The variability of the population in successive collections from the
same area is presented in Table 14. Supplementary data obtained in Areas
2, 4 and 7 support conclusions discussed below for Areas 1, 3 and 6. The
abundance of some species maintained a constant level, whereas that of
others varied.
TABLE 14. NUMBERS OF INDIVIDUALS COLLECTED BY MEANS OF THE SHOCKER
AT VARYING INTERVALS IN SEPTEMBER, 1959. THE NUMBER AT THE TOP OF
EACH COLUMN IS THE DATE WHEN THE COLLECTION WAS MADE.
======================================================================
| Area 1 | Area 3 | Area 6
SPECIES +-----+-----+-----+-----+-----+-----+-----+-----+-----
| 3 | 4 | 8 | 9 | 10 | 15 | 16 | 18 | 20
----------------+-----+-----+-----+-----+-----+-----+-----+-----+-----
Golden Redhorse | 2 | 2 | ... | 5 | 5 | 2 | ... | ... | 3
Creek Chub | 4 | 3 | 7 | 1 | ... | ... | 1 | 2 | ...
Sucker-mouthed | | | | | | | | |
Minnow | ... | ... | ... | 54 | 42 | 25 | 31 | 7 | 6
Red-finned | | | | | | | | |
Shiner | ... | ... | 1 | ... | ... | 4 | 31 | 13 | 4
Red Shiner | 44 | 7 | 211 | 117 | 170 | 438 | 186 | 209 | 62
Blunt-nosed | | | | | | | | |
Minnow | ... | ... | ... | 4 | 10 | 19 | 108 | 91 | 13
Fat-headed | | | | | | | | |
Minnow | 1 | ... | ... | 1 | 2 | 3 | 112 | 156 | 48
Stoneroller | 67 | 39 | 49 | 84 | 107 | 55 | 54 | 67 | 22
Black Bullhead | 5 | ... | 1 | 2 | 1 | ... | ... | 3 | 7
Yellow Bullhead | 1 | 1 | ... | 2 | 1 | ... | 1 | ... | 3
Channel Catfish | 14 | 7 | ... | 36 | 16 | ... | 3 | 1 | 23
Channel | | | | | | | | |
Catfish(yy)[H]| 23 | 16 | 17 | 34 | 34 | 22 | 40 | 23 | 28
Flathead | ... | ... | ... | 4 | 8 | 1 | 2 | ... | 1
Flathead(yy) | 4 | 1 | 1 | 2 | 1 | 1 | ... | ... | ...
Stonecat | 25 | 8 | 12 | 7 | 7 | 5 | ... | ... | ...
Green Sunfish | 27 | 17 | 12 | 13 | 16 | 17 | 62 | 62 | 74
Long-eared | | | | | | | | |
Sunfish | 13 | 12 | 1 | 6 | 3 | 3 | 10 | 22 | 31
Logperch | 1 | ... | ... | 2 | ... | ... | ... | ... | ...
Slender-headed | | | | | | | | |
Darter | ... | 1 | 2 | 55 | 45 | 23 | 15 | 1 | 1
Orange-throated | | | | | | | | |
Darter | 2 | 1 | 2 | 9 | 11 | 8 | 5 | ... | 1
----------------+-----+-----+-----+-----+-----+-----+-----+-----+-----
Total | 233 | 115 | 316 | 438 | 480 | 626 | 661 | 657 | 347
----------------+-----+-----+-----+-----+-----+-----+-----+-----+-----
[H] (yy) means young-of-the-year only.
Stoneroller, channel catfish (young-of-the-year), green sunfish, and
long-eared sunfish formed the most stable element of the population, in
that the numbers of these species varied less in successive collections
than did numbers of other species.
The number of orange-throated darters remained constant at Areas 1 and
3, and the number of stonecats changed little in successive collections
from Area 3. I suspect that an apparent decline in stonecats at Area 1
on September 4 was due to a slow rate of dispersal from the point of
release (see pages 413, 414).
Some species (sucker-mouthed minnow, red-finned shiner, slender-headed
darter, and fat-headed minnow) decreased significantly in successive
samples from the same area because of mortality in handling or movement
out of the area of initial capture.
The decrease in abundance of the sucker-mouthed minnow may have been due
to some mobility of the species. Evidence for mortality caused by
handling was obtained for the red-finned shiner and probably accounts
for the reduction of this species in Area 6. The red-finned shiner is
also probably a mobile species. The reduction in abundance of the
slender-headed darter seems unexplainable because no evidence was
obtained for either movement or mortality.
Fat-headed minnows also declined markedly in successive collections from
Area 6, the only area in which the species was common. No marked
fat-headed minnows were taken outside the area of release, indicating
low mobility of the species. I cannot certainly account for their
decline; possibly there was latent mortality due to shocking.
The numbers of red shiners, blunt-nosed minnows, and juvenile channel
catfish varied erratically in successive collections, probably as a
result of movement. This problem is discussed for all species in a later
section.