Bandama River Research Articles

Spatio-temporal characterization of the ecological state of the Bandama River in the Marahoué region using diatomic indices

Spatio-temporal characterization of the ecological state of the Bandama River in the Marahoué region using diatomic indices

Research for the Presence of Pesticides in Fish from the Sassandra and Bandama Rivers in the Localities of Bouafle, Guessabo and Soubre, Ivory Coast

Aims: This study aims to investigate the presence of pesticides in fresh fish caught in the Sassandra and Bandama rivers of the Sassandra-Marahoué district.
 Study Design: Fish is an important source of protein, the quality of which depends on many actions carried out directly or indirectly by man during fishing, fish trading, preservation operations (smoking, drying, refrigeration, etc.) the use of pesticides on cultivable areas along the rivers.
 Place and Duration of Study: Sampling was carried out in three fishing areas of the Sassandra-Marahoué district and the chemical analyzes were carried out at the Agrovalorization Laboratory of the Jean Lorougnon Guédé University in Daloa and at the National Laboratory for Agricultural Development Support (Côte d'Ivoire).
 Methodology: : A total of 390 samples of fresh fish, including 130 of each of the Tilapia, Chrysichthys and Labéo species, were collected randomly under aseptic conditions directly from various fishermen from the Sassandra River in the towns of Soubré and Guessabo and from the Bandama River in the locality of Bouaflé.
 Results: Analysis of the fish samples revealed about fifteen active substances from pesticides. Crimidine and Desisopropylatratzine showed the highest levels in Bouaflé Tilapia with 29.55% and 22.73% respectively, Metobromuron, Simazine and Fénuron at 29.55% each in Chrysichthys and Labeo, each substance was found in a single sample with a rate of 2.27%. In the Guéssabo samples, Metoxuron and Monuron are the highest substances in fresh Tilapia with 18.60% each. Certain substances such as Crimidine, Aldicarb, Parathion-ethyl and Parathion-methyl were not found in the Chrysichthys samples as well as Isoproturon, Metobromuron, Metoxuron and Monuron in the Labeo. The highest substances in the Soubré samples are Metobromuron at 18.60% in Tilapia, Parathion-methyl and Terbutryn at 18.60% in Chrysichthys and Crimidine in Labéo at 9.30%.
 Conclusion: This study clearly shows the presence of pesticide residues in fresh fish caught in the Bandama and Sassandra rivers. Precautions should be taken to eliminate or at least reduce the impacts of these on the environment and especially on human health.

Study of the Population Variability of Two Chrysichthys Species in Six Aquatic Ecosystems in Côte d'Ivoire

In Côte d'Ivoire, the genus Chrysichthys are subject to intense exploitation pressure and may be threatened by overfishing. The establishment of a sustainable management program for this resource requires in-depth knowledge of this fish. The population relationships were determined by evaluating the morphological variability of the two species of the subgenus Chrysichthys, which was identified in six rivers. Forty-one morphological measurements were carried out on 167 specimens of the species C. maurus and 160 specimens of the species C. nigrodigitatus. These descriptors were subjected to discriminant factor analysis and classification analysis. Within the C. maurus species, specimens from the Bia River and the Aby Lagoon show few morphological differences. These two populations are distinct from the Ebrié Lagoon and the Bandama River. Specimens of the species C. nigrodigitatus can be divided into three distinct groups. The Bia River population occupies an intermediate position between the lot formed by the Agneby River and the Ebrié Lagoon populations and the lot formed by the Bandama River, the Aby Lagoon, and the Grand-Lahou Lagoon populations. Within each lot, the specimens show a great morphological resemblance (similarity). The similarities of the subgenus Chrysichthys could be explained by a potential capacity for exchange of individuals between rivers. The differences between populations would indicate the probable existence of phenotypic plasticity linked to their environment.

CASE STUDY OF INTEGRATED COASTAL ZONE MANAGEMENT IN IVORY COAST: STABILIZATION OF A MIGRATING TIDAL INLET BY SOFT PROTECTION MEASURES

The village of Lahou Kpanda (Grand Lahou, Côte d'Ivoire), located to the immediate west of the mouth of the Bandama River, on the barrier island of the Tagba lagoon, is highly vulnerable to coastal erosion. It is directly threatened by the migration of the river mouth, which has been occurring at an average speed of 160 m/year over the last 10 years, as well as by the risks of flooding and coastal flooding which the effects of climate change will exacerbate further. This article presents the study, beginning in 2019 and financed by the WACA programme, which contributed to the choice and dimensioning of a sustainable solution for stabilization of the Grand-Lahou sandy barrier island.

First Data of the Ichthyological Fauna in the Bandama River at the Lamto Scientific Nature Reserve (Côte d'Ivoire, West Africa)

Fish species composition and organization of the Bandama River at the scientific nature reserve of Lamto have been investigated for the first time. The study was conducted from March 2021 to February 2022. Gillnets and traps were used to collect fish. A total of 41 species belonging to 35 genera, 13 families, and 5 orders were captured. The best-represented orders were the Siluriformes with 5 families and 11 species and the Perciformes with 3 families and 14 species of fish. The Cichlidae, Mormyridae, and Alestidae represented the best diversified family with 13, 5, and 5 species respectively.
 This study also showed a decrease in the average size of individuals of the main species retained, which could reflect overexploitation of the stocks. The Shannon index (2.21 bits/ind.) and equitability (0.58) values obtained reflect a more or less distribution of individuals by species. These results will make it possible to establish a database for the conservation of this fish population and its habitat.

Spatial and seasonal distribution of pesticides in the waters of Azagny area (Grand Lahou, Cote d'Ivoire).

This study provides comprehensive data on the seasonal variation and distribution of pesticides in the waters bordering Azagny National Park (ANP). Forty-six (46) samples of water from the Azagny area were analyzed using high-performance liquid chromatography (HPLC) coupled with a UV/visible detector to assess the level of thirty-one pesticide molecules divided into six families. These include triazines, phenylureas, organophosphates, carbamates, chloroacetanilides, dicarboximides, and crimidine, which are regularly used in this area. The respective average concentrations of pesticides are 54.54µg//L, 20.93µg/L, 18.24µg/L, 3.06µg/L, and 16.52µg/L in the Bandama, Azagny Canal, ANP, mangroves, and estuarine environment. The analyses also showed that herbicides were the most abundant pesticides in the three waters, Bandama, Azagny Canal, and Azagny Park, with levels of 100%, 63%, and 59%, respectively, followed by insecticides with a levels of 0%, 37%, and 41%, respectively. However, rodenticides (76%) were more frequently detected than herbicides (24% in the mangroves). Regarding seasonal variation, high levels of pesticides were detected in the Bandama River, the Azagny Canal, and the mangroves during the dry season, while multiple pesticide residues were detected during the rainy season. The waters bordering Azagny National Park (ANP) are contaminated with pesticide residues (triazines, phenylureas, organophosphates, carbamates, and chloroacetanilides). As a result, policymakers should implement measures to regularly monitor pesticide levels in plantations surrounding the Azagny region's waters in order to better preserve biodiversity.

Feeding Habits of Synodontis Species Found in Downstream of Taabo Dam of Bandama River in Côte d'Ivoire

The building of hydroelectric dams has consequences on the ecological conditions of ecosystems, such as the regression or disappearance of certain species that have a benthic entomophagous diet or a proliferation of omnivorous and planktivorous species. The study of fish feeding can provide data not only on the presence of prey, but also on the abundance and availability of trophic potential. In view of the new hydroelectric development project on the Bandama River, this study proposes to examine the diets of Synodontis bastiani, S. schall and S. punctifer that are captured in the area. Stomachs were collected and contents examined from fish caught monthly between November 2019 and October 2020 using gill nets in the N'Dènou locality. A total of 417 fish belonging to S. bastiani, S. schall, S. punctifer were examined. The food spectrum of the studied species is wide and diversified. It is mainly composed of Macrophytes, Insects, Worms, Mollusks, Zooplankton, Crustaceans. These species are all omnivorous with a benthophagous tendency. No difference was observed in the diet according to the size.

Perceived water-related risk factors of Buruli ulcer in two villages of south-central Côte d'Ivoire.

Buruli ulcer, caused by Mycobacterium ulcerans, is a neglected tropical skin disease that is primarily endemic in West and Central Africa, including Côte d'Ivoire. Studies indicate that M. ulcerans infections are caused by contact with an environmental reservoir of the bacteria, governed by specific human biological conditions. Yet, the nature of this reservoir and the exact mode of transmission remain unknown. To identify ecologic risk factors of Buruli ulcer in south-central Côte d'Ivoire, we pursued a qualitative study matched with geo-referencing inquiry. Embedded in a broader integrated wound management research project, we (i) mapped households and water sources of laboratory confirmed Buruli ulcer cases and (ii) interviewed 12 patients and four health care workers to assess exposure to surface water and to deepen the understanding of perceived transmission pathways. Water availability, accessibility, and affordability were reported as key determinants for choosing water resources. Furthermore, perceived risks were related to environmental, structural, and individual factors. Despite the presence of improved water sources (e.g., drilled wells), communities heavily relied on unprotected surface water for a multitude of activities. The nearby Bandama River and seasonal waterbodies were frequently used for washing, bathing, and collection of water for drinking and cooking. Many residents also reported to cross the river on a daily basis for agricultural chores, and hence, are exposed to stagnant water during farming activities. Our study in two Buruli ulcer endemic villages in south-central Côte d'Ivoire revealed a wide range of water-related domestic activities that might expose people to an increased risk of contracting the disease. Environmental, biological, social, and cultural risk factors are closely interlinked and should be considered in future investigations of Buruli ulcer transmission. Active participation of the communities is key to better understand their circumstances to advance research and fight against Buruli ulcer and other neglected tropical diseases.

Size structures and length-weight relationships of three freshwater fish, Brycinus imberi, Labeo coubie, Oreochromis niloticus, from the Bandama river section located in Haut-Bandama Widlife Reserve (North Central, Côte d'Ivoire)

The needs induced by the galloping demography and urbanization in the north-central part of Côte d'Ivoire have provoked strong anthropic pressures on the Bandama River, particularly its section located in the Haut-Bandama Wildlife reserve. This is reflected in the increased invasion of this watercourse by aquatic plants and algae, its enrichment in suspended matter and chemicals of all kinds. This state of the river could have repercussions on the development of biological organisms such as fish. Thus, the study aimed to determine the size structures and length-weight relationships of Brycinus imberi, Labeo coubie and Oreochromis niloticus from the Bandama River located in the Haut-Bandama wildlife Reserve. It was carried out along the longitudinal gradient (upstream-downstream) of the Bandama River, on 06 stations and during 08 sampling campaigns between January 2018 and February 2019. Fish specimens’ lengths measurements were made with an ichthyometer, and with an electronic scale, for the weights. The analysis focused on the size structure and length-weight relationships. Length-weight Relationship (LWR) was described by the equation: W = aLb. Brycinus imberi specimens’ sizes varied from 5.3 to 13.5 cm SL. At Labeo coubie, the specimens have sizes that oscillate between 7.6 and 51.2 cm SL. As for Oreochromis niloticus, the sizes were between 8.7 and 17 cm SL. Growth appeared allometric negative with b values of 2.70 for Brycinus imberi, 1.08 for Labeo coubie, and 2.51 for Oreochromis niloticus.

SOCIO-ECONOMIC ASPECTS OF THE FISHING IN THE SINGROBO-AHOUATY DAM PROJECT AREA (BANDAMA RIVER)

Dams bulding can lead to the disturbance of the living environment of aquatic species, directly impacting the fishing sector and indirectly the lives of riparian populations.A new hydroelectric dam is currently under construction on the Bandama River. This development could cause risks of disruption of the habits of the riparian populations who live from activities related to fishing. This study was conducted to obtain baseline data on the lives of the local populations before the dam is actually put in place in order to understand the long-term impacts of this hydroelectric development. Informationswerecollected every day, except holidays, in the villages of the area impacted by the development, between November 2019 and October 2020.A questionnaire was used with the actors (fishermen and fishmongers) and interviews were held to characterize their activities, income and socio-demographic profile. Most of the fishermen are natives who practice the activity on a part-time basis, with agriculture as a secondary activity while the non-native fishermen are full-time. The majority of fishermen are educated, with a rate of 48%. The others are either illiterate (31%) or have attended Koranic school (21%). They are adults in the 30 to 45 age group. The fishing activity is successful with excellent profit margins, despite the lack of organization noted in some localities. The distribution circuit observed involves sale by rope or by heap, and processing by smoking, with the involvement of fishmongers. In the study area, fishing provides a good income for the actors and is practiced mainly by Ivorians. The results of the characteristics of the fishing activities constitute a basis for assessing the future impact of the dam, and also for the managers in the implementation of a sustainable management plan of the fishery resources in this area.

Size structures and length-weight relationships of three freshwater fish, Brycinus imberi, Labeo coubie, Oreochromis niloticus, from the Bandama river section located in Haut-Bandama Widlife Reserve (North Central, Côte d'Ivoire)

Size structures and length-weight relationships of three freshwater fish, Brycinus imberi, Labeo coubie, Oreochromis niloticus, from the Bandama river section located in Haut-Bandama Widlife Reserve (North Central, Côte d'Ivoire)

CONDITION FACTOR AND LENGTH-MASS RELATIONSHIP OF THE MAIN FISH SPECIES IN THE BANDAMA RIVER DOWNSTREAM OF THE TAABO DAM (COTE DIVOIRE)

Length-mass relationship and condition factor are important tools used in biology, ecology and stock assessment for the management and conservation of fish populations and also to assess the level of disturbance of an aquatic ecosystem. The present study aims at providing baseline data on the length-mass relationship and condition factor of sixteen (16) fish species landed at NDènou, downstream of the Taabo dam, prior to the impoundment of the dam under construction on this part of the Bandama River. The fish were collected monthly from november 2019 to october 2020.They were measured (standard length in cm) and weighed (mass in g). The data were processed in Excel and Statistica 7.1 software. A total of 16047 fish were examined. The standard lengths of these fish varied from 3.50 to 40 cm with masses ranging from 2.87 to 1400 g. The values of the allometry coefficient ranged from 1.64 for Hemichromisbimaculatus to 2.99 for Labeocoubie. Fourteen (14) fish species studied have negative allometric growth (b < 3 p < 0.05). Distichodusrostratus and Labeocoubie species have isometric growth. The condition factor has values between 0.83 ± 0.39 (Mormyropsanguilloides) and 3.65 ± 0.74 (Coptodonhybrid).

DISTRIBUTION PATTERN OF THE AQUATIC ENTOMOFAUNA ABOUT ENVIRONMENTAL FACTORS IN THE HAUT-BANDAMA WILDLIFE RESERVE AREA OF THE BANDAMA RIVER (CENTRE-NORTH, COTE DIVOIRE)

The section of the Bandama River located in Haut-Bandama Wildlife Reserve was subject to several pressures induced by the anthropic activities that take place there. These activities could have impacts on the structure of biological communities such as aquatic insects which are indicators of the state of the ecological integrity of the environment. This study was conducted to evaluate the diversity and structure of the aquatic entomofauna of this part of Bandama River. Sampling was conducted from January 2018 to February 2019 at 06 sites defined according to the upstream-downstream gradient of the river. Insects were collected using a handled net and aVan Veen bucket. The inventory identified 127 species from 53 families and 10 orders. In this part of Bandama River, the order Hemiptera was the most prevalent with 30 species. The taxa Gerisella sp. (31% of individuals), Dineutus sp. (55%), and Laccophilus sp. (38%) wereabundant in the upstream, median and downstream sections of Bandama River respectively. Also, 33 species were common to all stations. Thraulus sp. AndLispe sp. wereonly found at station BYB, located downstream of this sectionof Bandama River. The distribution of entomofauna was influenced by pH, turbidity, dissolved oxygen, speed, depth and temperature. The entomological populations in this part of the Bandama River were well diversified and with awell balanced organisation.

English

The Bandama River contributes essentially to the well-being of the Ivorian population. Unfortunately its biodiversity is strongly threatened by human activities. In order to assess the water quality of the Bandama River and its impact on fish fauna, a scientific study was carried out from March 2019 to February 2020 in its estuarine zone. Thus, the physico-chemical variables of the water, the contents of Pb, Mn, Fe, Cd and Hg in the water and sediment matrices were measured in the three stations defined for the study. Twenty fish species were selected to assess the level of ecological stress observed on the fish fauna. The analysis of the water variables revealed a fairly oxygenated watercourse with temperature above 25°C, acidic pH, high conductivity and salinity above 10‰. The analysis of heavy metal contents revealed a high enrichment of the Bandama estuary in Mn and Hg due to human activities in the whole catchment area. Ecological stress data indicated high fish stress with negative allometric growth for most economically important fish collected in the Grand-Lahou area. Awareness raising among local communities and management measures should be implemented for the conservation of aquatic species in this freshwater Key Biodiversity Area.   Key words: Heavy metals, anthropic activity, conservation, Azagny National Park, coastal wetland.

Recent expansion of artisanal gold mining along the Bandama River (Côte d’Ivoire)

• Artisanal and small-scale gold mining is a serious threat to the environment. • In Ivory Côte d’Ivoire, this activity has developed very quickly recently. • The lack of geographical information is an obstacle to the regulation. • The monitoring of artisanal mining from space can help governements. Recent development of small-scale gold mining activities in Côte d’Ivoire is a serious threat to the environment because of deforestation, soil scrapping, pit mining, over-use of water resources and pollution of surface and ground waters by mercury, cyanides, and acids. The challenge for the governance of this activity is to resolve the tension between the desired development of a small-scale mining activity, which may benefit the local and national economy, and the impacts of this activity on the environment. The regulation of the exploration and exploitation of mining sites and the promotion of best practices was part of the National program for the rationalization of gold-panning in Côte d’Ivoire. The capacity of the government to monitor the expansion of numerous mining sites disseminated all over the country is one of the key aspects for successful implementation of these policies. This study explores the potential value of computer-assisted mapping of artisanal mining sites based on Sentinel-2 imagery. The detection method, using artificial intelligence and training data sets generated during field campaigns, was inspired from a previous experience in Senegal. It was applied to a region of about 600 km 2 in Central Côte d’Ivoire. Annual maps of areas affected by the mining activities were produced for the period 2018 – 2021. The areas affected by artisanal mining activities expanded from 3.39 km 2 to 8.80 km 2 in December 2021, corresponding to an average growth rate of 0.24 km 2 /month. The temporal and spatial resolution of the Sentinel satellite imagery proved to be useful to map and quantify the expansion rate of artisanal mining sites in Côte d’Ivoire. Recommendations are made for the integration of these tools into plans for the development of small-scale mining activities in Côte d’Ivoire that would be more respectful of the environment and societies.

Growth, exploitation parameters and sexual maturity of Chrysichthys nigrodigitatus (Lacépède, 1803) downstream of the Taabo dam (Bandama River, Côte d’Ivoire)

The objective of the present work is to study the growth, exploitation parameters and the size of first sexual maturity of Chrysichthys nigrodigitatus (Lacépède, 1803) landed in N'dènou, in order to evaluate the status of its stock. A total of 7635 fish were sampled monthly from November 2019 to October 2020. The individuals were measured, weighed and the data processed with the FiSAT II software. The calculated parameters are: allometry coefficient (b = 2.77); asymptotic length (L∞ = 51.98 cm); growth coefficient (K = 0.2 yr-1); growth performance index (φ' = 2.73); natural mortality (M = 0.54 yr-1); fishing mortality (F= 0.61 yr-1); total mortality (Z = 1.14 yr-1); exploitation rate (E = 0.53). The size of first capture is smaller than the size of first sexual maturity. Recruitment is continuous with the peak during the rainy season. The C. nigrodigitatus stock is under fishing pressure in the Bandama River.

Length-weight relationships and condition factor of the main species of fish caught on the Bandama River (Ivory Coast)

The Ivory Coast has economically and ecologically important rivers that contain various fish and shellfish resources. Thus, the present study aims to assess the length-weight relationships and the condition factor of fish stocks in selected sites on the Bandama River from July 2013 to June 2014. The growth pattern of each species was identified at the using a regression model calculated for the length-weight relationship. The condition factor (K) was analyzed for each species. There were six species of fish (Chrysichthys nigrodigitatus, Synodontis bastiani, Synodontis schall, Marcusenius senegalensis, Coptodon zillii and Labeo coubie). The length-weight relationship determined for the above six species showed a negative allometric growth pattern (b<3) indicating faster length increase relative to weight for five of them. They are Chrysichthys nigrodigitatus, Coptodon zillii, Synodontis bastiani, Synodontis schall and Marcusenius senegalensis, Only the species Labeo coubie presented a positive allometric growth (b>3) showing that this species put on weight faster than it grows. The habitat qualities of the majority of fish species were therefore in optimal environmental conditions. The results of the present study constitute a reference, which taken into account would be useful for the implementation of a plan for the sustainable management of fishery resources in Ivory Coast.

Comparative Study of Physico-Chemical Properties of Sediments from Two Sectors Close to Bandama in Northern Côte D’Ivoire (Sinematiali and Niakaramadougou)

This study aims to show the impact of successive floods on the spatial variation of the physico-chemical properties of sediments along the Bandama River in the localities of Sinématiali and Niakaramadougou because of their importance in the functioning of this ecosystem. Several samples were taken from both stations based on flood recurrence areas. The particle size analysis was done using the Robinson’s Pipette method. Traditional methods of sediment analysis have been used to measure organic carbon (O.C.), nitrogen (N), and other chemical properties including pH, organic matter (MO), and C/N ratio. Statistical analyzes were carried out to assess the differences between the physico-chemical parameters of the different sampling zones. In the area of niakamadougou, the lower values in MO were recorded in areas subject to more frequent flooding, thus close to the watercourse. In the Sinématiali area, lower M.O. values were recorded in sediments far from the stream. Total organic matter levels are higher in surface sediments with the lowest proportions of clay. The results show that the physico-chemical properties of the sediments vary at the level of the vertical distribution and according to their spatial distribution. Successive floods have a direct effect on the dynamics of the physico-chemical properties of sediments along the shore.

Structure of Benthic Macroinvertebrate Assemblages in Azagny Channel (Côte d’Ivoire)

The Azagny Channel is an estuarine ecosystem connecting Ebrié Lagoon to Bandama River estuary and it is adjacent to Azagny National Park. The aim of this study was to provide the first data on diversity and structure of macroinvertebrates in this estuarine area. Physicochemical parameters were measured monthly in three sampling stations S1, S2 and S3, and the benthic Macroinvertebrates was collected using a Van Veen grab. A total of 28 taxa distributed among 20 families and 11 orders belonging to Annelida, Mollusca, Crustacean and Insecta were collected. The taxonomic richness and diversity were higher in S1 compared to S2 and S3, probably due to its proximity to Bandama estuary. The relative abundance revealed that mollusks represented mainly by Pachymelania aurita (16.04%), P. fusca (15.83%), Anodonta anatina (13.02%) dominated the species assemblage; followed by crustaceans with Macrobrachium vollenhovenii (31.87%) and Potamon sp. (5.01%). Canonical correspondence analysis revealed that the main factors that influenced macroinvertebrates distribution in Azagny Channel were conductivity, salinity and Total Dissolved Solids (TDS). There is a strong correlation between these three abiotic factors and their influence on species assemblage would be linked to proximity of study area to Atlantic Ocean. These findings provide valuable information that can be used to establish biotic indices to monitor the water quality of Azagny Channel.

Socio-economic effects of fishing activities on the Bandama river in the Agneby-Tiassa region (Côte d'Ivoire)

Fishing is important in the fight against food insecurity, unemployment and in creating jobs. This study describes the socio-economic effects of fishing activities in the Agnéby-Tiassa region. Information was collected through a questionnaire, interview and direct observation in the field. Analysis of the data obtained showed that fishing activities in Agnéby-Tiassa is a source of jobs and earnings. Daily earnings vary between 15000 and 25000 FCFA. The fish marketing is carried out by women, 24% of whom are wholesalers, 18% of whom are smokers. Those who resell the fish represent 76%. The income derived from this activity allows the actors to mainly educate their children (35%). The consumption of fish contributes to the satisfaction of the food needs of the populations and to the improvement of health thanks to the intakes of proteins, iodine and vitamins.