Restoration of naturally reproducing and resident riverine lake sturgeon populations through capture and transfer

Abstract

The Winnebago System, Wisconsin, is home to one of the largest Lake Sturgeon Acipenser fulvescens populations in North America. Although there are >50 known spawning sites utilized by Lake Sturgeon in the 200 km of the lower Wolf River upstream of Lake Winnebago, the construction of two dams >90 years ago eliminated the ability of Lake Sturgeon to access 18.5 km of river up to their ancestral spawning grounds below Keshena Falls. Given the cultural importance of sturgeon to the Menominee Indian Tribe of Wisconsin, expanded efforts aimed at restoring Lake Sturgeon spawning and a resident population to the upper Wolf River commenced in 2011. To meet these objectives, 100 or more Lake Sturgeon per year were captured below the dams, and transferred upstream to the Wolf River within the Menominee Reservation. All transferred fish were PIT tagged and 245 fish were surgically implanted with 10 year acoustic transmitters to determine spawning locations and monitor post-release movement. The first five transfer cohorts contained 621 Lake Sturgeon, with spawning activity observed below Keshena Falls each spring following release. Gravid fish transferred within 3 weeks of spawning exhibited higher spawning rates above the upstream dam (70.2% females; 73.9% males) than gravid fish transferred in late fall (41.8% females; 41.2% males). Spawning documented below Keshena Falls and within the Red River represent the first spawning activity at these locations in >100 years. Lake Sturgeon transferred in early fall displayed higher retention rates, 2-5 years post-tagging, in the pool upstream of both dams (10.4%) compared to the late fall (3.1%) and spring transfers (7.4%). Natural reproduction was documented through capture of larval Lake Sturgeon immediately below Keshena Falls in 2013.These results demonstrate that capture and transfer can be utilized as a cost-effective and biologically-effective tool for Lake Sturgeon spawning stock and population restoration.

Post‐release dispersal and spawning movements of a translocated lake sturgeon (Acipenser fulvescens, Rafinesque 1817) population in the Mattagami River, Ontario

“…Although this translocation effort released individuals into a small reach it appears to have been successful in both reproduction and juvenile recruitment (Boothroyd et al, ). Other studies have reported lake sturgeon populations thriving in isolated river segments (Barth, Anderson, Henderson, & Peake, ; Koenigs et al, ), and in one case a 10 km section of river has been reported as being sufficient to support a self‐sustaining population (McDougall et al, ). Small river reaches such as the release area may therefore be viable for supporting lake sturgeon populations, although perhaps to a lesser degree than seen in pristine habitats (Haxton et al, ), providing there is sufficient suitable habitat to support all life stages, including reproduction, feeding and growth, and seasonal refugia, and all habitats are accessible through unobstructed corridors.…”

“…By comparison, other studies that have translocated lake sturgeon above a dam during the spring had lower instances of post‐release dispersal (McDougall, Hrenchuck, Anderson, & Peake, ; Olach, ). In the study by Koenigs et al (), adult sturgeon that were translocated upstream in the spring reproduced before dispersing downstream over a dam. Further research on release timing should be considered to minimize post‐release dispersal and maximize genetic contribution to the translocated population.…”

“…In a study similar to ours, a high rate of downstream emigration of radio‐tagged juvenile and adult lake sturgeon that were translocated into an isolated river segment was documented, with between 12% and 96% of radio‐tagged fish leaving (Runstrom, Bruch, Reiter, & Cox, ). A subsequent, larger scale effort noted that timing of fish capture and translocation had a significant effect on fish becoming residents rather than leaving (Koenigs et al, ).…”

“…Rapid movement away from release areas after translocation has been reported for many species (Griffith et al, ; Kleiman, ; Miller et al, ; Short et al, ) indicating that the individual may perceive the release area to be unsuitable (Stamps & Swaisgood, ). Koenigs et al () suggested that introducing large numbers of individuals into a site may result in greater success than using relatively few fish (Runstrom et al, ), although this has not been explicitly tested. Release areas should meet all the species' biotic and abiotic requirements, provide habitat for all life stages, adequate for seasonal needs, large enough to meet conservation goals, have adequate connectivity in fragmented systems, and be isolated from potential non‐habitat sink areas for the population (IUCN/SCC, ).…”

“…Lake sturgeon require diverse habitat for different life stages and can migrate extensive distance to fill these requirements, making them particularly sensitive to the impacts associated with dams (Auer, ; Haxton & Findlay, ; Haxton et al, ) and hindering natural recolonization of sturgeon populations that have been extirpated from river fragments. Translocations may be an effective tool for restoring lake sturgeon in previously occupied, contemporarily fragmented habitats (Koenigs, Bruch, Reiter, & Pyatskowit, ); assessments of translocations in small fragments are required to evaluate whether it is a viable option for the species.…”