the types and distribution of available prey. The porpoises spend significant time near river banks or at the merging of waterways, where prey might be concentrated.
Dietary Specialization and Conservation
The opportunistic feeding habits of the Yangtze finless porpoise make it susceptible to environmental changes affecting its food supply. A secure, abundant food source is necessary for their survival and reproduction. Changes in the river’s ecosystem can directly impact the availability of their prey.
Overfishing in the Yangtze River directly reduces the porpoise’s food sources. Pollution from agriculture and industry also degrades water quality, harming fish and invertebrate populations that the porpoises depend on. Habitat degradation, caused by factors such as dam construction, sand dredging, and increased vessel traffic, further disrupts their feeding grounds and indirectly affects prey availability.