Fig 1.
The study area encompassed 12 states 1042 counties and 66 watersheds (HUC4 Hydrologic Units) in the broader Great Lakes and upper Mississippi River basins in the northern and mid-western US.
Surveys of 2576 licensed anglers who fished within the study area in 2011 provided a representative sample from which to estimate the behaviors and patterns of movements of more than 6.5 million licensed US anglers who fished in waters of those states in a single year.
Fig 2.
Weighted sum of all fishing trips by anglers in the broader Great Lakes region in a single year to counties in 12 US states surrounding the Great Lakes and upper Mississippi River basins.
The estimated numbers of fishing trips with destinations to each of the 1042 individual counties ranged from 1199 (blue), to more than1.95 million (red) in the single year of 2011. Only 148 of the 1042 counties in the study area were not reported as fishing destinations (white).
Fig 3.
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).
Fig 4.
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.
Fig 5.
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.
Fig 6.
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.