Lakes was indeed first clustered having fun with a good k-means class data from exposure–absence data off nine primary sportfish variety about Wisconsin ponds guide dataset (Rates 1, 2; Second Dataset step 1; Wisconsin Agencies from Natural Information 2009 ). K-setting class research aims in order to partition available findings with the both a beneficial predefined or a vague amount of main tendencies based on member www.datingranking.net/de/europaische-dating-sites alternatives (Hartigan and you can Wong 1979 ). Our very own first k-function investigation resulted in six initial groups. Considering biologist feedback, these clusters was basically re-organized to the a couple the new level-one groups: “simple” and “complex” sportfish groups (Contour dos). Simple sportfish communities have been people identified as having under three sportfish varieties organizations no Walleyeplex sportfish organizations was in fact the individuals outlined because the which have over four sportfish kinds; all the Walleye and most Muskellunge lakes was indeed contained in this team.
Tier-a couple class
One or two the fresh new k-means cluster analyses was performed toward most of the people in the straightforward and you will cutting-edge tier-one to clusters playing with DD and you may Secchi depth study (Figure 2). All DD and you will Secchi depth analysis was normalized and you may centered having fun with an letter ? 1 conversion process (Bradley and you can Fayyad 1998 ). In people analyses, just how many terminal groups are pre-defined during the five so you’re able to methodically make combos of drinking water temperature and you will understanding characteristics (Figure step 3). While the clusters got outlined, lakes rather than temperatures research was indeed put in the brand new enjoying groups (more plentiful thermal group) with regards to clearness group subscription dependent on Secchi depth data (designed for nearly all ponds). Finally, we recognized transformation people in temperature and understanding classes since those lakes having the higher or lower 5% away from DD or imply Secchi thinking (Shape 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.