Atlantic whitefish (Coregonus huntsmani)
|Also known as:||Acadian whitefish, common whitefish, round whitefish, sault whitefish|
|Size||Length: 20 – 38 cm (2)|
Classified as Vulnerable (VU) on the IUCN Red List (1).
A member of the salmon and trout family (Salmonidae), the Atlantic whitefish has a typical salmon-like appearance, but can be distinguished from other species by its larger body scales (2). The colouration is uniform silver on the sides, becoming silvery-white on the belly, while the back is dark bluish black or dark green (2). The caudal fin is deeply forked, and a small, fleshy fin, termed an ‘adipose fin’, is located between the dusky-coloured dorsal and caudal fins (2) (3). The body is elongated, with a short head in which the jaws are located at the end of the snout rather than on the underside of the head (3). Prior to the decline of the Atlantic whitefish from much of its range, larger bodied anadromous specimens occurred, which reached lengths of up to 50 centimetres. Today’s surviving landlocked, freshwater populations are smaller-bodied, only reaching between 20 and 25 centimetres in length (2).
Endemic to Canada, the Atlantic whitefish is currently restricted to three semi-natural freshwater lakes: Minamkeak, Milipsigate, and Hebb, covering a total area of just 16 square kilometres within the upper Petite Rivière drainage of south-west Nova Scotia (2) (4). Historically, this species occupied a greater range, occupying the Tusket River drainage, as well as other watersheds in Nova Scotia. As an anadromous species, populations moved from the freshwater spawning grounds to adjacent estuaries and coastal bays around Nova Scotia. However, since the disappearance of this species from the Tusket River drainage in the 1980s, the Atlantic whitefish has become landlocked due to the presence of dams in the Petite Rivière drainage, which inhibit migration (2) (4).
The natural anadromous life history of the Atlantic whitefish involved periods in both saltwater and freshwater environments. However, as ocean-going populations no longer exist, little is known of this species’ marine habitat preferences. The existing landlocked, freshwater populations are dispersed throughout the three lakes that form this species’ total range, as well as in the streams that connect them (4). The juveniles typically occur in shallow waters, while the adults range throughout the water column, avoiding the warm surface waters during the summer months (3) (4).
The landlocked populations of the Atlantic whitefish feed on small fish and aquatic insects (2). Historical records describing the stomach contents of individuals caught in the marine environment indicate that shrimp, amphipods, fish, and marine worms formed the bulk of this species’ diet (4).
As its eggs are not saltwater tolerant, the Atlantic whitefish must spawn in freshwater (4). Historical records indicate that after spending the summer in coastal waters, the Atlantic whitefish would migrate upstream during late September to October (1) (4). Today, however, spawning migrations do not occur, and as wild individuals have not yet been observed to spawn in the wild, knowledge about this species’ reproduction is primarily limited to observations of captive specimens. These specimens produce eggs from late November to early January, and studies of the eggs in culture indicate that they sink to the bottom and may adhere to surrounding objects. The larvae hatch after around 260 days, which would correspond to the months of April and May in the wild. The young reach maturity at around 2 years old, at 20 centimetres in length. In the wild, the Atlantic whitefish is believed to live for four to five years (4).
The exact reasons for the historical decline in Atlantic whitefish are not entirely clear, but a major factor is likely to be the extensive construction of dams throughout the principal rivers and streams of south-western Nova Scotia which inhibit this species’ spawning migration. Damming and additional threats, such as unregulated fishing and increased acidification of the water from acid rain, are almost certainly responsible for the recent extirpation of the Atlantic whitefish from the Tusket River drainage (4). The presence of dams within the Petite Rivière drainage is also likely to have contributed to the only surviving Atlantic whitefish population’s current landlocked status (3) (4). Despite the protection of the remaining populations, they are accidently caught by recreational anglers, and are also threatened by acidification and the unauthorised introduction and spread of non-native fish species, such as the smallmouth bass (4).
Several conservation measures are in place for the Atlantic whitefish. Since 1970, fishing of this species has been illegal in Nova Scotia under the federal Fisheries Act (3). This was followed in 1984 by this species’ designation as ‘endangered’ by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC), and later under Schedule 1 of the 2003 Species at Risk Act (SARA) (2) (4). Both of these designations require initiatives to protect this species and its habitat, and promote its recovery (2) (4). To facilitate these objectives, a recovery plan is underway, which has resulted in the creation of monitoring programs and the successful development of captive breeding techniques, along with plans for reintroductions (3). One of the key factors to ensure the survival of the imperilled Atlantic whitefish is the reestablishment of anadromous populations, both in the Petite Rivière drainage and in areas of this species’ former range. This will require the development of techniques to bypass the current barriers presented by hydroelectric dams (4).
To learn more about the conservation of the Atlantic whitefish visit:
- Fisheries and Oceans Canada:
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- Amphipods: a group of small shrimp-like crustaceans that includes sandhoppers, beach hoppers, and water lice.
- Anadromous: in fish: those species that spend most of their lives at sea but migrate to fresh water to spawn.
- Caudal fin: the tail fin of a fish.
- Dorsal fin: the unpaired fin found on the back of the body of fish, or the raised structure on the back of most cetaceans.
- Endemic: a species or taxonomic group that is only found in one particular country or geographic area.
IUCN Red List (December, 2009)