Managing Risks from Invasive Marine Species:Is Post-Border Management Feasible?

摘要

Non-indigenous marine species are a major threat to marine environments andeconomies globally. This thesis examines whether management of pest organisms post-border(i.e, after they have established in New Zealand) is feasible in the marineenvironment, using the non-indigenous Asian kelp Undaria pinnatifida as a modelorganism. Background information on Undaria in Chapter 2 recognises the paucity ofinformation on Undaria's impacts. Hence, Chapter 3 investigates ecological effectsfrom Undaria in a low shore rocky habitat. Although negligible effects were described,the uncertainty in extrapolating findings to other places and times means that theprecautionary principle should be applied by managers, and 'worst-case' impactsassumed.Chapter 4 investigates mechanisms for Undaria's natural dispersal, and describesstrategies based on spore release and sporophyte drift that may lead to spread overscales of metres to kilometres. This work highlights the importance of human transportvectors (especially vessels and aquaculture) in the post-border spread of Undaria atregional and national scales. Hence, a case study in Chapter 5 describes aquacultureactivities that could be vectors for spread of Undaria in New Zealand, and presentscriteria for identifying present and future high risk pathways.Chapters 6 and 7 describe methods to reduce the accidental transport of Undaria andother biofouling pests with aquaculture, with a focus on mussel farming. Treatmentsbased on water blasting, air drying and freshwater immersion provide low cost optionsfor equipment such as floats and rope. For treatment of mussel seed-stock, immersionin dilute (4%) acetic acid (the active ingredient in vinegar) is identified as a method thatcould eliminate Undaria and other soft-bodied fouling organisms without resulting in anunacceptable level of mussel mortality.Chapter 8 proposes a risk-based framework for setting post-border managementpriorities based on the feasibility, benefits and costs of risk reduction. This chapterelucidates how knowledge generated from research in Chapters 2-7 can be used in abiosecurity risk management context. It shows that effective management post-borderis possible even when pest organisms become relatively well established, and that thebenefits gained from even limited successes have the potential to greatly outweigh theconsequences of uncontrolled invasion. However, as unwanted species become increasingly widespread, management will become increasingly focussed on theprotection of specific values.Chapter 9 extends some of the ideas proposed in Chapter 8, and considers a broad postbordermanagement framework for marine pests. A comprehensive system shouldconsist of vector management, surveillance, and incursion response that targetsparticular pests or suites of functionally similar species (e.g., biofouling organisms),coupled with generic vector management approaches that aim to reduce humanmediatedtransport of all organisms at a national scale. New Zealand's geographicisolation and low population, hence relatively low level of vector activity, makes themanagement of human-mediated pathways of spread entirely feasible in manycircumstances. Hence, while there are clearly many challenges in the post-bordermanagement of marine pests, this is nonetheless a realistic goal, and probably moreso inNew Zealand than in any other country in the world.