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Becker, George C. / Fishes of Wisconsin

Cod family - gadidae,   pp. 745-751 ff. PDF (2.7 MB)

Page 749

Burbot   749 
sery streams (Harlan and Speaker 1956). In Lake Hu- 
ron, burbot production occurs in the large bays, but, 
like smelt, the young disperse throughout the sur- 
face waters over deep water and display a limnetic 
pattern of distribution (Faber 1970). In Lake Erie, Fish 
(1932) noted larval and postlarval stages 3-15 mm long 
at 5-60 m from mid-June to mid-August. 
  Age is determined by counting the annular rings 
of the otoliths. Burbot from western Lake Superior 
(Bailey 1972) showed a considerable overlap in lengths 
from year to year, but the average estimated lengths 
were: 0-145 mm; 1-254 mm; 11-300 mm; III-340 
mm; IV-376 mm; V-409 mm; VI-439 mm; VII- 
478 mm; VIII-513 mm; IX-551 mm; X-594 mm; 
XI-645 mm, and XII-711 mm. The estimated an- 
nual weight increments ranged from 27 g to 118 g 
through age VI, and from 163 g to 586 g from age VII 
through age XII. 
  About 59% of the Lake Superior males, but only 
5% of the females, were mature at age I; all burbot of 
both sexes were mature at age V. The shortest ma- 
ture male was 246 mm (9.7 in) long; all males more 
than 417 mm (16.4 in) long were mature. The short- 
est mature female was 272 mm (10.7 in) long, and all 
females longer than 404 mm (15.9 in) were mature. 
  Burbot specimens up to 1 m (39.4 in) long, with 
weights of 25-30 kg (55-66 lb) and ages of 15-20 
years, have been reported, mainly from Siberia (Muus 
and Dahlstrom 1971). Large burbot from Lake Win- 
nebago reach a length of nearly 76 cm (30 in) and 
weigh 3.6-4.1 kg (8-9 lb) (Lewis 1970). 
  In Lake Superior (Bailey 1972), burbot of all ages 
had eaten fish and crustaceans. The fish consumed 
in order of frequency were sculpins (slimy and 
spoonheads), smelt, bloater, ninespine sticklebacks, 
trout-perch, and lake trout. Fish eggs, probably the 
eggs of lake herring (Coregonus artedii), occurred in 
21.4% of the burbot stomachs during the fall. The 
crustaceans Mysis relicta and Pontoporeia affinis ap- 
peared in over half of the stomachs examined, and 
fingernail clams occurred in 26% of the stomachs. In- 
sects were relatively unimportant. The presence in 
burbot stomachs of rocks, wood chips, clinkers, plas- 
tic, and other inert materials suggests that their feed- 
ing had been rather indiscriminate. 
  In Lake Michigan and Green Bay (Van Oosten and 
Deason 1938), food consisted of fish (74% volume) 
and invertebrates (26%). The dominant items in 
southern Lake Michigan were sculpins (76%); in 
northern Lake Michigan, coregonid chubs (51%) and 
Pontoporeia (37%); and in Green Bay, trout-perch (34%) 
and Mysis (26%). The consumption of invertebrates 
decreased with increases in the size of the burbot. 
Fishes were eaten after burbots reached 330 mm (13 
in) or more in size. One must keep in mind, how- 
ever, that this study of food habits was made before 
the advent of the alewife brought about dramatic 
changes in the fish populations of these waters. The 
diet of the burbot today may be quite different than 
it was in the 1930s, and it now probably includes the 
abundant alewife. 
  According to Scott and Crossman (1973), in streams 
small burbot 51-305 mm (2-12 in) long feed on Gam- 
marus, mayfly nymphs, and crayfish. Adult burbot 
become voracious, feeding on most available fishes 
and crayfishes, dead or alive. Perch up to 254 mm 
(10 in) long have been reported from Wisconsin bur- 
bot stomachs. A 559-mm (22-in) burbot, seined from 
Lake Winnebago, had swallowed all but the tail of a 
406-mm walleye (Colburn 1946). One 483-mm (19-in) 
burbot contained five 76-mm perch, six 51-mm cray- 
fish, six large burrowing mayfly nymphs, and one 
dragonfly nymph (Wis. Conserv. Bull. 1948 13141:31). 
Adams and Hankinson (1926) remarked about the 
burbot's capacity for food (p. 518): 
If he can procure food he will not desist from eating so 
long as there is room for another particle in his capacious 
abdomen. He is frequently taken with his abdomen so much 
distended with food as to give him the appearance of the 
globe or toad-fish. 
  Adult burbot do not feed during the spawning pe- 
riod, but begin to prey heavily on forage fish imme- 
diately after spawning. They supposedly come into 
shallow water to feed at night. 
  Optimum temperatures (Scott and Crossman 1973) 
for the burbot are 15.6-18.3°C (60-65°F); 23.3°C (74°F) 
appears to be its upper limit. The preferred temper- 
ature of young burbot as determined by laboratory 
experiments is 21.2°C (70.2°F) (Ferguson 1958). 
  During the warm summer months, and in the fall 
when the water temperature has declined, the larger 
burbot is usually found in the deepest part of a lake 
or stream. In the Apostle Islands region of Lake Su- 
perior the burbot shows a wide distribution from the 
shallowest water to 126 m, with the largest catches 
taken at 18-35 m. Koelz (1929) noted that the burbot 
was taken in numbers near Stannard Rock at a depth 
of 210 m. In northeastern Lake Michigan, there was 
a characteristic monthly inshore concentration of 
burbot at 13-18 m or at 19-21 m, and a second con- 
centration at 31-34 m, or at more than 34 m (Van 
Oosten et al. 1946). 
Burbots are eaten by other fishes. At Two Rivers (Lake 
Michigan), a lake trout 597 mm (23.5 in) long had 76 
mm (3 in) of a burbot tail projecting from its mouth; 

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