~ 173 ~ International Journal of Fisheries and Aquatic Studies 2017; 5(1): 173-177 E-ISSN: 2347-5129 P-ISSN: 2394-0506 (ICV-Poland) Impact Value: 5.62 (GIF) Impact Factor: 0.549 IJFAS 2017; 5(1): 173-177 © 2017 IJFAS www.fisheriesjournal.com Received: 27-11-2016 Accepted: 28-12-2016 Blahoua Kassi Georges Laboratory of Hydrobiology, UFR Biosciences, University of Félix Houphouët Boigny 22 P.O. Box 582 Abidjan 22, Côte d’Ivoire Etilé Raphaël N’Doua Laboratory of Hydrobiology, UFR Biosciences, University of Félix Houphouët Boigny 22 P.O. Box 582 Abidjan 22, Côte d’Ivoire Bédia Aké Théophile Laboratory of Hydrobiology, UFR Biosciences, University of Félix Houphouët Boigny 22 P.O. Box 582 Abidjan 22, Côte d’Ivoire Yao Stanislas Silvain Laboratory of Hydrobiology, UFR Biosciences, University of Félix Houphouët Boigny 22 P.O. Box 582 Abidjan 22, Côte d’Ivoire N’Douba Valentin Laboratory of Hydrobiology, UFR Biosciences, University of Félix Houphouët Boigny 22 P.O. Box 582 Abidjan 22, Côte d’Ivoire Correspondence Blahoua Kassi Georges Laboratory of Hydrobiology, UFR Biosciences, University of Félix Houphouët Boigny 22 P.O. Box 582 Abidjan 22, Côte d’Ivoire Seasonal variation in the length-weight relationships and condition factor of Synodontis schall (Bloch and Schneider, 1801) (Siluriformes: Mochokidae) in man- made Lake Ayamé 2 (Côte d’Ivoire) Blahoua Kassi Georges, Etilé Raphaël N’Doua, Bédia Aké Théophile, Yao Stanislas Silvain and N’Douba Valentin Abstract Length-weight relationship (LWR) and condition factor (K) of Synodontis schall (Bloch and Schneider, 1801) were studied in man-made Lake Ayamé 2. Samples of S. schall were collected from catches of artisanal fisheries using various mesh size of gill nets from May 2015 to April 2016. Length-weight data were analyzed and length-weight relationship graphs were plotted for the dry and rainy seasons of the sampling years. The b values in the LWR (W= aL b ) varied between 2.5163-2.7857 for the dry seasons and 3.0008-3.001 for the rainy season indicating that the growth pattern of S. schall had negative allometric and isometric in the seasons respectively. The average condition factor (K) were less than 1 (Mean: 0.315-0.647) during the dry season revealing that this fish species was not in good physiological sate of well-being. However, it was in better condition (K-values were greater than 1; Mean: 1.0375- 1.357) during the rainy season. Keywords: Synodontis schall, length-weight relationship, condition factor, man-made Lake Ayamé 2, Côte d’Ivoire 1. Introduction The genus Synodontis (Cuvier, 1816) commonly known as the up-side-down catfish belongs to the family Mochokidae [1] . The Family comprises three genera-Mochochus, Synodontis and Chiloglanis [2-4] . Synodontis species are currently restricted to freshwaters of Africa, occurring mostly in Central and West Africa [5] and throughout Africa except in the southern-most parts [6] . This genus is widely distributed in inland waters of West Africa [7] particularly and in man- made Lake Ayamé 2. Synodontis schall, Shield-head catfish, is important ecologically. Indeed, it plays silent roles in determining the dynamics and structure of the aquatic ecosystem. This fish represents a relatively cheap source of animal protein and other essential nutrient required in human diet [8] . Apart from its utilization as a food fish, it is important economic and commercial species as it occurs in both subsistence and artisanal fisheries landings. Knowledge of some quantitative aspects such as length-weight relationship is important in studying fish biology. Length and weight relationships are of great importance in fisheries research because they provide information on population parameters [9-11] . In fact, a change in length and weight tells the age and year-classes of fishes, which is important in fishery. The data can also be used to estimate the mortality rate, and furthermore they can be used to assess the sustaining power of the fishery stock. In addition, the data on length and weight can also provide important clues to climatic and environmental changes, and the change in human subsistence practices [12, 13] . At the same time, the relationship of length-weight estimates condition factor of the fish species and fish biomass through the frequency. In fisheries science, the condition factor is used in order to compare the “condition”, “fatness” or wellbeing of fish. And it is based on the hypothesis that heavier fish of a particular length are in a better physiological condition [14] . Condition factor is also a useful index for the monitoring of feeding intensity, age, and growth rates in fish [15] . It is strongly influenced by both biotic and abiotic environmental conditions and can be used as an index to assess the status of the aquatic ecosystem in which fish live.