COSEWIC assessment and status report on the Atlantic wolffish Anarhichas lupus in Canada
The Atlantic wolffish is found principally in the deep waters of the continental shelf on rocky or hard clay bottoms, and only occasionally on sand or mud. Like other wolffish species, its migrations are local and limited (Templeman, 1984) and it does not form large schools. It is, however, known to perform small seasonal inshore-offshore
Figure 2. Composite map of the western Atlantic distribution of Anarhichas lupus, from the ECNASAP website -http://www-orca.nos.noaa.gov/projects/ecnasap/maps/atlwol.gif
migrations (Keats et al., 1985). It is found anywhere from very shallow water to 500 m deep and is said to prefer depths between 100 and 150 m; this apparent preference, however, varies depending on the locality. The Atlantic wolffish is a cool to cold water fish, tolerating a broad temperature range of -1°C to 10°C, though preferring temperatures between -0.4°C and 6°C. These preferred temperature ranges can also vary with locality.
In addition to temperature and depth information, the DFO scientific survey trawl data also report the positions of all stations where a species is taken. This information can be used to develop a picture of trends over time in the range occupied. In 1984 the wolffish was widespread on the deep shelf off northeastern Newfoundland but by 1993 its range had contracted mostly to a band offshore along the edge of the shelf. In maps provided by DFO (2000, in Litt.) Atlantic wolffish appear to have moved to deeper, more peripheral portions of the range on the Scotian Shelf; maps for the Gulf of St. Lawrence show little pattern, but do make clear how rare the species is there in general.
Another indicator of the possibly shrinking range of this species, the percentage of all annual survey stations where the Atlantic wolffish was actually caught, is shown for all Canadian areas in Figure 3; the percentage declined steadily from near 35% in 1978 to about 10% in 1994. For the area off Newfoundland, the Atlantic wolffish occurred in 88% of the stations where it was expected (according to preferred depth and temperature ranges) in 1978, and that level of occurrence continued until about 1985. After 1985, the percentage declined steadily to only 33% in 1993.
Figure 3. Percentage of scientific survey stations that captured Atlantic wolffish, Anarhichas lupus, 1978-1999. Solid line, circles: Canadian waters, ECNASAP data. Dotted line, X’s: Newfoundlandwaters only, data provided by DFO in September 2000. Note sampling protocol changed in 1995.
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