Dynamic Interdependence between Anglers and Fishes in Spatially Coupled Inland Fisheries

The cumulative harvest pressure exerted by recreational anglers can be intense in some locations. Sustainable management and conservation of inland fisheries requires an understanding of the spatial ecology of fish-angler interactions (e.g., direct, indirect, and feedback). Advancement towards this goal requires study of the complex interdependencies of human and natural systems, which can be achieved, in part, by looking beyond the wetted confines of individual waterbodies towards the broader angling landscape. It has been hypothesized that fish stocks should experience strong reductions in areas near large aggregations of recreational anglers where fishing effort is presumed to be greatest. To test this hypothesis, we examined a complex of direct, indirect, and feedback effects among recreational anglers, bluegill sunfish Lepomis macrochirus, and largemouth bass Micropterous salmoides across inland recreational fisheries (n = 29 reservoirs) using path analysis and structural equation modeling. We found that recreational anglers imparted detectable effects on recreational bluegill (direct) and bass (indirect) fisheries across the landscape, which we attributed to (1) short travel distances of individuals at local scales (<40 km), and (2) a spatially and numerically heterogeneous distribution of anglers (i.e., anglers within counties) at the regional scale. Our study identified the presence of an emergent landscape-scale feedback, driven by angler numbers, mediated via angling effects on bluegill and bass populations, and which manifested as spatially variable movements of anglers. These dynamics collectively shaped inland fisheries across the landscape via a suite of direct, indirect, and feedback effects and highlight the complex relationships between fishes and anglers. Consideration of direct and indirect effects of angling pressure from the landscape should aid in prioritizing or identifying areas in need of management, conservation, public outreach, and education, and improve understanding of how changes to one or many species may feedback to other social, ecological, and economic systems.