Relative value of limnological, geographic, and human use variables as predictors of the presence of Bythotrephes longimanus in Canadian Shield lakes

Abstract

The Eurasian aquatic invader Bythotrephes longimanus has spread rapidly throughout the Great Lakes watershed, particularly in Ontario, Canada, since its introduction in 1982. To date, the documentation of its spread has been largely anecdotal, not the result of planned surveys, so the actual distribution of the invader and the determinants of its distribution in Ontario remain uncertain. We surveyed 193 lakes in south-central Ontario to determine the importance of lake size, lake location, hydrological connection, and various physical, chemical, and human activity parameters in predicting the spread of Bythotrephes within the 1600-lake Muskoka watershed, North America’s most heavily invaded lake region. Invaded lakes were larger than uninvaded lakes and had less acidic, more nutrient-poor, clearer waters. Contingency analyses indicated that invaded lakes were more accessible to humans and had more heavily developed shorelines. Shoreline coverage by cottages was the strongest predictor of Bythotrephes presence when all physical, chemical, and human use variables were included in a logistic regression model. Our results support the growing consensus that humans are primarily responsible for the spread of Bythotrephes.

Effects of chemical and physical conditions on hatching success of Bythotrephes longimanus resting eggs

“…It supports the hypothesis that dispersal to North America was by ship ballast water (Sprules et al 1990), and argues against vectors involving air exposure such as bird feathers. Intolerance to all but short-term desiccation is also consistent with recent observations in North America that motorized watercraft appear to be far more likely than nonmotorized watercraft at spreading B. longimanus between inland lakes Weisz and Yan 2010). Motorized watercraft support more enclosed wet spaces (e.g., engine coolant water and live well water).…”

“…A short period of desiccation tolerance may also explain why B. longimanus range expansion in North America has been slower than Daphnia lumholtzi, another recent invader. Studies documenting early range expansion of each species indicate that during a 12 yr period (1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001) D. lumholtzi expanded its range to about 180 lakes (Havel and Shurin 2004), whereas during a 28 yr period ) B. longimanus expanded to only about 130 lakes (Weisz and Yan 2010). One major challenge for management of nonnative species will be application of multiple decontamination methods simultaneously as short-term (, 1 d) desiccation, for example, may be effective against some species but not others (Ricciardi et al 1995).…”

“…Human recreational equipment (e.g., bait bucket, boat hull, or fishing line) is believed to be the primary overland dispersal vector of B. longimanus Weisz and Yan 2010 (Grigorovich et al 1998), their efficacy at killing resting eggs has not been evaluated. A lack of data on precise desiccation thresholds of the resting egg has also hampered efforts to model dispersal distances that could be achieved by human and nonhuman vectors.…”

Temperature, recreational fishing and diapause egg connections: dispersal of spiny water fleas (Bythotrephes longimanus)

“…Colonized lake sizes ranged between 0.5 and 858 km 2 (mean = 58 km 2 , SD = 177 km 2 ), heavily influenced by Voyageurs' large lakes, whereas lake maximum depth ranged between 7.6 and 56.1 m (mean = 22.7 m, SD = 14.7 m). When plotted with previous survey results (Boudreau and Yan 2004;Branstrator et al 2006;Weisz and Yan 2010), Bythotrephes appears to be actively spreading within a northern latitudinal band that stretches from Ontario to Minnesota (Fig. 1a).…”

“…Extreme measures were taken (formalin preservation of sediment samples, boiling water immersion of sampling gear, washing down canoes) to insure that Bythotrephes was not spread from lake to lake during surveys. Our survey results were added to a map prepared by John Zoltak for the Ontario Federation of Anglers and Hunters (2010), with additional records from Branstrator et al (2006), Alexander andHotchkiss (2009), EPA's National Lakes Assessment (2010), USGS (2010), and Weisz and Yan (2010).…”