Lake Sturgeon Acipenser Fulvescens Populations Research Articles

Variation in DNA methylation is associated with migratory phenotypes of lake sturgeon Acipenser fulvescens in the St. Clair River, MI, USA.

Lake sturgeon Acipenser fulvescens populations show a variety of movement patterns that are poorly understood. To compare two migratory phenotypes of A. fulvescens in the St. Clair River, MI, USA, multiple data types were analysed. Individual fish were classified into migratory phenotypes based on acoustic telemetry data collected 2012-2015. Acipenser fulvescens consistently showed movement from the St. Clair River upriver into Lake Huron or downriver into Lake St. Clair. The two migratory phenotypes were then compared for differences in morphometrics, genetics and epigenetics. Morphological differences based on linear measurements were not detected between phenotypes. Microsatellite data from 11 loci suggested one population with no genetic differentiation between migratory phenotypes. Our epigenetic results indicated that the migratory phenotypes are differentially methylated (P < 0.05), thus epigenetics may be associated with migratory differences in A. fulvescens. Only one restriction site was identified to be driving the differential methylation (P < 0.05). While little evidence at neutral loci occurred for genetic differentiation of A. fulvescens, DNA methylation may play a role in the observed movement pattern variation. When combined with microsatellite and morphometric analyses, our results suggested that different migratory patterns may reflect phenotypic plasticity, allowing A. fulvescens to acclimate to short-term environmental variability. Without an integrated approach, the role of epigenetics in the migratory phenotype of A. fulvescens may have been overlooked. Further characterization of migratory phenotypes could be important for management to conserve behavioural variation across the distribution of A. fulvescens and for design of stocking guidelines.

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

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.

The effect of multiple spawning events on cohort genetic diversity of lake sturgeon (Acipenser fulvescens) in the Kaministiquia River

Lake sturgeon Acipenser fulvescens populations have experienced declines throughout much of the Great Lakes. Understanding key demographic characteristics about lake sturgeon populations can help identify potential limiting factors to their recovery. Within a single spawning season, there may be multiple spawning events, which could affect genetic diversity of the resulting cohort. Our objective was to determine whether multiple discrete spawning events resulted in a larger effective number of breeders and higher genetic diversity. Larval samples were collected following the spawning periods in 2005 (n = 479) and 2006 (n = 279). In 2005, there were two discrete spawning events and a longer spawning season; in 2006, the spawning events were less discrete and the spawning season was shorter. Genetic samples from larval sturgeon were analyzed at 12 microsatellite loci. The effective number of breeders (Nb), genetic diversity (observed heterozygosity, expected heterozygosity, allelic richness, inbreeding coefficient), and relatedness were measured for each cohort. The effective population size (Ne) and genetic diversity were also measured in the adult population (n = 85). The larval cohorts had a high Nb (2005: 54; 2006: 73) relative to the Ne of the adult population (Ne = 28). Multiple spawning events did not result in more breeders, but did result in lower relatedness among the resulting offspring. Therefore, environmental factors should be maintained that encourage an extended spawning season, increasing the likelihood of multiple spawning events and decreasing the relatedness among individuals in the cohort.

Movement Patterns and Size‐Class Influence Entrainment Susceptibility of Lake Sturgeon in a Small Hydroelectric Reservoir

AbstractHydroelectric development is considered a threat to the recovery of Lake Sturgeon Acipenser fulvescens populations, in part because of injury and mortality concerns caused by interaction with hydroelectric facilities. Lake Sturgeon resident in small impoundments may be particularly susceptible to entrainment, depending on movement and habitat usage patterns. Using acoustic telemetry, we monitored coarse‐scale movements of 99 juvenile, subadult and adult Lake Sturgeon captured throughout a 10‐km‐long hydroelectric reservoir. Overall, adults moved over larger ranges than did smaller size‐classes. However, all size‐classes utilized habitat immediately upstream of hydroelectric facilities, and during the 18‐month study period, 27% of subadults tagged in the lowermost section of the reservoir, and 8.7% of adults tagged throughout the reservoir were entrained. Movements of juveniles and subadults were generally restricted to extended sections (2–6 km) of contiguous deepwater habitat (&gt;15 m), and passage through the two shallow river narrows that subdivide the reservoir were rare. Over half of the tagged adults (52%) moved upstream or downstream through one or both river narrows, albeit infrequently. Initial residency influenced entrainment susceptibility for juveniles and subadults but not for adults. Results suggest that Lake Sturgeon resident in small impoundments are susceptible to entrainment. However, the presence of river narrows, which function as natural movement restrictors, may largely preclude susceptibility of juveniles and subadults resident in upstream sections.

Genetically Derived Estimates of Contemporary Natural Straying Rates and Historical Gene Flow among Lake Michigan Lake Sturgeon Populations

AbstractNatural rates of straying are difficult to quantify over large spatial scales using direct observations, particularly for long‐lived fish species characterized by delayed sexual maturity and long interspawning intervals. Using multilocus microsatellite genotypes and likelihood‐based statistical methods, we quantified rates of immigration and emigration for six genetically differentiated (mean FST = 0.041) lake sturgeon Acipenser fulvescens populations in Lake Michigan based on adults (n = 437) captured in tributaries during the spawning season. Estimated rates of straying were high (mean = 0.105), asymmetrical, and highly variable across populations. We found no significant association between the total length (a surrogate measure of age) of individuals that strayed and those that did not. Linear distance between streams was more predictive of straying rates and FST than least‐cost distances estimated based on lakescape features (bathymetry and lake current patterns). Historical rates of gene flow estimated using coalescent analysis indicated a fully parameterized model with variable evolutionarily effective population sizes (θ range, 0.684–0.989), and variable and nonsymmetrical migration rates best explained the genetic data. Comparatively high estimates of relative historical gene flow from several numerically depressed populations suggest that these populations were once larger contributors to basinwide gene flow than indicated by estimates of contemporary straying rates. High rates of interpopulation straying contrast with high FST, suggesting that straying rates are poor indicators of successful reproduction following dispersal.

Seasonal Movement and Mesohabitat Usage of Adult and Juvenile Lake Sturgeon in the Grasse River, New York

AbstractLong‐term restoration efforts for lake sturgeon Acipenser fulvescens populations will benefit from better understanding of this species’ movements and habitat use in riverine systems. Radio transmitters were implanted in both juvenile and adult lake sturgeon in the Grasse River, New York, and individuals were relocated over a 2‐year period. Adult lake sturgeon demonstrated greater minimum daily distance moved, absolute distance moved, and mean home range size than juvenile lake sturgeon during the spring. During the course of the study, both adult and juvenile lake sturgeon exhibited movements upstream and downstream through a breached low‐head weir, and individuals did not necessarily remain resident on an annual basis in the Grasse River. Mesohabitat and substrate use patterns were determined based on comparisons of frequency distributions for relocated lake sturgeon and quantified mesohabitat and substrate over a 15‐km river reach. Lake sturgeon used pool mesohabitat and limited their use of run mesohabitat under both low‐ and mid‐flow conditions. During most of the year, adult and juvenile lake sturgeon were detected over silt substrate. This study illustrates behavioral differences and similarities between the movements and habitat use of adult and juvenile lake sturgeon in a riverine system.