It's pretty difficult to take sportfishers seriously about ANY conservation issues when the first solution that comes to mind is "shoot the varmint". .
Try dog repellant. Here is a copy of a study done last year to control river otter scat on docks.
Effectiveness of a Commercially Available Dog and Cat Repellent in Reducing River Otter Defecation On Docks
Robert Rorabaugh*, Eric Eisenhardt, Joseph Gaydos, SeaDoc Society, UC Davis Wildlife Health Center
River otters (Lontra canadensis) are widely distributed throughout the marine waters of the Georgia Basin Puget Sound where they primarily feed on numerous species of marine fish and invertebrates. They have a high metabolic rate and defecate at latrine sites on shorelines, playing an important role in the transfer of nitrogen and phosphorus from marine to terrestrial ecosystems. Otters also use docks and boats as latrine sites and offended private citizens have resorted to illegal trapping or shooting of otters in some areas. A commercially available granular dog and cat repellent was tested for its effectiveness in reducing or eliminating river otter defecation on docks. Three docks that contained river otter scat were treated with the repellent and three proximal docks that contained river otter scat were used as controls. River otter scat deposition was measured immediately before and weekly for four weeks following application and differences between treated and untreated docks were compared. Deposition on treated docks was significantly lower than on non-treated control docks, however treatment did not eliminate river otter defecation on docks. Treatment with this commercially available repellent could be suggested as an option to private dock owners frustrated by river otter defecation on docks.
