Incorporating Allee effects into the potential biological removal level

Abstract

Potential biological removal (PBR) is an approach used to calculate sustainable harvest and “take” limits for populations. PBR was originally derived assuming logistic growth while ignoring the effects of small population size (i.e., an Allee effect). We derived a version of PBR that includes an Allee effect (i.e., small population size or densities limiting population growth rates). We found that PBR becomes less conservative when it fails to consider an Allee effect. Specifically, sustainable harvest and take levels based upon PBR with an Allee effect were between approximately 51% and 66% of levels based upon PBR without an Allee effect. Managers and biologists using PBR may need to consider the limitations if an Allee effect may be present in the species being modeled. Considerations for Management. Based upon our finding, management considerations may include: acknowledging that populations under stress may also be subject to Allee effects; recognizing limitations of approaches such as PBR when applying them to small populations; and broadly considering the Allee effects when using population models for natural resource management.