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Fascinating ecosystems: How did the harbor porpoise become the ocean's apex predator?
The harbor porpoise (Phocoena phocoena) is one of eight extant species of porpoise and the smallest of the dolphin species. As its name suggests, the harbor porpoise is found in coastal areas or near estuaries and is a unique marine creature that often attracts the attention of whale watchers. The dolphins sometimes even venture into rivers and have been observed hundreds of kilometers from the ocean. The scientific community generally believes that harbor porpoises may have diverse geographical groups, such as P. p. phocoena from the North Atlantic and West Africa, P. p. relicta from the Black Sea and Sea of Azov, an unnamed group from the Northwest Pacific, and a group from the Northeast Pacific. P. p. vomerina.
The English word harbor porpoise comes from the French "pourpois", which is a compound word derived from "porcus" (pig) and "piscus" (fish). Ancient Latin also gave it a similar name.
Biometrics
Harbor porpoises are slightly smaller than other species of dolphins, measuring about 67 to 85 centimeters long at birth and weighing between 6.4 and 10 kilograms. The length of an adult dolphin can reach 1.4 to 1.9 meters. Females are heavier than males, with a maximum weight of 76 kilograms. These dolphins have a solid body structure, with the greatest girth usually located in front of the triangular dorsal fin. Their mouths are not distinctly shaped, their fins and dorsal fins are dark gray, their sides are slightly mottled light gray, and their belly is significantly whiter, often with a gray stripe on the throat. A few unusual white individuals have been identified in the North Atlantic, but the phenomenon is relatively rare.
Distribution range
Harbor porpoises are widely distributed in cooler coastal waters in the North Atlantic, North Pacific and Black Sea. In the Atlantic, harbor porpoises extend from the coast of West Africa to Portugal, Spain, the United Kingdom, Ireland, and the East Coast of the United States. According to a survey conducted at an international symposium in 2018, the population structure of harbor porpoises is more complex than previously thought, with at least three genetically distinct subspecies in the North Atlantic.
Natural History
Ecology
Harbor porpoises like to live in temperate and sub-Arctic waters and feed mainly on small fish, such as herring, cod and small sardines. The latest research shows that these dolphins can catch up to 200 fish per hour when hunting, and the peak number of catches can even reach 550 at night. They primarily fish close to the bottom, but will also come closer to the surface when catching certain fish species.
The study found that prey availability of harbor porpoises affects their vocal activity during season and diurnal activity, and that in some areas there is a clear nocturnal pattern of predatory behavior.
Threats
While the overall harbor porpoise population is not considered endangered, they still face many threats, including:
- Hunting and Overfishing: Traditionally, harbor porpoises have been hunted for food and other needs such as blubber.
- Fishing interactions: Static fishing gear such as nets and entanglement nets are one of the main causes of mortality.
- Noise pollution: Noise from ships and oil platforms may affect their activities and communication.
Conservation status
Overall, harbor porpoises are assessed as "Least Concern," but specific populations, such as those in the Baltic Sea and West Africa, are classified as "Vulnerable" or "Critically Endangered." They are protected in areas covered by multiple international agreements and conservation centres, such as the Convention on International Trade in Endangered Species of Wild Fauna and Flora and the Agreement for the Conservation of Marine Life. As scientific research continues, our understanding of these adorable dolphins and the challenges they face continues to grow.
The future of the harbor porpoise depends on efforts to protect its habitat and resources, so how can we act to protect such a unique and important marine life?
