Lakes was basically first clustered playing with a beneficial k-function cluster study regarding exposure–absence analysis out-of 9 no. 1 sportfish kinds regarding the Wisconsin lakes guide dataset (Figures 1, 2; Secondary Dataset 1; Wisconsin Agencies off Pure Info 2009 ). K-setting group investigation tries so you’re able to partition offered observations towards the both a beneficial predetermined or an undefined number of main inclinations according to representative possibilities (Hartigan and you will Wong 1979 ). Our initial k-means data triggered half dozen initial groups. According to biologist feedback, such groups was in fact re also-arranged into the a couple of brand new tier-you to groups: “simple” and you can “complex” sportfish organizations (Contour 2). Effortless sportfish organizations were those people recognized as with less than around three sportfish kinds groups without Walleyeplex sportfish groups were those individuals outlined because with more four sportfish kinds; all the Walleye and more than Muskellunge lakes was in this group.
Tier-two class
A couple this new k-means team analyses had https://datingranking.net/es/citas-sud/ been did towards the people in the simple and you may advanced level-you to definitely clusters playing with DD and you will Secchi breadth investigation (Figure dos). Most of the DD and you will Secchi breadth study had been stabilized and you may based using an n ? step one conversion (Bradley and you can Fayyad 1998 ). In both group analyses, just how many critical clusters was pre-discussed at four so you can methodically create combos from water temperature and understanding attributes (Profile step three). Since the groups is laid out, ponds in the place of temperatures data was basically added to this new warm categories (probably the most abundant thermal classification) with the clarity classification subscription dependent on Secchi breadth investigation (designed for nearly all ponds). Finally, i understood transitional members of heat and understanding classes since men and women ponds obtaining the upper or all the way down 5% away from DD otherwise mean Secchi philosophy (Figure step 3).
Special times
We identified several unique lake types a priori through lake lists already used in existing laws or policies. In Wisconsin, “two-story lakes” receive additional protection in the form of more stringent phosphorus water quality standards. Two-story lakes are deep stratified lakes with sufficient oxythermal habitat to support both warmwater and coldwater fisheries (Lyons et al. 2017a ; Parks and Rypel 2018 ). Two-story lakes were included in the tier-one cluster analysis, therefore, we combined results from that analysis with the existing two-story list to produce two terminal lake classes termed “simple–two-story,” and “complex–two-story” lakes. We identified riverine lakes a priori as those with brief hydrologic retention times (<15 d). This value is already used to define riverine lakes for existing phosphorus water quality standards. Again, we used the tier-one classification to first identify simple and complex lakes and, subsequently, “simple–riverine” and “complex–riverine” lakes.
Wisconsin also has a unique set of shallow coldwater lakes locally referred to as “spring ponds” (Carline 1980 ). These lakes are very small (typically <5 ha), and sourced by groundwater within and outside the catchment (Carline 1977 ). Spring ponds support naturally reproducing and stocked Brook Trout, Brown Trout, and Rainbow Trout populations. An updated list of spring ponds was developed by way of this study; however, this list remains a work in progress because of the large number of small and private ponds with limited to no access. It was also evident from our initial tier-one cluster analysis that one cluster incorporated most of the spring ponds. However, this same cluster also included small impoundments on trout streams that supported simple fish communities dominated by trout. Therefore, we retained Cluster 3 as a terminal lake class that incorporated both spring ponds and small impoundments on trout streams. This lake class was renamed “simple–trout ponds,” which we now define as small, shallow lakes with sufficient coldwater habitats to support trout fisheries. Example photos of all lake classes are presented in Figure 4.
