Review and development of best practices for toxicity tests with dreissenid mussels.

Since their introduction to North America in the 1980s, research to develop effective control tools for invasive mussels (Dreissena polymorpha and D. rostriformis bugensis) has been ongoing across various research institutions using a range of testing methods. Inconsistencies in experimental methods and reporting present challenges for comparing data, repeating experiments, and applying results. The Invasive Mussel Collaborative (IMC) established the Toxicity Testing Work Group (TTWG) in 2019 to identify "best practices" and guide development of a standard framework for dreissenid mussel toxicity testing protocols. We reviewed the literature related to laboratory-based dreissenid mussel toxicity tests and determined the degree to which standard guidelines have been used and their applicability to dreissenid mussel testing. We extracted detailed methodology from 99 studies from the peer-reviewed and grey literature and conducted a separate analysis for studies using pre-settlement and post-settlement mussels. We identified specific components of methods and approaches that could be refined or standardized for dreissenid mussels. These components included species identification, collection methods, size/age class distinction, maintenance practices, testing criteria, sample size, response measures, reporting parameters, exposure methods, and mortality criteria. We consulted experts in the field of aquatic toxicology and dreissenid mussel biology on our proposed. The final recommendations contained herein are based on published standard guidelines, methods reported in published and grey literature, and the expertise of TTWG members and an external panel. Additionally, the review identified research needs for dreissenid mussel testing including improved methods for early life stage testing, comparative data on life stages and between dreissenid mussel species, inclusion of a reference toxicant and additional testing of nontarget species (i.e., other aquatic organisms).