Evidence of a Year-Round Resident Population of Lake Sturgeon in the Kettle River, Minnesota, Based on Radiotelemetry and Tagging

Abstract

We used radiotelemetry to study the movement of lake sturgeon Acipenser fulvescens in the Kettle River of east-central Minnesota. Our objectives were to determine whether the tracked fish were seasonal or year-round residents of the river and to determine their seasonal movements, responses to changes in discharge, and activity centers. We were also interested in the response of these fish to the removal of a hydroelectric dam that had blocked upstream movement of fish for 87 years. Eight fish received transmitter implants and were tracked for about 7 months, from October 1994 through May 1995. Three tagged fish were not identified or located thereafter, but the remaining five were tracked weekly from April 1995 to September 1996. Lake sturgeon did not move upstream of the former hydroelectric dam or downstream of the Kettle River's confluence with the St. Croix River but rather remained within this 20-mi reach, despite the absence of physical barriers at either end. We found that sturgeon movement was highly correlated with change in discharge, with upstream movements occurring during periods of rising discharge and downstream movements during falling discharge. Lake sturgeon used activity centers, with approximately 80% of the weekly daytime observations falling within four activity centers. Using mark–recapture techniques, we also documented that the lake sturgeon population in the Kettle River is small, and it appeared to mix very little with adjacent populations. We believe that if this population does mix with other nearby populations, mixing probably occurs on a time scale of years rather than weeks or months.