Proportions of movements of anglers, ranging from 201x to 300x, among study area watersheds in the study year.

Lines showing the network of linkages among the 66 watersheds (HUC4 Hydrologic Units) that comprise the 12 US states surrounding the Great Lakes and upper Mississippi River basins. Lines between watersheds represent direct connections made by individual anglers fishing in multiple watersheds in the survey year. The multiple direct connections among watersheds demonstrate the potential for introduction and inter-basin spread of aquatic invasive species by anglers along linked pathways. Connecting lines represent the unweighted numbers of anglers among the 2576 survey participants who connected separate watersheds in a single year. Unweighted values, ranging from 201–300, represent proportions of the millions of licensed anglers in the study area; these three major linkages all connect watersheds to large metropolitan centers. (TIF)</p

Weighted sums of fishing trips to counties by anglers traveling from other counties in a single year in the broader Great Lakes region.

The calculated numbers of fishing trips to counties in the study area by anglers from other counties ranged from 1199 (blue), to more than 143,000 (red) in the single year of 2011. Of the 1042 counties, only 51 had all of the year’s fishing trips originating within the county (black); 148 counties in the study area were not reported as fishing destinations (white).</p

Proportions of movements of anglers, ranging from 1x to 10x, among study area watersheds in the study year.

Lines showing the network of linkages among the 66 watersheds (HUC4 Hydrologic Units) that comprise the 12 US states surrounding the Great Lakes and upper Mississippi River basins. Lines between watersheds represent direct connections made by individual anglers fishing in multiple watersheds in the survey year. The multiple direct connections among watersheds demonstrate the potential for introduction and inter-basin spread of aquatic invasive species by anglers along linked pathways. Connecting lines represent the unweighted numbers of anglers among the 2576 survey participants who connected separate watersheds in a single year. Unweighted values, ranging from 1–10, represent proportions of the millions of licensed anglers in the study area. (TIF)</p

Movements of anglers among study area counties with >10,000 linkages in the study year.

Connections and estimated magnitudes of movements of anglers among counties in the 13 US states surrounding the Great Lakes and upper Mississippi River basins. The estimated 14,766 links among counties in a single year demonstrate the likelihood of spread by anglers and the potential pathways of transfer of aquatic invasive species. Double-yellow lines represent annual connections between counties numbering from 10,017–15,000, and double-red lines range from 9001–10000 angler trips between counties in a single year. (TIF)</p

Anglers who fished in multiple counties.

Among the 2576 survey respondents in the 13 US states surrounding the Great Lakes and upper Mississippi River basins, 1806 individual anglers (70%) fished in more than one county during the survey year. For those anglers who fished in multiple counties, the mean number of additional counties fished was 3.0. One angler fished in their home county and 18 additional counties during the year.</p

Movements of anglers among study area counties with <5000 linkages in the study year.

Connections and estimated magnitudes of movements of anglers among counties in the 13 US states surrounding the Great Lakes and upper Mississippi River basins. The estimated 14,766 links among counties in a single year demonstrate the likelihood of spread by anglers and the potential pathways of transfer of aquatic invasive species. Black dotted lines represent annual connections between counties numbering from 1199–1580; blue dashed lines range from 1581–2259; yellow dashed lines range from 2260–3249; orange dashed lines range from 3250–4182; and red dashed lines range from 4183–5000 angler trips between counties in a single year. (TIF)</p

Network of linkages among the 66 watersheds (HUC4 Hydrologic Units) that comprise the 12 US states surrounding the Great Lakes and upper Mississippi River basins.

Lines between watersheds represent direct connections made by individual anglers fishing in multiple watersheds in the survey year. The multiple direct connections among watersheds demonstrate the potential for introduction and spread of aquatic invasive species by anglers along linked pathways. The 2576 survey participants were a subset of all anglers fishing in the study region; nevertheless, their fishing behavior connected 92% of the watersheds through inter-basin angler travel along 541 different potential linkage pathways.</p

Movements of anglers among study area counties with 5000–10,000 linkages in the study year.

Connections and estimated magnitudes of movements of anglers among counties in the 13 US states surrounding the Great Lakes and upper Mississippi River basins. The estimated 14,766 links among counties in a single year demonstrate the likelihood of spread by anglers and the potential pathways of transfer of aquatic invasive species. Black lines represent annual connections between counties numbering from 5000–6000; blue lines range from 6001–7000; green lines range from 7001–8000; yellow lines range from 8001–9000; orange lines range from 8001–9000; and red lines range from 9001–10,000 angler trips between counties in a single year. (TIF)</p

Proportions of movements of anglers, ranging from 11x to 50x, among study area watersheds in the study year.

Lines showing the network of linkages among the 66 watersheds (HUC4 Hydrologic Units) that comprise the 12 US states surrounding the Great Lakes and upper Mississippi River basins. Lines between watersheds represent direct connections made by individual anglers fishing in multiple watersheds in the survey year. The multiple direct connections among watersheds demonstrate the potential for introduction and inter-basin spread of aquatic invasive species by anglers along linked pathways. Connecting lines represent the unweighted numbers of anglers among the 2576 survey participants who connected separate watersheds in a single year. Unweighted values, ranging from 11–50, represent proportions of the millions of licensed anglers in the study area. (TIF)</p

Connections and estimated magnitudes of movements of anglers among counties in the 13 US states surrounding the Great Lakes and upper Mississippi River basins.

The estimated 14,766 links among counties in a single year demonstrate the likelihood of spread by anglers and the potential pathways of transfer of aquatic invasive species. Faint black lines represent annual connections between counties numbering from 1–5,000; red lines range from 5,000 (thinner lines), to 40,000 (thick lines) angler trips between counties in a single year.</p