522 
Fishery Bulletin 96(3), 1 998 
Table 4 
Size distribution in populations of Myxine glutinosa in the 
eastern and western North Atlantic. Total length measure- 
ments (in mm ) reported for eastern and western Atlantic popu- 
lations (all groups). See text for explanation of abbreviations. 
NWA 
OGM 
IGM 
MAC 
ENA 
315 
509 
280 
299 
Average 
190-405 
215-510 
195-724 
220-380 
227-392 
range 
(rc=ll) 2 
(n= 13) 7 
(n=306) 3 
(n=13) J 
(n = 179) 1 
529 
312 
103-405 
170-950 
220-420 
253-362 
(n= 8) 2 
( /i = 1 1 72 ) 4 
(n=37) 2 
(n= 8) 5 
<450 6 
‘ From Wisner and McMillan (1995). 
2 From raw data provided by R. Wisner (see Footnote 1 in main text). 
3 From Martini et al. (1997a). 
4 From Kuenstner ( 1996). 
5 From Fernholm (1981). 
6 From Adams and Strahan (1963). 
ing estimates of hagfish population density produce 
gross underestimates (Wakefield, 1990). Given the 
maximum swimming rate of adult Myxine (<1 m/sec, 
Foss, 1968), hagfish of any size are probably unable 
to outrun a trawl. We would predict that trapping 
would collect smaller individuals that might slip 
through the trawl mesh, whereas trawling could col- 
lect mature animals that might not be attracted to 
traps (breeding hagfish may not feed; Walvig, 1963). 
However, because we have no indication of allomet- 
ric effects of body size on any morphometric charac- 
ter for M. glutinosa, the statistical comparisons of 
slime pore counts, cusp counts, or proportional mea- 
surements should be unaffected by variations in to- 
tal length among the sample populations. Neither 
traps with large-bore entrances or trawl nets, the 
collection methods used for these data, should bias 
the maximum recorded size. 
Collections made at different times of the 
year may produce biased samples owing 
to seasonal migrations or breeding activities 
Although no large-scale tagging studies have been 
performed, field observations and their relatively 
inefficient and slow swimming speed suggest that 
M. glutinosa are relatively sedentary animals with 
small home ranges. Among hagfishes, only Eptatretus 
burgeri is known to have seasonal migrations 
(Fernholm, 1974), and their migration is related to a 
specific breeding cycle that is unique among 
hagfishes. Myxine glutinosa has no particular breed- 
ing period, and adults at all stages of gonadal devel- 
opment are present throughout the year (Walvig, 
Table 5 
Results of post-hoc multiple comparison tests of total lengths; 
asterisks (*) indicate values significant at the 5% level (Scheffe 
/'’-test). See text for explanation of abbreviations. 
Groups compared 
Mean difference 
P-value 
IGM vs. MAC 
231.490 
<0.0001* 
IGM vs. NWA 
213.798 
<0.0001* 
IGM vs. OGM 
196.381 
<0.0001* 
IGM vs. ENA 
213.099 
<0.0001* 
MAC vs. NWA 
-17.692 
0.9996 
MAC vs. OGM 
35.109 
0.9698 
MAC vs. ENA 
-18.391 
0.9943 
NWA vs. ENA 
-1.217 
>0.9999 
NWA vs. OGM 
-17.417 
0.9996 
OGM vs. ENA 
16.718 
0.9904 
1963; Martini et al., 1997b). There were no signifi- 
cant differences in the population profiles for ani- 
mals collected at our primary study site in June- 
September from one year to the next, and although 
weather and sea-state conditions prohibited collec- 
tion in midwinter, no population differences, in terms 
of size range or abundance, were apparent in ROV 
surveys performed in December-January as com- 
pared to July-August (Martini, personal obs.). 
Collections made at different depths may yield 
different sex ratios and population profiles 
The reported depth range of M. glutinosa is exten- 
sive (50-1100 m). There are no reports of depth strati- 
fication by size or sex for any species of Myxine, and 
only suggestions of unequal depth distribution (by size 
and sex) for two species of Eptatretus (E. stouti and E. 
deani) (Johnson, 1994; Wakefield, 1990). All known M. 
glutinosa populations have sex ratios that are highly 
skewed in favor of females, but above the size at sexual 
maturity there are males and females of all sizes. Any 
variations in the sex ratios would not affect the mor- 
phological parameters we compared because no sexual 
dimorphism has been reported for these characters in 
M. glutinosa or any other hagfish species. 
The IGM data were collected from fresh, 
rather than preserved, specimens 
Fixation shrinkage of 10-15% may occur in preserved 
specimens (Wisner 1 ). This shrinkage would not af- 
fect parameters such as cusp counts or slime pore 
counts, but it would potentially affect total length. 
Shrinkage alone, however, could not account for the 
magnitude of the observed differences in maximum 
total length (950 mm for IGM, versus a maximum of 
