optimization of dugout fisheries for climate change adaptation in northern region, ghana

JENRM, Vol. I, No. 1, 63-68, 2014Research Article

Optimization of dugout fisheries for climate changeadaptation in Northern Region, GhanaEtornyo Agbeko1*, Kwadwo Kwarfo-Apegyah1,Daniel Nsoh Akongyuure 2

AbstractThe fisheries sector is one of the climate sensitive areas that could be impacted by climate change. Increases in temperature,floods or drought will alter water level/availability for growth and survival of most fishes in dugouts. Adaptation strategiesare needed to respond or cope with actual and projected dwindling of inland fish stock. Northern Ghana abounds withnumerous dugouts and reservoirs which could be harnessed for higher fish production in view of climate change. A Tilapiais proliferous fish that can tolerate harsh climatic conditions including fluctuating water levels and high temperature. Thispaper assesses Tilapia; Oreochromis niloticus for fish stock enhancement in water stress dugouts. Effects on fish stocks wasdetermined through fish catch assessment and water quality monitoring. Total fish catch was sorted into species, enumeratedand weighed. Results showed that the survival rate of the Tilapia (O. niloticus) stocked under extensive culture system was99.6% excluding predation. This study indicates that O. niloticus was ideal for fish stock enhancement and could be adoptedto increase fish yield, improve adaptation to climate change and increase economic returns from dugout fisheries. The studyalso revealed that water quality of dugouts improved due to good fishery management intervention.

KeywordsFish stocks Tilapia Dugout Climate change fish catch

1Council for Scientific and Industrial Research - Water Research Institute, P. O. Box M. 32, Accra, Ghana.2University for Development Studies, Department of Fisheries & Aquatic Resources Management, P. O. Box TL 1882, Tamale, Ghana.*Corresponding author: [email protected]

Content

Introduction 63

1 Materials and Methods 641.1 Study Area . . . . . . . . . . . . . . . . . . . . . . . . . . . 641.2 Stocking and Fish Catch Assessment . . . . . . . . . 641.3 Water quality monitoring . . . . . . . . . . . . . . . . . . . 641.4 Statistical Analysis . . . . . . . . . . . . . . . . . . . . . . 64

2 Results 65

3 Discussion 67

4 Conclusion 67

Acknowledgments 67

References 67

IntroductionTilapia is the most cultured fish native to Africa. The fish is adelicacy and serves as significant nutritional source of protein-rich food. Ghanas fisheries sector employs over 2.2 % ofthe total national workforce compared to 1% from commerceand industry [18]. Two million people are said to be involvedin the fisheries sector. Ghana is purported to be among thehighest fish consuming countries in the world, with per capitafish consumption of 25 kilograms, while the world averageis 13 kilograms. The Ghana government imports fish to thetune of $157 million dollars to make up for the shortfall in

national production, despite having marine, brackish and nu-merous inland freshwater bodies in the country. National fishproduction interest is usually based on resources from Marine,Volta and Bosumtwi lakes, lagoons, rivers, dams, reservoirsand aquaculture. Average contribution of reservoir fisheries(culture-based) to national fish production is 150 kg/ha/yr. Theestimated production from the commercial cage culture fa-cility is 200 tonnes/ha/yr valued at US$ 0.316 million [11].Estimated growth rate of Gross Domestic Product (GDP) byfishing sector declined by 8.7 percent in 2011 [12]. Littleattention is paid to enhancement of depleting fish stock andmanagement of water bodies including dugouts. Dugouts are3-sided embankment troughs filled with water runoffs that flowalong the slope of open side. In water stress areas, dugoutsprovide potable water and serve as receptacles for fish stockthat have strayed into spillover water from flooded reservoirs,rivers, rivulets, and streams during rainy season. Global warm-ing/cooling and variability in rainfall pattern causing floods,long dry spells or drought have resultant effects on fish stock.According to the Food and Agriculture Organisation [10], cli-mate change coupled with over-capitalization and recruitmentoverfishing at lower densities could cause decline in ichthy-omass of individual fish species, reduction in population sizeand possible extinction of less thermal referenda fish species.In Ghana, it is estimated that temperature will continue to riseon average by about 0.8 0C, 2.5 0C and 5.4 0C by the year 2020,2050 and 2080, respectively [17]. Rainfall is also projectedto decrease in all agro-ecological zones [16]. Anthropogenic

Optimization of dugout fisheries for climate change adaptation in Northern Region, Ghana 64/68

activities such as recruitment over-fishing, crop farming, bushburning, deforestation and over-grazing on the embankmentand catchment areas have exacerbated the impacts of climatechange on water storage systems like reservoirs and dugouts.The availability of high quality protein foods like fish presentsuncertainties triggered in extreme ways by climate change.Adaptation is needed as a response strategy to adjust to ac-tual or expected climate and its effects, in order to moderateharm or harness potential opportunities [13], [6]. Adaptationto climate change in Ghana is in its early stages, especiallyin relations to fisheries and the aquatic ecosystem. Thus, nocomprehensive fishery policies exist on tilapia culture for cli-mate change adaptation. As a preliminary study, the paperaims to assess the performance of capture fish production withthe introduction of fast growing Tilapia species, improvedAkosombo strain of Oreochromis niloticus and its associatedactivities on water quality in water stress dugouts.

1. Materials and Methods1.1 Study AreaThe Mawulea and Zialuwa dugouts are perennial water re-source with an approximate area of 0.5 and 1.2 hectares, re-spectively. Both dugouts are located in the eastern corridor ofthe Northern Region of Ghana between Latitude 9o1530 N 9o1530 N and 0o1030W 0o1430W and 00o 150o

East (Figure 1). The Greenwich Meridian passes through anumber of human settlements around the catchment area of thedugouts. Mean annual rainfall for the area is 1,125 mm (Jan-uary - December). Mean wet season rainfall (April- October)is 1,150 mm. Mean dry season rainfall (November March)75mm. Mean annual deficit is between 500 mm and 600 mm[21]. Rainfall is seasonal and erratic. Atmospheric temperatureranges between 21oC - 40oC giving rise to high temperaturerange. Increasing atmospheric temperature, anthropogenic ac-tivities such as excessive bush burning and farming activitiesclose to dugouts affects the ecosystem and ecotone of dugouts.

Figure 1. Maps of Ghana showing Northern Region anddugouts studied

1.2 Stocking and Fish Catch AssessmentTilapia species, Oreochromis niloticus was selected basedon principles for stock enhancement adopted from [9]. Twodugouts were stocked with a total of 6,500 fingerlings of Ore-ochromis niloticus (improved Akosombo strain) with meanweight 30 g each. Five hundred (500) fingerlings out of the6,500 were tagged for identification and growth assessment.Capture-Release-Capture method for fish assessment was con-sidered for the tagged fishes. The survival rate (SR) of O.niloticus (Improved Akosombo strain) under extensive culturein the dugouts was calculated based on the formula below;

(Number of fish survived / Number of fish stocked)100Where, number of fish survived represents number of fishcaught from fish stocked. Assumption: no predation. Catch as-sessment was through the determination of fish species weightand composition. Identification of fish species were done withthe aid of fish identification guide by [8]. Sampling was donemonthly using a drag net 1.5 cm (knot to knot) mesh size and100 m long after stocking.

1.3 Water quality monitoringFor water quality sampling, the dugout was zoned into up-stream, midstream and downstream based on the directionof water flow into the dugout. Water quality data was com-piled monthly. Water quality sampling and analysis was doneaccording to [3]. Laboratory analysis was done at Water Re-search Institutes laboratories in Tamale. The following waterquality parameters were monitored; Dissolved Oxygen (DO),pH, Total alkalinity, turbidity, Conductivity, Total DissolvedSolids (TDS), phosphate - (PO4-P), nitrate-nitrogen (NO3-N)and Ammonia (NH4).

1.4 Statistical AnalysisComputer based program Microsoft Excel 2010 edition wasused to calculate percentage composition, mean and standarddeviations. Results were presented in tables.


Tabl

e1.

Perc

enta

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ffish

spec

ies

caug

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ters

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Spec

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%co

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posi

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omis

nilo

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28

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31.1

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ther

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aeus

21

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15.6

Tila

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i

2.74

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13.9

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Table 2. Weight of fish species caught after stockenhancement in Zialuwa dugout

Fish species Number Weight (kg)

Oreochromis niloticus 427 59.85Sarotherodon galilaeus 215 36.6Tilapia zillii 5 0.5Brycinus nurse 208 10.5Marcusenius senegalensis 22 0.5Synodontis sorex 42 7Labeo senegalensis 5 1.2Schilbe mystus 26 1.3Heterobranchus isoptenus 1 3.5Clarias gariepinus 39 16.1Synodontis schall 209 4.8Synodontis nigrita 175 2.9Total 1,374 144.75

2. ResultsA total of 17 fish species were identified during catch as-sessment. In Mawulea dugout, 16 fish species were encoun-tered while Zialuwa dugout had 12 fish species. The cich-lids; tilapiine species (Tilapia zillii, Oreochromis niloticusand Sarotherodon galilaeus) were the most dominant speciesin the dugouts. Mean percentage composition of tilapiinespecies caught before stock enhancement in both dugout was S.galilaeus (18.0%), O. niloticus (17.9%), T. zillii (1.2%). Lowfingerling morality was recorded after re-stocking, thus 99.6%of the fingerlings of Oreochromis niloticus introduced survived.Re-stocking for fish enhancement changed the order of percent-age composition of the dugout, it was O. niloticus (30.0%) , S.galilaeus (18.5%) , T. zillii (1.6%). African mudfish and otherfish species encountered included Brycinus nurse, Marcuse-nius senegalensis, Synodontis sorex, Schilbe intermedius andSynodontis schall. Percentage composition of fish caught fromeach dugout after stock enhancement is presented in table 1.O. niloticus dominated in terms of numbers in both Mawulea(28.9 %) and Ziawula (31.1 %). The species that recorded theleast in numbers was Ctenopoma petherici; Mawulea 0.4 %and Ziawulea 0 % (Table 1). Total bulk weight of 363.9 kg offish was caught through partial harvesting. Higher bulk weightof fish was encountered from Mawulea dugout as comparedto Zialuwa dugout (Tables 2 and 3). O. niloticus dominatedin both numbers and weight in the Ziawula dugout (Table 2)and in Mawulea dugout (Table 3). The impact of fish stockenhancement on water quality showed that mean concentrationfor most of the parameters monitored was relatively constantin both dugouts (Table 4). The mean surface water tempera-tures for the study period in Mawulea and Zialuwa dugoutswere 30.08 and 30.07 0C respectively. Dissolved oxygen (3.07mg/l) for both dugouts was low. The conductivity and nitrateconcentration were both high in Zialuwa than in Mawulea asshown Table 4.


Table 3. Weight of fish species caught after stockenhancement in Mawulea dugout

Fish species Number Weight (kg)

Oreochromis niloticus 401 50.45Sarotherodon galilaeus 297 43.05Tilapia zillii 38 2.6Brycinus nurse 192 15.8Marcusenius senegalensis 153 11.8Mormyrus macrophthalmus 15 1.5Parachanna obscura 5 4.5Schilbe intermedius 35 2.4Heterobranchus isoptenus 20 41.6Labeo senegalensis 46 2Schilbe mystus 11 0.6Clarias gariepinus 33 34.6Synodontis schall 70 2.45Synodontis nigrita 58 1.1Auchenoglanis occidentalis 7 1.6Ctenopoma petherici 5 3.1Total 1,386 219.15

Tabl

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Mea

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pH7.

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ity(l

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)85

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4.69

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3. DiscussionFish catch assessment indicated a rich biodiversity of 17 fishspecies in both dugouts. Dominant fish species was from thefish family; cichlidae. Similar fish species dominance has beenreported for most reservoir fishery in northern Ghana [19],[15]. The size of the dugouts did not affect the biodiversity andweight of fish species encountered in each dugout. The largerdugout (Zialuwa, 1.5 hectares) had lesser fish species biodi-versity and weight due to the fishing pressure and recruitmentover-fishing by migrant fishermen.

[2] asserted that for the last four decades, climatic variabil-ity has been positively correlated with fluctuations in the land-ings of the pelagic species (example Tilapia) upon which ma-jority of Ghanas fisher folk depend. Recruitment over-fishingcoupled with environmental challenges like climate changeprobably dwindle fish population even after stock enhancementintervention. Thus, a sustainable (selective) harvesting strategyadopted in this study allowed fry, fingerlings and juvenile fishto escape for further growth, spawning and replenishing offish stock in the dugout. The harvesting strategy ensured O.niloticus to become the dominant species (30%) coupled witha closed season during peaks of rainfall (August-September) toescape for spawning. O. niloticus (Improved Akosombo strain)probably exhibited an extent of auto stocking in the dugout thatreplenished the stock faster than expected as observed by [4].The survival rate of O. niloticus was 99.6% due to arguably thehardy nature of the improved Akosombo strain, participatoryeducation on stocking of fingerlings, care, and management ofthe dugout. Many studies have shown that proper managementof the inland fishery with native fish boosted the biodiversityand commercial benefits derived from the fishery [20], [5]. Assuch, fish revenue increased from GHc150.00 in 2011 underoutright sale of dugout to migrant fishermen, to GHc308.00 in2012 under fish stock enhancement with selective harvesting.

The effect of fish stock enhancement on water quality inZialuwa and Mawulea dugouts was less noticeable. High wa-ter temperature (300C) and low dissolved oxygen (3.5mg/l)concentrations recorded in this study were detrimental to fishproduction over a long period of time. Periodic fish kills mayoccur under such conditions especially with low dissolved oxy-gen levels [7]. This did not affect the growth of O. niloticus,which recorded an average weight of 140g. Other water qual-ity parameters monitored were fairly good for fish productionafter fish stock enhancement. According to [14], long-termeffects of climate change on water quality are diverse. Theobserved short-term changes in Zialuwa dugout revealed thatnitrate concentration of 5.54 mg/l was slightly high. The ni-trate concentrate in Zialuwa dugout could be a result of theoxidation of plants and animal debris and from the decom-position of animal (cow dung) and human excrement. Totalmonthly rainfall controlled the rate of Nitrate (NO3-N) andPhosphate (PO4-P) load into the dugouts. When rainfall inten-sified, more runoff from the watershed led to the accumulationof nutrient in the dugouts. Increased anthropogenic activitiessuch as farming (using fertilizers) before and during the rainy

season could increase nitrate concentrations in both dugouts.The important role of anthropogenic contributions to climatechange impacts on water quality cannot be underestimated.Some climate change impact studies have corroborated theintensity of observed changes to anthropogenic activities [1].The pH values of 7.70 - 7.67 encountered was optimum forfisheries productivity.

4. ConclusionThe study indicates that introduction of Tilapia; Oreochromisniloticus (improved Akosombo strain) had considerable posi-tive impact on fisheries and water quality in dugouts. Fish stockenhancement with Tilapia; O. niloticus and sustainable (selec-tive) harvesting strategies can revamp fish stock in dugouts.Arguably, dugouts have the ability to augment national fish pro-duction and adapt to climate change when given the necessarymanagement interventions.

AcknowledgmentsWe thank God for His Grace and Mercies towards us for thisstudy. We are grateful to Food for Life (F4L) project of theCommunity Life Improvement Programme (CLIP) for pro-viding funds for this study. The Institutional support of theCSIR-Water Research Institute and that of the entire Staff atTamale office is highly appreciated.

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[17] MOHAMMED, S.A. ET AL. (2013). The White VoltaBasin, climate change and food security: perspectives ofriparian communities in northern Ghana. Journal of Envi-ronmental Science and Engineering, B 2 350-356 .

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IntroductionMaterials and MethodsStudy AreaStocking and Fish Catch Assessment Water quality monitoringStatistical Analysis

ResultsDiscussionConclusionAcknowledgmentsReferences

optimization of dugout fisheries for climate change adaptation in northern region, ghana

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