Comparative evaluation of mahua ( Bassia latifolia ) oil cake and castor bean ( Ricinus communis ) seed as fish toxicants for tilapia ( Oreochromis mossambicus ) and panchax ( Aplocheilus panchax ) with residual toxicity assessment on Labeo bata

Comparative evaluation of mahua (Bassia latifolia) oil cake (MOC) and castor bean (Ricinus communis) seed (CBS) was tested as piscicides for tilapia (Oreochromis mossambicus) and panchax (Aplocheilus panchax), and residual toxicity test was done on Labeo bata. Delayed response of CBS compared with MOC was evident as first and total mortality of tilapia was encountered at 4th and 10th hour of application, against 26 hr and 42 hr in panchax respectively. Susceptibility of the test fish to the piscicides was highly variable as tilapia was more susceptible than panchax under both the piscicides tested especially in CBS. Residual toxicity decreased polynomialy over time (R2 ≥ 0.99) and reduced to below 10% on day 13–14 in both MOC and CBS treatments. Both MOC and CBS contributed positively to the nutrient pool of water in which CBS provided more nitrogen compared with MOC. N: P ratio of water in CBS treatment increased exponentially to more than 18 indicating phosphorus limitation.