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Table 4 Morphological and behavioural observations of fingerling of O. niloticus in low pH and control

From: Tolerance level of different life stages of Nile tilapia Oreochromis niloticus (Linnaeus, 1758) to low pH and acidified waters

Observations

pH 3

pH 4

pH 5

pH 6

Control

Morphological

None as mortality was recorded

Very dark body colouration, slimy mucous secretions on the gills and body surface; peeling and skin erosion, bleeding from the dorsal fins and bending of the caudal fin, some fins became disintegrated

Very dark body colouration, slimy mucous secretions on the gills and body surface; peeling and skin erosion, bleeding from the dorsal fins and bending of the caudal fin, some fins became disintegrated

Normal body colouration except some few dark patches, no morphological abnormalities observed.

Normal body colouration, no morphological abnormalities seen

Behavioural

None as mortality was recorded

Lethargy, they were confined to the bottom of the tanks and only moved when agitated with the movement being in one direction, feeding impaired

Swimming velocity decreased

Lethargy, they were confined to the bottom of the tanks and only moved when agitated with the movement being in one direction, feeding impaired Swimming velocity decreased

Movement not impaired, they were seen on the surface of tanks, no abnormal behavioural activities observed

Normal movement and behavioural responses observed