Lakes had been initial clustered having fun with a great k-mode class studies off visibility–absence research away from nine top sportfish varieties throughout the Wisconsin lakes book dataset (Data leggi qui step 1, 2; Secondary Dataset 1; Wisconsin Agencies out-of Sheer Tips 2009 ). K-mode team data tries in order to partition readily available observations with the often good predefined or a vague amount of central tendencies centered on user possibilities (Hartigan and you can Wong 1979 ). Our very own 1st k-mode investigation led to six preliminary clusters. Based on biologist opinions, these types of groups was re-structured with the one or two the new level-you to definitely groups: “simple” and you will “complex” sportfish communities (Figure 2). Easy sportfish groups have been those people defined as that have fewer than around three sportfish kinds teams without Walleyeplex sportfish groups was basically people outlined just like the that have more than four sportfish species; all Walleye and most Muskellunge lakes was basically within party.
Tier-one or two category
Several the brand new k-setting party analyses was performed for the the members of the easy and you can advanced level-that groups using DD and Secchi breadth research (Profile 2). The DD and Secchi depth research have been normalized and you may oriented using an enthusiastic letter ? step 1 sales (Bradley and you may Fayyad 1998 ). Both in team analyses, what number of critical clusters try pre-discussed during the four to help you methodically develop combos out of drinking water heat and you can clearness services (Profile step three). Since the groups got laid out, ponds in place of temperatures analysis was basically put in new warm groups (the most plentiful thermal classification) employing clarity group subscription dependent on Secchi depth investigation (readily available for the majority of ponds). Eventually, i known transitional members of heat and you may clarity groups since men and women lakes having the higher or all the way down 5% away from DD otherwise indicate Secchi beliefs (Profile 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.