Bias and Error Propagation in Logistic Production Models

Abstract

Maximum sustainable yield (MSY) and the effort at MSY (EMSY) are estimated from simulated catch and effort data to determine the biasing and susceptibility to error propagation of three commonly used techniques. The effects of smoothing, distribution of error between catch and effort, and delays in the density-dependent growth are investigated with respect to forming such estimates. It is found that MSY and EMSY levels derived from these methods suffer in varying degrees to bias (sometimes greater than a factor of 2) and variability (sometimes a coefficient of variation greater than 1). These results are dependent upon the method used and the parameters used to produce the data, especially how dynamic the modeled stock is. Therefore, information about the biological nature of the stock, especially the intrinsic growth rate, is important to correct the biasing of an estimation method. It is concluded that Gulland's and Schnute's methods should both be used keeping in mind the expected biases from this study.Key words: production model, management, maximum sustainable yield, error propagation