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Intensive polyculture of fish in freshwater ponds. I. Substitution of expensive feeds by liquid cow manure
Aquaculture, 10 (1977) 25-43 o Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands
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INTENSIVE POLYCULTURE OF FISH IN FRESHWATER PONDS. I. SUBSTITUTION OF EXPENSIVE FEEDS BY LIQUID COW MANURE
ROM MOAV*’ H. BARASH**
, G. WOHLFARTH
**, G.L. SCHROEDER**,
G. HULATA**
and
*Department of Genetics, The Hebrew University of Jerusalem, Jerusalem (Israel) **Fish and Aquaculture Research Station, Institute of Animal Science, Agricultural Research Organization, Dor (Israel)
’ Present address: Institute of Animal Science, Agricultural Research Organization, Volcani Center, Bet-Dagan (Israel) (Received 1 September
The
1976)
ABSTRACT Moav, R., Wohlfarth, G., Schroeder, G.L., Hulata, G. and Barash, H., 1977. Intensive polyculture of fish in freshwater ponds. I. Substitution of expensive feeds by liquid cow manure. Aquaculture, 10:25-43. In 1974 and 1975 nine experimental treatments of fiih polyculture in stagnant water ponds without aeration were conducted at Dor. The polyculture was composed of common carp, silver carp, white amur (grass carp) and Tilapia. The treatments differed in stocking densities, feeding and manuring levels. The most productive treatment of the experiment, in which the fish were fed with protein-rich pellets, produced 50 kg/ha per day, probably a record for unaerated ponds of stagnant water. Two treatments (low and high stocking densities) fed exclusively with liquid cow manure produced an average yield of around 32 kg/ha per day. The yields of the treatments receiving high-protein pellets exceeded those of the treatments receiving grain pellets by 20 and 9.6 kg/day per ha, at high and low stocking densities, respectively, and in both cases the yield increments justified the extra cost of high-protein feed. The responses of the four fish species to the different levels of feeding and stocking densities were widely different. The common carp and white amur showed the greatest responses to increased feeding inputs while the silver carp and Tilapia, even at high densities, have done equally well at low feeding levels. Total body fat contents of the common carp were 20%, 15% and 6.2% when fed with highprotein pellets, grains pellets and liquid cow manure, respectively. Intermittent harvesting did not result in increased yields.
INTRODUCTION
The increasing costs of animal feeds (grain, fish meal, oilcake, etc.) created an urgent need for cheaper and more abundant substitutes. This holds true for all farm livestock and particularly for pond-raised fish because with increased scarcity of feeds, it is likely that fish would be the last on the line for feeds that can be consumed by man, or by farm livestock, i.e., dairy cows,
26
poultry and pigs. The Chinese fish-farmers developed, long ago, a high-yielding fish culture system based primarily on mixed stocking of several fish species (polyculture) and feeding with manures and organic wastes (Hoffmann, 1934; Lin, 1954; Tang, 1970; Bardach et al., 1972). In many countries where a high proportion of the animal feed is being bought with hardly available foreign currency an extra strong argument is added to the need for cheap feed substitutes in aquaculture and therefore to “rediscovering” Chinese fish-farming techniques. Schroeder (1973) showed that microorganisms present in stagnant water commercial fish ponds are a major component determining the efficiency of utilization of supplemented feeds. He also showed that liquid cow manure is relatively safe when fish pathology and oxygen demand for its decay in the pond are considered, and that it is a highly effective nutrient for the intense, in-situ culture of natural foods suitable for fish growth (Schroeder, 1974). Following Schroeder’s preliminary examination we tested in 1974, at Dor, a complete substitution of feeds with liquid cow manure. The ponds were stocked with the following four fish species: common carp, Tilupia, silver carp and white amur (grass carp). A control treatment of this experiment, in which the fish were fed with protein-rich pellets, produced 49.9 kg/ha/day (probably a record for unaerated ponds of stagnant water) while the treatment fed exclusively by liquid cow manure produced 19.6 kg/ha/day. This result led to further tests in 1975 of exclusive manure feeding resulting in the production of 31.7 kg/ha/day - a higher yield than the apparently record yield of India for ponds in which Chinese and Indian carps were grown in polyculture with heavy feeding and mauring (Chaudhuri et al., 1975). In the present paper we report the zootechnical and management aspects of the experiments. In a separate paper the contribution of genetic selection and hybridization for specific adaptation to varying feed input levels will be described. This may prove to be an essential factor in the successful maintenance of high production while down-grading the quality of the fish’s environment (Moav et al., 1976). MATERIALS AND METHODS
Fish stocks All the test ponds were co-stocked with four different fish species: (i) The benthophagic common carp (Cyprinus curpio, L.). In the present experiments environmental treatments (feeding, manuring, and stocking densities) were integrated with genetic tests on carp. Consequently, the carp population was divided into several stocks comprising the European and Chinese races and their hybrids (Wohlfarth et al., 1975) but in this paper all are treated as a single group. (ii) Tilupiu. In 1974 we used small T. aurea fry and in 1975, l-year-old males of T. aurea plus small F1 hybrids between T. vulcani (0) and T. aurea
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(d) having a high proportion of males (Pruginin et al., 1975). (iii) The phytoplanktophagic silver carp (Hypophthalmicthys molitrix, Val.). Two groups of fish with different initial weights were used in 1975. (iv) The macrophytophagic grass carp (Ctenopharyngodon idella, Val.). Experimental procedures The experiments were carried out in 400-m’ ponds of a mean depth of about 1 m. In 1974 the tests started on July 1st and were terminated after 126 days on November 4th. In 1975 they started on July 2nd and were terminated on November 6th. Water was added only to supplement for losses. Aeration devices (Schroeder, 1975) were installed as a “stand-by” for use in emergencies but in both years the ponds were aerated only during a single week for several hours nightly when signs of dangerously low oxygen levels were detected Feeding Predetermined feed rations (not ad lib) were administered as pellets through demand feeders (Berka, 1973). Two types of feeds were used: (i) Commercial pellets (henceforth, high-protein pellets) were made of 15% fish meal, 69% grains (wheat and sorghum) and 16% soybean cake. (ii) Grain pellets were made of ground sorghum grains. Liquid cow manure was brought from neighbouring dairy farms at about weekly intervals and stored in 750-l asbestos tanks installed near the ponds. The ponds were manured 6 days a week. Since the contents of the dry matter varied between batches, the applied rations of manure were standardized to 12% dry matter. The two ponds of the “manure only” treatment of 1974 received a daily ration of 250 l/ha/day for 83 days and on September 22nd the ration was doubled. Analysis of the 1974 results indicated that heavier TABLE I Daily and accumulated amounts of liquid cow manure, standardized to 12% dry matter, supplied to all the 16 ponds of 1975 Dates 2.7-24.7
25.7-16.8
17.8-18.9
No. of days
23
21
33
Daily ration (l/ha)
250
500
750
Accumulated (I/ha)
5 750
16 250
Accumulated dry matter W/ha)
690
1950
41000
4 920
19.9-23.9 5
24.9-4.10
5.10-13.10
14.10-5.11
11
9
23
1 000
1 250
1 500
1 750
46 000
59 750
73 250
113 500
5 520
7 170
8 790
13 620
II
19 700 11450 2 500 5 000 750 19 700
Total
C. carp
T. aureo G. carp
Total
Cow manure + low stocking density
Grain pellets + low stocking density
High-protein pellets + low stocking density
Grain pellets + high stocking density
6380
T. aurea G. carp
Total
80.4
6 130
Total
3.6 8.7 1.2 3.5
T. aurea G. carp
479 1 228 159 603
96.7 64.0 57.5 96.2
22 133 4 165
3 050 1 250 1 500 330
c. carp s. carp
85.2
92.0 80.0 73.8 88.5
82.0
81.9 71.0 75.5 94.6
81.8
84.2 75.5 77.6 93.3
6 380
4.6 8.2 1.2 2.8
8.0 9.0 1.4 5.0
1.5 6.1 0.9 1.8
77.1
79.8 66.7 73.0 97.7
Total
609 1176 153 539
1024 1 267 186 801
214 910 119 406
3.7 6.5 1.1 3.7
T. aurea G. carp
22 139 4 189
22 132 4 165
22 139 4 182
486 951 146 619
(9)
(g)
22 133 4 152
(%’
gain (g)
Survival
Final
Initial
Daily
Mean weights
3 300 1 250 1 500 330
c. carp s. carp
S. carp
3 300 1 250 1 500 330
c. carp
s. carp
11450 2 500 5 000 750
Common carp Silver carp Tilapia ourea Grass carp
1974
High-protein pellets + high stocking density
Stocking (fish/ha)
Species
Treatment
2 462
1345 845 132 140
3 032
1778 1 000 162 92
4 244
2 895 952 205 192
3 766
1808 1370 440 148
6 282
4 182 1 252 510 338
126 days
19.5
10.7 6.7 1.0 1.1
24.0
14.1 7.9 1.3 0.7
33.7
23.0 7.6 1.6 1.5
29.9
14.3 10.9 3.5 1.2
49.8
33.2 9.9 4.0 2.7
Daily
Yield (kg/ha)
100.0
54.6 34.3 5.4 5.7
100.0
58.6 33.0 5.4 3.0
100.0
68.2 22.4 4.8 4.5
100.0
48.0 36.4 11.7 3.9
100.0
66.6 19.9 8.1 5.4
%
-
3.83
2.90
3.22
2.46
conversion ratio
Detailed results of the nine combinations of stocking densities, feeding and manuring of the 1974 and 1975 tests (in 1975 two groups of silver carp and two groups of Tikzpia were stocked, hut on harvesting they were pooled for yield calculations)
TABLE
1975
Manure only + low stocking density
Manure + grains + low stocking density
Manure only + high stocking density
Manure + grains + high stocking density
050 080 000 320 680 850
9 240 4 800 520 1 000 1 650 850 420 9 240
Total
c. carp
2 Tilapia 1 2 G. carp
Total
S.carpl
4 800 520 1000 1 650 850 420
17 980
9 1 2 3 1
17 980
9 050 1080 2 000 3 320 1 680 850
c. carp s. carp 1 2 Tilapia 1 2 G. carp
Total
c. carp s. carp 1 2 Tilapia 1 2 G. carp
Total
2 Tilapia 1 2 G. carp
S.carpl
c. carp
30 464 45 97 21 205
30 464 45 97 21 205
30 464 45 97 21 205
30 464 45 97 21 205
546 1 140 712 446 256 726
732 1 178 708 462 252 843
258 928 524 416 220 584
436 942 516 430 221 623
4.1 5.4 5.3 2.7 1.9 4.1
5.6 5.6 5.3 2.9 1.8 5.0
1.8 3.7 3.8 2.5 1.6 3.0
3.2 3.8 3.8 2.6 1.6 3.3
270
263
90.7
31.5
1.7
212 3 967
5.4
686
93.0 94.2
7.0
17.4 875
2 194
39.1
2.1
91.4
89.1
4 923
677
87.0 100.0 91.0
7.3
923
5.4
24.3
3 060
91.7
32.6
93.1
4 121
1072
88.5 97.1 90.7
8.5
1 184
2.1
9.4
1 595
90.6
12.6
41.3
94.0
5 212
2.6
325
89.0
8.9
1 117
91.5 100.0
8.8
21.0
95.7
2 650 1 120
84.6
100.0
5.4
17.1
22.2
55.3
100.0
5.4
13.8
18.6
62.2
100.0
6.4
26.5
28.5
38.6
100.0
6.3
21.6
21.3
50.8
-
1.19
-
1.28
30
manuring should be applied and this was implemented in 1975, as shown in Table I. A total of 9 different treatments were tested in 1974 and 1975, eight of which took place in four replicated ponds while the “manure only” treatment of 1974 took place in only two ponds. Two different “high” and “low” stocking densities were used in 1974 and in 1975 (Table II). All the ponds of all the 9 treatments received at 2-week intervals 150 kg/ha poultry manure, 50 kg/ha ammonium sulphate and 50 kg/ha superphosphate. The chemical fertilizers were given on alternate weeks to the poultry manure. EXPERIMENTAL
RESULTS
In the present experiments we attempted to answer four major pond management questions: (i) What are the benefits of adding fish meal to the feed? (ii) Can supplemental feed be substituted completely, or partially, by liquid cow manure? (iii) How does each species respond to increased stocking density? (iv) What are the effects of intermittent harvesting on production? In the following, the experimental results are discussed in relation to these questions. Adding fish meal to the feed In 1974 we fed eight ponds with the high-protein pellets and eight ponds with grain pellets, four out of the eight ponds for each feed treatment being stocked at a high density and the remaining four at a low density (Table II). This factorial design permitted a comparison between the two feeding treatments at the two densities. The results may be summarized as follows: (i) A remarkably high production of almost 50 kg/ha/day was realized at high density plus high-protein pellets with a relatively high proportion (67%) of carp in the total yield. (ii) The yields of the ponds receiving high-protein pellets exceeded those of the ponds fed with grain pellets by 20 and 9.6 kg/day/ha, at high and low stocking densities, respectively. In both cases the yield increments justified the extra cost of the fish meal. (iii) The response to fish meal varied widely between the four species (Table III, part A). The common carp and the grass carp showed the highest response, accounting for most of the extra production brought about by the extra protein. Tilapia responded only slightly while the silver carp showed a negative response. These results verify that the common carp and grass carp needed the high-protein diet for optimal growth rate, while Tilapia and silver carp, even at high density, could get their protein requirements from natural foods in the pond. The silver carp probably suffered slightly from the larger total biomass in the ponds fed with high-protein pellets.
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TABLE III The proportional responses of the four fish species to varying levels of feeding and crowding (based on results of Table II) Common carp
Silver carp
A. High-protein pellets minus grain pellets 1. high density 1974 2. low density 1974
131% 51%
-8% -5%
B. High-protein pellets minus manure only (low density 1974)
100%
Grain pellets minus manure only (low density 1974) C. Manure plus grain pellets minus manure only 1. high density 1975 2. low density 1975
Comparison
Tilapia
Grass carp
Total difference
15% 24%
123% 111%
67% 40%
13%
52%
36%
72%
32%
18%
22%
66% 39%
-5% 5%
5% -1%
20% 24%
27% 24%
55% 2%
31% 37%
146% 167%
76% 67%
46% 24%
22% 35%
66% 56%
25% 29%
6% 4%
._
______-
D. High density minus low density 1. high-protein pellets 1974 2. grain pellets 1974 3. manure + grain pellets 1975 4. manure only 1975
-13% -27%
-36%
23%
(iv) In 1974 we measured the fat content of the common carp employing the method described by Ankorion et al. (1967). In the high-protein treatment we found an average fat content of 15% of total body weight as compared with 20% under “grain only” feeding. (v) The unweighted feed conversion ratio, i.e., feed weight divided by gained weight (henceforth FCR) was considerably lower in the high-protein treatments than in the “grain” treatments (Table II). However, after compensating for the higher cost of the former pellets, the cost efficiency becomes similar for the two feeding treatments at each stocking density. Complete
substitution
The two ponds day as compared fed, respectively, differently to the
of feeds by liquid cow manure
fed exclusively with liquid cow manure yielded to 33.7 and 24.1 kg/ha/day for the ponds of the with high-protein and grain pellets. Each species change in diet (Table III, part B). The common
19.6 kg/ha/ same density responded carp showed
32
the highest response to added food. The negative response of the grass carp to grain pellets is not understood and was not repeated in 1975. The fat content of the common carp in the “manure” treatment was 6.2% as compared with 15% and 20% for high-protein and grain feeding, respectively This pleasantly surprising result means that fish protein production in the “manure only” treatment was considerably higher than appears from comparison of total weights only. Furthermore, it shows that manure has a very high direct or indirect protein value and that it can substitute fish meal. Indeed, the difference in intra-muscular fat was so high that we were able to identify the fish grown in the “manure” treatment by the deeper red colour of their meat. In 1975 we compared “manure only” to manure supplemented with grain pellets. The comparison was conducted again at high and low stocking densities (Table II) and its results may be summarized by the following points: (i) Daily manure applications without supplementary feeding resulted in the remarkably high production of 32.7 and 31.5 kg/ha/day at the high and low densities, respectively. The increased production over that of the same treatment of the previous year (19.6 kg/ha/day) was presumably due to the higher rate of manuring (Table I). (ii) Supplementing the manure with grain pellets increased production by 8 kg/ha/day at both stocking densities. The common carp accounted for most of the added production (Fig. 1 and Table III, part C). -
COMMON
B
SILVER
CARP CARP
~UIDGRASS CARP 0
HIGH DENSITY FISHMEAL PELLETS
T/L APIA
HIGH LOW LOW LOW DENWY DEN.YTY DENSE DENSITY GRAINS fMM4L GRAlNS MhW?E PELLETS FTLLzrs /WLETS ONLY I 7 9 4
Fig.1. Total fish yields in tons/ha/l26 and 1975.
HIGH HIGH LOW LOW tK.fTY DENS.0-Y DENSITY DE&SfTY h%ANU&- MN#X MA&WE MANURE *GRAINS ONLY *GRAINS QNLY 1 9 7 S
days for the nine experimental treatments of 1974
33
(iii) The total amount of liquid cow manure added to the ponds throughout the whole season was 90 m3/ha, containing 10.8 tons of dry matter and yielding around 4 tons of liveweight of fish, that is a conversion of 2.7 kg manure (dry matter) to 1 kg of fish - a remarkable efficiency comparable to that of expensive grain. (iv) The FCR of the added grain at both stocking densities was about 1.2, not taking the manure into account (Table II). However, its marginal efficiency, i.e., the weight of supplemented grain pellets divided by the extra yield, was about 6.1. Thus, the addition of grain resulted in an inefficient increase in production. Response
to crowding
The proportional differences of “high” and “low” stocking densities at four levels of feeding inputs are shown for each species in Table III, part D, and are presented as regressions on feeding levels in Fig. 2. These results show: (i) The total response of production level to crowding is, clearly, a function of the feeding inputs (right-hand column, Table III, part D). Thus, under the best feeding regime, i.e., high-protein pellets, “high” stocking density was 46% more productive than “low” density; under the second best (grain pellets), it decreased to 24%; under the third (manure supplemented by grain) it dropped
MANURE ONi Y I975
MANURE PLUS GRAINS /97s
GRAINS PELL E TS 1974
FISH MEAL PE;L E TS 1974
Fig.2. The relationships of the proportional differences of the four fish species, between “high” and “low” stocking densities, to feeding levels.
34
down to 6% and under the lowest feeding level (manure only) to 4%. We may conclude, therefore, that in the last three treatments food constituted the major limiting factor to realizing the larger potential production of the high stocking. (ii) The individual response to crowding of each species is much more revealing than the average response. Thus, increased density of the common carp reduced its production by as much as 27% (Fig. 2). Silver carp, which feeds on phytoplankton, showed 22%-37% increased production at the high densities, independently of the feeding regime. Tilapia responded better than the other species to crowding at all feeding levels, indicating that higher densities than those tested may further increase production of this species. The varying responses of the different species may serve as useful guides in the search for an optimal “mix”.
Intermittent
harvesting
In the high stocking densities of 1975 we performed thinning-out by seining six times. The cumulative weights of fish removed are shown in Fig. 3, which also shows that the thinning-out procedures did not yield much higher yields than the single terminal harvest of the low stocking treatments. The total thinned-out harvest constituted about 40% of the total production. A probable cause for this failure was unbalanced thinning-out procedures. That is, most of the fish removed by the intermittent harvestings were silver carp and Tilapia. while it was the common carp that suffered most from the high densities. Thus, it is likely that the removal of the silver carp and Tilapia pushed the polyculture “mix” away from the optimum.
Growth curves The growth curves of the different fish species in all the nine treatments are shown in the diagrams of Fig. 4. Grass carp was omitted because only small numbers of this species were caught during the periodic weighings. Generally speaking, its growth curves appeared to resemble those of the common carp. Fig. 4. shows: (i) In 1974 and 1975 the common carp responded sharply to reduced crowding and improved feeding throughout the whole season. Thus, the common carp grew fastest in the low-density plus high-protein treatment of 1974 where it gained an average of slightly over 1000 g per fish in 126 days, that is 8 g per day. At the same stocking density, but with grain pellets, the average daily gain of carp was only 4.8 g. Furthermore, the divergence of the growth curves started almost from the beginning of the test, demonstrating, again, that under high stocking density carp requires protein-rich added feeds. (ii) Growth of the common carp during the first month in the “manure only” treatment of 1974 was faster than in all the other treatments, but subsequently it slowed down to almost a complete stop. This led us to double the amount of
35
COW
MANURE
m COMMON
PLUS
CARP
BISILVER
CARP
UUUGRASS
cA RP
0
GRAINS
HIGH DENSITY
TIL APIA
30.7
13.8 27.8
/7.9 DATE
COW MANURE
2.7
30.7
13.0 27.8
--
ONLY
I Z9
I.:0 /liO
5./f
5.‘/ DATE
Fig.3. The cumulative yields removed by multiple harvesting from the “high” density treatments of 1975. (The single harvest yields of the “low” density treatments were added for comparison.)
daily manure from 250 l/ha to 500 l/ha resulting in an immediate and dramatic improvement. Apparently the initial amount of manure became insufficient for maintenance and growth at the higher biomass. Only the common carp showed this marked dependence on the quantity of added manure. (iii) The silver carp responded to crowding but not to the type of feed. In 1975 growth of the silver carp ceased at the beginning of October in all the treatments. This may be due to deterioration of pond conditions at high fish biomasses or due to seasonal changes such as lower temperatures, shorter
36
n
LOW Dwslrr:
FLY-IMEAL f?zLErs
0
LOW DENsIrK
GQ/thvS PELLErs
lzDo,-
+
LOW DEAWrY.MAMJ?E
r I oo-
a M3i
1300.
,3OO
I200
ONLY
LxN.wY
fTiH MmL FELLETS OHIGHCEhs/ry.GRAINS PELLET-S
looo~2
SILVER
CAR
,,oo
1000
900.-
/
cw
2
900
cw
600.500.. 400..
‘7
30.7
26.8
29.9
4.0
I. 7
327
268
DA rE
WEGHJ
PWJ
61
WEIGHT /2W t
(G)
WEIGHT [GJ
---umDEmv MANl.Gf ONLY -¤HfG’iDENyJY MANLRE*GRM,S ---OLQYDENYJYMANU~E ONLY l LOW DEbiYJY MANLC)t.GRA,h,_?
.‘,W.
h30~ PJO 800
.
COMMON C
7001
J/L APIA
S/L VER CARP
s;:Ki7’278
::; I.10 DAJE
IN:,::::27
JO.7
278
::: L/O DA Jf
5.5 Y7
JOT
‘2Zh
b/O DATE
Fig.4. Growth curves of the common carp, silver carp and Tilapia. A (above): treatments of 1974; B (below): The four treatments of 1975.
5. Ii
The five
photo-period or changes in the phytoplankton population. (iv) In the case of Tilapiu, individual growth rates responded very little to feeding or crowding indicating that the present densities of Tilupia were suboptimal.
37
Daily production and feed conversion Figs 5A and 6A show the average daily yield increments, and Figs 5B and 6B show the equivalent FCR for the short periods of 2-4 weeks between sample weighings by seining. These curves show: (i) The highest daily yield increment (77 kg/ha/day) was reached in October 1974 in the treatment with high-density plus high-protein pellets, at a fish biomass of about 5 500 kg/ha. (ii) The two treatments with high-protein pellets showed an increase in daily yield increment up to a maximum reached in September-October. In the remaining treatments the highest daily yield increments were reached
0, 17
0 2 F
I57
3W
Ii!8
‘.
,4, .
8 LOW LXNS/JY. FLY-i MEAL ELLEJS 0 LOW DENSfrY. GRAINS PELLETS
12* ’
*LOW
DENS/TY. MANURE
0
fEx
29.9
Is./0
29.9
/S/O
r29
/6.’
0 MGH mmy. 5 $
26.8
DArE
4/f
ONLY
MEAL pELLErs
HIGH DENSITY. GRAINS PELLEJS
8,.
/7
/57
30.7
128
26.8
/29
4/l DA J.5 _
Fig&. Curves of daily yield increments and feed conversion ratios in the 1974 experiment. A: Average daily increments; B: Feed conversion ratios.
38
0 27
/6.7
307
13.8
2Z8
179
I/O
t5.10
5 II DA TE
Fig.6. Curves of daily yield increments and feed conversion ratios in the 1975 experiment. A: Average daily increments; B: feed conversion ratios.
in the first month of the tests. This suggests that some natural protein-rich food elements were in a limited supply and their relative scarcity increased with increased biomass. When high-protein feed was added, the size of the fish, particularly that of the common carp, became the limiting factor to growth so that with increased size daily production increased until the high biomass substituted feed as a limiting factor. (iii) The sharp rise in FCR in all the treatments towards the end of the experiment reached a disastrous level of 16 in the most productive treatment. This shows how important it is to harvest the fish before the marginal FCR becomes too high even if growth rate continues at a satisfactory level. DISCUSSION
The present experiments demonstrate that freshwater ponds without aera-
39
tion or water circulation can produce an average yield of 50 kg/ha/day for a period of 126 days in balanced polyculture and high densities when supplied with abundant high-protein feed. More impressive is the production of 32.7 kg/ha/day when liquid cow manure was substituted for feed. A quantity of 22.6 1 liquid manure of 12% dry weight was required for the production of 1 kg fish, that is, a conversion ratio of 2.7 kg dry matter of manure to 1 kg fish. Our results were compared with those of two other experiments reporting record yields (Table IV). Rappoport and Sarig (1975) tested monoculture of carp and Tilapiu at very high densities in ponds continuously and intensely aerated and fed with high-protein pellets. Both carp and Tilapiu yielded over 120 kg/ha/day at FCR levels similar to or poorer than those common for wellfed unaerated ponds (unfortunately the experiment did not have a control). Chaudhuri et al, (1975) tested polyculture mixes of Indian and Chinese carps with heavy feeding and manuring. The experiment lasted for a full year but the authors noted that “application of fertilizers and feed was reduced and, at times, suspended during the summer months when the water level was low and algal blooms developed”. To compensate for this period of reduced growth we arbitrarily standardized the experiment to 300 full days of growth. With this the computed daily production was 30.3 kg/ha/day, a reported new record for India. Multiple harvesting should result in higher yields than a single seasonal or annual harvest as is illustrated schematically in Fig. 7. A pond filled with fresh water at the beginning of a “season” must have some optimal fish biomass level for maximal daily gain. At lower biomass levels the pond’s poten tial is not fully utilized, while at higher levels over-crowding has detrimental effects on yields and FCR. Under intensive fish culture of high stocking and feeding rates in stagnant water the pond conditions, as a medium for fish growth, gradually deteriorate. This may be due to: (i) sub-optimal disolved oxygen levels, particularly at night; (ii) accumulation of growth-inhibiting factors; (iii) smaller volumes of pond organisms serving as food for the fish; and (iv) increased density of the pond organisms not serving as fish food while competing with them for food and oxygen. Thus, the optimal biomass level probably decreases gradually as shown in Fig. 7. Under a single harvest system the fish biomass is far from the optimal level for most of the season. High initial (stocking) biomass plus frequent harvesting should overcome this limitation. With polyculture the rate of deterioration in pond conditions is presumably slower than with a monoculture system of equivalent biomass and management. Unbalanced thinning-out in polyculture makes the system more similar to monoculture and therefore may not result in the expected enhancement of production or may even have detrimental effects. The apparent absence of a positive response to thinning-out procedures in our 1975 experiment may be due to the relatively severe thinning-out of the plankton-eaters, silver carp and Tihpia, rather than the overcrowded benthos-eater, common carp.
126
126
111 105
High-protein pellets + high stocking density + polyculture
Manure only + high stocking density + polyculture
Manure + grains + high stocking density + polyculture
Forced aeration + carp monoculture + very high stocking density ponds 16-18 pond B
1. Dor, 1974 Present results
2. Dor, 1975 Present results
3. Dor, 1975 Present results
4. Genosar, 1975 (Rappoport and Sarig, 1975)
126
Duration (days)
Treatment of ponds
Experiment and reference
Comparisons of present results with others
TABLE IV
15 550 12 630
5 212
4 121
6 282
140.1 120.3
41.3
32.6
49.8
57 100 32 000
6 670
-
15455
(kg/ha)
(kg/ha)
-
-
-
-
Aquatic weeds
Concentrates
Daily
Total
Bran
Feeds and manure (kg/ha)
Fish production
113 500
113 500
Cow dung**
3.7 2.5
1.28
0
2.46
FCR*
41
0 0 N
42
. CUtlMULATlVE HARVEST)
BIOMASS UNDER
(INCLUDING
,
’
/
‘MULTIPLE
/
HARVESTING’
/ /
/ /
‘SINGLE HARVEST’ BIOMASS
y
TtilNlNG
2N” T. OUT
&MA,
1 e’oMASS
t $0
$I
T. OUT
1. OUT
OUT
1
POND FILLED WI Ttt FRESH WATER AND STOCKED WITH FfSH
m4E ALL
f POND EMPTIED F/SH REMOVED
Fig.7. Schematic presentation of the expected relationships between optimal, single-harvest and multiple-harvest biomasses and yields.
As discussed elsewhere (Hepher and Schroeder, 1975), the effectiveness of liquid cow manure in fish culture may be based on a food chain that starts with bacteria and protozoa active in the decomposition of the organic matter in the manure. Since this chain is not directly dependent on photosynthesis (as is the case with chemical fertilizers), the inherent limits of sunlight penetra tion into the pond water are by-passed and the production of natural foods may be limited only by nutrient supply, i.e., by the amount of manure and dissolved oxygen present in the pond water. In liquid manure of&n more than 30% of the total dry matter is colloidal. These “fines” provide a base for bacterial and protozoan growth throughout the water column, as well as on the pond bottom. Thus the entire pond is made to be productive. ACKNOWLEDGEMENTS
This research was supported by a grant from the United States-Israel Binational Science Foundation (BSF), Jerusalem, Israel. We gratefully extend our thanks to the many technicians, colleagues and students who helped us in carrying out the many chores of running these complex and labour-intensive experiments.
43
REFERENCES Ankorion, J., Moav, R. and Wohlfarth, G., 1967. A “modified Gerber method” for rapid determination of fat contents in fish. Bamidgeh, 19: 46-49. Bardach, J.E., Ryther, J.H. and McLarny, W.O., 1972. Aquaculture. The farming and husbandry of freshwater and marine organisms. John Wiley, New York, 868 pp. Berka, R., 1973. A review of feeding equipment in fish culture. EIFAC Occas. Pap., 9: l-32. Chaudhuri, H., Chakrabarty, R.D., Sen, P.R., Rao, N.G.S. and Jena, S., 1975. A new high in fish production in India with record yields by composite fish culture in freshwater ponds. Aquaculture, 6: 343-355. Hepher, B. and Schroeder, G.L., 1975. Wastewater utilization in Israeli aquaculture. Proc. Int. Conf. on Renovation and Recycling of Wastewater through Aquatic and Terrestrial Systems, Rockerfeller Foundation and Institute of Water Research, Michigan State University, 29 pp. Hoffmann, W.E., 1934. Preliminary notes on the fresh water fish industry of South China, especially Kwangtung province. Lingnan Univ. Sci. Bull., No. 5, 70 pp. (Lingnan Univ., Canton, China). Lin, S.Y., 1954. Chinese system of pond stocking. Proc. Indo-Pacific Fish. Council, 65-71 Moav, R., Soller, M., Hulata, G. and Wohlfarth, G., 1976. Genetic aspects of the transition from traditional to modern fish farming. Theoret. Appl. Genet., 47: 285-290. Pruginin, Y., Rothbard, S., Wohlfarth, G., Halevy, A., Moav, R. and Hulata, G., 1975. All-male broods of Tilapia nolotico X T. aurea hybrids. Aquaculture, 6: 11-21. Rappoport, U. and Sarig, S., 1975. The results of tests in intensive growth of fish at the Genosar (Israel) station ponds in 1974. Bamidgeh, 27: 75-82. Schroeder, G.L., 1973. Factors affecting feed conversion ratio in fish ponds. Bamidgeh, 25: 104-113. Schroeder, G.L., 1974. Use of fluid cowshed manure in fish ponds. Bamidgeh, 26: 84-96. Schroeder, G.L., 1975. Nighttime material balance for oxygen in fish ponds receiving organic wastes. Bamidgeh, 27 : 65-74. Tang, Y.A., 1970. Evaluation of balance between fishes and available fish foods in multispecies fish culture ponds in Taiwan. Trans. Amer. Fish, Sot., 99: 708-718. Wohlfarth, G., Moav, R. and Hulata, G., 1975. Genetic differences between the Chinese and European races of the common carp. II. Multi-character variation - a response to the diverse methods of fish cultivation in Europe and China. Heredity, 34: 341-350.
25
INTENSIVE POLYCULTURE OF FISH IN FRESHWATER PONDS. I. SUBSTITUTION OF EXPENSIVE FEEDS BY LIQUID COW MANURE
ROM MOAV*’ H. BARASH**
, G. WOHLFARTH
**, G.L. SCHROEDER**,
G. HULATA**
and
*Department of Genetics, The Hebrew University of Jerusalem, Jerusalem (Israel) **Fish and Aquaculture Research Station, Institute of Animal Science, Agricultural Research Organization, Dor (Israel)
’ Present address: Institute of Animal Science, Agricultural Research Organization, Volcani Center, Bet-Dagan (Israel) (Received 1 September
The
1976)
ABSTRACT Moav, R., Wohlfarth, G., Schroeder, G.L., Hulata, G. and Barash, H., 1977. Intensive polyculture of fish in freshwater ponds. I. Substitution of expensive feeds by liquid cow manure. Aquaculture, 10:25-43. In 1974 and 1975 nine experimental treatments of fiih polyculture in stagnant water ponds without aeration were conducted at Dor. The polyculture was composed of common carp, silver carp, white amur (grass carp) and Tilapia. The treatments differed in stocking densities, feeding and manuring levels. The most productive treatment of the experiment, in which the fish were fed with protein-rich pellets, produced 50 kg/ha per day, probably a record for unaerated ponds of stagnant water. Two treatments (low and high stocking densities) fed exclusively with liquid cow manure produced an average yield of around 32 kg/ha per day. The yields of the treatments receiving high-protein pellets exceeded those of the treatments receiving grain pellets by 20 and 9.6 kg/day per ha, at high and low stocking densities, respectively, and in both cases the yield increments justified the extra cost of high-protein feed. The responses of the four fish species to the different levels of feeding and stocking densities were widely different. The common carp and white amur showed the greatest responses to increased feeding inputs while the silver carp and Tilapia, even at high densities, have done equally well at low feeding levels. Total body fat contents of the common carp were 20%, 15% and 6.2% when fed with highprotein pellets, grains pellets and liquid cow manure, respectively. Intermittent harvesting did not result in increased yields.
INTRODUCTION
The increasing costs of animal feeds (grain, fish meal, oilcake, etc.) created an urgent need for cheaper and more abundant substitutes. This holds true for all farm livestock and particularly for pond-raised fish because with increased scarcity of feeds, it is likely that fish would be the last on the line for feeds that can be consumed by man, or by farm livestock, i.e., dairy cows,
26
poultry and pigs. The Chinese fish-farmers developed, long ago, a high-yielding fish culture system based primarily on mixed stocking of several fish species (polyculture) and feeding with manures and organic wastes (Hoffmann, 1934; Lin, 1954; Tang, 1970; Bardach et al., 1972). In many countries where a high proportion of the animal feed is being bought with hardly available foreign currency an extra strong argument is added to the need for cheap feed substitutes in aquaculture and therefore to “rediscovering” Chinese fish-farming techniques. Schroeder (1973) showed that microorganisms present in stagnant water commercial fish ponds are a major component determining the efficiency of utilization of supplemented feeds. He also showed that liquid cow manure is relatively safe when fish pathology and oxygen demand for its decay in the pond are considered, and that it is a highly effective nutrient for the intense, in-situ culture of natural foods suitable for fish growth (Schroeder, 1974). Following Schroeder’s preliminary examination we tested in 1974, at Dor, a complete substitution of feeds with liquid cow manure. The ponds were stocked with the following four fish species: common carp, Tilupia, silver carp and white amur (grass carp). A control treatment of this experiment, in which the fish were fed with protein-rich pellets, produced 49.9 kg/ha/day (probably a record for unaerated ponds of stagnant water) while the treatment fed exclusively by liquid cow manure produced 19.6 kg/ha/day. This result led to further tests in 1975 of exclusive manure feeding resulting in the production of 31.7 kg/ha/day - a higher yield than the apparently record yield of India for ponds in which Chinese and Indian carps were grown in polyculture with heavy feeding and mauring (Chaudhuri et al., 1975). In the present paper we report the zootechnical and management aspects of the experiments. In a separate paper the contribution of genetic selection and hybridization for specific adaptation to varying feed input levels will be described. This may prove to be an essential factor in the successful maintenance of high production while down-grading the quality of the fish’s environment (Moav et al., 1976). MATERIALS AND METHODS
Fish stocks All the test ponds were co-stocked with four different fish species: (i) The benthophagic common carp (Cyprinus curpio, L.). In the present experiments environmental treatments (feeding, manuring, and stocking densities) were integrated with genetic tests on carp. Consequently, the carp population was divided into several stocks comprising the European and Chinese races and their hybrids (Wohlfarth et al., 1975) but in this paper all are treated as a single group. (ii) Tilupiu. In 1974 we used small T. aurea fry and in 1975, l-year-old males of T. aurea plus small F1 hybrids between T. vulcani (0) and T. aurea
27
(d) having a high proportion of males (Pruginin et al., 1975). (iii) The phytoplanktophagic silver carp (Hypophthalmicthys molitrix, Val.). Two groups of fish with different initial weights were used in 1975. (iv) The macrophytophagic grass carp (Ctenopharyngodon idella, Val.). Experimental procedures The experiments were carried out in 400-m’ ponds of a mean depth of about 1 m. In 1974 the tests started on July 1st and were terminated after 126 days on November 4th. In 1975 they started on July 2nd and were terminated on November 6th. Water was added only to supplement for losses. Aeration devices (Schroeder, 1975) were installed as a “stand-by” for use in emergencies but in both years the ponds were aerated only during a single week for several hours nightly when signs of dangerously low oxygen levels were detected Feeding Predetermined feed rations (not ad lib) were administered as pellets through demand feeders (Berka, 1973). Two types of feeds were used: (i) Commercial pellets (henceforth, high-protein pellets) were made of 15% fish meal, 69% grains (wheat and sorghum) and 16% soybean cake. (ii) Grain pellets were made of ground sorghum grains. Liquid cow manure was brought from neighbouring dairy farms at about weekly intervals and stored in 750-l asbestos tanks installed near the ponds. The ponds were manured 6 days a week. Since the contents of the dry matter varied between batches, the applied rations of manure were standardized to 12% dry matter. The two ponds of the “manure only” treatment of 1974 received a daily ration of 250 l/ha/day for 83 days and on September 22nd the ration was doubled. Analysis of the 1974 results indicated that heavier TABLE I Daily and accumulated amounts of liquid cow manure, standardized to 12% dry matter, supplied to all the 16 ponds of 1975 Dates 2.7-24.7
25.7-16.8
17.8-18.9
No. of days
23
21
33
Daily ration (l/ha)
250
500
750
Accumulated (I/ha)
5 750
16 250
Accumulated dry matter W/ha)
690
1950
41000
4 920
19.9-23.9 5
24.9-4.10
5.10-13.10
14.10-5.11
11
9
23
1 000
1 250
1 500
1 750
46 000
59 750
73 250
113 500
5 520
7 170
8 790
13 620
II
19 700 11450 2 500 5 000 750 19 700
Total
C. carp
T. aureo G. carp
Total
Cow manure + low stocking density
Grain pellets + low stocking density
High-protein pellets + low stocking density
Grain pellets + high stocking density
6380
T. aurea G. carp
Total
80.4
6 130
Total
3.6 8.7 1.2 3.5
T. aurea G. carp
479 1 228 159 603
96.7 64.0 57.5 96.2
22 133 4 165
3 050 1 250 1 500 330
c. carp s. carp
85.2
92.0 80.0 73.8 88.5
82.0
81.9 71.0 75.5 94.6
81.8
84.2 75.5 77.6 93.3
6 380
4.6 8.2 1.2 2.8
8.0 9.0 1.4 5.0
1.5 6.1 0.9 1.8
77.1
79.8 66.7 73.0 97.7
Total
609 1176 153 539
1024 1 267 186 801
214 910 119 406
3.7 6.5 1.1 3.7
T. aurea G. carp
22 139 4 189
22 132 4 165
22 139 4 182
486 951 146 619
(9)
(g)
22 133 4 152
(%’
gain (g)
Survival
Final
Initial
Daily
Mean weights
3 300 1 250 1 500 330
c. carp s. carp
S. carp
3 300 1 250 1 500 330
c. carp
s. carp
11450 2 500 5 000 750
Common carp Silver carp Tilapia ourea Grass carp
1974
High-protein pellets + high stocking density
Stocking (fish/ha)
Species
Treatment
2 462
1345 845 132 140
3 032
1778 1 000 162 92
4 244
2 895 952 205 192
3 766
1808 1370 440 148
6 282
4 182 1 252 510 338
126 days
19.5
10.7 6.7 1.0 1.1
24.0
14.1 7.9 1.3 0.7
33.7
23.0 7.6 1.6 1.5
29.9
14.3 10.9 3.5 1.2
49.8
33.2 9.9 4.0 2.7
Daily
Yield (kg/ha)
100.0
54.6 34.3 5.4 5.7
100.0
58.6 33.0 5.4 3.0
100.0
68.2 22.4 4.8 4.5
100.0
48.0 36.4 11.7 3.9
100.0
66.6 19.9 8.1 5.4
%
-
3.83
2.90
3.22
2.46
conversion ratio
Detailed results of the nine combinations of stocking densities, feeding and manuring of the 1974 and 1975 tests (in 1975 two groups of silver carp and two groups of Tikzpia were stocked, hut on harvesting they were pooled for yield calculations)
TABLE
1975
Manure only + low stocking density
Manure + grains + low stocking density
Manure only + high stocking density
Manure + grains + high stocking density
050 080 000 320 680 850
9 240 4 800 520 1 000 1 650 850 420 9 240
Total
c. carp
2 Tilapia 1 2 G. carp
Total
S.carpl
4 800 520 1000 1 650 850 420
17 980
9 1 2 3 1
17 980
9 050 1080 2 000 3 320 1 680 850
c. carp s. carp 1 2 Tilapia 1 2 G. carp
Total
c. carp s. carp 1 2 Tilapia 1 2 G. carp
Total
2 Tilapia 1 2 G. carp
S.carpl
c. carp
30 464 45 97 21 205
30 464 45 97 21 205
30 464 45 97 21 205
30 464 45 97 21 205
546 1 140 712 446 256 726
732 1 178 708 462 252 843
258 928 524 416 220 584
436 942 516 430 221 623
4.1 5.4 5.3 2.7 1.9 4.1
5.6 5.6 5.3 2.9 1.8 5.0
1.8 3.7 3.8 2.5 1.6 3.0
3.2 3.8 3.8 2.6 1.6 3.3
270
263
90.7
31.5
1.7
212 3 967
5.4
686
93.0 94.2
7.0
17.4 875
2 194
39.1
2.1
91.4
89.1
4 923
677
87.0 100.0 91.0
7.3
923
5.4
24.3
3 060
91.7
32.6
93.1
4 121
1072
88.5 97.1 90.7
8.5
1 184
2.1
9.4
1 595
90.6
12.6
41.3
94.0
5 212
2.6
325
89.0
8.9
1 117
91.5 100.0
8.8
21.0
95.7
2 650 1 120
84.6
100.0
5.4
17.1
22.2
55.3
100.0
5.4
13.8
18.6
62.2
100.0
6.4
26.5
28.5
38.6
100.0
6.3
21.6
21.3
50.8
-
1.19
-
1.28
30
manuring should be applied and this was implemented in 1975, as shown in Table I. A total of 9 different treatments were tested in 1974 and 1975, eight of which took place in four replicated ponds while the “manure only” treatment of 1974 took place in only two ponds. Two different “high” and “low” stocking densities were used in 1974 and in 1975 (Table II). All the ponds of all the 9 treatments received at 2-week intervals 150 kg/ha poultry manure, 50 kg/ha ammonium sulphate and 50 kg/ha superphosphate. The chemical fertilizers were given on alternate weeks to the poultry manure. EXPERIMENTAL
RESULTS
In the present experiments we attempted to answer four major pond management questions: (i) What are the benefits of adding fish meal to the feed? (ii) Can supplemental feed be substituted completely, or partially, by liquid cow manure? (iii) How does each species respond to increased stocking density? (iv) What are the effects of intermittent harvesting on production? In the following, the experimental results are discussed in relation to these questions. Adding fish meal to the feed In 1974 we fed eight ponds with the high-protein pellets and eight ponds with grain pellets, four out of the eight ponds for each feed treatment being stocked at a high density and the remaining four at a low density (Table II). This factorial design permitted a comparison between the two feeding treatments at the two densities. The results may be summarized as follows: (i) A remarkably high production of almost 50 kg/ha/day was realized at high density plus high-protein pellets with a relatively high proportion (67%) of carp in the total yield. (ii) The yields of the ponds receiving high-protein pellets exceeded those of the ponds fed with grain pellets by 20 and 9.6 kg/day/ha, at high and low stocking densities, respectively. In both cases the yield increments justified the extra cost of the fish meal. (iii) The response to fish meal varied widely between the four species (Table III, part A). The common carp and the grass carp showed the highest response, accounting for most of the extra production brought about by the extra protein. Tilapia responded only slightly while the silver carp showed a negative response. These results verify that the common carp and grass carp needed the high-protein diet for optimal growth rate, while Tilapia and silver carp, even at high density, could get their protein requirements from natural foods in the pond. The silver carp probably suffered slightly from the larger total biomass in the ponds fed with high-protein pellets.
31
TABLE III The proportional responses of the four fish species to varying levels of feeding and crowding (based on results of Table II) Common carp
Silver carp
A. High-protein pellets minus grain pellets 1. high density 1974 2. low density 1974
131% 51%
-8% -5%
B. High-protein pellets minus manure only (low density 1974)
100%
Grain pellets minus manure only (low density 1974) C. Manure plus grain pellets minus manure only 1. high density 1975 2. low density 1975
Comparison
Tilapia
Grass carp
Total difference
15% 24%
123% 111%
67% 40%
13%
52%
36%
72%
32%
18%
22%
66% 39%
-5% 5%
5% -1%
20% 24%
27% 24%
55% 2%
31% 37%
146% 167%
76% 67%
46% 24%
22% 35%
66% 56%
25% 29%
6% 4%
._
______-
D. High density minus low density 1. high-protein pellets 1974 2. grain pellets 1974 3. manure + grain pellets 1975 4. manure only 1975
-13% -27%
-36%
23%
(iv) In 1974 we measured the fat content of the common carp employing the method described by Ankorion et al. (1967). In the high-protein treatment we found an average fat content of 15% of total body weight as compared with 20% under “grain only” feeding. (v) The unweighted feed conversion ratio, i.e., feed weight divided by gained weight (henceforth FCR) was considerably lower in the high-protein treatments than in the “grain” treatments (Table II). However, after compensating for the higher cost of the former pellets, the cost efficiency becomes similar for the two feeding treatments at each stocking density. Complete
substitution
The two ponds day as compared fed, respectively, differently to the
of feeds by liquid cow manure
fed exclusively with liquid cow manure yielded to 33.7 and 24.1 kg/ha/day for the ponds of the with high-protein and grain pellets. Each species change in diet (Table III, part B). The common
19.6 kg/ha/ same density responded carp showed
32
the highest response to added food. The negative response of the grass carp to grain pellets is not understood and was not repeated in 1975. The fat content of the common carp in the “manure” treatment was 6.2% as compared with 15% and 20% for high-protein and grain feeding, respectively This pleasantly surprising result means that fish protein production in the “manure only” treatment was considerably higher than appears from comparison of total weights only. Furthermore, it shows that manure has a very high direct or indirect protein value and that it can substitute fish meal. Indeed, the difference in intra-muscular fat was so high that we were able to identify the fish grown in the “manure” treatment by the deeper red colour of their meat. In 1975 we compared “manure only” to manure supplemented with grain pellets. The comparison was conducted again at high and low stocking densities (Table II) and its results may be summarized by the following points: (i) Daily manure applications without supplementary feeding resulted in the remarkably high production of 32.7 and 31.5 kg/ha/day at the high and low densities, respectively. The increased production over that of the same treatment of the previous year (19.6 kg/ha/day) was presumably due to the higher rate of manuring (Table I). (ii) Supplementing the manure with grain pellets increased production by 8 kg/ha/day at both stocking densities. The common carp accounted for most of the added production (Fig. 1 and Table III, part C). -
COMMON
B
SILVER
CARP CARP
~UIDGRASS CARP 0
HIGH DENSITY FISHMEAL PELLETS
T/L APIA
HIGH LOW LOW LOW DENWY DEN.YTY DENSE DENSITY GRAINS fMM4L GRAlNS MhW?E PELLETS FTLLzrs /WLETS ONLY I 7 9 4
Fig.1. Total fish yields in tons/ha/l26 and 1975.
HIGH HIGH LOW LOW tK.fTY DENS.0-Y DENSITY DE&SfTY h%ANU&- MN#X MA&WE MANURE *GRAINS ONLY *GRAINS QNLY 1 9 7 S
days for the nine experimental treatments of 1974
33
(iii) The total amount of liquid cow manure added to the ponds throughout the whole season was 90 m3/ha, containing 10.8 tons of dry matter and yielding around 4 tons of liveweight of fish, that is a conversion of 2.7 kg manure (dry matter) to 1 kg of fish - a remarkable efficiency comparable to that of expensive grain. (iv) The FCR of the added grain at both stocking densities was about 1.2, not taking the manure into account (Table II). However, its marginal efficiency, i.e., the weight of supplemented grain pellets divided by the extra yield, was about 6.1. Thus, the addition of grain resulted in an inefficient increase in production. Response
to crowding
The proportional differences of “high” and “low” stocking densities at four levels of feeding inputs are shown for each species in Table III, part D, and are presented as regressions on feeding levels in Fig. 2. These results show: (i) The total response of production level to crowding is, clearly, a function of the feeding inputs (right-hand column, Table III, part D). Thus, under the best feeding regime, i.e., high-protein pellets, “high” stocking density was 46% more productive than “low” density; under the second best (grain pellets), it decreased to 24%; under the third (manure supplemented by grain) it dropped
MANURE ONi Y I975
MANURE PLUS GRAINS /97s
GRAINS PELL E TS 1974
FISH MEAL PE;L E TS 1974
Fig.2. The relationships of the proportional differences of the four fish species, between “high” and “low” stocking densities, to feeding levels.
34
down to 6% and under the lowest feeding level (manure only) to 4%. We may conclude, therefore, that in the last three treatments food constituted the major limiting factor to realizing the larger potential production of the high stocking. (ii) The individual response to crowding of each species is much more revealing than the average response. Thus, increased density of the common carp reduced its production by as much as 27% (Fig. 2). Silver carp, which feeds on phytoplankton, showed 22%-37% increased production at the high densities, independently of the feeding regime. Tilapia responded better than the other species to crowding at all feeding levels, indicating that higher densities than those tested may further increase production of this species. The varying responses of the different species may serve as useful guides in the search for an optimal “mix”.
Intermittent
harvesting
In the high stocking densities of 1975 we performed thinning-out by seining six times. The cumulative weights of fish removed are shown in Fig. 3, which also shows that the thinning-out procedures did not yield much higher yields than the single terminal harvest of the low stocking treatments. The total thinned-out harvest constituted about 40% of the total production. A probable cause for this failure was unbalanced thinning-out procedures. That is, most of the fish removed by the intermittent harvestings were silver carp and Tilapia. while it was the common carp that suffered most from the high densities. Thus, it is likely that the removal of the silver carp and Tilapia pushed the polyculture “mix” away from the optimum.
Growth curves The growth curves of the different fish species in all the nine treatments are shown in the diagrams of Fig. 4. Grass carp was omitted because only small numbers of this species were caught during the periodic weighings. Generally speaking, its growth curves appeared to resemble those of the common carp. Fig. 4. shows: (i) In 1974 and 1975 the common carp responded sharply to reduced crowding and improved feeding throughout the whole season. Thus, the common carp grew fastest in the low-density plus high-protein treatment of 1974 where it gained an average of slightly over 1000 g per fish in 126 days, that is 8 g per day. At the same stocking density, but with grain pellets, the average daily gain of carp was only 4.8 g. Furthermore, the divergence of the growth curves started almost from the beginning of the test, demonstrating, again, that under high stocking density carp requires protein-rich added feeds. (ii) Growth of the common carp during the first month in the “manure only” treatment of 1974 was faster than in all the other treatments, but subsequently it slowed down to almost a complete stop. This led us to double the amount of
35
COW
MANURE
m COMMON
PLUS
CARP
BISILVER
CARP
UUUGRASS
cA RP
0
GRAINS
HIGH DENSITY
TIL APIA
30.7
13.8 27.8
/7.9 DATE
COW MANURE
2.7
30.7
13.0 27.8
--
ONLY
I Z9
I.:0 /liO
5./f
5.‘/ DATE
Fig.3. The cumulative yields removed by multiple harvesting from the “high” density treatments of 1975. (The single harvest yields of the “low” density treatments were added for comparison.)
daily manure from 250 l/ha to 500 l/ha resulting in an immediate and dramatic improvement. Apparently the initial amount of manure became insufficient for maintenance and growth at the higher biomass. Only the common carp showed this marked dependence on the quantity of added manure. (iii) The silver carp responded to crowding but not to the type of feed. In 1975 growth of the silver carp ceased at the beginning of October in all the treatments. This may be due to deterioration of pond conditions at high fish biomasses or due to seasonal changes such as lower temperatures, shorter
36
n
LOW Dwslrr:
FLY-IMEAL f?zLErs
0
LOW DENsIrK
GQ/thvS PELLErs
lzDo,-
+
LOW DEAWrY.MAMJ?E
r I oo-
a M3i
1300.
,3OO
I200
ONLY
LxN.wY
fTiH MmL FELLETS OHIGHCEhs/ry.GRAINS PELLET-S
looo~2
SILVER
CAR
,,oo
1000
900.-
/
cw
2
900
cw
600.500.. 400..
‘7
30.7
26.8
29.9
4.0
I. 7
327
268
DA rE
WEGHJ
PWJ
61
WEIGHT /2W t
(G)
WEIGHT [GJ
---umDEmv MANl.Gf ONLY -¤HfG’iDENyJY MANLRE*GRM,S ---OLQYDENYJYMANU~E ONLY l LOW DEbiYJY MANLC)t.GRA,h,_?
.‘,W.
h30~ PJO 800
.
COMMON C
7001
J/L APIA
S/L VER CARP
s;:Ki7’278
::; I.10 DAJE
IN:,::::27
JO.7
278
::: L/O DA Jf
5.5 Y7
JOT
‘2Zh
b/O DATE
Fig.4. Growth curves of the common carp, silver carp and Tilapia. A (above): treatments of 1974; B (below): The four treatments of 1975.
5. Ii
The five
photo-period or changes in the phytoplankton population. (iv) In the case of Tilapiu, individual growth rates responded very little to feeding or crowding indicating that the present densities of Tilupia were suboptimal.
37
Daily production and feed conversion Figs 5A and 6A show the average daily yield increments, and Figs 5B and 6B show the equivalent FCR for the short periods of 2-4 weeks between sample weighings by seining. These curves show: (i) The highest daily yield increment (77 kg/ha/day) was reached in October 1974 in the treatment with high-density plus high-protein pellets, at a fish biomass of about 5 500 kg/ha. (ii) The two treatments with high-protein pellets showed an increase in daily yield increment up to a maximum reached in September-October. In the remaining treatments the highest daily yield increments were reached
0, 17
0 2 F
I57
3W
Ii!8
‘.
,4, .
8 LOW LXNS/JY. FLY-i MEAL ELLEJS 0 LOW DENSfrY. GRAINS PELLETS
12* ’
*LOW
DENS/TY. MANURE
0
fEx
29.9
Is./0
29.9
/S/O
r29
/6.’
0 MGH mmy. 5 $
26.8
DArE
4/f
ONLY
MEAL pELLErs
HIGH DENSITY. GRAINS PELLEJS
8,.
/7
/57
30.7
128
26.8
/29
4/l DA J.5 _
Fig&. Curves of daily yield increments and feed conversion ratios in the 1974 experiment. A: Average daily increments; B: Feed conversion ratios.
38
0 27
/6.7
307
13.8
2Z8
179
I/O
t5.10
5 II DA TE
Fig.6. Curves of daily yield increments and feed conversion ratios in the 1975 experiment. A: Average daily increments; B: feed conversion ratios.
in the first month of the tests. This suggests that some natural protein-rich food elements were in a limited supply and their relative scarcity increased with increased biomass. When high-protein feed was added, the size of the fish, particularly that of the common carp, became the limiting factor to growth so that with increased size daily production increased until the high biomass substituted feed as a limiting factor. (iii) The sharp rise in FCR in all the treatments towards the end of the experiment reached a disastrous level of 16 in the most productive treatment. This shows how important it is to harvest the fish before the marginal FCR becomes too high even if growth rate continues at a satisfactory level. DISCUSSION
The present experiments demonstrate that freshwater ponds without aera-
39
tion or water circulation can produce an average yield of 50 kg/ha/day for a period of 126 days in balanced polyculture and high densities when supplied with abundant high-protein feed. More impressive is the production of 32.7 kg/ha/day when liquid cow manure was substituted for feed. A quantity of 22.6 1 liquid manure of 12% dry weight was required for the production of 1 kg fish, that is, a conversion ratio of 2.7 kg dry matter of manure to 1 kg fish. Our results were compared with those of two other experiments reporting record yields (Table IV). Rappoport and Sarig (1975) tested monoculture of carp and Tilapiu at very high densities in ponds continuously and intensely aerated and fed with high-protein pellets. Both carp and Tilapiu yielded over 120 kg/ha/day at FCR levels similar to or poorer than those common for wellfed unaerated ponds (unfortunately the experiment did not have a control). Chaudhuri et al, (1975) tested polyculture mixes of Indian and Chinese carps with heavy feeding and manuring. The experiment lasted for a full year but the authors noted that “application of fertilizers and feed was reduced and, at times, suspended during the summer months when the water level was low and algal blooms developed”. To compensate for this period of reduced growth we arbitrarily standardized the experiment to 300 full days of growth. With this the computed daily production was 30.3 kg/ha/day, a reported new record for India. Multiple harvesting should result in higher yields than a single seasonal or annual harvest as is illustrated schematically in Fig. 7. A pond filled with fresh water at the beginning of a “season” must have some optimal fish biomass level for maximal daily gain. At lower biomass levels the pond’s poten tial is not fully utilized, while at higher levels over-crowding has detrimental effects on yields and FCR. Under intensive fish culture of high stocking and feeding rates in stagnant water the pond conditions, as a medium for fish growth, gradually deteriorate. This may be due to: (i) sub-optimal disolved oxygen levels, particularly at night; (ii) accumulation of growth-inhibiting factors; (iii) smaller volumes of pond organisms serving as food for the fish; and (iv) increased density of the pond organisms not serving as fish food while competing with them for food and oxygen. Thus, the optimal biomass level probably decreases gradually as shown in Fig. 7. Under a single harvest system the fish biomass is far from the optimal level for most of the season. High initial (stocking) biomass plus frequent harvesting should overcome this limitation. With polyculture the rate of deterioration in pond conditions is presumably slower than with a monoculture system of equivalent biomass and management. Unbalanced thinning-out in polyculture makes the system more similar to monoculture and therefore may not result in the expected enhancement of production or may even have detrimental effects. The apparent absence of a positive response to thinning-out procedures in our 1975 experiment may be due to the relatively severe thinning-out of the plankton-eaters, silver carp and Tihpia, rather than the overcrowded benthos-eater, common carp.
126
126
111 105
High-protein pellets + high stocking density + polyculture
Manure only + high stocking density + polyculture
Manure + grains + high stocking density + polyculture
Forced aeration + carp monoculture + very high stocking density ponds 16-18 pond B
1. Dor, 1974 Present results
2. Dor, 1975 Present results
3. Dor, 1975 Present results
4. Genosar, 1975 (Rappoport and Sarig, 1975)
126
Duration (days)
Treatment of ponds
Experiment and reference
Comparisons of present results with others
TABLE IV
15 550 12 630
5 212
4 121
6 282
140.1 120.3
41.3
32.6
49.8
57 100 32 000
6 670
-
15455
(kg/ha)
(kg/ha)
-
-
-
-
Aquatic weeds
Concentrates
Daily
Total
Bran
Feeds and manure (kg/ha)
Fish production
113 500
113 500
Cow dung**
3.7 2.5
1.28
0
2.46
FCR*
41
0 0 N
42
. CUtlMULATlVE HARVEST)
BIOMASS UNDER
(INCLUDING
,
’
/
‘MULTIPLE
/
HARVESTING’
/ /
/ /
‘SINGLE HARVEST’ BIOMASS
y
TtilNlNG
2N” T. OUT
&MA,
1 e’oMASS
t $0
$I
T. OUT
1. OUT
OUT
1
POND FILLED WI Ttt FRESH WATER AND STOCKED WITH FfSH
m4E ALL
f POND EMPTIED F/SH REMOVED
Fig.7. Schematic presentation of the expected relationships between optimal, single-harvest and multiple-harvest biomasses and yields.
As discussed elsewhere (Hepher and Schroeder, 1975), the effectiveness of liquid cow manure in fish culture may be based on a food chain that starts with bacteria and protozoa active in the decomposition of the organic matter in the manure. Since this chain is not directly dependent on photosynthesis (as is the case with chemical fertilizers), the inherent limits of sunlight penetra tion into the pond water are by-passed and the production of natural foods may be limited only by nutrient supply, i.e., by the amount of manure and dissolved oxygen present in the pond water. In liquid manure of&n more than 30% of the total dry matter is colloidal. These “fines” provide a base for bacterial and protozoan growth throughout the water column, as well as on the pond bottom. Thus the entire pond is made to be productive. ACKNOWLEDGEMENTS
This research was supported by a grant from the United States-Israel Binational Science Foundation (BSF), Jerusalem, Israel. We gratefully extend our thanks to the many technicians, colleagues and students who helped us in carrying out the many chores of running these complex and labour-intensive experiments.
43
REFERENCES Ankorion, J., Moav, R. and Wohlfarth, G., 1967. A “modified Gerber method” for rapid determination of fat contents in fish. Bamidgeh, 19: 46-49. Bardach, J.E., Ryther, J.H. and McLarny, W.O., 1972. Aquaculture. The farming and husbandry of freshwater and marine organisms. John Wiley, New York, 868 pp. Berka, R., 1973. A review of feeding equipment in fish culture. EIFAC Occas. Pap., 9: l-32. Chaudhuri, H., Chakrabarty, R.D., Sen, P.R., Rao, N.G.S. and Jena, S., 1975. A new high in fish production in India with record yields by composite fish culture in freshwater ponds. Aquaculture, 6: 343-355. Hepher, B. and Schroeder, G.L., 1975. Wastewater utilization in Israeli aquaculture. Proc. Int. Conf. on Renovation and Recycling of Wastewater through Aquatic and Terrestrial Systems, Rockerfeller Foundation and Institute of Water Research, Michigan State University, 29 pp. Hoffmann, W.E., 1934. Preliminary notes on the fresh water fish industry of South China, especially Kwangtung province. Lingnan Univ. Sci. Bull., No. 5, 70 pp. (Lingnan Univ., Canton, China). Lin, S.Y., 1954. Chinese system of pond stocking. Proc. Indo-Pacific Fish. Council, 65-71 Moav, R., Soller, M., Hulata, G. and Wohlfarth, G., 1976. Genetic aspects of the transition from traditional to modern fish farming. Theoret. Appl. Genet., 47: 285-290. Pruginin, Y., Rothbard, S., Wohlfarth, G., Halevy, A., Moav, R. and Hulata, G., 1975. All-male broods of Tilapia nolotico X T. aurea hybrids. Aquaculture, 6: 11-21. Rappoport, U. and Sarig, S., 1975. The results of tests in intensive growth of fish at the Genosar (Israel) station ponds in 1974. Bamidgeh, 27: 75-82. Schroeder, G.L., 1973. Factors affecting feed conversion ratio in fish ponds. Bamidgeh, 25: 104-113. Schroeder, G.L., 1974. Use of fluid cowshed manure in fish ponds. Bamidgeh, 26: 84-96. Schroeder, G.L., 1975. Nighttime material balance for oxygen in fish ponds receiving organic wastes. Bamidgeh, 27 : 65-74. Tang, Y.A., 1970. Evaluation of balance between fishes and available fish foods in multispecies fish culture ponds in Taiwan. Trans. Amer. Fish, Sot., 99: 708-718. Wohlfarth, G., Moav, R. and Hulata, G., 1975. Genetic differences between the Chinese and European races of the common carp. II. Multi-character variation - a response to the diverse methods of fish cultivation in Europe and China. Heredity, 34: 341-350.