A twenty four week fish sampling (twice weekly) was conducted to determine the status of the fish species in the middle reach of the Sombreiro River in Rivers State. The results revealed a composition of 31 species from 20 families from a total fish catch of 40,509. The Sardinella maderensis was the most prominent species followed by the Mugilidae- Liza falcipinnis and Mugil cephalus. There were 13 species that were least, including the Illisha africana. The abundance score showed that some species like the Sardinella maderensis were dominant(D), some Abundant( A), some Few, some Common (C), others like the Lophius. vailanti were Rare (R). However, the abundance also varied significantly during the period of the study, indicating a seasonal abundance with the 1st to 6th weeks higher abundance for most species, and then a drop in abundance from the 7th week, when some species became unavailable (Dasyatis margarita), to 24th week when many decreased in abundance. Interestingly, some species increased in number (Pomadasys jubelini , Arius lasticutatus) and others (Seratherodon melanotheron) remained stable. The analysis of variance (ANOVA, P < 0.05) showed that there was significant difference between weeks of the study with the 1st and the 2nd weeks being highly significant, and clusters of weeks signifying the dry season significantly different from the weeks of the rainy season.