National Screening-Level Risk Assessment (SLRA) of Goldfish, Prussian Carp, Chain Pickerel, and Black Crappie in Canada

Abstract

A Screening-Level Risk Assessment (SLRA) was completed on the potential invasiveness of four freshwater fish species - Goldfish (Carassius auratus), Prussian Carp (Carassius gibelio), Chain Pickerel (Esox niger), and Black Crappie (Pomoxis nigromaculatus) - across 21 Canadian freshwater ecoregions using an adaptation of the Canadian Marine Invasive Screening Tool (CMIST). CMIST applies a series of questions about the invasion process and associated certainty levels. Invasion risk was estimated as the likelihood of invasion (potential for natural and anthropogenic movement, habitat suitability, and establishment) multiplied by invasion impacts (multiple impacts on aquatic populations, communities, habitat, and ecosystem function). High-risk species were Goldfish in the majority of southern ecoregions, Prussian Carp in most of Alberta, Saskatchewan and British Columbia, and Chain Pickerel in Nova Scotia and New Brunswick. Black Crappie was not identified as a high-risk species. Six ecoregions, located across five provinces, were predicted to have high invasion risk from two species; Goldfish and Prussian Carp in British Columbia, Saskatchewan, and Alberta; and Goldfish and Chain Pickerel in Nova Scotia and New Brunswick. Southern ecoregions were more at risk due to a higher likelihood of invasion than northern ecoregions. Southern ecoregions had greater potential for human-mediated introductions and a greater likelihood of secondary spread. Results represent status quo ecological and anthropogenic conditions. Data on how climate change will affect the likelihood of invasion and impact were not available to inform this SLRA. Similarly, data on predicted changes to human-mediated introductions were not available. Important knowledge gaps include limited availability of biological, habitat, and climate data for the Arctic and sub-Arctic regions, and limited information on Black Crappie invasion impacts. These knowledge gaps increased uncertainty in the likelihood of invasion in the Arctic and impacts from Black Crappie, reducing the precision of these invasion risk results. Mapped invasion risk and plots of likelihood and invasion risk, produced in this SLRA, should be interpreted together to better understand the variation among ecoregions.