Mitigation measures to reduce the risk of introduction and spread of aquatic invasive species through Shellfish and Macroalgal movements

Abstract

Shellfish and macroalgal movements are a known vector for the introduction and spread of Aquatic Invasive Species (AIS). Physical or chemical treatments are one means to reduce this risk, although a comprehensive review of the effectiveness of available options has not been conducted in Canada. To understand the effectiveness and limitations of these various treatments, a literature review of existing options was conducted. That review covered both mortality/removal of AIS and survival of shellfish and macroalgal species being moved. No single treatment was found applicable to all AIS while also maintaining shellfish survival in the context of species movements. Numerous physical and chemical treatment options were identified as being effective (100% mortality/removal) at killing/removing specific AIS. Numerous physical and chemical treatment options were identified as having no/low impacts (≥90% survival) on moved shellfish species, while impacts on moved macroalgae remain a significant gap. Only a few physical and chemical treatment options applicable to multiple AIS, while keeping moved shellfish species alive, were identified (see Tables 3 and 4). There are a number of considerations that may limit the usefulness of those treatments in real-world settings or for other AIS or shellfish and macroalgal species. Key uncertainties include comparing results between taxa, field and laboratory studies, and different experimental designs, scales, and methods of measuring AIS mortality and the use of quantitative and qualitative data. This literature review identified a significant number of gaps (e.g., longer-term impacts on moved species, lack of data on macroalgae, lack of information at commercial scales) with respect to the effectiveness of physical and chemical treatments on specific AIS and their impacts on moved species (shellfish and macroalgae), especially combined treatment options (e.g., heat and chemical applications). Additional considerations such as taxa, season, and site-specific characteristics (e.g., temperature, salinity, pH, humidity) will need to be considered when applying this advice.