Northern Minke Whale

Northern Minke Whale: Balaenoptera acutorostrata

IUCN status: Least Concern

Status and distribution summary:

Previously considered to be a single species with a world-wide distribution, including polar areas, research in the 1990s determined that there are two species; Northern Minke Whale and Antarctic Minke Whale B bonaerensis. A southern hemisphere population of so-called Dwarf Minke Whale is thought by some to be a third species but seems most likely to be a race of B acutorostrata. The northern populations in the Atlantic and Pacific are isolated and may deserve specific status.

Minke Whale is most common in high latitudes, but abundance reduces with increasing water temperature.

Exploitation:

Although hunted locally for hundreds of years, commercial exploitation didn't begin in earnest until the 1970s when more valuable species had been depleted beyond economic harvest.

Minke Whales are still hunted in the northern Atlantic, theoretically to reduce competition for fish stocks in Icelandic and Norwegian waters, and in the southern Oceans and western Pacific by the Japanese for so-called scientific reasons.

Other threats:

Occasionally caught in fishing gear. Some populations including some in NW Europe occur in areas with heavy pollution loads, which may impact on Minke Whale immune systems.

Where it is seen:

Much less likely to be seen over deep water than other rorquals, and more commonly seen in the channel and the northern Bay than in the southern Bay.

Frequency of sightings:

Regularly seen in small numbers in summer, less frequently seen from October to May.

Recognition:

Medium sized (7-10m)

The smallest rorqual, and only 1/3 the size of a Fin Whale, however as they are usually seen alone there is often nothing to compare with.

In regular surfacing they usually show the following features:

  • Mostly blackish upper parts with grey on the flanks extending up onto the back and is visible in good light.
  • White bands on pectoral fins can be seen when breaching or when at the surface in good viewing and are diagnostic. 
  • The highly falcate (hooked back) dorsal fin is set well back (2/3) to tail, and is proportionally tall.
  • Blow is usually indistinct, making this a good feature.

Behaviour:

Usually occurs singly, but sometimes in small family groups.

Usually surfaces rostrum first (nose first), and sometimes shows pale lower lip, but both are only apparent in calm sea states.

Tail stock arches on diving, but flukes do not break the surface.

Often unobtrusive, and only seen rolling at the surface, but breaching is fairly common, often several times in sequence, emerging at around 45°, before belly flopping.

Confusion species:

  • Fin Whale; is much larger, with strong visible blow.
  • Sei Whale; is larger with a more erect dorsal fin and distinct blow.
  • Cuvier's Beaked Whale; usually paler and browner with a pale area on the domed forehead.
  • Northern Bottlenose Whale; is paler and has a strongly bulging forehead, and usually occurs in groups.