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.

Improvement in fish production is achieved, in part, by enhancing the zootechnical performance. This study evaluated the growth performance of two strains (Bouaké and Brazil) of Nile tilapia Oreochromis niloticus reared in floating cages, in Côte d’Ivoire. The Brazil strain is descended from a long line of the Bouaké strain and are both the only strains officially approved for farming in Côte d'Ivoire. Juvenile males with an average body weight of 60.42 and 60.50 g for the Bouaké and Brazil strains respectively. They were reared in 6 floating cages of 50 m3 at an initial density of 90 fish m-3. After 120 days, both strains' final body weights were 354.74 g for Bouaké and 385.76 g for Brazil. Individual daily growth was better for the Brazil strain than for the Bouaké strain. The survival rate was 97.80% for the Brazil strain and 95.91% for the Bouaké strain, with no significant difference. In financial terms, the Brazil strain had a better gross profit than the Bouaké strain.

The artificial reproduction of the silver catfish (Chrysichthys nigrodigitatus) is traditionally limited to once-a-year forced pairing. This study evaluated the effectiveness of hormonal treatments to stimulate oocyte maturation and induce spawning. Forty-two female silver catfish weighing 152 to 528 g received intramuscular injections of gonadotropin-releasing hormone analogues (GnRHa, administered as Ovaprim; 0.1, 0.3, and 0.6 mL/kg), human chorionic gonadotropin (hCG, 500 and 1000 IU/kg), or saline (control). Oocyte development was monitored by measuring oocyte diameter at 4, 8, 12, and 24 hours after injection. GnRHa treatment caused a significant increase in oocyte diameter from initial values (1.90-2.27 mm) to ≥2.5 mm within 8 hours at all tested doses (p < 0.05), whereas hCG and control treatments showed no significant changes. Despite successful oocyte maturation with GnRHa, no spawning occurred. These results indicate that GnRHa promotes final oocyte maturation in C. nigrodigitatus but remains insufficient to induce spawning under the conditions tested.