Abstract
Identifying which nonindigenous species will become invasive and forecasting the damage they will cause is difficult and presents a significant problem for natural resource management. Often, the data or resources necessary for ecological risk assessment are incomplete or absent, leaving environmental decision makers ill equipped to effectively manage valuable natural resources. Structured expert judgment (SEJ) is a mathematical and performance-based method of eliciting, weighting, and aggregating expert judgments. In contrast to other methods of eliciting and aggregating expert judgments (where, for example, equal weights may be assigned to experts), SEJ weights each expert on the basis of his or her statistical accuracy and informativeness through performance measurement on a set of calibration variables. We used SEJ to forecast impacts of nonindigenous Asian carp (Hypophthalmichthys spp.) in Lake Erie, where it is believed not to be established. Experts quantified Asian carp biomass, production, and consumption and their impact on 4 fish species if Asian carp were to become established. According to experts, in Lake Erie Asian carp have the potential to achieve biomass levels that are similar to the sum of biomasses for several fishes that are harvested commercially or recreationally. However, the impact of Asian carp on the biomass of these fishes was estimated by experts to be small, relative to long term average biomasses, with little uncertainty. Impacts of Asian carp in tributaries and on recreational activities, water quality, or other species were not addressed. SEJ can be used to quantify key uncertainties of invasion biology and also provide a decision-support tool when the necessary information for natural resource management and policy is not available.
Highlights
Nonindigenous species introductions are increasing along with human populations, international trade, and transportation (Lockwood et al 2013)
We focused on the recent invasion of Asian carp in North America and on the potential ecological threat they pose to the Laurentian Great Lakes, to Lake Erie
Uncertainty ranges for WY11 and RS11 were wider than those estimated for RG11, and experts frequently attributed this to the variability observed in the historical data for those species
Summary
Nonindigenous species introductions are increasing along with human populations, international trade, and transportation (Lockwood et al 2013). A small proportion of these introductions lead to unwanted establishments with serious negative economic impacts, consequences for human health, and effects on biodiversity and ecosystem function (Williamson & Fitter 1996; Pimentel et al 2005; Tatem et al 2006). Determining which species can establish and cause harm in novel environments is of great scientific and practical interest. Despite this interest, it remains difficult to predict which species will invade (Ricciardi et al 2013). Most invasions are left unmanaged because resource managers and policy makers are ill equipped to determine and implement policies to prevent unwanted effects (Keller et al 2009)
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