Atlantic wolffish (Anarhichas lupus) COSEWIC assessment and status report 2012: chapter 7
The Atlantic Wolffish is widely distributed on both sides of the North Atlantic and in the Arctic. In the northeastern Atlantic, it occurs from Iceland, the Faroe Islands, and the North Sea to the Barents Sea and the White Sea (Scott and Scott 1988) (Figure 2). In the western North Atlantic, it occurs nearly continuously from Davis Strait to Cape Hatteras (Kulka et al. 2007).
Figure 2. Potential global range of the Atlantic Wolffish. Source: Kaschner et al. (2008).
Description of Figure 2
Map of the potential global range of the Atlantic Wolffish showing its wide distribution on both sides of the North Atlantic and in the Arctic. Relative probabilities of occurrence are indicated. In the northeastern Atlantic, the species occurs from Iceland, the Faroe Islands, and the North Sea to the Barents Sea and the White Sea. In the western North Atlantic, it occurs nearly continuously from Davis Strait to Cape Hatteras.
Table 3 presents the sources used to determine the distribution of the Atlantic Wolffish in Canadian waters. Fisheries and Oceans Canada (DFO) research trawl surveys provide the primary source of information (see “Sampling Effort and Methods”). However, these surveys do not cover shallow coastal waters (less than 40 m depth), where the Atlantic Wolffish occurs (Kulka et al. 2004). Similarly, some rocky sectors are not covered by the surveys due to the risk of damage to bottom trawl gear. Figure 3 shows the locations of the areas mentioned in this report, and Figure 4 shows the NAFO Divisions.
Figure 3. Map of geographic locations mentioned in this document.
Description of Figure 3
Map showing geographic locations mentioned in this report. Labelled locations include the Labrador Sea, Grand Banks, Bonne Bay, Gulf of St. Lawrence, Scotian Shelf, Bay of Fundy and Gulf of Maine.
Figure 4. Northwest Atlantic Fisheries Organization (NAFO) Convention Areas.
Description of Figure 4
Map showing Northwest Atlantic Fisheries Organization Convention subareas and divisions.
In recent years, additional surveys have been conducted in collaboration with the fishing industry, such as the Groundfish Sentinel Program, which conducts mobile gear surveys (bottom trawl) and fixed gear surveys (longline and gill net). The Canadian At-Sea Fisheries Observer Program is also a source of information on the distribution of marine fish species and composition of commercial catches, but the data are not directly comparable to DFO’s research trawl surveys and are therefore not included here. Other occasional studies covering small areas in coastal environments include an inventory of sites on the Gaspé Peninsula coast in Quebec (Laroque et al. 2008), and a study of fish communities in Bonne Bay, Newfoundland (Currie et al. 2009).
In Canadian waters, the Atlantic Wolffish occurs off Baffin Island, in the Labrador Sea, off Newfoundland, in the Gulf of St. Lawrence, on the Scotian Shelf, in the Bay of Fundy and Gulf of Maine (Figure 5). This species is very rare in the northern part of its range (the Arctic). It is most abundant in the waters of the continental shelf, off northeastern Newfoundland, on the Labrador Shelf and in the Grand Banks off Newfoundland.
Figure 5. Extent of occurrence in Canada of Atlantic Wolffish based on Department of Fisheries and Oceans Canada research trawl survey catches.
Description of Figure 5
Map showing extent of occurrence (EO) of the Atlantic Wolffish in Canada based on Fisheries and Oceans Canada research trawl catches. EO is 2.792 million square kilometres within Canadian jurisdiction and 1.807 million square kilometres when unsuitable habitat (such as major land masses) is excluded. The species occurs off Baffin Island, in the Labrador Sea, off Newfoundland, in the Gulf of St. Lawrence, on the Scotian Shelf, in the Bay of Fundy and in the Gulf of Maine. The species is very rare in the Arctic and most abundant in the waters of the continental shelf, off northeastern Newfoundland, on the Labrador Shelf and in the Grand Banks off Newfoundland.
In the Gulf of St. Lawrence, it occurs primarily in coastal areas and on the edge of deep channels and avoids the bottoms of deep channels (Dutil et al. 2010). The highest concentrations are off western Newfoundland (Dutil et al. 2010, Ouellet et al. 2010). It has also been reported in Bonne Bay in Gros Morne National Park in western Newfoundland (Currie et al. 2009), in the Saguenay–St. Lawrence Marine Park, and Forillon National Park in Quebec.
Distribution indices were calculated by the COSEWIC Secretariat. The extent of occurrence was determined by calculating the area of the minimum convex polygon encompassing regions well covered by research trawl surveys in Canada, excluding major land masses (Figure 5). The extent of occurrence in the entire Canadian range is estimated at 2.792 million km2. This area includes some major landmasses. If these are excluded, the figure is 1.807 million km2.
An index of area of occupancy was calculated using kriging based on a 2-km × 2-km cell grid of the entire area inhabited by Atlantic Wolffish (Figure 6). This index for the entire Canadian range is estimated at 37,332 km2.
Figure 6. Index of area of occupancy in Canada of Atlantic Wolffish based on Department of Fisheries and Oceans Canada research trawl survey catches.
Description of Figure 6
Map showing index of area of occupancy (IAO) in Canada of Atlantic Wolffish based on Fisheries and Oceans Canada research trawl catches. IAO is 37 332 square kilometres.
The design-weighted area of occupancy (DWAO) index was calculated by DFO as follows:
At = n where I = 1 if Yi > 0, 0 otherwise
∑ AiI
i=1
where n is the number of tows in the survey, Yi is the number of individuals caught in tow i, and Ai is the area of the stratum fished by tow i divided by the number of sites fished in the stratum.
Labrador Shelf and Newfoundland Grand Banks
The area of occupancy index for the Labrador Shelf (Div. 2J3K), which includes the majority of the population, was calculated for the Newfoundland and Labrador region (fall and spring research trawl surveys). This index declined from the 1980s to the mid-1990s, but has increased since 1995 (Figure 7, Simpson et al. 2011). On the Newfoundland Grand Banks (Div. 3LNO, see Figure 7), the index calculated in the spring and fall shows no decline in the 1980s and 1990s, and an increase since the mid-1990s. It is important to bear in mind that due to gear changes, different data series values and trends cannot be compared directly.
Figure 7. Index of area of occupancy (DWAO) of the Atlantic Wolffish for the Newfoundland Grand Banks (3LNO) and the Labrador Sea (2J3K) based on Newfoundland spring and fall research trawl surveys. The vertical lines indicate a fishing gear change (blue line for the spring, black for fall). During fall, only Division 3L was surveyed prior to 1990. From Simpson et al. (2011).
Description of Figure 7
Chart showing design-weighted index of area of occupancy (DWAO) of the Atlantic Wolffish on the Newfoundland Grand Banks (3LNO) and in the Labrador Sea (2J3K) based on Newfoundland spring and fall research trawl surveys. Data are shown for the spring 3LNO survey, fall 3LNO survey, and fall 2J3K survey. The area of occupancy index for the Labrador Shelf (2J3K) declined from the 1980s to the mid-1990s, but has increased since 1995. On the Newfoundland Grand Banks (3LNO), the index shows no decline in the 1980s and 1990s, and an increase since the mid-1990s.
Scotian Shelf, Southern Newfoundland and Gulf of St. Lawrence
The area of occupancy index was calculated from Maritimes summer research trawl surveys (Simon et al. 2011). There was a general downward trend in the Scotian Shelf (Div. 4VWX) since the 1970s (Figure 8), falling from close to 17 000 km2 in 1976 to 5,484 km2 in 2009. In 2010, the value was 6,919 km2. In southern Newfoundland waters (Div. 3Ps) and the Southern Gulf of St. Lawrence (Div. 4T), the index shows some variation without trends since 1971 (Figure 8). In contrast, the Northern Gulf of St. Lawrence has shown an increasing trend in DWAO since the early 1990s (Figure 9). The index value went from 7,216 km2 in 1990 to 16,662 km2 in 2009.
Figure 8. Index of area of occupancy (DWAO) of Atlantic Wolffish for the Scotian Shelf (NAFO Divisions 4VWX), Southern Newfoundland (3Ps), and the Southern Gulf (4T). The vertical lines indicate a fishing gear change. From Simon et al. (2011).
Description of Figure 8
Chart showing design-weighted index of area of occupancy of Atlantic Wolffish, from the early 1970s, for the Scotian Shelf (4VWX), Southern Newfoundland, and the Southern Gulf.
Figure 9. Index of area of occupancy (DWAO) of Atlantic Wolffish for the Gulf of St Lawrence (NAFO Division 4RST). From Bourdage and Ouellet (in prep.).
Description of Figure 9
Chart tracking design-weighted index of area of occupancy of Atlantic Wolffish, from the early 1990s, for the Gulf of St Lawrence.
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