The lagoon is separated from the sea by a sandbar and much of the terrain close to the lagoon is swampy, with taller vegetation and some trees. In the shallow parts of the lagoon there are a range of invertebrates including polychaete worms, nemertean worms, oligochaetes, isopods, amphipods and prawns. Over a hundred species of fish have been recorded in the lagoon, and it and the surrounding swamps are home to the African manatee, the pygmy hippopotamus, the Nile crocodile, the West African slender-snouted crocodile and the dwarf crocodile. Birds such as the African darter, the Pel's fishing owl, the white-crested tiger heron and the goliath heron breed here. Parts of the lagoon are highly polluted. Chemical pollution comes from the agricultural and industrial activity in the catchment area, with fertiliser run off occurring particularly in the wet season. Organic and bacterial pollution occurs mainly in urban areas, with high levels of "Escherichia coli" and "Clostridium perfringens" being detected. There is an artisanal fishery on the lagoon, employing about seven thousand people using four thousand boats with a potential annual catch of around . The bonga shad ("Ethmalosa fimbriata") accounts for about 75% of the catch, especially in the more polluted waters near Abidjan where it is more abundant than other species. Other fish are found away from the urban areas in unpolluted waters, with the Atlantic bumper ("Chloroscombrus chrysurus") and the Madeiran sardinella ("Sardinella maderensis") being abundant, and the Guinean striped mojarra ("Gerres nigri") and Senegal jack ("Caranx senegallus") also contributing to the catch.