Fish-continue - CR95

tion. Larval, juvenile and adult life stages were

primarily of lake herring (49%), white suckers

examined at seven sites, with sampling locations

(17%), northern pike (12%), yellow perch (6%) and

at each site ranging from the navigation channel

both walleye and rainbow smelt (5%).

to nearshore zones. There were 896 samples of

The yellow perch catch was considered mea-

ichthyoplankton collected during the summers

ger in winter, perhaps due to their generally lower

of 1982 and 1983, which yielded nearly 30,000

mobility. Significantly, more fish were collected

larvae of 34 taxa. The density of fish larvae and

nearshore than near the channel, which is con-

the number of taxa were generally greatest in the

trary to claims that they move into deeper water

upper littoral zone and lowest in the channel.

areas of the St. Marys during winter. Most yel-

Rainbow smelt, cyprinid, yellow perch and em-

low perch were found to be in good condition,

erald shiner larvae dominated the samples, re-

but there was a moderate level of parasitization,

flecting their dominance as adults. Thirty-four taxa

which Liston and McNabb speculated could be

were identified, though not all were found each

increased if the fish were to be further stressed.

year, with temperature cited as a possible cause

The number of white suckers sampled was con-

for differences. They also provided detailed de-

siderably lower in winter than during open wa-

scriptions of spatial and temporal distributions

ter, and it was felt that their movements are very

for the dominant taxa sampled.

restricted during that time. More suckers and

Some 140,000 fish of 64 taxa were collected using

northern pike were found near the shore than near

trap nets, trawls and gill nets (Liston and McNabb

the channel.

1986). They also tagged 14,946 fish, of which 42

There was no significant difference in catch per

were recovered, to document their movements.

unit effort between nearchannel and nearshore

The shallow littoral zone was dominated annu-

areas for walleyes, lake herring or rainbow smelt

ally by emerald shiners, spottail shiners, mimic

sampled in winter. The catch per unit effort (CPE)

shiners, bluntnose minnows, yellow perch and

was greater during summer for walleyes and rain-

white suckers, though brown bullheads, rainbow

bow smelt but less during summer for herring.

smelt, gizzard shad and black crappies were also

The peak CPE for herring occurred during fall

prominent during the warmer year of 1983. The

spawning activities. While other fish were cap-

demersal, offshore community was dominated by

tured during the winter period, their numbers

several small forage fish: trout-perch, spottail

were insufficient for comparison. For example,

shiners, johnny darters, ninespine sticklebacks,

only one brown bullhead and three rock bass were

yellow perch, mottled sculpins and mimic shin-

collected in winter gill nets, all at the same sta-

ers. Top piscivores dominant in the river were

tion. Other smaller fish were collected only inci-

northern pike and walleyes, followed by small-

dentally (or not at all) in the gill net samplings.

mouth and rock bass. Lake herring were a domi-

The authors noted that the effects of winter

nant species in the deeper, offshore areas. Shan-

navigation on fish populations are limited to con-

nonWeaver diversity indices ranged from 1.4 to

jecture. They cited potential changes due to di-

2.8, with mid-river diversity the greatest at 2.4

rect mortality, alterations in suspended solids and

2.8. Cold-water species such as salmonids were

alterations of macrophyte beds. For substantial

more prevalent in upstream areas, while down-

direct mortalities to occur, fish would have to be

stream areas had both warm-water species such

concentrated in or near the shipping channels and

as centrarchids and cyprinids and cold-water spe-

exacerbated by low winter metabolic rates. This

cies such as lake whitefish.

does not appear to be the case on the St. Marys

Liston and McNabb (1986) also made a sig-

River. From their studies on the SCDRS, Haas et

nificant effort, based on gill net sampling, to de-

al. (1985) concluded that fish concentrations are

fine the winter fish community. Almost half of

substantially reduced in the vicinity of the navi-

the total samples were taken during winter, most

gation channel during winter and that fish that

from late January to mid-March. While open-water

remain near the channel seek out adjacent marshes

gill net sampling collected 6354 fish of 37 spe-

and channels as overwintering sites. There has

cies, the winter catch consisted of 1904 fish of 19

been no documentation of extended season navi-

species. The summer catch was dominated by lake

gation effects on macrophyte beds, but Liston and

herring (27%), followed by white suckers (18%),

McNabb have speculated that they might be ad-

northern pike (11.4%), rainbow smelt (10%), yel-

versely affected by scour or excessive sedimen-

low perch (9.7%), walleyes (9.5%) and rock bass

tation. Such scour or sedimentation processes have

(4.6%). In contrast, the winter catch consisted

not been documented, however. Hudson et al.