Crayfish represent important links in aquatic food webs because they have diverse, omnivorous diets and are an important source of energy for fishes and birds. Crayfish have the ability to increase sediment transport through bioturbation, some are considered ecosystem engineers due to their burrowing habits, and crayfish invasions have been linked to large declines in biodiversity and changes in ecosystem structure and function. Despite their ecological importance and the threats that invasive crayfishes pose, the distribution of crayfishes in the Laurentian Great Lakes is not well studied. Here, we report on four years of intensive crayfish surveys in the southwestern portion of the Lake Michigan Basin, a region with diverse freshwater ecosystems and few previous records of crayfish distribution. From 2015 to 2018, baited minnow traps and SCUBA were used to document the distribution and abundance of crayfish across streams, rivers, inland lakes, and Lake Michigan. Six species of crayfish were captured, including two invasive species. The invaders are the widely distributed and abundant Faxonius rusticus (rusty crayfish) and Procambarus clarkii (red Swamp crayfish), a species early in the invasion phase. Native species were found in fewer habitat types and were less abundant than invasive F. rusticus. Comparing our results to previous sampling showed that native crayfish distribution and diversity have declined at the same time that F. rusticus has spread over recent decades. There is potential for new and recently introduced invaders, such as the red swamp crayfish, to further alter ecosystems.

小龙虾是水生食物网中的重要环节，因为它们具有多样化的杂食性饮食，是鱼类和鸟类的重要能量来源。小龙虾有能力通过生物扰动增加沉积物运输，有些小龙虾因其穴居习性而被认为是生态系统工程师，小龙虾入侵与生物多样性的大幅下降以及生态系统结构和功能的变化有关。尽管它们的生态重要性和侵入性小龙虾构成的威胁，劳伦森五大湖中小龙虾的分布尚未得到很好的研究。在这里，我们报告了密歇根湖盆地西南部四年的密集小龙虾调查，该地区淡水生态系统多样，以前的小龙虾分布记录很少。从 2015 年到 2018 年，诱饵小鱼陷阱和 SCUBA 被用来记录小龙虾在溪流、河流、内陆湖泊和密歇根湖的分布和丰度。捕获了六种小龙虾，包括两种入侵物种。入侵者分布广泛，数量众多Faxonius rusticus（生锈的小龙虾）和Procambarus clarkii（红沼泽小龙虾），一种处于入侵阶段早期的物种。在较少的栖息地类型中发现了本地物种，并且比入侵的F. rusticus数量更少。将我们的结果与之前的抽样进行比较表明，近几十年来，本地小龙虾的分布和多样性在F. rusticus传播的同时有所下降。新的和最近引入的入侵者，如红色沼泽小龙虾，有可能进一步改变生态系统。