Observations made over a three-year period at the Fish Diseases Laboratory of the African Regional Aquaculture Centre (ARAC), Nigeria, revealed the gradual emergence of a new, highly infectious septicaemic condition in some widely cultivated freshwater fish species. The broad host range included: Heterobanchus bidorsalis, Clarias gariepinus, "Heteroclarias" (a hybrid of these two species, male and female respectively), Chrysichthys nigrodigitatus, and Cyprinus carpio. Clinical signs and pathological lesions associated with the condition were ty ical, irrespective of the fish species affected; natural outbreaks ap eared to be associated with stress &e to environmental factors. The bacterium isolated from moribuncfand freshly-dead fishes was identified as a Bacillus sp., based on the observed cultural, morphological and biochemical characteristics. Fish reinfection trials confirmed that the isolate was the causative agent of the condition. Antibiotic sensitivity tests showed that the organism was sensitive to tetracycline hydrochloride.

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ABSTRACT1. The Nigerian coastal system-estuaries, lagoons, creeks and wetlands-extends for a distance of approximately 850 km with the Niger Delta (area: 75 000 km2) dominating the entire ecosystem.2. Human activities-(oil exploration, haphazard mining of sand from coastal areas, sand filling of wetlands for industrial use, heavy pollution by industries)-severely destroyed the breeding and nursery grounds of commercial fish species between 1973 and 1992.3. As a result, fish landings from capture fisheries decreased from 500 OOO t in the late 1980s to the present 300 OOO t.4. With the Nigerian population increasing at a rate of 3010-4% per year, there is an urgent need for the Federal Government to protect the 850 km coastline, and the riverine wetlands.5. Conservation education should be vigorously pursued on the socio-economic benefits of coastal and riverine wetlands.6. The Federal Government should encourage States and Local Governments to enact environmental laws and regulations. Stiff penalties for violations should be vigorously enforced.7. Companies involved in exploitation and manufacturing in coastal areas should increase their funding of research directed at minimizing oil spillages and discharge of wastes in their areas of operation.

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