Control Strategy of Invasive Alien Mammals 2008

Abstract for Control Strategy of Invasive Alien Mammals 2008
http://reg.let.hokudai.ac.jp/csiam2008.html
Effect of demographic stochasticity on eradication probability of an exotic species.
Hiroyuki Matsuda (Yokohama National University)
Possibility of eradication of an exotic species depends on nonlinearity of CPUE (catch per unit effort). If CPUE is a concave function of the population size N, the cost of eradication is infinitely large under some deterministic population dynamics model. However, if I incorporate demographic stochasticity into the population dynamics, the probability of eradication becomes positive with a finite expected cost. To elucidate this expectation, I consider the following model:N(t+1) = N(t)exp[r – aN(t)] – C(t)+ SX(t)Sqrt[N(t)], C(t) = [1–exp{–qE(t)(N(t)/A)^z}]N(t), where C(t) is catch in number in year t, SX(t) is the magnitude of demographic stochasticity, q is catchability, z is nonlinearity of CPUE, E(t) is the eradication effort, I obtained the eradication probability is positive even when the CPUE is concave (z > 0). Because extinction is a stochastic event, it is impossible to predict when the population goes extinct. Therefore the total cost of eradication and the time length until eradication are uncertain. I just estimate the expected values of the cost and time length.