Abstract: Based on observation of the predatory behavior of ladybirds, it is considered that the predator's activity on different prey densities can be expressed by the differential equation, dNa/d(N^-1)=-bNa. The integral equation of functional response is expressed as Na=a穚積xp(-b穚^1-m種^-1)Where, a: maximum number of prey attacked, b: optimum density of prey for the activity of predator. Na: total number of prey attacked. N: density of prey. P: density of predator. m: interference coefficient among natural enemies.

Key words: Lead, Goldfish, Particulate lead, Bioavailability