Fish mortality due to acute ammonia exposure

Abstract. Fish mortality in the River Umia, near Villagarcia de Arosa, Pontevedra, Spain, which occurred after a discharge from a food sewage works, is studied. Physico‐chemical parameters of water samples from sewage and from the River Umia were studied and concentrations of ammonia sufficiently high to cause toxic effects in fish (702 mg/1 and 302 mg/1 as total ammonia) were found. The toxicity of two concentrations of ammonia was investigated on goldfish, Carassius auratus (L.), using water quality values the same as found in the River Umia, to obtain the same concentrations of un‐ionized ammonia (2·13 mg/1 and 0·91 mg/1). Fish exposed to high concentrations died within 24 h and three of six, which were exposed to the lowest concentration died within 96h. All fish at first showed symptoms of hyper excitability and hyperventilation, and at times of rest showed a decrease in respiration. Post‐mortem findings generally included gill congestion and haemorrhage. Copyright © 1987, Wiley Blackwell. All rights reserve

Histopathological changes in two potential indicator fish species from a hyper-eutrophic freshwater ecosystem in South Africa: a baseline study

Histopatholigical changes were identified in selected target organs from two freshwater fish species, Clarias gariepinus and Oreochromis mossambicus, inhabiting a hyper-eutrophic freshwater aquatic system. The approach was to use a histology-based fish health assessment protocol which included a semi-quantitative histopathological assessment of six target organs (gills, liver, ovaries, testes, kidney, and heart). Results of water quality analysis showed selected variables to be above the recommended levels including pH, ammonia, nitrogen, chloride, and phosphorus. A number of histopathological alterations were identified in the target organs of both species, with the highest number observed in the liver. Species differences were identified in terms of the severity of the alterations within all the organs, with most alterations being regressive in nature. The results of this study provide valuable baseline data for two indicator species inhabiting a hyper-eutrophic system that could be useful for future bio-monitoring studies.The National Research Foundation of South Africahttp://tandfonline.com/loi/taas2