الفهرس 
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Abstract
Photosensitizers in particularly hematoporphyrin (HP), photomolluscicide, has been investigated. The results indicated that the 96 hrs LC50 of HP to Nile tilapia, Oreochromis niloticus was 0.4 X 10-5 Mol/l in case of fry fish (2 g) and 0.2×10-3 Mol/l in case of adult fish (50 g). Hatchability rate revealed a decrease in eggs collected from fish exposed to 0.2 X 10-4 Mol HP/l for 12 weeks and recording zero in eggs of fish exposed to half lethal concentration, 0.2 X 10-3 Mol HP/l, for 96 hrs. Fish exposed to 2 X 10-7 Mol HP/l and 2 X 10-6 Mol HP/l for 24 hrs revealed normal hematological parameters as well as liver and kidney functions and other studied serum constituents and nonsignificantly different in comparison with those of control group fish. However, exposure of fish to 2 X 10-5 Mol HP/l for 24 hrs showed disturbances in the physiological status and clear damage in gills, liver and kidneys of fish. Trials were carried out to treat the physiological disturbances and histopathological damage occurred by the action of fish exposure to sublethal concentration of hematoporphyrin for 24 hrs by refreshing and rearing fish in dechlorinated tap water for two weeks. In comparison with the traditional molluscicide, copper sulphate disturb the physiological status of fish, deteriorate fish meat quality (decrease in muscle total protein and total lipids with an increase in muscle water content), bioaccumulate and damage fish tissues (gills, liver and kidneys) and hence become a threat to man. The results revealed that hematoporphyrin is much safer than other chemical molluscicide as its degradation within 2 – 3 hours in sunlight.