Myxospore detection in soil and angler movement in Southwestern Montana : implications for whirling disease transport

Abstract

Movement of anglers among rivers in southwestern Montana presents a potential pathway for the spread of whirling disease and other aquatic nuisance species (ANS) on soil laden angling equipment. The objectives of this study were to 1) determine the effectiveness of a density extraction to isolate myxospores from soil and the effectiveness of polymerase chain reaction (PCR) at detecting M. cerebralis myxospores in soil; 2) quantify movement of resident and non-resident anglers in southwestern Montana and soil quantity carried on angling equipment; and 3) determine myxospore adherence to wading equipment materials. Myxospores were extracted from soil using a soil particle density separation technique. A single blind study was used for PCR experiments with varying quantities of myxospores and soil. Angler movement was assessed with a survey at fishing access sites on six southwestern Montana rivers. Soil samples were taken during the survey from boots and waders with a pressure sprayer to assess quantity of soil carried on angling equipment. Myxospore adherence to wading materials (lightweight, neoprene, rubber, and felt) was tested by exposing myxospores to material and rinsing with a pressure sprayer.

Mean percent myxospore recovery with density extraction declined as soil quantity increased. Polymerase chain reaction experiments detected myxospores in treatments with less than or equal to 0.25 g of soil and greater than or equal to 100 myxospores/0.25 g soil. Resident and non-resident anglers did not differ significantly in the number of fishing access sites used or drainages fished in during the previous 30 days. Non-residents fished in more states in the previous 30 days than residents and traveled greater distances to fish in the previous 7 and 30 days than residents. Mean quantity of sediment carried on one boot-wader leg was 8.39 g (± 1.5, 95% CI). Lightweight waders and felt soled boots were the most prominent types of wading equipment materials used by anglers and myxospores adhered to felt more than rubber and the glass control. Integration of angler movement patterns and mean sediment quantities transported with angler numbers suggests that anglers in southwestern Montana are potentially moving tons of sediment among fishing access sites every year, thereby making transport of ANS likely.