The East Asian finless porpoise is a unique marine mammal, often observed in coastal waters and major river systems. Its subtle coloration and the absence of a prominent dorsal fin make it distinct among cetaceans. The challenges it faces highlight broader concerns about marine environmental health.
Distinct Features and Subspecies
The East Asian finless porpoise, classified within the porpoise family Phocoenidae, is characterized by unique anatomical features. Unlike most other porpoises, it lacks a true dorsal fin, instead possessing a low ridge of thick skin on its back with tiny tubercles. This species also has a notably steep forehead and no beak, distinguishing its head shape. Adults typically display a uniform light grey coloration, though some may exhibit lighter patches around the mouth or darker areas near the flippers.
These porpoises are generally slender, with average adults measuring between 1.5 to 1.8 meters (5 to 6 feet) in length and weighing around 45 kilograms (100 pounds). Their flippers are moderately large. Two subspecies are recognized: the Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) and the coastal East Asian finless porpoise (Neophocaena asiaeorientalis sunameri). The Yangtze finless porpoise, a freshwater cetacean, is found exclusively in the Yangtze River and its associated lakes, while the East Asian finless porpoise inhabits coastal waters of the Yellow Sea, East China Sea, and the seas around Japan.
Natural Habitat and Daily Life
East Asian finless porpoises are distributed across the coastal waters of East Asia, extending from mainland China south to the Penghu Islands, with the Matsu Islands marking their northern limit. They prefer shallow waters, less than 50 meters deep, close to the shore, and are often found in areas with soft or sandy seabeds, estuaries, and mangrove swamps.
These porpoises are carnivores, with their diet consisting primarily of fish, shrimp, squid, cuttlefish, and octopuses. They use echolocation for navigation and foraging, emitting biosonar pulses to detect prey and surroundings. Foraging activity for the Yangtze finless porpoise is often higher during crepuscular and nocturnal hours. While they can be observed individually or in pairs, groups of up to 20 individuals have been reported, with larger aggregations occasionally seen in Chinese waters. The average lifespan for this species is between 18 to 25 years, with some living longer in captivity.
Threats to Survival
The East Asian finless porpoise faces numerous threats contributing to its population decline. Pollution, including chemical runoff and waste, directly impacts their health and habitats. Habitat loss also occurs due to extensive coastal development and the construction of dams, which fragment their living areas and disrupt natural water flows. This development can block tributaries, preventing migratory fish from reaching spawning grounds, thereby reducing the porpoise’s food sources.
Fishing entanglement poses a danger, as porpoises are often incidentally captured in nets, leading to injury or death. Overfishing further depletes their prey, forcing them to expend more energy searching for food. Vessel traffic and associated noise pollution represent another serious threat; the constant movement of ships creates underwater noise that interferes with the porpoises’ echolocation, their primary method for navigating and finding food. Collisions with vessels are also a direct cause of injury and mortality. Climate change presents a long-term threat by altering habitats and reducing prey fish populations.
Protecting the Species
Conservation efforts for the East Asian finless porpoise involve a multi-faceted approach, with a focus on establishing protected areas to safeguard their habitats. Marine protected areas (MPAs) and nature reserves have been created to offer refuge from human activities and allow populations to recover. For instance, several natural and ex-situ reserves have been established along the Yangtze River for the Yangtze finless porpoise subspecies.
International and national laws also play a role in their protection. The species is listed in Appendix I of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), which strictly prohibits international trade. Additionally, the Convention on Migratory Species (CMS) encourages international cooperation among countries where the porpoises are found to develop conservation measures.
Initiatives to mitigate human impacts include research into developing “porpoise-friendly” fishing gear and promoting alternative fishing methods to reduce incidental capture. Fishing restrictions during breeding seasons have shown effectiveness in reducing fishery-related mortality. Captive breeding programs are also in place, particularly for the Yangtze finless porpoise, with successful births demonstrating the potential for maintaining populations and studying their reproductive biology.
Public awareness campaigns and educational programs are conducted to inform local communities and fishermen about conservation needs and relevant legislation, though awareness of all fishing restrictions remains varied. Ongoing scientific studies continue to monitor populations, assess threats, and inform conservation strategies, providing data on distribution, abundance, and behavioral patterns.