Propagule pressure (i.e., the frequency and abundance of introductions) is a common indicator of the likelihood of nonindigenous aquatic species (NAS) establishment success. Evaluating propagule pressure associated with multiple introduction pathways relative to present NAS distribution patterns may identify which pathway presents the greatest risk. Our objective was to develop and evaluate three geospatial metrics for the Laurentian Great Lakes as proxies of propagule pressure associated with three major introduction pathways: maritime commerce, organisms in trade, and water recreation. Logistic and linear regression analyses were conducted between NAS presence and introduction pathway intensity (e.g., number of vessel trips received by a port) for 23 NAS over a five-decade period (1970–2013). Notably, city population size was the best predictor of NAS presence, even for NAS introduced through ballast water discharge. Moreover, through time, city population size was an increasingly significant predictor of the presence of organisms in trade, signaling a change in both the types of organisms introduced and places where introductions are occurring. Nonetheless, all three metrics are reasonable proxies for propagule pressure and as such are applicable for risk assessment, monitoring, and control strategies.

中文翻译：

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劳伦大湖中与非本土水生物种引入相关的途径和地点

繁殖压力（即引入的频率和丰度）是非本地水生物种 (NAS) 建立成功可能性的常见指标。评估与当前 NAS 分布模式相关的多个引入途径相关的繁殖压力可以确定哪条途径存在最大风险。我们的目标是开发和评估劳伦森五大湖的三个地理空间指标，作为与三个主要引入途径相关的繁殖压力的代理：海上贸易、贸易中的生物和水上娱乐。对 23 家 NAS 的 NAS 存在和引入途径强度（例如，港口接收的船舶航行次数）在 5 个十年期间（1970-2013 年）进行了逻辑和线性回归分析。尤其，城市人口规模是 NAS 存在的最佳预测指标，即使对于通过压载水排放引入的 NAS 也是如此。此外，随着时间的推移，城市人口规模成为贸易中生物存在的越来越重要的预测指标，表明引入的生物类型和发生引入的地方都发生了变化。尽管如此，所有三个指标都是繁殖压力的合理代理，因此适用于风险评估、监测和控制策略。