Discovery, distribution, and eradication potential of the introduced mud crab, Rhithropanopeus harrisii, in the Panama Canal

Eradication of invasive species is an eminent concept in conservation biology. After prevention is no longer an option, many ecologists argue that eradication is the most effective way to mitigate the risk of impacts from invasive species, given the elevated costs and often prolonged environmental effects of long-term control strategies. In the majority of systems, eradication is most likely to succeed early in the invasion process, when an invader is localized. However, rarely is early eradication considered in practice. This paradox may result from the many uncertainties regarding the future spread and impacts of novel invaders and managers lacking practical guidance to make logical decisions to manage them. In this thesis, I use a case study of an introduced mud crab, Rhithropanopeus harrisii, to propose guidelines for rapidly assessing and communicating the feasibility and the benefits of early eradication. First, I document the recent discovery of an established population of R. harrisii in the Panama Canal, highlighting how maritime traffic in this hub of international shipping may further increase the spread of this invader worldwide. Second, I evaluate the distribution, abundance, and demographics of R. harrisii across the Panama Canal with a standardized quantitative survey; I also assess the crab's potential for spread beyond its distribution in the Canal with two laboratory experiments. Third, I develop an analytical framework for evaluating the feasibility of a rapid response to eradicate R. harrisii and for communicating the potential benefits of this management strategy to decision-makers. My results indicate that R. harrisii currently occupies a limited range within two manmade lagoons adjacent to the Panama Canal, suggesting that eradication may be feasible. Furthermore, salinity tolerance experiments revealed that adults and juveniles could survive in locations within the Canal proper, should their habitat be modified according to the Panama Canal expansion plan. Building on this case study, I suggest a general framework to contend with major challenges of rapid response efforts: limited information about novel invaders, limited time for management, and limited communication between scientists and decision-makers.