A study was carried out to estimate the populations of the periwinkles Tympanotonus fuscatus and Pachymelania aurita at the Rumuolumeni mangrove swamp creek in the Nigeria, Niger Delta sub-region. Weekly sampling of the gastropods was done and the capture mark-releaserecapture method was used for the population estimation. The Lincoln index was used for the calculation of the total population. The results indicated that T. fuscatus was more abundant in the area than P. aurita. It was opined that since P. aurita was more susceptible to pollution than T. fuscatus, its reduced population density could be attributed to the activities of oil companies operating in the Niger Delta region and their attendant pollution of the brackish water ecosystem, in addition to reproductive failure resulting from climate change.

The food habits of the mudskipper Periophthalmus keolreuteri (Pallas) from the mudflats at Rumuolumeni Creek, Niger Delta, Nigeria were studied. The frequency of occurrence and 'point' methods was used for the gut content analysis. The results indicate that the juveniles were herbivorous feeding more on aquatic macrophytes, diatoms and algal filaments while the adults had a dietary shift towards crustaceans, aquatic and terrestrial insects and polychaetes. The amphibious lifestyle of the mudskipper confers on it the trophic position of a zoobenthivore and a predator.

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