Biologie de la reproduction de Elagatis bipinnulata (Guoy & Gaimard, 1824) capturé dans le golfe de guinée par la flottille artisanale en Côte d’ivoire

Objectif : le but de ce travail est d’étudier la biologie de la reproduction de Elagatis bipinnulata dans l’océan Atlantique Est, à travers la détermination de quelques paramètres tels la sex-ratio, taille de première maturité sexuelle, fécondité et la période de reproduction.Méthodologie et résultats : cette étude a été entreprise de septembre 2015 à Août 2016 sur des individus capturés au filet maillant par les pêcheurs artisans exerçant dans le golfe de guinée. Des prélèvements mensuels de poissons ont été effectués au quai piroguier d’Abobo-doumé (port de pêche d’Abidjan). Au total 736 spécimens ont été examinés avec 479 femelles et 257 mâles dont la longueur à la fourche varie de 40 à 93 cm. La sex-ratio globale montre une prédominance des femelles par rapport aux mâles (1,89:1; x2 = 66.89 ; p=0,03 < 0,05). La taille de première maturité sexuelle déterminée pour l’espèce est de 60,33 cm chez les femelles et de 63,69 cm pour les mâles Les paramètres de reproduction étudiés révèlent que cette espèce se reproduit dans le golfe de guinée au cours du premier semestre de l’année plus précisément dans la grande saison chaude de mars à juin. La fécondité absolue varie de 52279 à 313282 ovocytes avec une moyenne de 167873±72108 ovocytes. Quant à la fécondité relative, elle oscille entre 31791 à 94778 avec une moyenne de 60155±26708 ovocytes.Mots clés : Elagatis bipinnulata, période de reproduction, fécondité, sex-ratio, Abobo-doum

Pêche Et Caractéristiques Morphologiques D’un Poisson-Chat Endémique Synodontis Punctifer (Daget, 1964) Dans Le Barrage Électrique De Taabo (Côte d’Ivoire)

A study of Synodontis punctifer (family: Mochokidae) of Taabo Lake was conducted from October 2015 to September 2016. This was carried out so as to evaluate its quantity (biomass) caught by fishing and also its morphological characteristics. The fish were caught using gillnets at 4 sites of the lake and different measurements were made. The fishing effort was 23 to 11 fishermen / day in Taabo city, 17 to 11 fishermen / day in Courandjourou, 13 to 5 fishermen / day in Ahondo, and 8 to 3 fishermen / day in Taabo village. The catch per unit effort (CPUE) ranged from 17.7 to 3.7 g / fisherman / day, 9.2 to 1.2 g / fisherman / day, 8.3 to 0.7 g / fisherman /day, 8 to 1g / fisherman / day at Ahondo, Courandjourou, Taabo city and Taabo village, respectively. The overall annual production was estimated at 2199.3 kg, i.e. 817 kg (40%) at Ahondo, 788.3 kg (35%) at Courandjourou, 462.5 kg (20%) at Taabo, and 131.5 kg (5%) in Taabo village. The overall sex ratio (1: 1.33) was in favor of females. Individuals have negative allometric growth at all sites with values ranging from 1.72 to 2.89. The condition factor does not vary significantly between different categories of individuals (ANOVA, F = 2.79, p ˃ 0.05). A significant difference was observed between the average sizes of the individuals of the different sites (test, p˂0,05). The large size specimens were captured at Ahondo, mean (avg = 15.38 ± 1.68 cm FL). In Courandjourou, the sizes were intermediate (avg = 13.63 ± 1.64 cm LF). Smalls sizes have been observed in Taabo city (mean= 12.37 ± 1.24 cm FL) and Taabo village (mean= 15.58 ± 1.58 cm FL)

Diet of Elagatis bipinnulata (Guoy & Gaimard, 1824) in Côte d’Ivoire (Gulf of Guinea)

The rainbow runner, Elagatis bipinnulata, which belongs to the Carangidae family, is regularly encountered in the landing of artisanal fishing in Abobo-Doumé (Republic of Côte d’Ivoire). The object of this work is to study the diet of Elagatis bipinnulata according to the marine seasons and the size of the various specimens (immature and mature). About 900 fish measuring between 43 and 93 cm (fork length - FL) were examined from September 2015 to August 2017. On the 900 examined stomachs, 541 were empty, which is giving a vacuity coefficient of 60.11%. A feeding index (IRI: index of relative importance of food item) combining three methods percentage occurrence, numerical method and weight method) was used. The identification of the items found in the stomach contents revealed that the principals food items were fish (%IRI=48.85) and crustaceans (%IRI=45.78). Cephalopods (%IRI=4.17), fish detritus (%IRI=1.2) and crustaceans (Portunus puber) (%IRI=0.55) are accidental food. The diet of the species does not change according to the seasons and the size of fish

Variations Saisonnières Des Paramètres De Reproduction Et Relation Taille-Poids De Auxis thazard (Lacepède, 1800) Capturé Dans Le Golfe De Guinée Par La Flottille Artisanale Ivoirienne

In this study, the seasonal variation in sex ratio, macroscopic stages of sexual maturity, gonado-somatic ratio, hepatostatic ratio, condition factor, and size-weight relationship in Auxis thazard from Gulf of Guinea were studied from January to December 2016. Sex ratio observed was in favor of males (1: 0,78; X² observed = 20,16 ˃ theoretical X² = 3,84 ; p ˂ 0,05). The variation of maturity stages associated with GSI, HSI, and K during different seasons of the year showed that this specie spawns throughout the year. Length-weight relationship was W = 0,0039 L 3, 4108 (R2 = 0,93 ; N = 291) for males, W = 0,0036 L 3, 4376 (R2 = 0,91 ; N = 227) for females, and W = 0,004 L 3, 4118 (R2 = 0,92 ; N = 519) for the combined sexes. The b value was significantly higher than the theoretical value of 3 for males (t-test, t = 233,218, p ˂ 0,05), for females (t-test, t = 227,776, p ˂ 0,05), and for all individuals (t-test, t = 315,821, p ˂ 0,05). This situation however indicates a faster increase of the fish in weight rather than in length

Seasonal habitat and length influence on the trophic niche of co-occurring tropical tunas in the eastern Atlantic Ocean

In the Gulf of Guinea, bigeye Thunnus obesus (BET) and yellowfin tuna Thunnus albacares (YFT) are important for commercial fisheries and play a prominent ecological role as top predators. Using fatty acid profiles and carbon and nitrogen stable isotopes we examined their niche partitioning in this understudied region. Niche overlap was high (>70%), similar to percentages in other ocean basins. BET occupied a higher trophic position than YFT and fed on deeper prey (high δ15N values and high proportions of mono-unsaturated fatty acids). The trophic position of YFT decreased slightly in the last 15 years (δ15N values decrease ~0.5 ⠰) suggesting a change in epipelagic communities, as observed in the eastern Pacific Ocean. Ontogenic changes were limited to BET. For both species, the dietary proportion of the diatoms marker (20:5n-3) increased in the seasonal upwelling area, highlighting the seasonal habitat influence on tunas diet. The relatively lipid-rich muscle (~6 % dry weight) of Atlantic tropical tunas suggested a richer diet in this region than for Indian Ocean tropical tunas and/or differences in energy allocation strategies.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Differentiation of Spatial Units of Genus <i>Euthynnus</i> from the Eastern Atlantic and the Mediterranean Using Otolith Shape Analysis

The shape of sagitta otoliths was used to compare individuals of little tunny (Euthynnus alleteratus) harvested on board commercial fishing vessels from the coastal areas along the Eastern Atlantic, including the Mediterranean Sea. Fish sampling and selection was designed to cover possible seasonal changes and tuna size. The research encompassed both morphometric and shape analyses of left sagittal otoliths extracted of 504 fish specimens. Four shape indices (Circularity, Roundness, Rectangularity, and Form-Factor) were significantly different between two groups, showing a statistical differentiation between two clear spatial units. The degree of divergence was even more pronounced along the rostrum, postrostrum, and excisura of the generated otolith outlines between these two groups. One group corresponds to the samples from the coastal areas in the Northeast Temperate Atlantic and Mediterranean Sea (NETAM Area) and a second group from the coastal areas off the Eastern Tropical Atlantic coast of Africa (ETA Area). This study is the first to use otolith shape to differentiate tunas from separate spatial units. These results could be used to re-classify previously collected samples and to correct time series of data collected