118

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;

120

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):

121

- 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".

123

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.

124

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

125

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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