Analysis of Food Items and Diet Preference in the Stomach of Synodontis obesus (Boulenger, 1898: Siluriformes, Mochokidae) in the Lower Cross River, Nigeria

Abstract

Analysis of stomach contents of Synodontis obesus (BOULENGER, 1898: SILURIFORMES, MOCHOKIDAE) in the Lower Cross River, Nigeria was carried out with standard methods to assess the food items and diet preference of the S. obesus. A total of 160 individuals of S. obesus (Mochokidae) were collected from October 2022 - January, 2023 at Akan Obio Uraun fishing port in Itu Local Government Area, Lower Cross River, Nigeria from local fishers and used for the study. Analysis of the fullness of stomach showed that 84.4% had food contents while 15.60% were empty stomachs. Samples with one quarter (25%) stomach fullness had the highest value of 28.13% while samples with 100% stomach fullness (18.75%) were more than those with half (50%) stomach fullness (17.52%). Twelve food items were found in the digestive tubes of the species, indicating that the fish has a high level of food selectivity and rich nutrition regime. The percentage frequency of occurrence of the food items with respect to whole sample indicated that plants part accounted for 36.98 %, animal items 21.93%, and palm fruits 16.05%, detritus 9.49%, sand grains 7.30%, insect /insect appendages 6.80%, and unidentified items 1.45 %. The wider food spectrum exhibited by the species revealed trophic flexibility. Food items increased as the fish grows in size but declined at old age indicating transitional diet shift as the fish grows bigger. The fish species is omnivore, feeding on a wide variety of food items including detritus. The results of this study are useful in determining the relationships between food availability, diet favorite and growth of the species in freshwater ecosystem.