Research Document 2017/031

Overland Spread of Aquatic Invasive Species among Freshwater Ecosystems due to Recreational Boating in Canada

By Drake, D.A.R

Abstract

A literature review was conducted to summarize the overland spread of aquatic invasive species (AIS) among freshwater ecosystems due to recreational boating in Canada. Based on a review of 57 primary publications, factors contributing to overland spread involved heterogeneity in individual boater behaviour, such as differences in trip-taking frequency, the timing between trips, and the spatial distribution of boating locations relative to source populations of AIS. These factors, in addition to measures taken by boaters to remove AIS from boats and related equipment (such as picking visible material from anchors or cleaning hulls) dictate the variety, density, and viability of transported AIS between source and recipient ecosystems, ultimately determining the likelihood of overland spread. Therefore, as with other pathways of AIS introduction and spread within Canada, a subset of human-mediated events pose the majority of invasion risk due to context-dependent environmental and behavioural factors.

Contamination of boats and equipment with AIS can be classified based on the functional fouling characteristics of species, such as:

1. plankton and organisms with planktonic stages, transported in live wells, bilge water, and other whole-water niche spaces;
2. organisms with direct attachment potential (i.e., freshwater molluscs), transported by direct attachment on hulls and trailers; and,
3. organisms with indirect fouling potential, commonly entangled on trailers and related equipment such as anchor lines (i.e., aquatic macrophytes, benthic invertebrates).

The overland movement of recreational boats has led to the spread of several high-profile AIS in Canada, such as Spiny Waterflea (Bythotrephes longimanus), Fishhook Waterflea (Cercopagis pengoi), and Dreissenid spp. (predominantly transported as veligers), and is suspected in the transport of Eurasian watermilfoil (Myriophyllum spicatum) and Bloody-red Mysid (Hemimysis anomola). Future AIS having functional characteristics similar to these species are expected to undergo boater-mediated overland spread in Canada. Moreover, because the spatial distribution of several high-profile AIS correlates strongly with overland boat movements, future spread appears to be predictable with relatively high fidelity. A first-order estimate of the number of inland boaters (1.5 million) and inland boating trips (24.7 million/y) likely underestimates the scale of the pathway among freshwater ecosystems in Canada. Based on a simulated range of per-boating-trip probabilities of AIS introduction, even infrequent rates of overland AIS transfer (e.g., 1 in 1,000, 1 in 10,000, or 1 in 100,000 boating trips) will lead to at least 10, 100, or 1,000 nationwide AIS introduction events per year. Results of this assessment support the management of AIS in Canada by documenting the scale of the pathway, identifying species and functional groups of regional and national concern, and informing the development of offensive and defensive AIS management programs.

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