The distribution of the Atlantic white-sided dolphin is the cool temperate and subartic waters of the north Atlantic Ocean from southern Greenland to Massachusetts, and from the British Isles to western Norway. It has also been reported as far as the sourthern Barents Sea, the Baltic Sea, the Azores, and the Adriatic Sea.

Biogeographic Regions: atlantic ocean (Native )

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: Cooler temperate waters of the North Atlantic. Off the northeastern U.S. and southeastern Canada, most abundant apparently in the Gulf of Maine (Gaskin 1992).

Lagenorhynchus acutus ranges from 2.5 to 3 meters in length. The pectoral fin is about 30 cm in length and the dorsal fin may be up to 50 cm in height. The tail flukes range from 30 to 60 cm across. Females may be considerably smaller than males and average only 182 kg.

The dorsal region of L. acutus is black, while its sides are gray. The ventral regions are white from the lower jaw to just past the anus. Within the gray sides are yellowish white patches, which are probably its most distinct characteristic (Minasian et al., 1984). Black rings around the eyes are also present. The dorsal fin is tall, sharply curved and pointed at the tip, giving the species the name acutus or, Latin for "sharp". Lagenorhynchus acutus has a stocky body with sickle shaped fins and a thick tail stock. The beak is prominent with 30 to 40 pairs of pointed teeth.

Range mass: 180 to 250 kg.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: male larger

Length: 2700 cm

• Marine

Lagenorhynchus acutus is typically found in cool pelagic waters, where its major predators are killer whales and sharks. Since it usually prefers the open water, L. acutus is not commonly seen from shore. It mostly occupies waters of 40 to 270 m in depth around the continental shelf. L. acutus seems to prefer a surface temperature between 6 to 20 degrees Celsius and areas with low salinity.

Habitat Type: Marine

Comments: Mainly continental shelf waters; most abundant in areas of steepest subsurface topographic relief; mean water depth for U.S. sightings was 165 m (Gaskin 1992). Inhabits offshore waters. Occurs where water temperature is 1-15 C, mainly less than 12 C (IUCN 1991).

The species associated with this page are major players in the pelagic ecosystem of the Stellwagen Bank National Marine Sanctuary. Stellwagen Bank is an undersea gravel and sand deposit stretching between Cape Cod and Cape Ann off the coast of Massachussets. Protected since 1993 as the region’s first National Marine Sanctuary, the bank is known primarily for whale-watching and commercial fishing of cod, lobster, hake, and other species (Eldredge 1993). 

Massachusetts Bay, and Stellwagen Bank in particular, show a marked concentration of biodiversity in comparison to the broader coastal North Atlantic. This diversity is supported from the bottom of the food chain. The pattern of currents and bathymetry in the area support high levels of phytoplankton productivity, which in turn support dense populations of schooling fish such as sand lance, herring, and mackerel, all important prey for larger fish, mammals, and seabirds (NOAA 2010). Sightings of many species of whales and seabirds are best predicted by spatial and temporal distribution of prey species (Jiang et al 2007; NOAA 2010), providing support for the theory that the region’s diversity is productivity-driven.

Stellwagen Bank is utilized as a significant migration stopover point for many species of shorebird. Summer visitors include Wilson’s storm-petrel, shearwaters, Arctic terns, and red phalaropes, while winter visitors include black-legged kittiwakes, great cormorants, Atlantic puffins, and razorbills. Various cormorants and gulls, the common murre, and the common eider all form significant breeding colonies in the sanctuary as well (NOAA 2010). The community of locally-breeding birds in particular is adversely affected by human activity. As land use along the shore changes and fishing activity increases, the prevalence of garbage and detritus favors gulls, especially herring and black-backed gulls. As gull survivorship increases, gulls begin to dominate competition for nesting sites, to the detriment of other species (NOAA 2010). 

In addition to various other cetaceans and pinnipeds, the world’s only remaining population of North Atlantic right whales summers in the Stellwagen Bank sanctuary. Right whales and other baleen whales feed on the abundant copepods and phytoplankton of the region, while toothed whales, pinnipeds, and belugas feed on fish and cephalopods (NOAA 2010). The greatest direct threats to cetaceans in the sanctuary are entanglement with fishing gear and death by vessel strikes (NOAA 2010), but a growing body of evidence suggests that noise pollution harms marine mammals by masking their acoustic communication and damaging their hearing (Clark et al 2009).

General threats to the ecosystem as a whole include overfishing and environmental contaminants. Fishing pressure in the Gulf of Maine area has three negative effects. First and most obviously, it reduces the abundance of fish species, harming both the fish and all organisms dependent on the fish as food sources. Secondly, human preference for large fish disproportionately damages the resilience of fish populations, as large females produce more abundant, higher quality eggs than small females. Third, by preferentially catching large fish, humans have exerted an intense selective pressure on food fish species for smaller body size. This extreme selective pressure has caused a selective sweep, diminishing the variation in gene pools of many commercial fisheries (NOAA 2010). While the waters of the SBNMS are significantly cleaner than Massachusetts Bay as a whole, elevated levels of PCBs have been measured in cetaceans and seabird eggs (NOAA 2010). Additionally, iron and copper leaching from the contaminated sediments of Boston Harbor occasionally reach the preserve (Li et al 2010). 

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

The prey of L. acutus is usually a combination of shrimp, smelt, hake, squid and herring. These animals may separate from their school in order to feed more efficiently.

Animal Foods: fish; mollusks; aquatic crustaceans

Primary Diet: carnivore (Piscivore )

Comments: Diet consists primarily of small pelagic fishes and squid (e.g., sand lance, silver hake, herring, common squid).

Gregarious. Inshore, group size generally is around 6-8; offshore, may form groups of up to several hundred; groups may segregate partially by age and/or sex (IUCN 1991).

Comments: Active day and night.

Average lifespan

Sex: female

Status: wild: 27.0 years.

Average lifespan

Sex: male

Status: wild: 22.0 years.

Information on the mating system of these animals is not available.

The gestation period is about 10 months long. The calves are usually born in June and July. There is usually one young per a birth, averaging about 25 kg and 107 to 122 cm in size when born. The young are usually weaned at 18 months. The calving interval is 2 to 3 years.

Males become sexually mature between 2.1 and 2.4 m in length. Females become sexually mature between 1.94 and 2.22 m in length, which probably corresponds to 12 years of age (Klinowska, 1991). The maximum longevity of males is probably 22 years, whereas female longevity is 27 years.

Breeding interval: The calving interval is 2 to 3 years.

Average number of offspring: 1.

Average gestation period: 10 months.

Average weaning age: 18 months.

Average age at sexual or reproductive maturity (male): 12 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization ; viviparous

Average birth mass: 24000 g.

Average gestation period: 316 days.

Average number of offspring: 1.25.

Average age at sexual or reproductive maturity (female)

Sex: female: 2231 days.

Mates in early fall. Gestation apparently lasts about 11 months. Single calf is born May-early August (mainly June/July) in western Atlantic. Young is weaned in about 18 months. Total length of the reproductive cycle may be at least 2.5 years. Females sexually mature in about 6-8 years, males in about 8-9 years.

Data on the population size of L. acutus is scarce but, the species is usually considered regionally abundant. The main threats today come from pollutants and entanglement in fishing gear (Whale and Dolphin Species Information, Humpback Whale and others, 1999).

US Federal List: no special status

CITES: appendix ii

IUCN Red List of Threatened Species: least concern

Canada

Rounded National Status Rank: N4 - Apparently Secure

United States

Rounded National Status Rank: NU - Unrankable

Rounded Global Status Rank: G4 - Apparently Secure

Comments: No direct threats at present; potential threats include groundfish gill nets off eastern U.S. and Canada, salmon drift nets in the Labrador Sea, and possible spills from future offshore oil development (Gaskin 1992).

A small number are caught in fishing nets each year, causing damage to fishing productivity.

Occasionally, L. acutus is captured deliberately by fisherman off Newfoundland, Norway, and the British Isles, presumably to be sold in fresh meat markets (Nowak, 1999). Historically, L. acutus has also been hunted by Greenland. The Faeroe Islands take hundreds of L. acutus every year, by driving large schools ashore (Cetacea: Lagenorhynchus acutus, 1999). Unlike many other dolphin species, L. acutus has not been reported to be in captivity (Atlantic white-sided dolphin, 1999).

Comments: Not important as a subsistence or commercial resource. Taken directly in small number in Greenland (IUCN 1991).

Comments: LeDuc et al. (1999) used cytochrome b gene sequences to examine phylogenetic relationships among delphinids and found that Lagenorhynchus albirostris (type species for the genus) and L. acutus are not closely related to each other or to nominal congeners; acutus was therefore assigned to the genus Leucopleurus. The remaining four Lagenorhynchus species are closely related to Lissodelphis and Cephalorhynchus and were placed in the genus Sagmatias. However, this revision has not been widely accepted and, pending further evidence, the mammal checklists by Baker et al. (2003) and Mead and Brownell (in Wilson and Reeder 2005) maintained acutus and obliquidens in the genus Lagenorhynchus.