|Scientific Name:||Lagenorhynchus acutus|
|Species Authority:||(Gray, 1828)|
|Taxonomic Notes:||The Atlantic White-sided Dolphin is currently placed in a multi-species genus (Cipriano 1997). However, molecular analyses suggest that it is not closely-related to any of those other species, and it is possible that it will be split-off from them into its own genus (Leucopleurus) in the next few years (LeDuc et al. 1999, Harlin-Cognato and Honeycutt 2006)|
|Red List Category & Criteria:||Least Concern ver 3.1|
|Assessor/s:||Hammond, P.S., Bearzi, G., Bjørge, A., Forney, K., Karczmarski, L., Kasuya, T., Perrin, W.F., Scott, M.D., Wang, J.Y., Wells, R.S. & Wilson, B.|
|Reviewer/s:||Rojas-Bracho, L. & Smith, B.D. (Cetacean Red List Authority)|
The species is widespread and abundant (with current population estimates exceeding 100,000) and there have been no reported population declines or major threats identified.
|Range Description:||Atlantic white-sided dolphins are found in cold temperate to subpolar waters of the North Atlantic, from about 38°N (south of Cape Cod) in the west and the Brittany coast of France in the east, north to southern Greenland, Iceland, and southern Svalbard (Reeves et al. 1999; Cipriano 2002). The range includes the U.K. and the northern coasts of Scandinavia, although they rarely enter the Baltic Sea. They also sometimes move quite far up the Saint Lawrence River of eastern Canada, and they have been seen as far south as Strait of Gibraltar (Hashmi and Adloff 1991, 1992).|
Native:Belgium; Canada; Denmark; Faroe Islands; France; Greenland; Iceland; Ireland; Netherlands; Norway; Russian Federation; Sweden; United Kingdom; United States
Vagrant:Gibraltar; Portugal; Spain
|FAO Marine Fishing Areas:||
Atlantic – northeast; Atlantic – northwest
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||This species is quite abundant throughout its range. There are an estimated 51,640 (CV=38%) Atlantic white-sided dolphins off the eastern North American shoreline (Waring et al. 2006) and about 96,000 (CV=54%) off the west coast of Scotland (MacLeod 2004). The number of Atlantic white-sided dolphins in the western North Atlantic, from the southern Gulf of Maine and north-eastward on the continental shelf and slope to Cabot Strait was about 27,000 in July - September 1995 (Palka et al. 1997) and was at least 11,740 (CV = 47%) in the Gulf of St. Lawrence (Kingsley and Reeves, 1998). There is currently little evidence for separate subpopulations (Mikkelsen and Lund 1994).|
|Habitat and Ecology:||
The Atlantic white-sided dolphin is found primarily in waters of the continental shelf and slope, but it also occurs in oceanic waters across the North Atlantic. Along the continental slope of North America, it seems to associate with high sea-bed relief along the continental shelf (Palka et al. 1997).
These dolphins often associate and feed with large baleen whales (fin and humpback whales), and are known to form mixed groups with pilot whales and a number of other dolphin species (including bottlenose and white-beaked dolphins). Atlantic white-sided dolphins feed mostly on small schooling fish (such as herring, mackerel, cod, smelt, hake, and sandlance), shrimp, and squid.
Some hunting for this species occurred in the past, especially in Norway. Some dolphins are still taken in Greenland, the Faroe Islands, and eastern Canada (Jefferson et al. 1993; Reeves et al. 1999). Recent catches in Faroe Islands were 333 and 310 in 2004 and 2005, respectively (NAMMCO 2005). No assessment is associated with the Faroese hunting of white-sided dolphins, but there is no evidence that this aspect of the drive fishery has a long history, such as that of the pilot whale component (Reeves et al. 2003).
Incidental mortality in fishing gear has been documented off Canada, the United States, the United Kingdom and Ireland. Gaskin (1992) judged Atlantic white-sided dolphins to be less vulnerable to capture in pelagic near-surface drift nets and fixed groundfish gill nets than are many other small cetaceans. They may, however, be especially susceptible to capture in midwater trawl nets (Addink et al. 1997). Substantial numbers have been bycaught in pelagic trawl fisheries for horse mackerel and mackerel south-west of Ireland (Reeves et al. 1999).
Morizur et al. (1999) investigated marine mammal bycatch in 11 pelagic trawl fisheries operated by four different countries in the Northeast Atlantic. One of the main marine mammal species identified in bycatches was L. acutus. Mean dolphin catch rate for all fisheries combined was 0.048+0.013 per tow (one dolphin per 20.7 tows), or 0.0185+0.0019 per hour of towing (one dolphin per 98 h of towing). All dolphin by-catches occurred during the night. White-sided dolphins were observed feeding around the net during towing; this behaviour may make them more vulnerable to capture. Operational difficulties in observing bycatch and potentially significant annual fluctuation in catch rates warrant further observer studies of these and other trawl fisheries. Substantial numbers have been by-caught in trawl fisheries south-west of Ireland (Couperus 1997a, b), and takes have also been recorded in gill-net and trawl fisheries along the US Atlantic coast (Waring et al. 2008).
Like other North Atlantic marine mammals, Atlantic white-sided dolphins are contaminated by organochlorines, other anthropogenic compounds and heavy metals (Reeves et al. 1999); although the effects of pollutants are not well understood in this species, they may affect reproduction or render them susceptible to other mortality factors.
The species is listed in Appendix II of CITES.
Existing direct takes are currently not regulated by any hunting quotas. Operational difficulties in observing bycatch and potentially significant annual fluctuation in catch rates warrant further observer studies of these and other trawl fisheries (Morizur et al. 1999; Waring et al. 2006). The impact of combined anthropogenic removals should be assessed.
|Citation:||Hammond, P.S., Bearzi, G., Bjørge, A., Forney, K., Karczmarski, L., Kasuya, T., Perrin, W.F., Scott, M.D., Wang, J.Y., Wells, R.S. & Wilson, B. 2008. Lagenorhynchus acutus. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. <www.iucnredlist.org>. Downloaded on 25 May 2013.|
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