Atlantic wolffish (Anarhichas lupus) COSEWIC assessment and status report 2012: chapter 10

Population Sizes and Trends

Sampling Effort and Methods

Changes in Atlantic Wolffish abundance were assessed using the results of DFO research trawl surveys, which assess the abundance of several groundfish and invertebrate species (Table 4). It should be noted throughout that there are regional differences in gear as well as changes over time in some areas, which preclude direct comparisons.

Table 4. Research surveys used in this report to determine Atlantic Wolffish abundance trends. Department of Fisheries and Oceans research trawl surveys.
Survey NAFO Division Year Gear
Summer survey (Maritimes) 4V, 4W and 4X 1970–1981 Yankee 36 trawl
Summer survey (Maritimes) 4V, 4W and 4X 1982 to present Western IIA trawl
Northern Gulf survey 4RS and deep areas of 4T 1990–2003 URI 81’/114 trawl
Northern Gulf survey 4RS and deep areas of 4T 2004 to present Campelen trawl
Southern Gulf survey 4T 1971–1985 Yankee 41.5 trawl
Southern Gulf survey 4T 1986 to present Western IIA trawl
Spring surveys
(Newfoundland & Labrador)
3N, 3O, 3Ps and 3L 1971–1982 Yankee 41.5 trawl
Spring surveys
(Newfoundland & Labrador)
3N, 3O, 3Ps and 3L 1983–1995 Engel 45 trawl
Spring surveys
(Newfoundland & Labrador)
3N, 3O, 3Ps and 3L 1996 to present Campelen trawl
Fall surveys
(Newfoundland & Labrador)
2G, 2H, 2J, 3N, 3O, 3K and 3L 1977–1994 Engel 45 trawl
Fall surveys
(Newfoundland & Labrador)
2G, 2H, 2J, 3N, 3O, 3K and 3L 1995 to present Campelen trawl

The research trawl surveys, some of which have been conducted for over 40 years, use a stratified random sampling protocol. Collectively, they cover a large range of demersal species in Canada (and even some international waters in 3LNO). Essentially, only coastal areas or regions at the northern limit of the species’ range (NAFO Subarea 0) are not covered or only sparsely by the research surveys. Coverage is weaker in northern regions, with surveys conducted by DFO in Baffin Bay (NAFO Subarea 0A) in 1999, 2001, 2004, 2006, and 2008 and in Davis Strait (Subarea 0B) in 2000 and 2001.

The results of the surveys are extrapolated to the entire area covered and presented in the form of “minimum trawlable abundance” estimates. These estimates underestimate actual abundance because some areas where wolffish live are not surveyed (near-shore, northern areas, and rocky substrates), and the fishing gear does not capture all fish within the trawl footprint. Thus, some fish may avoid or escape from the trawl or may occur in areas unreachable by the trawl (e.g., crevices in rocks).

DFO has conducted spring and fall research trawl surveys on the Grand Banks, off Newfoundland and in the Labrador Sea since the early 1970s. There have been vessel and gear changes (Table 4), and the area covered has varied in some locations. Similarly, some areas have not been surveyed in some years. Table 5 shows the NAFO subdivisions covered by surveys from 1971 to 2010.

Table 5. DFO-NL research trawl surveys were conducted in spring on the Grand Banks (Div. 3LNOPs; refer to Fig.4) and Fall/Winter on the Labrador Shelf to Grand Banks (Div. 2GHJ3KLNO). Dark boxes with an "X" indicate a survey was undertaken. Accessible version of Table 5
Year NAFO Division
Fall research trawl survey Spring research trawl survey
2G 2H 2J 3K 3L 3N 3O 3L 3N 3O 3Ps
1971               X X X  
1972               X X   X
1973               X X X X
1974               X X   X
1975               X X X X
1976               X X X X
1977     X X       X X X X
1978 X X X X       X X X X
1979     X X       X X X X
1980 X X X X X     X X X X
1981     X X X     X X X X
1982     X X X     X X X X
1983     X X X           X
1984     X X X     X X X X
1985     X X X     X X X X
1986     X X X     X X X X
1987 X X X X X     X X X X
1988 X X X X X     X X X X
1989     X X X     X X X X
1990     X X X X X X X X X
1991 X X X X X X X X X X X
1992     X X X X X X X X X
1993     X X X X X X X X X
1994     X X X X X X X X X
1995     X X X X X X X X X
1996 X X X X X X X X X X X
1997 X X X X X X X X X X X
1998 X X X X X X X X X X X
1999 X X X X X X X X X X X
2000     X X X X X X X X X
2001   X X X X X X X X X X
2002     X X X X X X X X X
2003     X X X X X X X X X
2004   X X X X X X X X X X
2005     X X X X X X X X X
2006   X X X X X X X X X  
2007     X X X X X X X X X
2008   X X X X X X X X X X
2009     X X X X X X X X X
2010               X X X X

Figure 11 presents the size frequencies of catches in the Newfoundland fall research trawl surveys from 1981-1994 and 1995-2010. This shows that small sizes (under 20 cm) have been caught to a larger extent since the gear change in 1995 to Campelen from Engel.


Figure 11. Length frequency of Atlantic Wolffish based on raw catch data from the Newfoundland and Labrador fall research trawl surveys from 1981 to 1994 and 1995 to 2010. Individuals > 51 cm were considered mature. Source: Data provided by Mark Simpson, pers. comm. 2010 and 2012.

Chart showing length frequency of Atlantic Wolffish based on raw catch data from the Newfoundland and Labrador fall research trawl surveys from 1981 to 1994 and 1995 to 2010 (see long description below).
Description of Figure 11

Chart showing length frequency of Atlantic Wolffish based on raw catch data from the Newfoundland and Labrador fall research trawl surveys from 1981 to 1994 and 1995 to 2010. The chart indicates that small sizes (less than 20 centimetres) have been caught to a greater extent since the 1995 gear change from Engel to Campelen.

Research trawl surveys began in 1970 in the Scotian Shelf and Bay of Fundy (NAFO Divisions 4VWX, Maritimes summer research trawl surveys). There was a gear change in 1982, when the Yankee 36 was replaced by the Western IIa trawl, which may affect catch rates.

Two research trawl surveys are done in the Gulf of St. Lawrence. One covers Divisions 4R and 4S including the Esquiman Channel in Division 4T (northern Gulf research trawl survey) and the other is in Division 4T (southern Gulf research trawl survey).

For the northern Gulf research trawl survey, the vessel CCGS Alfred Needler equipped with a URI 81’/114’ bottom trawl was used from 1990 to 2003 and then replaced by the CCGS Teleost equipped with a shrimp trawl. In the southern Gulf, research trawl surveys have been conducted in September since 1971. A gear change from the Yankee 36 to the Western IIA occurred in 1985.

Abundance

Abundance can be estimated as stratified random estimates from research trawl survey data (Table 6). The number of Atlantic Wolffish individuals in Canadian waters is estimated to exceed 49 million. This is a conservative estimate, given that the surveys do not catch all individuals in the trawl area, some areas are not covered (e.g., rocky bottoms and coastal zones) and estimates are not available in some low-abundance regions, such as the Canadian Arctic. The number of mature individuals is estimated to exceed 5 million (Table 6).

Table 6. Current minimum trawlable abundance estimates of Atlantic Wolffish (total and mature populations) in each NAFO Division based on DFO research trawl surveys. Values are not comparable between surveys due to different catchability of the different gears used. Individuals > 51 cm total length are considered mature, except those from the Maritimes summer survey (> 67 cm).
NAFO Division Total Abundance1 (millions) Abundance of Mature Individuals (millions) Survey
2G 2.952 [1999] 0.55 Newfoundland & Labrador fall survey
2H 6.692 [2008] 1.24 Newfoundland & Labrador fall survey
2J 10.922 [2009] 2.02 Newfoundland & Labrador fall survey
3K 3.542 [2009] 0.66 Newfoundland & Labrador fall survey
3L 9.382 [2009] 1.74 Newfoundland & Labrador fall survey
3N 3.532 [2009] 0.65 Newfoundland & Labrador fall survey
3O 3.802 [2009] 0.70 Newfoundland & Labrador fall survey
Subtotal 40.81 4.01  
3Ps 3.172 [2010] 0.59 Newfoundland & Labrador spring survey
4VWX 1.623 [2010] 0.02 Maritimes summer survey
4T 0.074 [2010] Very low Southern Gulf survey (September)
Subtotal 4.86 0.61  
4RS 3.985 [2010] 0.45 Northern Gulf survey (Summer)
Total >49.62 >5.07  

1 The year of the most recent assessment is in square brackets.
2 Simpson et al. 2011.
3 Simon et al. 2011
4 Hugues Benoit, pers. comm. 2012
5 Bourdage and Ouellet, in prep.

Fluctuations and Trends

Labrador Shelf and Grand Banks

Maximum abundance of this species in Canada is concentrated in this region (2J3KLNO). Abundance indices generally declined from the 1970s to the mid-1990s. Since then, there has been a strong increase.

The relative abundance index estimated from the fall research trawl survey fell from 1978 to 1994 in NAFO Divisions 2J3K (southern Labrador Sea and eastern Newfoundland) (Table 7, Figure 12). However, since 1995, an upward trend has been observed. The gear changed in 1995, which prevents the two series (1977 to 1995 and 1996 to 2009) from being compared directly. Figure 13 presents the total abundance of NAFO Divisions 2J3KL, which have been systematically surveyed since 1981. A marked decrease in the abundance indices occurred, from 11.76 million in 1981 to 0.98 million in 1994. The rates of decrease were 91% and 96% from 1981 to 1994 for total and mature populations respectively (Table 8, Figure 14). A marked increase occurred from 1995 to 2007 (from 10.37 to 42.51 million), and the abundance index decreased afterward (23.83 million in 2009). The rate of increase is 150% and 294% since 1995 for total and adult populations, respectively (Table 8), primarily in NAFO Divisions 2J and 3L (Figure 12). In the other divisions, the indices varied, but without clear trends. There has also been an increase in the adult population since 1996 (Figures 13 and 14).

Table 7. Atlantic Wolffish abundance indices for the Grand Banks and southern Labrador Shelf based on Newfoundland & Labrador fall research trawl survey data. (Totals for 3LNO are presented for the spring survey in Table 9.)Accessible version of Table 7
Year Abundance Index (millions)*  
2G 2H 2J 3K 3L 3N 3O 2J3KL Mature 2J3KL**
1977     12.35 2.24          
1978 1.61 5.62 16.94 17.42          
1979 1.48 4.77 8.64 9.71          
1980     8.09 8.48          
1981 0.61 2.42 4.21 5.21 2.34     11.76 4.28
1982     5.39 4.83 2.40     12.61 3.67
1983     6.02 5.26 1.64     12.91 4.77
1984     4.46 4.23 2.95     11.64 4.15
1985     4.39 3.58 2.17     10.14 2.07
1986     3.44 2.01 1.36     6.81 1.49
1987 0.33 0.40 2.30 1.95 3.59     7.84 1.12
1988 0.04 0.92 2.32 2.25 3.37     7.94 1.75
1989     2.01 1.69 1.36     5.06 0.88
1990     1.28 0.84 2.32 0.50 0.56 4.44 0.69
1991   0.13 0.67 1.47 0.81 0.55 0.45 2.94 0.57
1992     0.63 0.57 0.71 1.26 0.31 1.91 0.24
1993     0.85 0.72 0.69 0.41 0.45 2.26 0.33
1994     0.22 0.42 0.35 0.38 0.23 0.98 0.22
Survey Gear Change
1995     1.50 5.13 3.73 3.58 1.35 10.37 0.51
1996 1.42 1.69 6.11 7.93 3.31 1.36 0.65 17.35 0.24
1997 3.38 2.26 8.01 3.10 2.18 2.58 1.80 13.30 0.82
1998 1.13 5.65 9.19 5.65 3.93 1.84 2.07 18.77 1.21
1999 2.95 4.10 9.59 6.96 6.16 1.82 1.93 22.72 1.21
2000     10.10 5.90 4.88 1.36 3.77 20.88 1.37
2001   0.73 4.53 8.98 9.50 1.68 3.24 23.01 1.98
2002     4.40 3.58 7.81 2.54 3.38 15.79 0.00
2003     3.58 4.82 3.89 3.99 2.74 12.29 1.07
2004   10.66 10.92 6.78 1.94 1.26 0.51 19.63 0.30
2005     7.74 10.17 16.80 3.63 1.96 34.70 1.84
2006   11.40 7.49 9.78 21.41 1.15 4.14 38.68 1.50
2007     17.37 7.98 17.17 2.48 1.80 42.51 1.92
2008   6.69 9.51 4.57 12.68 2.11 0.96 26.76 2.02
2009     10.92 3.54 9.38 3.53 3.80 23.83 2.56

* Blanks indicate that no survey was conducted.
** Abundance of mature is based on the proportion of fish > 51 cm in Newfoundland & Labrador fall research trawl survey catches each year

Table 8. Trends in Atlantic Wolffish abundance indices based on research trawl survey data. Accessible version of Table 8
        Rate of change Natural log regression parameters
Survey NAFO divisions Years Total/mature % Number of Years R2 P-values Slope
Newfoundland & Labrador Fall Survey 2J3KL
S. Labrador Shelf
1981-1994 Total -91 13 0.88 0.001 -0.18
Newfoundland & Labrador Fall Survey 2J3KL
S. Labrador Shelf
1981-1994 Mature -96 13 0.93 <0.001 -0.25
Newfoundland & Labrador Fall Survey 2J3KL
S. Labrador Shelf
1995-2009 Total 150 14 0.50 <0.003 0.07
Newfoundland & Labrador Fall Survey 2J3KL
S. Labrador Shelf
1995-2009 Mature 294 14 0.38 0.018 0.10
Newfoundland & Labrador Spring Survey 3LNO
Grand Banks
1971-1982 Total 219 11 0.36 0.040 0.11
Newfoundland & Labrador Spring Survey 3LNO
Grand Banks
1984-1995 Total -44 11 0.12 0.278 -0.05
Newfoundland & Labrador Spring Survey 3LNO
Grand Banks
1984-1995 Mature -70 11 0.40 0.027 -0.10
Newfoundland & Labrador Spring Survey 3LNO
Grand Banks
1996-2010 Total 124 14 0.33 0.026 0.05
Newfoundland & Labrador Spring Survey 3LNO
Grand Banks
1996-2010 Mature 247 14 0.53 0.003 0.09
Maritimes Summer Survey 4VWX
Scotian Shelf
1970-1981 Total -0.2 11 5X106 0.994 -0.0002
Maritimes Summer Survey 4VWX
Scotian Shelf
1970-1981 Mature 79 11 0.21 0.132 0.05
Maritimes Summer Survey 4VWX
Scotian Shelf
1982-2010 Total -27 298 0.05 0.258 -0.01
Maritimes Summer Survey 4VWX
Scotian Shelf
1982-2010 Mature -96 28 0.61 <0.001 -0.11
Newfoundland & Labrador Spring Survey 3Ps
S. Newfoundland
1971-1982 Total -36 10 0.11 0.313 -0.04
Newfoundland & Labrador Spring Survey 3Ps
S. Newfoundland
1984-1995 Total -77 11 0.62 0.002 -0.13
Newfoundland & Labrador Spring Survey 3Ps
S. Newfoundland
1984-1995 Mature -87 11 0.73 0.000 -0.19
Newfoundland & Labrador Spring Survey 3Ps
S. Newfoundland
1996-2010 Total 92 14 0.14 0.195 0.47
Newfoundland & Labrador Spring Survey 3Ps
S. Newfoundland
1996-2010 Mature 226 14 0.30 0.042 0.08
Southern Gulf Survey 4T
S. Gulf
1971-1985 Total 65 14 0.02 0.641 0.11
Southern Gulf Survey 4T
S. Gulf
1986-2010 Total -60 24 0.18 0.045 -0.04
Northern Gulf Summer Survey 4RST
N. Gulf
1990-2009 Total 56 19 0.07 0.264 0.02
Northern Gulf Summer Survey 4RST
N. Gulf
1990-2009 Mature 150 16 0.10 0.216 0.05


Figure 12. Atlantic Wolffish abundance estimates (± CI) from Newfoundland and Labrador fall research trawl surveys for the Grand Banks (3LNO) and southern Labrador Shelf (2J3KL).

Chart presenting Atlantic Wolffish abundance (see long description below).
Description of Figure 12

Chart presenting Atlantic Wolffish abundance based on Newfoundland and Labrador fall research trawl surveys for the Grand Banks (3LNO) and southern Labrador Shelf (2J3KL). The dotted vertical line indicates a fishing gear change.


Figure 13. Atlantic Wolffish abundance (total and mature fish ≥ 51 cm) based on Newfoundland and Labrador fall research trawl surveys for the southern Labrador Shelf (NAFO Divisions 2J3KL) from 1981 to 2009.

Chart presenting Atlantic Wolffish abundance (see long description below).
Description of Figure 13

Chart presenting Atlantic Wolffish abundance based on Newfoundland and Labrador fall research trawl surveys for the southern Labrador Shelf (NAFO Divisions 2J3KL) from 1981 to 2009. The vertical line indicates a fishing gear change.


Figure 14. Natural log of Atlantic Wolffish abundance estimates from Newfoundland fall research trawl surveys for the southern Labrador Shelf (NAFO Divisions 2J3KL). Fitted regressions are shown.

Chart presenting natural log of Atlantic Wolffish abundance estimates (see long description below).
Description of Figure 14

Chart presenting natural log of Atlantic Wolffish abundance estimates from Newfoundland fall research trawl surveys for the southern Labrador Shelf (2J3KL). Fitted regressions are shown. The vertical line indicates a gear change.

For the Grand Banks (Div. 3LNO), the spring research trawl surveys show some variability without trend in the period from 1971-1982 and 1984-1994 (Table 9, Figure 15). Since then, abundance has increased considerably, and the values recorded in recent years are by far the highest since the start of the data series in 1996, though the Campelen trawl used since the mid-1990s has higher catchability. Total abundance was estimated at 21.87 million in 2007 (maximum), compared to 5.10 million in 1998 (minimum). The rate of increase was 247% for the mature population from 1996 to 2010 (Figure 16, Table 8). This increase occurred primarily in Division 3L (northern Grand Bank). The three data series (1971-1982, 1983-1995 and 1996 to the present) cannot be compared directly due to the gear changes.

Table 9. Atlantic Wolffish abundance indices for the Grand Banks based on Newfoundland spring research trawl survey data. Accessible version of Table 9
Year Abundance Index (millions)*  
3L 3N 3O Total Total Mature**
1971 4.02 0.04      
1972 0.32 0.50      
1973 0.38 0.56 0.56 1.49  
1974 1.30 0.36   1.66  
1975 4.50 0.75 0.25 5.50  
1976 2.91 0.50 1.23 4.64  
1977 3.95 0.35 0.12 4.42  
1978 1.11 0.68 0.45 2.25  
1979 4.15 0.68 0.41 5.24  
1980 3.60 0.93 0.45 4.98  
1981 4.27 0.40 0.13 4.80 3.02
1982 3.15 1.52 0.55 5.22 2.96
1983 Survey Gear Change  
1984 0.00 0.80 0.37 1.16 1.08
1985 1.05 1.14 0.55 2.74 1.89
1986 1.57 1.38 0.31 3.26 2.35
1987 3.11 0.89 0.81 4.81 2.47
1988 2.02 0.79 1.23 4.04 2.24
1989 2.29 0.67 0.92 3.88 1.92
1990 2.14 1.35 0.66 4.15 2.09
1991 0.28 0.82 1.00 2.10 1.11
1992 0.58 0.70 0.36 1.64 0.76
1993 0.63 0.87 0.45 1.95 0.99
1994 0.84 1.48 0.47 2.79 1.40
1995 0.20 0.39 0.20 0.79 0.29
Survey Gear Change   
1996 3.32 2.03 1.27 6.62 0.55
1997 3.32 2.05 2.44 7.82 0.79
1998 1.88 1.49 1.73 5.10 1.07
1999 3.99 1.37 3.15 8.51 1.87
2000 8.28 1.66 1.83 11.77 2.22
2001 3.24 3.42 2.10 8.75 1.87
2002 5.48 2.21 2.67 10.36 1.28
2003 4.36 2.77 1.29 8.42 1.90
2004 4.79 2.52 1.30 8.61 2.44
2005 17.13 2.21 1.54 20.88 2.25
2006 17.51 0.54 3.80 21.85 3.75
2007 17.14 2.62 1.24 21.00 4.12
2008 8.10 3.35 3.74 15.20 2.99
2009 3.09 2.08 1.76 6.93 1.36
2010 7.89 1.96 2.47 12.32 3.09

* Blanks indicate that no survey was conducted.
** Abundance of mature is based on the proportion of fish ≥ 51.0 cm in Newfoundland & Labrador spring research trawl survey catches each year


Figure 15. Atlantic Wolffish abundance estimates (± 1 CI) for the Grand Banks (NAFO Division 3LNO) based on Newfoundland spring research trawl surveys.

Chart presenting Atlantic Wolffish abundance estimates for the Grand Banks (see long description below).
Description of Figure 15

Chart presenting Atlantic Wolffish abundance estimates for the Grand Banks (3LNO) based on Newfoundland spring research trawl surveys. Vertical lines indicate a fishing gear change. The “total” line indicates the sum of the abundances for all divisions only when all divisions were surveyed. Source: Raw data provided by Mark Simpson, pers. comm., 2010.


Figure 16. Natural log of Atlantic Wolffish abundance estimates for the Grand Banks (NAFO Division 3LNO) based on Newfoundland spring research trawl surveys.

Chart giving natural log of Atlantic Wolffish abundance estimates for the Grand Banks (see long description below).
Description of Figure 16

Chart giving natural log of Atlantic Wolffish abundance estimates for the Grand Banks (3LNO) based on Newfoundland spring research trawl surveys. Fitted regressions are shown. The vertical lines indicate fishing gear changes.

Scotian Shelf, Southern Newfoundland and Gulf of St. Lawrence

In the southern part of the Canadian range, Atlantic Wolffish abundance estimates from the Maritimes research trawl survey show considerable interannual variability (Table 10, Figure 17). There was no clear trend from 1971 to 1981. However, in the 1980s, total abundance increased from 1.75 million in 1984 to over 6 million in 1989. Since 1990, estimates have fluctuated from year to year with no particular trend, except in the last two years (2009 and 2010), when the lowest abundance estimates were recorded since the surveys began in 1982 (0.89 and 1.62 million, respectively) (Figure 17). From the whole 1982-2010 series, total abundance varied without trend (Table 8 and Figure 18).

Table 10. Atlantic Wolffish abundance indices from the Scotian Shelf, Southern Gulf, and Southern Newfoundland based on the Maritime summer research trawl survey data (Div. 4VWX and Subdivision 5Y), or Newfoundland spring research trawl survey data (Subdivision 3Ps) and Southern Gulf research trawl survey (Div. 4T) and the Northern Gulf summer research trawl survey data (Division 4RST). Accessible version of Table 10
Year Abundance Index (millions)
4VWX5Y 3PS 4T 4RST
Adults*
(≥  68 cm)
Total Adults
(≥  51 cm)
Total Total Adults Total
1970 0.35 1.93          
1971 0.60 2.84     0.02    
1972 0.70 1.91   0.88 0.03    
1973 0.61 2.74   2.36 0.09    
1974 0.45 2.45   1.10 0.01    
1975 1.39 3.95   0.97 0.09    
1976 0.48 3.81   1.29 0.00    
1977 1.30 2.34   1.38 0.07    
1978 0.57 2.74   0.63 0.00    
1979 0.64 1.91   0.75 0.03    
1980 0.80 3.09   0.50 0.06    
1981 0.99 1.82 0.98 1.55 0.04    
  Survey Gear Change          
1982 0.93 3.50 0.55 0.96 0.06    
1983 0.82 2.19 Survey Gear Change 0.03    
1984 0.69 1.75 0.39 0.42 0.04    
1985 0.56 3.38 0.27 0.39 0.06    
          Survey Gear Change
1986 0.41 1.93 0.45 0.62 0.03 Survey    
1987 0.59 2.81 0.19 0.37 0.08    
1988 0.47 3.55 0.14 0.26 0.24    
1989 0.34 6.16 0.05 0.11 0.05    
1990 0.33 4.25 0.08 0.15 0.19 2.43 0
1991 0.21 4.91 0.10 0.18 0.11 4.66 0.167
1992 0.04 1.70 0.05 0.10 0.20 4.41 0
1993 0.12 4.82 0.06 0.13 0.02 2.05 0.060
1994 0.11 3.76 0.06 0.13 0.13 4.97 0.883
1995 0.44 3.48 0.07 0.18 0.07 4.41 0.424
      Survey Gear Change      
1996 0.65 3.91 0.37 4.44 0.17 4.69 0.573
1997 0.59 3.29 0.11 1.05 0.12 20.23 1.477
1998 0.41 4.86 0.19 0.89 0.06 5.01 0.388
1999 0.18 2.11 1.31 5.95 0.03 6.63 1.472
2000 0.10 4.04 0.41 2.17 0.06 14.61 1.237
2001 0.29 3.19 0.79 3.71 0.03 3.54 0.184
2002 0.17 3.23 0.49 4.01 0.08 5.62 0
2003 0.08 5.89 0.68 3.02 0.02 10.33 0.626
2004 0.12 2.24 1.40 4.93 0.04 6.16 0.790
2005 0.07 1.86 0.65 6.02 0.08 5.45 0.618
2006 0.15 2.27     0.06 7.04 0.782
2007 0.03 2.80 0.67 3.39 0.06 4.73 1.135
2008 0.01 4.07 0.58 2.96 0.03 5.16 0.322
2009 0.01 0.89 0.91 4.63 0.03 3.98 0.457
2010 0.02 1.62 0.80 3.17 0.07    

Sources : Simon et al. 2011, Simpson et al. 2011, Hugues Benoit, pers. comm. 2012, Bourdage and Ouellet, in prep.
* Abundance of mature is based on the proportion of fish ≥ 51.0 cm in Northern Gulf research trawl survey catches each year


Figure 17. Mature and total Atlantic Wolffish abundances (± CI) estimated from the Maritimes summer research trawl survey on the Scotian Shelf and part of the Gulf of Maine (NAFO Divisions 4VWX) and of Southern Newfoundland (NAFO Division 3Ps)

Chart showing mature and total Atlantic Wolffish abundances (see long description below).

Note: Black vertical dotted line indicates a fishing gear change in 4VWX and blue vertical dotted lines indicate a vessel change in 3Ps.

Description of Figure 17

Chart showing mature and total Atlantic Wolffish abundances estimated from the Maritimes summer research trawl survey of the Scotian Shelf and part of the Gulf of Maine and of Southern Newfoundland. Data are given for 1970 to 2010. Sources: 4VWX from Simon et al. (2011), 3Ps from Simpson et al. (2011).


Figure 18. Natural log of Atlantic Wolffish abundance estimates for the Scotian Shelf (NAFO Division 4VWX) based on Maritimes research trawl surveys.

Chart presenting natural log of Atlantic Wolffish abundance (see long description below).
Description of Figure 18

Chart presenting natural log of Atlantic Wolffish abundance estimates for the Scotian Shelf (4VWX) based on Maritimes research trawl surveys. Fitted regressions are shown. The vertical line indicates a fishing gear change.

The abundance of mature individuals in the surveys declined sharply at the end of the 1971-1981 series and from 1982 to the start of the 1990s, and again from 1996 (0.65 million) to 2010 (0.02 million) (Table 10 and Figure 18). There was an annual rate of decrease of 27% and 96% from 1982 to 2010 for the total and adult population, respectively (Table 8 and Figure 18). An analysis of length frequencies (Figure 19) shows that catches of large Atlantic Wolffish have declined and catches of smaller individuals apparently increased since the 1980s.


Figure 19. Length frequency of Atlantic Wolffish from the Scotian Shelf Maritimes summer research trawl survey (based on total stratified random sampling abundance estimates). See text for caveats about gear changes.

Chart presenting length frequencies for Atlantic Wolffish (see long description below).
Description of Figure 19

Chart presenting length frequencies for Atlantic Wolffish from the Scotian Shelf Maritimes summer research trawl survey between 1971 and 2010 (based on total stratified random sampling abundance estimates). The chart suggests that catches of large Atlantic Wolffish have declined and catches of smaller individuals have increased since the 1980s. See text for caveats about gear changes.

In southern Newfoundland (subdiv. 3Ps), there were no trends in abundance from 1971-1982 followed by a decrease from 1984 to 1995 (Table 10, Figures 17 and 20). From 1985 to 1995, the rate of decline was 87% for mature individuals (Table 8). The annual rate of decline was 13% (Table 8 and Figure 20). Adults showed a similar pattern for that period, with an increase since 1998 (Figures 17 and 20). The abundance index rose from 0.89 and 0.19 million in 1998 to 3.17 and 0.80 million in 2010 for total and mature populations, respectively.


Figure 20. Natural log of Atlantic Wolffish abundance estimates for southern Newfoundland (NAFO Division 3Ps) based on Newfoundland spring research trawl surveys.

Chart showing natural log of Atlantic Wolffish abundance estimates for southern Newfoundland (3Ps) (see long description below).
Description of Figure 20

Chart showing natural log of Atlantic Wolffish abundance estimates for southern Newfoundland (3Ps) based on Newfoundland spring research trawl surveys. Fitted regressions are shown. The breaks are due to fishing gear changes.

The abundance of Atlantic Wolffish is low in the southern Gulf of St. Lawrence (Table 10 and Figure 21). Some annual variations occurred from 1971 to 1985, but without trend. From 1986 to 2012, there was a decline of 60% (Table 8, Figure 22). In the Northern Gulf, the abundance index varied from 2.05 to 20.23 million without trend from 1990 to 2010 (Table 10; Figures 23 and 24). There was an increase of 150% for the mature population, but the trend is not significant (P = 0.216; Table 8).


Figure 21. Total Atlantic Wolffish abundance (± 1 CI) for the Southern Gulf (NAFO Division 4T).

Chart presenting total Atlantic Wolffish abundance for the Southern Gulf (4T) (see long description below).
Description of Figure 21

Chart presenting total Atlantic Wolffish abundance for the Southern Gulf (4T). The vertical line indicates a fishing gear change. There were too few adults to allow them to be depicted separately (Table 6). Source: Benoit, H. pers. comm. (2012).


Figure 22. Natural log of Atlantic Wolffish abundance estimates from Southern Gulf research trawl surveys for NAFO Division 4T.

Chart presenting natural log of Atlantic Wolffish abundance estimates (see long description below).
Description of Figure 22

Chart presenting natural log of Atlantic Wolffish abundance estimates from Southern Gulf research trawl surveys of Northwest Atlantic Fisheries Organization Division 4T conducted from 1970 to 2010. Fitted regressions are shown. Fitted regressions are shown. The vertical line indicates a fishing gear change. There were too few adults to allow them to be depicted separately (Table 6).


Figure 23. Atlantic Wolffish abundance estimates (± 1 CI) from summer research trawl surveys for the Gulf of St. Lawrence (NAFO Division 4RST).

Chart presenting Atlantic Wolffish abundance estimates from summer research trawl surveys in the Gulf of St. Lawrence (4RST) (see long description below).
Description of Figure 23

Chart presenting Atlantic Wolffish abundance estimates from summer research trawl surveys in the Gulf of St. Lawrence (4RST). The abundance of mature fish is based on the proportion of fish greater or equal to 51 centimetres in length.


Figure 24. Natural log of Atlantic Wolffish abundance estimates from summer research trawl surveys for the Gulf of St. Lawrence (NAFO Division 4RST).

Chart presenting natural log of Atlantic Wolffish abundance estimates from summer research trawl surveys for the Gulf of St. Lawrence (4RST) (see long description below).
Description of Figure 24

Chart presenting natural log of Atlantic Wolffish abundance estimates from summer research trawl surveys for the Gulf of St. Lawrence (4RST). Fitted regressions are shown.

Summary for Canada

Over much of its range, including its historical stronghold in waters east and south of Newfoundland, this species underwent strong declines from the 1980s until the mid-1990s, followed by increases. These trends largely match those for the area occupied. Recovery has not been as strong in the southern part of its range. Data are insufficient to establish status in the northern-most portion of its Canadian range, in Davis Strait.

Differences among regions in survey methods and changes in gear over time preclude formal calculations of an overall trend for this species in Canada. However, a general indication is needed to assess this species’ overall status. We can get a rough approximation by weighting the rates of change of each area by the number of fish in that area at the start of its time series.

The southern Labrador Shelf (2J3KL) was the historical stronghold, with about 4.2 million mature individuals over the first three years of the time series at the start of the 1980s. These fish declined by about 96% up to the time of the gear change in the mid-1990s (Table 8). The remaining 4% of fish then increased to about 15% of the original numbers at the start of the 1980s, which means an overall decline of about 85%. Some of the apparent increase was probably driven by higher catchability of the gear used in the second half of the time series, though this is partly accounted for in the above calculation by multiplying the fish that remained prior to the gear change by the rate of increase afterward. Fish on the Grand Banks (3LNO) historically numbered only around 1.8 million, and they declined in the first half of the time series by about 70%. They then rebounded toward their original number, with the same caveat about higher catchability of the survey trawl. Fish in the next three areas (Scotian Shelf 4VWX, southern Newfoundland 3Ps, and the Gulf of St Lawrence 4T and 4RST) were progressively less numerous than in the two preceding areas, so their trends have less impact on the overall conclusions.

When the trends for all six regions are combined in this way, the overall rate of decline for Atlantic Wolffish is about 60% over 30 years, which is two generations. It should be emphasized that these are back-of-the-envelope calculations, intended only to give a general impression of the magnitude of decline relative to the ranges that are used by IUCN criteria.

Rescue Effect

South of Canada, Atlantic Wolffish is found in the Gulf of Maine and on Georges Bank in low densities, where surveys indicate a decline over the past two to three decades (Keith and Nitschke 2008). The possibility of rescue is from US waters is therefore limited at best.

Abundance off West Greenland was estimated at 2.8 million in 2009 from a Northern Shrimp (Pandalus borealis) research survey conducted by a Danish team (Nygaard and Jørgensen 2010). Abundance increased from the start of the survey (1992) to 2005, but has since declined (Figure 25). Estimates from a bottom trawl survey conducted by a German research institute off west Greenland (NAFO Divisions 1C to 1F) (Figure 25) show fluctuations in abundance since the 1980s, but with no clear trend (Fock and Stransky 2009). However, in recent years, abundance has declined.

To the east, this species is found in several NAFO divisions that are partially (Divisions 3NO) or entirely (3M) in international waters (see Figure 2). On the Flemish Cap (NAFO Division 3M), abundance was estimated at over 10 million in 2006 (Figure 26, Gonzáles-Troncoso and Paz 2007). The abundance index has declined since 1996, but remains close to the values recorded in the 1980s. Rescue from the east is possible, but given the sedentary nature of adults, this would need to come from dispersal of larvae.


Figure 25. Atlantic Wolffish abundance indices based on two surveys conducted west of Greenland.

Chart presenting Atlantic Wolffish abundance indices based on two surveys conducted west of Greenland (see long description below).
Description of Figure 25

Chart presenting Atlantic Wolffish abundance indices based on two surveys conducted west of Greenland. Coverage of the Danish survey (Nygaard and Jørgensen 2010) varied over time. The German survey covered Northwest Atlantic Fisheries Organization Divisions 1C to 1F. The two surveys followed different protocols and used different gear. The Danish survey shows abundance increasing from the start of the survey (1992) to 2005, then declining. The German survey shows fluctuations but no clear trend, although there is a decline in recent years.


Figure 26. Atlantic Wolffish abundance estimates from surveys on the Flemish Cap (NAFO Division 3M). Source: González-Troncoso and Paz (2007).

Chart presenting Atlantic Wolffish abundance estimates from surveys on the Flemish Cap (3M) (see long description below).
Description of Figure 26

Chart presenting Atlantic Wolffish abundance estimates from surveys on the Flemish Cap (3M). Abundance peaks in 1996 and, while it has since declined, it remains close to values recorded in the 1980s.

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