Fairchild et al.: Spring feeding of Anarhichas lupus on Stellwagen Bank, Massachusetts 
197 
Table 2 
Size and age, by sex, of Atlantic wolffish (Anarhichas lupus ) sampled from 23 May to 8 June 2011 
on Stellwagen Bank National Marine Sanctuary, Massachusetts. P-values denote results of Mann- 
Whitney rank sum tests between sexes for each category. Atlantic wolffish with damage to caudal fins 
were not included in analyses of total lengths. SD=standard deviation of the mean. 
Total Length (cm) 
Weight (kg) 
Age (year) 
Mean 
SD 
n 
Mean 
SD 
n 
Mean 
SD 
n 
Females 
80.49 
11.91 
148 
5.79 
2.85 
155 
19.20 
4.48 
155 
Males 
85.19 
12.71 
142 
6.52 
2.93 
148 
20.97 
4.39 
148 
P-value 
<0.001 
0.014 
<0.001 
years old, supporting the theory that Atlantic wolffish 
occupy deeper, warmer waters until they are sexually 
mature (Keats et al., 1986; Nelson and Ross, 1992). In 
this study of shallow (27-46 m) SBNMS waters, Atlan- 
tic wolffish ranged from 59 cm TL (age 7) to 130 cm TL 
(Fig. 2) — a finding that corroborates a seasonal separa- 
tion of fish size by water depth in the GOM. 
This movement pattern also has been found in Ice- 
landic waters and the White Sea where Atlantic wolffish 
move into colder (3°C) waters before spawning (Jons- 
son, 1982; Pavlov and Novikov, 1993). However, spring 
and summer surveys at similar depths and tempera- 
tures throughout the period 1971-1980 in Newfound- 
land yielded no Atlantic wolffish (Albikovskaya, 1982) 
and indicated that concentrations of 
wolffish may occur at other depths 
elsewhere or be very discrete. During 
the study period, bottom temperatures 
on the SBNMS where wolffish concen- 
trations occurred ranged from 5°C to 
7°C (Table 1). From hatchery studies, 
it is known that Atlantic wolffish egg 
survival decreases if oocyte maturation 
and ovulation occur at temperatures 
>8°C (Tveiten et al., 2001). Therefore, 
it follows that this spring in-shore 
movement of prespawning, mature At- 
lantic wolffish into shallower, colder 
water likely is linked to the mainte- 
nance of thermal homeostasis as fish 
prepare for the fall spawning season. 
Age, growth, and sex 
In the GOM-GB region, Atlantic wolf- 
fish may attain TLs of 150 cm and 
weights of 18 kg (40 lb) (Rountree, 
2002), yet scant age and growth data 
are available for larger sized (>100 
cm TL) fish. Although we were fortu- 
nate enough to capture many large 
individuals, including a 130-cm-TL 
fish, we were prevented from calculating meaningful 
growth equations because no individuals <7 years old 
were collected. Our age data for older fish may be more 
accurate than data from previous studies. Nelson and 
Ross (1992) aged whole, polished otoliths, which can 
be difficult to read because they grow thicker in older 
fish; whereas, we aged sectioned otoliths. It is possible 
that slightly younger fish were present in the SBNMS 
group but, because of gear selectivity, were excluded 
from the catch. In spring surveys conducted in shallow 
depths (<40 m) over a span of 26 years, Atlantic wolf- 
fish always were >50 cm TL (Nelson and Ross, 1992). 
On the SBNMS during May-June, male Atlantic 
wolffish are larger (heavier and longer; Table 2) than 
oo o o o o o o- o o o 
O 
-2 W 
5 10 15 20 25 30 35 
Age (years) 
Figure 3 
Mean gonadosomatic indices (GSIs) by age for female and male Atlantic 
wolffish ( Anarhichas lupus) captured on the Stellwagen Bank National 
Marine Sanctuary, Massachusetts, from 23 May to 8 June 2011. Error 
bars indicate 1 standard deviation. 
