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 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 gray literature and conducted a separate analysis for studies using presettlement and postsettlement 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 in the present review are based on published standard guidelines, methods reported in the published and gray literature, and the expertise of TTWG members and an external panel. In addition, our review identifies 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). Environ Toxicol Chem 2023;42:1649–1666. © 2023 His Majesty the King in Right of Canada. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. Reproduced with the permission of the Minister of Environment and Climate Change Canada. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

The live marine baitworm trade harvests, packages, and ships polychaete worms and packing algae (wormweed) from Maine, USA to consumers globally, inadvertently transferring numerous invertebrates that naturally occur in the algal habitat. Here, we use a focal taxa, the globally invasive European green crab Carcinus maenas, to examine costs associated with the successful introductions via this vector and suggest an alternative packaging, already in use in Europe. We show that restricting the use of wormweed at the source could solve the problem of transferring hitchhikers without a change in product cost. However, to the extent that baitworms in wormweed are what US consumers are accustomed to receiving, alternative packing might restrict demand for baitworms, lower producer prices, and reduce quantities traded. Avoiding such economic costs and receiving the benefits of reduced likelihood of unwanted invasion at low or no cost to producers should be of interest to policymakers and practitioners tasked with protecting ecosystems.

Zebra mussels (Dreissena polymorpha, Pallas, 1771) are an aquatic invasive species in the United States, and new infestations of zebra mussels can rapidly expand into dense colonies. Zebra mussels were first reported in Marion Lake, Dakota County, Minnesota, in September 2017, and surveys indicated the infestation was likely isolated near a public boat access. A 2.4-hectare area containing the known zebra mussel infestation was enclosed and treated by area resource managers for 9 days with EarthTec QZ (target concentration: 0.5 milligrams per liter as copper), a copper-based molluscicide, to eradicate the zebra mussels. Researchers led an onsite bioassay to provide an estimate of the treatment efficacy within the enclosure. The bioassay was conducted in a mobile assay trailer that received a continuous flow of treated lake water. Bioassay tanks (n=9; 350 liters) within the trailer were stocked with zebra mussels (25 mussels per containment bag; 7 bags per tank) collected from White Bear Lake, Ramsey County, Minn. Mortality in the treated bioassay tanks reached a mean of 99 percent (95-percent confidence interval: 98-100 percent), there were no mortalities in the control tanks. However, a predictive model produced for timely delivery to area resource managers indicated zebra mussel mortality within the treated enclosure may have been as low as 85 percent. Onsite bioassays are a viable and important tool for treatment evaluation particularly in newly infested waterbodies with low zebra mussel densities.

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