TABLE 2.—Fall standing crops after one and two growing seasons for channel catfish (CC), both caged and free ij 
ponds, when in the stocking combinations shown. Listed weights represent averages for two populations of each of th 
types indicated, except as noted. 
0 
Standing Crops Per Unit of Catfish® 
i — — 
Standing Crops Per Hectare 
1970 
Species Measured 
1971 1970 1971 
Number Kilograms Number Kilograms Number Kilograms Number Kilogram 
CC caged (when in pond with free CC) 764 83.64 
CC caged (when in pond 
with BG and LMB) 783" 71.36” 
CC caged (when in pond 
with BG, LMB and free CC) 704 73.55 
GC free (when in pond with caged CC) 794 100.54 
CC free (when in pond 
with BG, LMB and caged CC) 515 76.30 
698 319.44 e : ; e 
695° «= «274.96 «3,870 «= 852.66 «= 3,442 §=— 1,428. 678 
686 —-278.59 e : : e 
“Teg 873i a - 
654 361.50 e e e : 
a Catfish were Age 1, 12 grams in average weight, and numbered 800 per stocking unit (1,600 per pond) when stocked in 197( 
the same fish averaged 96 grams and numbered 700 per stocking unit, or 1,400 per pond, when stocked in 1971. 
b Average of four, rather than two units of caged catfish. These averages are high because one of the four units was inadye 
tently stocked with 900, rather than 800 fish. 
ce Average of three, rather than two units of caged catfish. 
4 For one pond only due to loss of fish by asphyxiation. 
e Could not be accurately computed because half of the catfish in 
TABLE 3.—Average standing crops in kilograms per hec- 
tare after one and two growing seasons for two populations 
of each of the combinations indicated. 
ee ee 
Channel Catfish All 
a Species 
Caged Free Bass Bluegills? Combined 
1970 206.70 248.48 455.18 
1971 789.452 883.59" 1,673.04? 
1970 ISL al 188.56 36.88 99.16 506.31 
1971 688.50 893.39 80.14 301.95 1,963.98 
1970 352.91 39.66 7g) NG 471.68 
1971 yA snONe 80.68 204.37 1,708.72 
1970 33.88 67.76 101.64 
1971 2.20 232.56 304.79 
a Data from one pond only. 
b Standing crops of bluegills for 1970 are incomplete because 
of the stranding and loss in drainage of relatively small but un- 
known weights of young-of-the-year in small sizes. 
in the later evaluation of data from both years we 
will see that the differences were probably not sig- 
nificant. 
There was a surprising difference in production 
in the two ponds which contained catfish only. Caged 
populations had similar survivals (98 and 93 percent ) 
and weights (181 and 187 pounds) (82.1 and 84.8 
kilograms) in the two ponds, but the populations 
of unconfined fishes showed marked differences. In 
one pond the total weight of the free catfish was 
less than that of the caged fish, and this was associated 
with very clear water (average turbidity 10 ppm) 
and heavy weed growths (mostly Najas spp.). Ob- 
servations made at the time of drainage disclosed a 
marked scarcity of damselflies and burrowing may- 
flies. In the replicate pond the standing crop of free 
catfish exceeded the weight of the caged population 
by almost 100 pounds (45.36 kilograms), or slightly 
over 50 percent, and this greater weight was associated 
4 
any individual pond were caged and half were free. 
with a higher average turbidity (35 ppm), an absenc 
of weeds, and an abundance of those natural fooc 
observed to be scarce in the other pond. 
1971 EXPERIMENTS 
Materials and Methods 
Numbers and weights of bass and bluegills r 
stocked in October, 1970 to establish the 1971 popul 
tions are shown in Tables 4 and 5, along with standir 
crops recovered in the drainage censuses of Octob 
1971. 
The number of catfish available for stocking in tl 
spring of 1971 was reduced below the 1970 level | 
intervening mortalities. The number recovered ‘ 
April 13 from the overwinter holding pond was suf 
cient to provide only 662 in each population unit, 
1,324 in each of the six ponds. These were stock 
on April 13 and 14. In an effort to achieve a rando 
distribution of fishes of equal sizes, the fish to | 
stocked were pooled in a large holding tank and we 
netted, weighed, and stocked in consecutive lots 
50 to each unit until each had received nine lots tot 
ing 450 fish, then in lots of 40 until each had receiv! 
an additional 120, and in progressively smaller k 
until each unit contained 662 fish. On May 19, 19) 
38 additional fish were stocked in each unit whi 
brought the totals to 700 per unit, or 1,400 catti 
in each l-acre (0.4-hectare) pond. 
In 1971 in one pond, which happened to be co 
pletely weedless, it was possible to make a compl 
recovery of all of the bluegills including the small 
of the Age 0 fish. Numbers and weights of strand 
small fish were estimated in all other ponds. i 
estimates were based upon complete counts of sm 
fish stranded in randomly chosen sample areas. \ 
