designing new fish farming models adapted to rural côte d
TRANSCRIPT
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Designing New Fish Farming ModelsAdapted to Rural Cote d'lvoire
P. MORISSENS·Centre de cooperation internationale en recherche agronomique pour le
developpementDepertement ci'elevege et de rnedecine veterinelre (C1RAD-EMVT)
Programme aquaculture et pecheBP 5095, 34033-Montpellier Cedex I, France
andInstitut des Savanes (IDESSA)
BP 621 Boueke 01, Cote d'Ivolre
M.OSWALDMission de cooperation et d'ection culturelle (MCAC)
oI BP 1839 Abidjan 0 IProjet de developpement de la pisciculture en milieu rural
BP 494 Bouake 0 I, C6te d Tvoire
F. SANCHEZAssociation Irenceise des volontaires du progres (AFVP)
BP 2532 Abidjan 01, C6te d'Ivoire
S. HEMCentre de recherches oceenologiques
Institut tren cels de recherche sclentitique pour le developpernent encooperation (CROjORSTOM)
BP VI8 Abldjen, C6te d Tvotre
MORISSENS, P., M. OSWALD, F. SANCHEZ and S. HEM. 1996. Designing new fish farming modelsadapted to rural COte d'lvoire, p. 118-12.8. In R.S.V. Pullin. J. Laz.ard , M. Legendre, J.B. AmonKothias and D. Pauly (eds.) The Third International Symposium on Tilapia in Aquaculture. ICLARMConf. Proc. 41,575 p.
Abstract
The study of constraints affecting the development of fish culture in rural Cote d'lvoire hasshown that it is impossible to use farming methods that require expensive inputs such as supplementaryfeed. In contrast, farmers are willing to devote much of their time to fish culture if their work isadequately compensated.
When available, most inputs really accessible to farmers have a poor nutritional and/or fertilizingvalue. The efficient use of the limited trophic resources can be done through: (1) the qualitativeand/or quantitative improvement of the flow of substances in the different levels of the pondtrophic web (direct feeding, autotrophic productivity and heterotrophic microbial productivity)and (2.) improvement of the accessibility to trophic resources by the fish. The present study isbased on on-farm and on-station experiments focusing on: (1) the improvement of culture environment(treatments based on use of rice bran to which green manure mayor may not be added, and oncombined fish and rabbit culture) and (2.) the use of a substratum made of bamboo or branches(acadja) to improve fish accessibility to primary production (attempts to substitute commercialfeed by acadja system in lagoon pens have already been giving promising results).
-Current address: clo PCAMRD, Dr. Alfonso Eusebio Bldg., BPI Economic Garden, Los Bafios, Laguna,Philippines.
1 19
The results from this study confirm the importance of adding substrate for primary producers,of combining fish and rabbit culture and of using green manure for the improvement of pondproduction. New approaches for research and R&.D in low input fish culture are suggested.
Introduction
During the last 15 years, considerable efforts have been made to developtilapia culture in rural environments invast areas of Cote d'lvoire (see also Koffiet aI., this vol.). The extension ofaquaculture to these areas has beenbased on three types of pond inputs:
- commercial feed containing about25% protein;
- combined chicken and fish culture;and
- the use, in the form of a compostgenerally located in a corner of the pond,of inputs available on-farm and oftenof low nutritional and/or fertilizing value.
The treatments giving the highest fishyields are-provided that fish farms areadequately managed-those consistingin commercial feed and combined livestock farming. However, the use of thesetechniques in rural areas is paradoxically declining whereas "poor" treatments essentially based on the use ofrefuse from artisanal processing of riceor other cereals continue to develop(Morissens et al. 1993). For Copin andOswald (1988), Oswald and Copin(1992), and Koffi (1989 and 1992), thisphenomenon is basically due to the factthat returns on cash investments areconsidered by farmers to be lower infish culture than in other agriculturalundertakings. In contrast, farmers arewilling to devote a substantial part oftheir time to fish culture if their workis adequately remunerated. This trendof culture diversification is reinforcedby the current crisis affecting cash crops(coffee and cocoa).
Today, the development of fish culture in rural areas is influenced to a largeextent by the possibility of introduc-
ing farming systems that are essentiallybased on labor inputs. The establishment of these systems will be all themore important as the requirements forworking capital will be low, even nil.
In addition, the absence of agricultural by-products for use in fish cultureis a general characteristic in most Ivorianvillages and, generally, on the Africancontinent. Only large villages, with smallartisanal hulling machines, can producerice bran or maize bran of relatively poornutritional and/or fertilizing value forlocal use. In this context, the challengeis to introduce farming systems thatwould eliminate constraints related tosupply of inputs for most farmers. Preserving self-reliance, the only guarantee of a sustainable development in thecurrent context, is a concern that mustlead to studies on the efficient use offresh plant biomass (grass) for fish culture, by perhaps establishing a smallscale animal breeding unit for its transformation.
In this context, the use of resourcesof low nutritional and/or fertilizing valueis inevitable. One of the major characteristics of these "poor" treatments istheir poor palatability for the fish. Consequently. their effect through directconsumption by the fish is limited, buttheir fertilizing effect is certain (Dernbeleetal. 1991).
The more efficient use of trophic resources produced by this type of fertilization is made possible through:
1. The qualitative and/or quantitative improvement of the flow of substances in different trophic levels of the"pond" ecosystem. Solutions proposedin this area are:
combined rabbit and fish culturewithout supplementary rice bran;
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combined rabbit and fish culturewith supplementary rice bran; and
association of a burrowing fish,to resuspend sediments, and thus stimulates the heterotrophic web.
2. Improved accessibility of the fishto resources of the trophic web. Here,the proposed systems are polyculture(systematically practiced in rural areas)and the establishment of a substratumof bamboo or branches, based on theacadja system used for capture fisheries in the lagoons of Benin. Experimentsusing a bamboo substrate in freshwater ponds have shown significant increases in biomass harvested comparedto control ponds without artificial increase of substrate (Hem 1991). Thistechnique mobilizes the mineral resources of the pond for growth of algae or related organisms (periphytonor aufwuchs) around the bamboo poles,a primary resource that is accessible tofish. In the ponds without substrate, mostof the primary production derives fromnanoplankton that cannot be used byfilter-feeders such as tilapia (Spataru1977).
Experiments with farmers combinerabbit and fish culture, implantation ofacadjas and use of rice bran. Other related experiments using green manureand acadjas are conducted at the fishresearch station of the Institut desSavanes (IDESSA) in Bouake.
On-farm Experiments In RuralMidwestern Cote d'lvolre
Methodology
The small group of test farmers withwhom experiments were conducted issocially homogeneous (Koffi et aI., thisvol.). All know fish culture well. Oncethe phase of pond construction wascompleted, all farmers met problems in
the supply of pond inputs (rice bran ornutrients). This showed the poor levelof adaptation of the model to socioeconomic conditions. However, some fishfarmers showed interest in testing newproduction models. In Midwestern Coted ' Ivoi re, test farmers were extremelymotivated as fish culture constitutes anessential activity of their work calendar and their ponds are well constructed(dikes, monk drain and drainage system).
The results presented here are thoseof culture cycles in farms that are fullyproductive. This production setup implied a minimum of five ponds (average surface = 0.045 ha) of which twowere used for broodfish and fingerlingproduction. The water used for theseponds was not suitable for fish culture,with pH values varying between 5.5 and7, and very low conductivity (siliceoussoils or water high in humic acids).
Innovations for which the farmersshowed interest were:
1. The acadja system: In ponds thatcan be drained, the implantation of asubstrate made of 10 bamboom' represents an investment that will be amortized over several years.
2. Combined rabbit and fish culture:The association of livestock to othercultures is always described as a veryefficient production system. Under smallscale farming cond itions, the onlyintensive (battery) production systemthat requires hardly any of the costlycommercial feeds-and therefore involves limited cash expenses-is rabbitculture. Farmers who attempted theintensive farming of pigs and chickenswere soon confronted with diseasescaused by inadequate feeding practices.Moreover, intensive farming systemsrequire large quantities of inputs anda working capital that farmers cannotsustain. The use of rabbits in integratedfarming systems has been described aspromising (Little and Muir t 987).
Fish culture here is always based onpolyculture, the dominant species being the male Oreochromis niloticus inassociation with a strictly carnivorousfish (Parachanna obscura or Hemichromisfasciatus) , Heterotis niloticus and catfish (generally, Heterobranchus isopterusand rarely H. longifilis). Labeo coubiewas used on two occasions.
The proposed techniques were derivedfrom the results of a biotechnical andsocioeconomic analysis of the farms.Discussions with fish farmers were essential to assess their constraints.
Support services proposed a range oftechniques among which the farmercould choose. They also had the optionto reject the proposed techniques. Whena particular technique required funds,the support services contributed to theinvestment (purchase of rabbits, transportation of bamboos, etc.) but theynever contributed to operating costs.
It is difficult to draw scientific conclusions from the comparison of technicalresults obtained from different fish farmers.Too many varying factors are involved.However. even under these conditions,the results from a single culture operation(and its development with time) areinteresting and their analysis by the fishfarmers themselves contribute to tryingnew approaches when necessary.
TechnIcal Results
Research was conducted on the following farming systems (see also Tables 1 and 2):
1. Rice bran-based treatments (TableI ):
- use of rice bran alone;- use of rice bran in the acadja sys-
tem; and- use of rice bran with rabbit culture
(rabbit pens on stilts).2. Treatments without rice bran (Ta
ble 2):
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- rabbit culture alone;- acadja fertilization using the feces
of rabbits reared outside fishponds; and- acadja and rabbit culture (rabbit pens
on stilts).
Discussion and Conclusions
TechnIcal Results
The acadja production system, and theuse of rabbits, are excellent techniquesto complement rice bran-based treatments. Yields of 2.3 t-hat-year' (acadjarabbits) are produced without any inputother than grass (fresh plant biomass),l.e., this technique does not require anycash expense. Fertilization is assuredby using three rabbits, weighing a totalof about 5 kg and producing 800 g offeces-day': which corresponds to about200 g of dry matter (4.6 kgDM·ha,l·day,I). Inputs of dry matter
remain very low compared to the usualstandards applied to tropical integratedlivestock farming, Le., 75-50 kgDM'ha"'day,1 (Hopkins and Cruz 1982;Morissens et al. 1993).
It appears, but this should be confirmed,that the association of tilapia-Labeo withacadja is detrimental to tilapias becauseof their identical, and therefore, competingdiet. It seems also that H. longifilis is apredator of P. obscura, another predatorof tilapias. This arrangement would reduceeffective control of 0. niloticuspopulations.
Several parameters are still to be defined: stocking densities for differentspecies used, number of rabbits andbamboo density. In any case, the acadjarabbit technique can be efficient onlyif fish farmers gain mastery of the stocking of ponds with carnivorous fish tocontrol the proliferation, due to sexingerrors, of tilapia fry and of the rigorousmanagement of pond water (no overflow at the monk drain).
Table 1. Results of culture experiments using rice bran alone, rice bran and acadja, and rice bran with rabbits and 0.04 to0.05-ha fishponds.
NN
Treatment
Rice bran alone
Rice bran withacadja''
Rice bran' andrabbit culturein pens on stilts
(283 rabbits'ha')13 rabbits/0.046 ha
Density Duration lOG' Net yield
Cycle Species (Indrn") (day) (g'day") (t'ha"'year")
1 Oreochromis niloticus 1.6 253 0.3 1.12 O. niloticus 1.7 181 0.3 1.33 O. niloticus 1.3 95 0.6 1.6
O. niloticus 1.43 134 0.88 4.75Heterobranchus isopterus 0.1 134 0.86 0.3
0. niloticus 1.57 119 1.2 6.1Heterotis niloticus 0.01 119 2.9 0.1fry H. niloticus 0.3H. isopterus 0.11 119 0.9 0.3Parachanna obscura 0.03 119 0.2 0
'lOG: individual daily growth.
b6 kg rice bran vday: and 10 barn bo o st m".'6 kg rice branclay".
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Table 2. Combined fish and rabbit culture (hutch on stilts), with or without acadja, in 0.04 to 0.05-haearthen ponds + rice bran.
Density Duration lOG' Net yield
Treatment Cycle Species (Indrn") (day) (g'day") (t'ha"'year")
Rabbits 1 Oreochromis niloticus 1.8 82 0,3 1.517 rabbitsl Heterotis niloticus 0.01 82 0.3 0.2
(370 rabblts-ha') 0.046 ha Hererobranchus isopterus 0.11 82 -0.3 0Peractienne obscura 0.03 82 0,3 0
2(180 rabbits'ha") 9 rabbits! 0, niloticus 1.2 168 0.13 <0.6
0.05 ha
Rabbits + acadja+ terttttze tton" O. niloticus 1.0 122 0.7 1.6
feces fry 0, niloticus 0.98 rabbits! H. isopterus 0, t 3 122 -0.6 0.2
(178 rabbits'ha") 0,045 ha Heterobranchus longifilis 0,004 122 12.9 0.2Labeo coubie 0,01 150 3.6 0.1
Rabbits + acadja- 1 O. niloticus 0.8 141 0.7 2,13 rabbits! H. niloticus 0.2 141 3.0 0.1
(71 rabbtts-ha') 0.0425 ha fry H. niloticus 0.3H. isopterus 0.08 141 -0.18 0P. obscura 0,03 141 0.1 0more fry(mean weight about 2 g)
2 0, niloticus 0.6 56 0.6 1.27 rabbits! H. niloticus 0,02 56 12.4 0,8
(156 rabbl t s-ha") 0.045 ha H, isopterus 0,11 56 0.3 0.1L. coubie 0.01 56 1.6 0P, obscura 0,01 56 -0.2 0
'IDG: individual daily growth.bAcadjas and fertilization using feces produced outside the farm, A bucket of the excreta of eight rabbitswas poured each day in the pond (an average of 3.75 kg of manure per day corresponds to 500-600 g ofdry matter. Pond ~ 0.045 ha).<During this cycle. water management was poor: frequent overflow at the monk drain with possible negativeeffects on production (loss of nutrients),
Chifnges In Fish Farmers' Behdvlor
Fish farmers have been favorably impressed by increases in yields and ingrowth rates observed in the cyclesacadja-s rice bran and rabblt se rlce bran.However, the supply of rice bran is stilla constraint for them. Surprisingly, themodel rabbite bamboo has modified thebehavior of the two fish farmers concerned, i.e., they have been devotingmore time to fish culture since theyobtained their first results. One of them
suggested to plant himself a second pondwith bamboos (only the transportationof bamboo is subsidized). The most characteristic comment on their part was:"these fish are gifts!"
E.xperiments without rice bran did notyield expected results. Yields in marketable fish remained low compared to theamount of work involved. A significantincrease in yields is still possible witha few improvements in water management, stocking, and in the number ofrabbits used.
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Nevertheless, the motivation expressed and demonstrated by the farmersto continue the experiment, and theirappreciation of the first results, areencouraging. This will contribute to theestablishment of culture systems likelyto resolve the constraints that todayhinder the development of fish culturein rural Cote d'lvoire and generally insubSaharan Africa.
On-station Experiments
Supplementary fertilization usingrice bran with dry chicken manureor grass
OBJECTIVE
The experiment aimed at assessingthe effects of supplementing coarse ricebran (first polishing) as standard feedin the fishponds with dry chicken manure or grass. Dry chicken manure isreadily available in pert-urban areas.
METHODOLOGY
The experiment was conducted in 400m 2 ponds at IDESSA fish culture stationin Bouake using a mixed population ofO. niloticus males (1.95 lnd m,2) andClerles gariepinus (0.25 lnd-rn"). Threetreatments were applied and replicatedat a different time: rice bran alone (control); rice bran with supplementary fertilization using dry chicken manure; andrice bran with supplementary fertilization using fresh grass (Pennisetumpurpureum) .
Daily rice bran application rates varied from 52 kg-daytpond' at the startof the culture period, to 11.6 kg·day,l.pond:' at the end of the period (seventh month). For the entire productionperiod, dry chicken manure was usedat a rate of 2.4 kg'day-I'pond'l and fresh
grass at 32 kg-d ayI-pond". These twofertilization regimes were almost equivalent in terms of nitrogen input. At theend of the culture period, the quantityof dry matter used in the ponds reacheda maximum of 240 kg' hal-day' for ricebran alone, 300 kg' hatday' for ricebran s chlcken manure and 360 kg-ha.":day' for rice bran-igrass.
RESULTS
Tables 3 and 4 present the results ofthe experiment. Comparisons of treatments relying on randomized blockanalysis of variance (ANOVA) did notshow any significant difference amongtreatments in terms of yields for O.niloticus and for combined O. niloticusand C. gariepinus, nor in terms of feedconversion ratios. However, results onmean daily growth and mean yield werehigher in the grass treatments. Additional replicates are needed to confirmthis trend. The analysis of variance revealed a "block" effect and significantlyhigher values in terms of growth andyield for C. gariepinus in the treatmentusing rice bran+grass.
DISCUSSION
Yields ranging from 4 to 6.3 tha":year,l are "normal" with regard to feedand fertilizers. We can, of course,question the need to cut and distribute 292 t'ha,l'year-1 of fresh grass foran increase in production of 1.4 t·ha-I.year' over the volume obtained usingonly rice bran. The remuneration for cutting the grass depends essentially onthe quantity of grass available and itsproximity, and on the time spent for agiven harvest. We can estimate, therefore, that an annual distribution of 290t-ha' will require a minimum of 4,500hours of world However, it is possiblethat in the context of small-scale farming
characterized by limited access to ricebran and low or irregular inputs of thisresource, the "grass effect" could bemore significant even if the yields arelower than those recorded here (seeabove for the yield results in treatmentsusing rice bran in on-farm experiments).
The significant differences recordedbetween the grass treatment and theother treatments in terms of individualgrowth and yield for Clarias show a linkbetween treatment and stimulation ofa trophic resource specifically accessible to CIarias. This demonstrates thatin these conditions, polyculture is morelikely to optimize the use of this treatment than monospecific stocking usingO. niloticus males.
It would be interesting to assess theeffect of a grass treatment on a culturecombining 0. niloticus, catfish, and H.niloticus. The burrowing behavior of H.niloticus, which is largely establishedin rural fish farms, is likely to promotethe suspension of great quantities ofgrass-derived sediments which, in turn,promote microbial production (CostaPierce and Craven 1987; Costa-Pierceand Pullin 1989) and may have positive effects on the entire heterotrophicand autotrophic webs (Schroeder 1983;Spataru et al. 1983).
In addition, following the first testsconducted in lagoons and in ponds (Hem1991), an experiment was set up at the
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IDESSA station using four replicatedtreatments. These treatments consistedin: (1) using rice bran (without substrate);(2) providing a substrate made of 10barnboosm" without feed supplement;(3) providing a substrate constituted by10 barnboosm" with rice bran as feed;and (4) providing a substrate made of32 branches of Cesslertv? with rice branas feed. The objective of this experimental design was to assess the significance of feed-substrate interactionand the ability of a substrate made ofordinary branches to provide a vertical surface roughly equivalent to thatof the bamboo substrate.
The few tests done so far on-farm aswell as on-station have not yet led tothe development of farming techniquesthat would totally free the farmers fromtheir input constraints. Further testingis needed on systems combiningsubstrate, green manure, polyculture andresuspension of sediment, as well as onthe stocking densities best adapted tothe productivity of these systems. Theidentification of the interactions that theassociation of these techniques involvesrequires much experimental support.Ideally, this type of research should besupported by a more fundamental studyof the complex trophic mechanisms thatlink farming techniques and treatments.on the one hand, and farming techniquesand production. on the other. Regarding
Table 3. Summary results from different tests (net yields in t·ha-I. y ea r")."
Rice bran-basedtreatment
Without rabbits With rabbits
Culture systemwithout rice bran
With rabbits
Without acadjaWith acadja
< 2 (3)5 (t)
6 (1)
(0)
< 2 (2)2.3 (2)
"Figures in parentheses represent the number of cycles studied.
Table 4. Supplementary fertilization using dry chicken manure or grass in a culture experiment with Oreochromis niloticus and Clarlas garlepinus fedwith rice bran in 400-m ' ponds.
Density Individual daily growth Feed conversion Yield(Indm") (g-d ay ") ratio (kg-hat-year")
Species/treatmen t Block 1 B·lock 2 Block 1 Block 2 Mean' Block 1 Block 2 Block 1 Block 2 Mean'--O. nilottcus
Rice bran alone 1.95 1.95 1.12 0.82 0.97 11.91 15.23 5.488 4.023 4.755.5(0.15) (732.5)
Rice bran + manure 1.95 1.95 1.13 0.92 1.025 10.32 13.57 6,337 4.545 5.441(0.115) (896)
Rice bran + grass 1.95 1.95 1.13 1.16 1.145 10.97 10.06 5.643 5,864 5.753.5(0.015) (110.5)
C. gariepinusRice bran alone 0.25 0.25 0.55 0.30 0.425 11.91 15.23 236 44 140
(0.125) (96)Rice bran + manure 0.25 0.25 1.56 0.30 0.59 10.32 13.57 379 23 201
(0.03) ( 178)Rice bran + grass 0.25 0.25 0.96 0.62 0.79 10.97 10.06 674 294 484
(0.17) (190)
'Figure in parentheses are standard deviations.
N01
this point, research work based on twocomplementary approaches is proposed:
1. Study of the flow of matter in thedifferent levels of the food chain byplotting stable isotopes of carbon (CIZand C13) (Schroeder 1978, 1983 and1987), and investigation on what becomes of the major minerals contributed by the treatments (Krorn et al. 1985and 1989).
2. Companion study on the environment potential trophic resources andof the fish's stomach contents (Spataruet al. t 983; Milstein et al. 1985a, 1985band t 988; Hepher et al. 1989).
These approaches should lead to acomprehensive assessment of the impact of different techniques or combination of techniques used at differentlevels of the ecosystem and to the identification of bottlenecks and trophicdeadends.
The adaptability of the proposed techniques to rural conditions will be determined by the fish farmers themselves.To this effect, it is important to notethat the feedback between fish farmers and support services has had Cl majorimpact on the direction of the ideaspresented here on the use of "poor"treatments.
It is possible to imagine that a technical model tested in rural conditions(example: acadja-i-grass-r polyculture including burrowing fish) will be massivelyadopted by farmers. In this context, therewill be scope for its rapid optimizationby the fish farmers themselves dependingon their specific constraints.
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