Short-beaked Common Dolphin

Short-beaked Common Dolphin: Delphinus delphis

IUCN Status: least concern

Status and distribution summary:

Several populations occur in different oceans of  the world, but without continuous distribution and some may be isolated. Its distribution is associated with warm temperate to tropical waters, but mostly where upwellings occur eg along continental shelf slopes and seamounts. Globally abundant with population estimates in the millions. However, if as some authorities consider there are more than one species, with two suggested in the Pacific Ocean, and at least one elsewhere, then its conservation status would need to be reviewed. 

Exploitation: heavily hunted in the Black Sea until the 1980s and the population has not recovered.

Other threats: heavily entrapped in fishing gear, especially in seine gear targeting tuna, but also in significant numbers in large trawl gear in European Atlantic waters including the outer Channel. 12-15,000 are thought to be killed annually in drift nets in the Straits of Gibraltar.

Over-fishing leading to depletion in food availability; declines in abundance in Biscay may be associated with the crash in Anchovy there. This fishery is now closed until stocks recover.

Where it is seen:

Throughout the Bay of Biscay and well into the Channel to at least the Channel Islands at times. Greatest abundance is associated with the continental shelf break, and over deep waters.

Frequency of sightings:

The most frequently encountered cetacean in the region. Seen in pods of from 3 or 4, up to hundreds. There is a northerly movement in winter leading to it being more frequently encountered shallow shelf waters in the Northern Bay and Channel than in deep water in the Southern Bay.

Recognition:

Highly distinctive small dolphin.

Up to 2.5 metres in length. Sleek but quite chunky.

Blackish or charcoal grey upper parts with a sharp deliniation from the flank pattern, with a diagnostic inverted black triangle beneath the dorsal fin, and 'hourglass' pattern when viewed from the side.

Often has a brownish tinge to pelage, with a usually pale tan or dull yellow panel back from the eye to the inverted V at the mid point, with grey tail stock.

Has a pronounced beak and a relatively tall pointed dorsal fin, usually with a swept back, quite straight leading edge, and concave trailing edge.

Behaviour:

In tight or dispersed groups.

Often very active at the surface, with frequent leaps when traveling, though not as prone to acrobatic somersaults some species.

Bow and wake rides frequently. And will play with moving ships, charging under the ferry from one side to the other.

Sometimes mixes with other species, and occasionally forages around large whales.

Possibly aggressive to potential predators of their calves, such as Bottlenose Dolphin and Pilot Whales.

Confusion species:

  • Striped Dolphin; is similar in size and behaviour and is also patterned. However, lacks inverted triangle and hourglass.
  • Atlantic White-sided Dolphin; has similar combinations of colours, but lacks the inverted triangle and hourglass, and is rare in the area.