Harbour Porpoise

Harbour Porpoise: Phocoena phocoena

IUCN Status: least concern

Status and distribution summary:

World population is likely to exceed 700,000, but with perhaps half of this estimate thought to occur in the North Sea. However some isolated populations are very small and endangered, eg there are only c250 surviving in the Baltic.

Occupies colder shelf waters in the Northern Atlantic and Northern Pacific oceans. Range in the Atlantic extends south to Senegal associated with cold water currents. An isolated population occurs in the Black Sea.

Exploitation:

Currently hunted around Greenland where catch estimates are on the increase. Also until recently hunted in the Black Sea despite being outlawed.

Other threats:

By-catch in fishing nets is significant with over 5,000 taken a year in the North Sea, and most other populations also affected. Having an often coastal distribution, pollution, especially around estuaries, poses a significant problem and over-fishing of prey items is impacting in some populations. There is some evidence that a decline in sand eels in the North Sea, perhaps caused by climate change factors, is implicated in local starvation in Harbour Porpoise.

Where it is seen:

Usually in shallow, shelf waters of the English Channel, Northern Bay and Western Approaches.

Frequency of sightings:

Variable from year to year. In good years can be commonly encountered as individuals or in large groups. In poor years can be absent. Most sightings are in late summer.

Recognition:

Smallest cetacean in the region, reaching no more than 1.7 metres.

Dark grey above, usually without any markings or scars. With small low dorsal fin, with a broad base giving a triangular appearance. Underside is rarely seen but is pale with a thin dark line from below the eye to the pectoral fin.

Tapering head, with no beak.

Behaviour:

Usually in small groups of 2 to 10, occasionally in large dispersed groups.

When steady swimming only shows very briefly at the surface to breath, revealing only a small part of back and a quick glimpse of the dorsal fin, so is often difficult to see, and almost impossible in rougher seas.

When fast swimming, often creates a characteristic splash ('rooster tail') may leave the water (hence 'porpoising'), otherwise is not normally demonstrative at the surface.

Audible, but not visible, exhalation.

Confusion species:

  • Unlikely to be confused unless at long range or in poor weather, its small size and the low broad-based dorsal fin should distinguish it at other times.