Both behavioral and histological analyses were carried out for durations of 7, 14, 28 and 56 days of exposure. This study was focused on behavioral and histo-pathological changes (gills, liver and kidney) of striped catfish (Pangasionodon hypopththalmas) exposed to four salinities (0, 4, 8 and 12 ppt), each with three replications for 56 days. Salinity intrusion due to climate changes in the coastal area is substantially jeopardized for sustainable aquaculture. Overall, the study provided useful information on the ecological pollution status of the Forcados Estuary and this will serve as a baseline for future research on the assessment of the ecological integrity of the estuary. Canonical correspondence analysis (CCA) revealed differential responses of macroinvertebrates to physico-chemical variables, with species such as Callinectes latimanus and Mactra nitida increasing the non-disturbed Stations 4 and 5, whereas Corixa punctata and Thias callifera dominated the disturbed Stations 1 and 2. The non-metric multi-dimensional scaling (NMDS) showed no distinct cluster for macroinvertebrates collected in both wet and dry seasons. Coenagrion pulchellum (damselfly) was the least represented taxa, with only one taxon recorded throughout the study period. Pachymelania fusca (freshwater snail) was the most preponderant taxa with 2,095 individuals recorded during the study period, followed by Tympanotonus fuscatus (brackish water snail) with 2,011 individuals. A total of 14,685 macroinvertebrate individuals were recorded in the entire study period. Principal Component Analysis (PCA) conducted for both wet and dry seasons showed that season played a key role in the pollution gradient of the estuary. Whereas the highest mean zinc concentration was recorded in Station 2 (23.12 ± 11.96 mg L− 1). There was a relatively high mean concentration of iron (39.7 ± 20.71 mg L− 1), copper (12.22 ± 5.33 mg L− 1) and lead (2.97 ± 1.98 mg L− 1) in Station 1 compared to the remaining four stations. Physico-chemical variables collected in the estuary classified the sampling stations into potential ecological categories, reflecting an increasing pollution gradient, with Stations 1 and 2 classified as heavily polluted stations. Physico-chemical variables and macroinvertebrates were sampled in five stations for 24 months between April 2012 and March 2014. In this study, we investigated the structural assemblage of macroinvertebrates of the estuary to provide an exploratory account of the water quality status of the estuary. However, the ecological health integrity of the estuary is seriously degrading due to crude oil and gas production, as well as run-off from surrounding communities. Our results therefore suggest that the occurrence of nodular alterations is not an acute, seasonal response, but rather a chronic, and possibly, and more interestingly, a species-specific, pathological response.įorcados Estuary is a key water body in Delta State, Nigeria, serving various purposes such as fishing and oil exploration sites. However, we could not establish a seasonal pattern regarding the occurrence of these alterations and therefore no association between the occurrence of the liver pathology and the cyanobacterial blooms. The microscopic characteristics of the nodules were primarily associated with pre-neoplastic, focal areas of cellular alterations most prevalent were focal areas of steatosis. Affected fish also showed an increase in the ratio of liver mass to body mass, i.e., the hepatosomatic index. gariepinus and no macroscopically visible alterations in O. We found a species difference with a 48% prevalence of nodular alterations in C. Nodular alterations in livers were assessed both macroscopically and microscopically. A total of 115 Clarias gariepinus (Burchell) and 98 Oreochromis mossambicus (Peters) were collected seasonally across six different surveys over a period of 3 years. This freshwater system is characterized by seasonal cyanobacterial algal blooms which release bio-toxins, including hepato-toxins, which can have negative effects on the health of the resident fish population.
This paper reports on the seasonal and species comparison of hepatic nodular alterations in two indicator fish species from the hyper-eutrophic Roodeplaat Dam in South Africa.
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