Anadromous Sturgeons: Habitats, Threats, and Management

<em>Abstract.</em>—In 1999 and 2000, gill-net sampling was used to determine the effect of sediment deposition (sand) on the relative abundance (catch per unit effort [CPUE]) of Atlantic sturgeon <em>Acipenser oxyrinchus</em> and lake sturgeon <em>A. fulvescens</em> frequenting the Île Madame open-water disposal site using a before–after and control–impact sampling design. A total of 1,108 fish of 11 different species were captured in the vicinity of the sediment disposal site. Sauger <em>Sander canadensis</em>, longnose sucker <em>Catostomus catostomus</em>, Atlantic sturgeon and lake sturgeon were the four most abundant species. Atlantic sturgeon CPUE was significantly higher in 1999 than in 2000, while lake sturgeon CPUE was similar in both years. After sediment disposal operations, we observed a significant decrease (3–7 times lower) in the Atlantic sturgeon CPUE at the impacted station compared to the control stations: CPUE dropped from 5.8 to 0.8 fish/ station-day in 1999 and from 1.8 to 0.5 fish/station-day in 2000. A significant reduction in CPUE values was also noted in the sediment dispersal area downstream from the disposal site after dumping. For both years, lake sturgeon CPUE at the impacted station was not significantly different from control stations after sediment disposal. These results suggest site avoidance and a negative impact of sediment disposal operations for Atlantic sturgeon but not for lake sturgeon. Management implications of these results are discussed in relation to sediment disposal operations in the St. Lawrence estuarine transition zone, an important habitat for both sturgeon species.