Center for Marine and Oceanographic Research

Fish farming in Côte d’Ivoire has been promoted as a diversification strategy for cocoa producers, yet the sector exhibits significant heterogeneity in farming practices, which remains poorly documented. This study aimed to classify fish farming systems and identify key determinants of their performance. Surveys were conducted with 45 farmers across three cocoa-producing regions - Bédiala, Méagui, and Sinfra - and data were analyzed using Factor Analysis of Mixed Data (FAMD) and clustering analysis, leading to the identification of three distinct farm types. Type 1 farms, found in Bédiala, have the largest production areas (median: 2.9 ha) and predominantly practice polyculture of Nile tilapia ( Oreochromis niloticus ), bony tongue ( Heterotis niloticus ), and catfish ( Clarias spp.), often integrated with rice farming. Type 2 farms, found in Sinfra, employ the most intensive practices, characterized by the use of monosex tilapia fingerlings and reproductive control via banded jewelfish ( Hemichromis fasciatus ), resulting in the highest yields (median: 1033 kg ha⁻¹ yr⁻¹). Type 3 farms, found in Méagui and Sinfra, are the least productive (median: 450 kg ha⁻¹ yr⁻¹), constrained by longer production cycles and limited technological adoption. These findings reveal significant regional disparities in fish farming practices and productivity, underscoring the need for tailored policy interventions. Strategies should focus on promoting improved production techniques in low-yielding systems while supporting sustainable intensification in more advanced farms to enhance the sector’s contribution to rural livelihoods and food security. • Fish farming in Côte d’Ivoire is diverse, with three distinct farm types identified. • Farm typologies vary in size, species composition, and management intensity. • Type 1 farms mostly integrate rice-fish polyculture in large ponds. • Type 2 farms employ the most intensive practices and achieve the highest yields. • Type 3 farms are the least productive, with longer production cycles and limited inputs.

In response to the growing problem of water contamination by heavy metals, this work presents the design of an innovative and promising bioadsorbent: a cellulose fabric functionalized through covalent grafting of ethylenediamine (Cell-EDA). The chemical modification was carried out in three successive steps: alkaline mercerization, tosylation in pyridine medium, and nucleophilic substitution. FTIR spectroscopy, supported by a semi-quantitative analysis of characteristic absorption bands, confirmed the successful introduction of amine groups. The adsorption performance was evaluated for Cu(II) and Pb(II) ions as a function of pH, contact time, and initial concentration. Maximum removal efficiencies reached 90% for Cu(II) at pH 4 and 96% for Pb(II) at pH 8. Kinetic studies followed a pseudo-second-order model, indicating chemisorption. The Freundlich and Temkin isotherms revealed multilayer adsorption on heterogeneous surfaces, while the Langmuir model yielded maximum adsorption capacities of 55.9 mg/g for Cu(II) and 131.6 mg/g for Pb(II), highlighting the strong retention capacity of the material. The Cell-EDA fabric retained over 75% of its adsorption efficiency after five consecutive cycles, demonstrating good stability and excellent reusability. The use of cellulose fabric, which offers greater mechanical strength than powder or paper-based supports, gives Cell-EDA significant potential for sustainable applications in the treatment of heavy metal-contaminated effluents.

The main objective of this study is to highlight the role of fisheries management in the productivity and sustainability of fisheries-related activities. The study ran from December 2020 to May 2021 and from December 2021 to May 2022. Sampling was carried out on catches from an artisanal fishery using purse seines in both fishing environments. The results for the reserves showed a reduction in fishing effort in year 2 compared with year 1. In terms of profit per fishing trip in the reserves. The highest Catch Per Unit Effort (CPUE) was recorded in Ehoussou (3,526.87 kg) and Abiaty (2,624 kg) during the first year, and in Bèdoubegnin/Mauricekro (1,774 kg), Abiaty (1,288.88 kg), Aby (1,283.57 kg) and Eplemlan (1,240 kg) during the second year. The largest quantities of fish caught per reserve were observed at Ehoussou (56,430 Kg) and Abiaty (39,360 Kg) during year 1, and at Aby (17,970 Kg) and Bèdoubegnin/Mauricekro (17,740 Kg) during year 2. On the portion of the Aby lagoon to which access is free, the fishing effort amounted to 2,315 trips (year 1), compared with 1,812 trips in year 2. In this free-fishing zone, the CPUE was 291.12 kg in year 1, compared with 193.17 kg in year 2. The quantity of fish produced annually in this unprotected portion was 673,935 kg in year 1, and 350,029 kg in year 2. These results showed that for the small amount of fishing effort made in the reserves (250 trips) over the sampling period, the average profit from one fishing trip was as high as possible (1,177.31 kg). The opposite was observed in the lagoon portion with free access, since with an effort of 4,127 fishing trips over the entire survey period, the average gain from one fishing trip was only 248.11 kg. This study serves to alert fisheries managers to the fact that productivity is not correlated with the increase in fishing pressure, and that the profit per fishing team in terms of biomass is higher in reserves under protection. This experiment needs to be replicated in other hydro-systems of bio-ecological interest, to better safeguard fishing in a sustainable manner.

Polycyclic aromatic hydrocarbons are organic contaminants, some of which are known to be toxic, carcinogenic and mutagenic for humans. These molecules are ubiquitous pollutants of the environment, and can contaminate foodstuffs such as fish. The aim of this study was to assess the level of polycyclic aromatic hydrocarbons contamination in the flesh of a species of freshwater fish, Chrysichthys nigrodigitatus, smoked and dried in the locality of Guessabo. The method used for the determination of these analytes in the matrices was high performance liquid chromatography with UV/Visible detector. Results obtained indicate disproportionate contamination of Benzo(a)pyrene, Benzo(b)fluoranthene, Benzo(a)anthracene and Chrysene molecules depending on the mode of transformation and the season. The highest levels of contamination were recorded during the rainy season in the flesh of Chrysichthys nigrodigitatus smoked for Benzo(a)pyrene (10.39 ± 1.10 µg/kg), Benzo(b)fluoranthene (46.44 ± 3.77 µg/kg) and the sum of the PAH4 (59.88 µg/kg). These levels exceed the standard set by Ivorian regulations (5 µg/kg). In dried fish flesh, a low level of toxicity was recorded whatever the season. There were no significant differences between seasons for most of the molecules studied. The flesh of Chrysichthys nigrodigitatus dried is less contaminated than smoked Chrysichthys nigrodigitatus.

A study was carried out to evaluate the effect of stocking density on the growth and survival of Sarotherodon melanotheron juveniles. To do this, 300 individuals with an initial average weight 4.13 ± 1.96 g and an initial average length 5.79 ± 0.89 cm were monitored for 42 days, in triplicate, at four densities (0.2; 0.4; 0.6 and 0.8 ind. /L) in happas of 50 liters volume. Fish were fed at 10% of their biomass with koudijs feed. A weekly sampling was carried out, during which ten (10) individuals were taken at random, they were weighed and measured individually. The physico-chemical parameters of water were measured daily. At the end of the experiment, the 0.8 ind. /L density gave the best growth results, with values of 16.27 ± 2.36g; 9.17 ± 0.92 cm; 0.29 ± 0.08 g/d ; 2.11 ± 0.08 and 443.67 ± 56.44 g, respectively for final average weight, final average length, ADG, condition factor and total biomass. For the survival rate, the highest value (95.00 ± 1.33%) was recorded in individuals with a density of 0.4 ind./L while those with a density of 0.8 ind./ L gave the lowest survival (80.00 ± 1.33%). Other densities could be tested and in other breeding structures to better appreciate the influence of this factor on the growth and survival of this species.

Habitats of three marine fish species of major interest (Epinephelus aeneus, Pseudotolithus senegalensis, and Pagellus bellottii) at both juvenile and adult life stages were identified and mapped in the western part of the Gulf of Guinea. Habitat suitability models (HSMs) were designed to quantify species- and stage-specific fish densities from scientific survey data collected for the last 40 years according to two environmental descriptors (bathymetry, distance to river mouth) and accounting for temporal contrasts. Delta general linear models were selected to fit with the 0-inflated distribution of the fish density data. Despite their high residual deviance, both the prediction accuracy and robustness of these HSMs were satisfactory. HSMs showed a strong influence of bathymetry on stage-specific fish distribution and a lower and non systematic influence of proximity to river mouths. The spatial distribution of juveniles of E. aeneus and P. senegalensis evidenced their concentration in shallow coastal nurseries. The adults of P. senegalensis were also located in nearshore habitats under estuarine influence, whereas adults of E. aeneus were spread towards deeper waters. P. bellottii did not rely on coastal fringes at juvenile or adult stages. Finally, model outputs showed a decrease in abundance in recent decades for all species at both life stages. These HSMs and maps reveal the importance of the coastal fringe as a critical essential habitat for two of the three studied species and the usefulness of space-based management measures to maintain populations and ensure sustainable fishing exploitation.

Abstract Surface sediments from the intertidal area of Côte d’Ivoire were sampled to investigate trace metals (Hg, Cd, Cr, Cu, Pb, Zn, and As) concentrations to illustrate their spatial distribution and ecological risk of pollution. The average total organic carbon content was 2.04 ± 0.01%. Except for Cr and Zn, the spatial distribution exhibited a similar pattern for TOC, Hg, Cd, Cu, Pb, and As. The average concentrations of trace metals were less than their corresponding UCC values, except for Cd and Cr. The pollution indices indicated that sediment quality in the studied area has been impacted by Cd and the Assinie and Bleron sites were the most contaminated. A few ecological risks were posed by Hg, Cd, Cr, and Cu, based on sediment quality guidelines (SQGs). The Pearson correlation showed a significant (p < 0.05) correlation between As, Cd, Pb, Cr, and Hg, suggesting a common origin in sediments. Although this study presents the current status of littoral trace metals contamination level in sediments, further studies should integrate the statistical multivariate approach to determine the anthropogenic sources of the trace metals in the intertidal area of Côte d’Ivoire.

Sardinellas are amongst the principal fishery resources of the Ivorian coastal areas, being the prey of predatory fishes, of which tunas. A close observation of the trophic ecology and fisheries data in the scientific literature permitted to gain insights into previously-held relationship between the Spanish mackerel and the Sardinellas regarding feeding. We recall past facts accounting for the disappearance of both species from the landings, following the scarceness of the round Sardinella (Sardinella aurita). This study was carried out to investigate the current relationship between both species, selecting a fishery for its heavy catches for Sardinellas. Samples of Scomber colias were taken each week of July and August from that fishery in 2022. A total of 115 specimens were collected at the landing stage of Sassandra (Southwestern Côte d’Ivoire). The fish were measured and weighed, and stages for sexual maturity of their gonads were estimated. The results indicated that specimens ranged in size from 20.4 to 35.5 cmFL while their stomachs measured between 1.8 and 9.6 cm. Stomach contents weights ranged from 0.05 to 36.5 g. The stomach contents analysis showed a feeding regime made up mainly of small organism-prey, of which the mantel shrimp Scyllarides herklotsii, the pink shrimp Farfantepenaeus notialis, the spiny lobster Nephropsis atlantica, juvenile fish species of the Myctophidae family, juvenile Cephalopods (squids), and almost no fish of the genus Sardinella. The occurrence of a large proportion of empty stomachs (whose weight was <2.0 g) was noticeable, since the Spanish mackerel mainly fed on small prey.

This study showed clearly the effect of adding palm oil to the diet of farmed fish to replace marine animal oils. For this purpose, four foods based on maggot flour at 35% protein with the incorporation of palm oil, at different levels at 0, 2, 5 and 10% were tested in the to assess their impact on the improved growth performance, food utilization, survival rate and biochemical composition of Heterobranchus longifilis larvae
 Four experimental diets were formulated based on the maggot meal as the main protein source. These diets were formulated at 35 % protein levels with maggot meal and maize flour as the major ingredients containing different concentrations of palm oil levels at 0, 2, 5, and 10 %. This study was carried out in the reproduction laboratory, at Oceanological Research Center, Abidjan, Côte d’Ivoire, between the periods of September to November 2022.
 The diets were offered to the larvae (average initial weight 0.004 ± 0.001 g) three times a day ad libitum for 49 days. At the end of rearing, the results showed that the different experimental foods distributed did not influence the quality of the rearing environment.
 The best growth was obtained with the larvae subjected to diet containing 2% palm oil with a final average weight of 3.21 g and a conversion index of 1.63. Beyond this rate, larval growth decreases. Survival rates vary from 70 to 73 %. The conversion ratios are not significantly different and ranged between 1.63 and 2.3. On the biochemical larvae submitted to diet containing 10 % of palm oil had body lipid content (2 %) and high ash rich. As against a gain of protein is observed with larvae submitted to diets containing 2 % palm oil reflects an effect of protein. 
 From the present results, diet containing 2 % crude palm oil is considered optimal for Heterobranchus longifilis larvae.