The world’s only true freshwater porpoise is the Yangtze finless porpoise, a distinct species found exclusively in China’s Yangtze River basin. This unique aquatic mammal represents a rare adaptation among cetaceans to a riverine environment. Its continued survival is now a significant focus for conservationists worldwide.
Unveiling the Yangtze Finless Porpoise
The Yangtze finless porpoise (Neophocaena asiaeorientalis) is characterized by its sleek, streamlined body and a notable absence of a dorsal fin. Instead of a fin, it possesses a narrow ridge along its back, which is covered in wart-like tubercles. These porpoises have a rounded head without a beak and their flippers are moderately large, curved, and pointed at the ends, making up about 20% of their total body length.
Adults measure between 1.5 to 1.8 meters (approximately 5 to 6 feet) in length and weigh around 45 kilograms (about 100 pounds). Their coloration ranges from dark to pale gray, with lighter patches sometimes present around the mouth and genitals. Yangtze finless porpoises are known for their intelligence and display active behaviors such as darting quickly under the water surface and performing “tail stands” where they appear to stand upright in the water. They communicate using high-frequency narrow-band ultrasonic pulses for echolocation to navigate and locate prey, rather than whistles.
Life in Freshwater Environments
The Yangtze finless porpoise inhabits connected large lakes like Poyang and Dongting, as well as relocated populations in oxbow lakes such as Tian-E-Zhou and He Wangmiao. Unlike their marine relatives, these porpoises have developed unique genetic adaptations to thrive in freshwater. Their kidneys have evolved to efficiently conserve salt in a low-salinity river environment.
These porpoises are non-migratory and are found year-round in shallow bay areas, swamps, and estuaries, though their distribution can shift seasonally, with higher concentrations observed in the middle and lower Yangtze regions during winter. As carnivores, their diet primarily consists of fish, mollusks, and crustaceans. They are opportunistic feeders, capable of chasing fish at high speeds and making sharp turns.
Facing Extinction
The Yangtze finless porpoise is currently classified as critically endangered by the IUCN, with an estimated population of approximately 1,249 individuals in 2023. This decline is largely due to human-induced factors, including overfishing, which depletes their food sources and leads to accidental entanglement in fishing gear. Habitat degradation is another major threat, stemming from activities such as sand mining, dam construction, and dredging, which alter natural river flows and fragment their living spaces.
Pollution from industrial and agricultural runoff, as well as noise pollution from increased vessel traffic, impacts their health and ability to navigate, communicate, and forage. Collisions with motorized boats and ships contribute to porpoise fatalities. Climate change exacerbates these challenges by increasing water temperatures, storm frequency, and altering river currents, which can reduce their survival rates and food availability within their confined riverine habitat.
Protecting a Rare Species
To safeguard the Yangtze finless porpoise, a comprehensive conservation strategy has been implemented, combining in-situ and ex-situ measures. In-situ efforts focus on protecting their natural habitat within the Yangtze River basin, including the establishment of protected areas and the enforcement of fishing bans, such as the ten-year fishing ban enacted in 2021.
Ex-situ conservation involves relocating porpoises to protected oxbow lakes, creating “insurance populations” outside the main river. The Tian’e-Zhou semi-natural reserve has successfully housed and bred porpoises since 1990, with over 30 calves born there, demonstrating the viability of off-site protection. Additionally, captive breeding programs at facilities like the Institute of Hydrobiology of the Chinese Academy of Sciences have resulted in the birth of freshwater cetaceans in captivity, providing insights for population recovery. Scientific research and public awareness campaigns also play a role in understanding the species and garnering support for its survival.