Novel trophic interaction between lake sturgeon (<i>Acipenser fulvescens</i>) and non-native species in an altered food web

Abstract

Lake sturgeon (Acipenser fulvescens) were once abundantly distributed throughout the Laurentian Great Lakes. However, widespread overharvesting and habitat degradation has diminished their numbers. The lower Niagara River contains one of the few remnant lake sturgeon populations in New York State. This study determined the diet of adult lake sturgeon and quantified their trophic position in a food web dominated by non-native species. Stomach content analysis assessed recent diet, and stable isotope analysis (δ 15 N and δ 13 C) of blood and fin tissue quantified trophic position and carbon source over varying time scales. Two non-native species dominated the diet of lake sturgeon — the amphipod Echinogammarus ischnus (62% by number) and the round goby (Neogobius melanostomus) (44% by mass). Stable isotope analysis revealed that round goby was the primary contributor to the long-term (i.e., fin) average diet, whereas short-term (i.e., blood) diet was more diverse. In contrast with findings from other systems, we found that adult lake sturgeon in the lower Niagara River were primarily piscivorous, actively targeting live fish prey. The recovery of this population is potentially supported by the high availability of energetically rich but non-native food resources.