Control of invasive sea lamprey (Petromyzon marinus) populations in the Great Lakes is dependent upon migration barriers in suitable tributaries to limit spawning habitat, but these barriers are occasionally overcome by spawning-phase adults, leading to observable larval production upstream of these barriers. Despite this, empirical evidence of escapement events at barriers is rare. Escapement is hypothesized to be influenced by warmer stream temperatures and high discharge, therefore shifting regional patterns of water temperature and hydrological conditions under climate change could lead to less effective barriers and higher larval production. Increased escapement over barriers would negatively affect control efforts by increasing larval habitat and diluting treatment resources across additional reaches. We applied Bayesian belief network models to categorize the probability of observing adult lamprey upstream of terminal barriers across the Great Lakes Basin and understand the influence of climatic, landscape, and hydrological variables on this parameter. Sensitivity analyses were used to assess the relative importance of each variable and indicated that variation in the size of the spawning run in a stream, and the proportion that subsequently reaches a barrier, have the largest effect on both the probability of passing a moderate or high abundance of adult sea lampreys above a barrier. Incorporating future climate projections into the model to evaluate the effect of climate change did not lead to substantial changes in the probability of escapement at each barrier, suggesting that any potential changes in barrier permeability or spawning run size are masked by the large uncertainties in sea lamprey spawning phenology that will require further research to elucidate.
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