Impact of extracted substance from neem seed on hatching rate and survival of Tilapia fry

At the present, many agricultural govemmental sectors have recommended and urged farmers to use plant extracted substances to control pests in replacement of synthetic chemicals. As the formers substances are less hazardous to human beings and less impact on environment than the synthetic ones. However, information of the plant extracted substances particularly crude neem (Azadirachta indica) seed extracted substances on aqua-ecology and environment is rather limited. Therefore, it is essential to find out whether these natural pesticides would be phytotoxic to hatching rate and survival of Tilapia fry (Oreochromis niloticus) variety Jitladda No.3 : this fish is reported to be tolerant to environmental constraints. The results obtained from the studies under controlled laboratory conditions showed large effects of the crude neem seed extracted substances on hatching rates, hatched fry and fry survivals. The hatching rates were 93.3, 55.0, 23.3 and 7.5 percent at 0, 2.5, 5.0 and 7.5 mg/L, respectively, at the tested period of 374 hours. The fries obtained from the hatching were then raised for a period of 14 days in the absence of the extracted substances. It was found that the survivals of the fries were markedly decreased with increasing extracted substance concentrations. No survival fry was observed at 7.5 mg/L. only 6.5 and 2.5 percent of the survivals were found at 2.5 and 5.0 mg/L. Interestingly, the eggs hatched in the present of the extracted substances were abnormal fries i.e. banded backbone. LC sub(50) levels of the substaces for the fries at the age of 2 days and 4 weeks old were also investigated. The results showed a variation of tolerance between ages of the fries and duration tested. The LC sub(50) for the 2 days-fry were 23.0, 20.0, 12.0 and 8.0 mg/L at 24, 48, 72 and 96 hours respectively, while the LC sub(50) for the 4 weeks-fry with corresponding with the above times were 30.0, 26.0, 22.0 and 19.0 mg/L. The impacts of substance extracted from plants must be carefully studies before they are recommended to be used as they might have impact on other useful living organisms and environment.