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Size Structures, Length-Weight Relationships and Condition Factors of Synodontis obesus ((Boulenger, 1898: Siluiformes, Mochokidae) were carried out with standard methods in the Lower Cross River, Nigeria to assess the population dynamics of the rarely studied but commercially important species. A total of 241 specimens (124: wet season and 117: dry season) were collected at Ayadehe Head Bridge fishing port in Itu Local Government Area, Akwa Ibom State, Nigeria from August 2020 to January 2021. The overall abundance showed high size variability within months and between seasons. The total biomass of the specimens collected was heavier in the wet season (12020.33g =12.02Kg) than in the dry season (10709.3g =10.7Kg) with an overall biomass of (22729.63g =22.7Kg). The overall size structures were: 15.0 – 28.30 cm, mean: 21.52.44 cm TL; 12.0 – 20.5 cm, mean: 15.881.6 cm SL and 13.20 – 21.50 cm, mean: 16.881.64 cm FL. The total weight of the species varied from 42.30 – 166.0g with overall mean value of 94.31603g. The length and body weight of fish samples caught for both wet and dry season were significantly different (p<0.05).The length composition of the species exhibits unimodal, bimodal and trimodal growth patterns. The species had heterogeneous groups or cohorts (1+, 2+ and 3+) with variation in body weight. The length-at-first maturity of S. obesus was 20.85 cm mid length. Growth coefficient (b) varied between (2.497) for the wet season and (2.617) for the dry season respectively with the mean growth coefficient (b=2.532) in the LWR (W= aLb). The species exhibited negative allometric growth pattern with an increase in length resulting to increase in weight of the fish. The condition factor (K) decreased with increased in the size of fish and ranged from 2.17-2.57 (Mean: 2.35) in both wet and dry seasons. The average condition factor (K) (2.35±0.15) was 1.0 for both seasons revealing that the species was in good physiological state of well-being. The condition factor (K) of S. obesus by size category showed K-values for recruitssexually mature fishaged fish. Thus fish size is an exponential index of condition factor. The results of this study constitute valuable fisheries data that would enhance the availability, conservation, valorization, exploitation and sustainability of S. obesus in the Lower Cross River, Nigeria.

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.