The model is

dP/dt = aP - bPH

dH/dt = cPH - dH

impulse

P(ti^+) = (1-e)P(ti^-)

where P is prey population

where H is predator population

where a is growth rate of prey

where b is predation rate

where c is conversion rate

where d is death rate of predator

where e is culling rate for prey