Lake Sturgeon Populations Research Articles

Molecular phylogeny of sturgeon mimiviruses and Bayesian hierarchical modeling of their effect on wild Lake Sturgeon (Acipenser fulvescens) in Central Canada

Sturgeon mimiviruses can cause a lethal disease of the integumentary systems of sturgeon (Acipenseridae). Here we provide phylogeographic evidence that sturgeon mimivirus is endemic in endangered populations of wild Lake Sturgeon within Canada's Hudson Bay drainage basin. Namao virus (NV) variants were diagnosed in 24% of Lake Sturgeon samples (n = 1329) collected between 2010–2015. Lake Sturgeon populations with the highest virus prevalence were from the Nelson River (58%) in 2015, Saskatchewan River (41%) in 2010 and South Saskatchewan River (36%) in 2011. Bayesian phylogenetic reconstructions suggested that four NV variants, designated HBDB I-IV, co-circulate temporally and spatially within and between the genetically and biogeographically distinct Lake Sturgeon populations. Evidence from recapture studies suggested that Lake Sturgeon across the basin are persistently infected with NV at prevalence and titer (103.6 equivalent plasmid copies per μg DNA) levels consistent with the hypothesis that wild Lake Sturgeon populations serve as a maintenance population and reservoir for sturgeon mimiviruses. Bayesian hierarchical modeling of NV in the Landing River population of Lake Sturgeon suggested that host weight and age were the best predictors of sturgeon mimivirus presence and titer, respectively, whereas water flow rate, level and temperature, and number of previous captures did not significantly improve model fit. A negative relationship was estimated between sturgeon mimivirus presence and Lake Sturgeon weight and between virus titer and Lake Sturgeon age.

Adult lake sturgeon ( Acipenser fulvescens Rafinesque, 1817) occurrence in the Muskegon River system, a Lake Michigan drowned river mouth, USA

Recent advancements in telemetry have allowed managers and researchers to conduct comprehensive studies on the movement ecology of lake sturgeon (Acipenser fulvescens), a species of conservation concern in most of the Laurentian Great Lakes basin. In Michigan waters of Lake Michigan, drowned river mouth systems (a protected lake-like habitat that connects a river to lake) support 4 of 11 remaining lake sturgeon populations. One of those remnant populations is supported by the Muskegon River, a drowned river mouth system consisting of both Muskegon Lake and the Muskegon River. The objectives of this 6-year telemetry study were to determine whether adult lake sturgeon occupied the Muskegon River system outside of the spawning season (defined as March to July), to quantify their use of the system annually, and to identify and characterize patterns in occurrence. A total of 21 adult lake sturgeon implanted with acoustic transmitters were passively monitored throughout the year during 2012–2017. Eighty-two percent of tagged fish at large were detected ≥1 day in the Muskegon River system annually, and tagged lake sturgeon were frequently detected during both spawning and non-spawning time periods. Residency index (i.e., no. detection days/365 days) values indicated that adult lake sturgeon were not only detected throughout the year but that they occupied the Muskegon River system for an average of 130 days each year (residency index = 0.36 ± 0.05 SE) during our most spatially intensive acoustic monitoring in 2016–2017. Additionally, 24% of tagged lake sturgeon were primary residents (i.e., residency index >0.5) of the Muskegon River system in both years. Adult lake sturgeon followed 1 of 3 patterns of occurrence based on individual detection histories, and those patterns varied temporally and by the relative amount of use (i.e., high, medium, and low). Our findings build on previous research that found drowned river mouth systems in Lake Michigan can be important nursery habitats for juvenile lake sturgeon by showing that these habitats also can be used extensively by adult lake sturgeon throughout the year.

Implications of the sea lamprey control program for lake sturgeon conservation and rehabilitation efforts

Lake sturgeon, a species of conservation concern, can be affected by sea lamprey control activities in the Great Lakes basin. Specifically, age-0 lake sturgeon are sensitive to the pesticides used to kill larval stage sea lampreys; and, as tributary spawners, barriers that restrict access to habitat for adult sea lampreys can also restrict access to spawning lake sturgeon habitat. Conversely, lake sturgeon are also potentially prey for juvenile sea lampreys, so they benefit from control measures that reduce sea lamprey abundance. Over the past 20 years research has defined conditions under which treatments to control sea lampreys, such as high tributary alkalinity levels, are of highest risk for age-0 lake sturgeon mortality. Adult lake sturgeon are likely to survive a sea lamprey attack, and adult wounding rates vary through time and space across the Great Lakes basin and in Lake Champlain. Juvenile lake sturgeon are at higher risk of mortality from a sea lamprey attack, yet rarely display wounds. There are mitigation measures, including treating tributaries later in the year, capturing and holding age-0 lake sturgeon prior to treatment in high-risk tributaries, maximizing the time between treatments, and providing passage for spawning lake sturgeon above sea lamprey barriers that can minimize risks to lake sturgeon populations. As such, we believe that there remains room for both a robust sea lamprey control program moving forward in concert with lake sturgeon rehabilitation across the Great Lakes basin.

Seasonal use of two unregulated Lake Superior tributaries by lake sturgeon

Lake sturgeon movement in two adjacent unregulated Lake Superior tributaries, the Pic and White rivers, was assessed over several years to determine seasonal use, identify potential contributing factors for entry or exit migrations, and evaluate whether sturgeon using these tributaries constituted one or two populations. A total of 95 lake sturgeon implanted with radio transmitters were tracked using multiple stationary receivers augmented with boat-based manual surveillance during peak movement times. Both rivers were used by lake sturgeon during the open water (“ice off”) season. In general, spawning sturgeon moved to the first insuperable barrier (i.e., natural rapids) during the spawning season, and then moved downstream to deeper pools in mid- to late summer. Non-spawning sturgeon moved into the river concurrently but remained in lower portions of the river. Lake sturgeon emigrated from the Pic River and resided in Lake Superior during the winter season whereas a small portion of radio transmittered sturgeon, originally sampled in the Pic River, overwintered in the White River. River discharge and the interaction between discharge and water temperature were correlated with upstream movement, and river discharge was also correlated with outmigration. No genetic structuring was apparent between Sturgeon within the two rivers, consistent with telemetry data showing radio-tagged fish moving readily between the rivers. This study provided pertinent seasonal use information of unregulated Great Lake tributaries and may contribute to planning processes for future hydroelectric developments to minimize disruptions to lake Sturgeon populations.

Characterization of pharmaceuticals, personal care products, and polybrominated diphenyl ethers in lake sturgeon serum and gametes

Recent research suggests contaminants of emerging concern (CECs) are widespread and environmentally relevant concentrations can impact fishes. However, little is known about impacts of CECs to long-lived or rare species. The objective of this study was to characterize CEC concentrations in lake sturgeon (Acipenser fulvescens) serum and gametes. Blood serum was collected non-lethally from lake sturgeon at four lower Great Lakes basin sites: Detroit, upper Niagara, lower Niagara, and St. Lawrence rivers; additionally, gametes were collected from lake sturgeon in the St. Lawrence River. Samples were analyzed for pharmaceuticals and personal care products (PPCPs) and polybrominated diphenyl ethers (PBDEs). Overall, 44 different PPCPs were identified in serum and gamete samples across sites, with 22 PPCPs identified in at least 25% of serum samples and three PPCPs identified in 25% of gamete samples. PPCP concentrations in serum and gametes ranged from 0.00208 to 130 ppb and 0.00538–190 ppb, respectively. NMDS ordination revealed differences in the presence and concentrations of PPCPs in lake sturgeon serum across sites, however, N,N-diethyl-meta-toluamide (DEET), hydrocortisone, benztropine, and amitriptyline were detected in at least one serum sample at all sites. Additionally, DEET, 10-hydroxy-amitriptyline, and sertraline were detected in ≥25% of gamete samples collected from the St. Lawrence River. Twenty-six PBDE congeners were identified in 25% of serum samples and 24 were identified in 25% of gamete samples. PBDEs in serum were present across all sites and in gametes of St. Lawrence River lake sturgeon, and total PBDE concentrations in serum and gametes ranged from 0.184 to 12.7 ppb and 0.0826–0.44 ppb, respectively. Managers of lake sturgeon populations may need to consider the impacts of CECs if reproductive, developmental, behavioral, growth effects, or mortality are observed in the Great Lakes basin or other areas that are impacted by increased exposures to PPCPs and PBDEs.

Detecting fine-scale population structure in the age of genomics: a case study of lake sturgeon in the Great Lakes

Great Lakes-wide population structure analyses using neutral markers have provided an understanding of broad-scale genetic structure of lake sturgeon. To assess the fine-scale genetic structure of lake sturgeon populations in two different rivers, we combined both microsatellites and genome-wide SNP markers. The St. Clair-Detroit River System (SCDRS) is entirely freshwater with no known impediments to sturgeon movement. In contrast, the St. Lawrence River (SLR) outlets into the Atlantic Ocean and is fragmented by hydroelectric dams. Both microsatellites and SNPs provided evidence of differentiation between the rivers. When applied to fine-scale structure, microsatellites failed to detect population structure using a Bayesian approach for within either river and FST values using microsatellites identified only a low level of differentiation between the upper and lower St. Clair River. Using the full set of SNPs for each comparison yielded similar results to the microsatellite results. Discriminant analysis of principal components using both markers partitioned the samples into spatially structured clusters. The SNP datasets filtered for high FST values had greater success for detecting fine-scale population structure and had the highest accuracy for reassignment to prior populations. This reduced SNP dataset may represent a more meaningful set of loci that can be used to estimate lake sturgeon fine-scale population structure, which is complicated by their long-generation times.

Genetic origins and diversity of lake sturgeon in the St. Louis River Estuary

Lake sturgeon Acipenser fulvescens were extirpated from the St. Louis River Estuary (SLRE) by the early 1900’s due to overfishing and habitat degradation. A restoration stocking program began in 1983, and continued almost annually until 2000. Lake sturgeon stocked into the SLRE were primarily obtained from the Wolf River (Lake Winnebago) genetic stock (n = 861,000) but some sturgeon were obtained from the Sturgeon River (Lake Superior) genetic stock (n = 61,380). Recently, spawning and natural recruitment has been documented near the Fond du Lac Dam, the upstream limit for lake sturgeon migrating from Lake Superior. However, the genetic origin of lake sturgeon spawning in the SLRE was unknown. Our objectives were to determine (1) the genetic origins and (2) genetic diversity of lake sturgeon spawning in the SLRE. Using both GENECLASS2 and ONCOR, a majority (79–81%) of lake sturgeon captured in the SLRE during spawning (2016–2018) assigned to the Wolf River genetic stock (Lake Winnebago) with greater than 80% probability using established microsatellites and a standardized genetic baseline. Other genetic stocks present (≥1%) included the Pic and Goulais rivers and possibly the Black Sturgeon River (identified using GENECLASS2, but not ONCOR); no fish assigned to the Sturgeon River using either method. Genetic diversity metrics showed that the SLRE lake sturgeon population was similar to other Lake Superior lake sturgeon populations. Overall, the SLRE Sturgeon population appears headed towards recovery. Adaptive management practices currently being employed should be continued to help guide further recovery of this population.

Larval lake sturgeon production and drift behaviour in the Menominee and Oconto Rivers, Wisconsin

AbstractLake sturgeon (Acipenser fulvescens) have been negatively impacted by barriers to migration, pollution and overharvest. Biological data such as the timing of spawning activity and larval drift have provided a better understanding of larval production success or failure on a site‐specific basis. However, many river systems that serve as reproductive locations for remnant lake sturgeon populations remain understudied. The objective of this study was to compare and contrast aspects of larval lake sturgeon drift within and between the Oconto and Menominee Rivers over multiple reproductive seasons. Differences in larval drift chronology, the size of drifting larvae during the season and the cross‐sectional profile of drifting individuals as a function of river velocity were evaluated. D‐frame drift nets were deployed at a single transect below spawning sites in the Menominee (2012, 2013 and 2014) and Oconto Rivers (2013, 2014 and 2015). A total of 4,442 larvae were captured across all seasons. Larvae exhibited nonrandom drift profiles related to water velocity, and larvae size was related to horizontal drift location. The seasonal increase in body size of drifting larvae also differed among drift events within and between years and across rivers. This information will provide a better understanding of lake sturgeon early life history and has practical management connections including spawning site protection/enhancement and river flow mitigation.

Trends and Effects of a Recreational Lake Sturgeon Fishery in the St. Clair System

AbstractOne frequently desired outcome of Lake Sturgeon Acipenser fulvescens rehabilitation is to create a recreational fishery for the species. However, few waterbodies offer a recreational fishery where anglers can catch Lake Sturgeon regularly. Lake St. Clair and the St. Clair River (hereafter, “St. Clair system”) contain large, stable populations of Lake Sturgeon, and a recreational fishery allowing harvest has been present since 1950. Over the last several decades, the Michigan Department of Natural Resources (MDNR) has monitored the recreational Lake Sturgeon fishery in the St. Clair system by using numerous methods to assess angler participation, harvest rates, and population effects of the fishery. Lake Sturgeon anglers in the St. Clair system are predominantly male (89%) and largely reside in the three nearest counties (72%), although the geographic footprint of Lake Sturgeon anglers appears to be increasing. Estimates of angler abundance, trends in angler recapture of tagged Lake Sturgeon, sturgeon harvest data, and reported capture of MDNR “Master Angler”‐sized Lake Sturgeon by anglers all indicated that angling effort in this Lake Sturgeon fishery has steadily increased since monitoring began. Despite increasing angler participation, the recreational fishery has had no detectable population‐level effect on Lake Sturgeon in the St. Clair system. Harvest rates of tagged Lake Sturgeon are low, with most anglers practicing catch and release. Recapture rates of angler‐caught fish in comparison to MDNR survey‐caught fish suggested that hooking mortality is low. Additionally, apparent survival estimates of Lake Sturgeon have been constant. Information gained from monitoring the recreational Lake Sturgeon fishery in the St. Clair system will be valuable to managers assessing whether to establish a sturgeon fishery in other systems.

A Genetic Assessment of Missouri's Lake Sturgeon after 30 Years of Restoration Releases

AbstractThe Lake Sturgeon Acipenser fulvescens is native to three major watersheds in the USA: the Great Lakes, Hudson Bay, and Mississippi River drainages. However, they have declined across much of their range due to overfishing, pollution, and major river alterations. After their near extirpation in Missouri, the Missouri Department of Conservation initiated a reintroduction program to restore the Lake Sturgeon in the state's largest waterways. From 1984 to 2015, offspring originating from Lake Winnebago (1984–2001) and from upper Mississippi River tributaries (2004–2015) were reared in captivity and released into portions of the Mississippi and Missouri rivers. After 32 years of restorative releases, we screened Lake Sturgeon samples from the state of Missouri by using 11 microsatellite loci and mitochondrial DNA control region sequences. We examined overall genetic diversity and genetic structure of Lake Sturgeon captured in the Mississippi and Missouri rivers for differences between rivers and among groups within rivers. We found high levels of genetic diversity within both rivers, with very little genetic differentiation between them. Higher‐than‐average relatedness within sample groups and heterozygote excess were consistent with the pattern expected from stocked fish and suggested that closely related fish may have aggregated at stocking sites. We detected two genetic groups in Missouri, reflecting the change in stock source. Haplotypes that may be unique to the Mississippi and Ohio River systems were observed at very low frequencies. Though largely the product of stocking, reproductively mature Lake Sturgeon will likely have sufficient genetic diversity and will have experienced selection pressures in Missouri's large rivers, making them the most appropriate source for further supplementation if it is deemed necessary. We recommend continued research and monitoring of reproductive habits and preservation of multiple spawning sites to continue the long path toward a self‐sustaining Lake Sturgeon population in Missouri's waters.

Effects of Latitude, Season, and Temperature on Lake Sturgeon Movement

AbstractEcologists have a limited understanding of the rangewide variation in movement behavior in freshwater fishes, but recent expansion of biotelemetry allows biologists to investigate how fish movement can help to predict behavioral shifts in response to changing environments. The Lake Sturgeon Acipenser fulvescens is a wide‐ranging, migratory, coolwater species, making it a candidate species for studying patterns in movement ecology. We conducted a literature review and meta‐analysis of seasonal movement data compiled from 38 Lake Sturgeon telemetry studies in North America to build an understanding of spatiotemporal variation in movement behavior. Lake Sturgeon movement studies were underrepresented for low‐latitude populations in the Mississippi, Missouri, and Ohio/Tennessee River basins. Highest movement usually occurred during spring spawning migrations, whereas other populations exhibited their highest movement in the fall, potentially in order to overwinter near spawning grounds. Our meta‐regression analysis indicated that latitude or summer maximum temperature best predicted standardized mean difference between spring and summer movement in Lake Sturgeon populations across the species’ range. Our results suggest that Lake Sturgeon populations at lower latitudes and those that experience warmer summer temperatures have lower summer movement relative to spring movement. Managers may use this information to prioritize actions promoting the conservation of seasonally important habitats for the continued recovery of migratory coolwater fish (e.g., Lake Sturgeon) that potentially experience stressful thermal conditions.

Tracking Stocking Success in a Long‐Lived Species through Genetics and Demographics: Evidence of Natural Reproduction in Lake Sturgeon after Twenty‐Two Years

AbstractLake Sturgeon Acipenser fulvescens populations throughout the Great Lakes have experienced declines. Therefore, Lake Sturgeon have been stocked at several locations, including the Oswegatchie River in New York State, where Lake Sturgeon are listed as threatened. The goal of New York's Lake Sturgeon stocking program has been the establishment of self‐sustaining populations in six out of the seven management units in order to meet delisting criteria. Due to Lake Sturgeon's long lifespan and late sexual maturity, there is a significant delay before it can be determined whether natural reproduction is occurring at the reintroduction site. Our objective was to determine whether recently captured Lake Sturgeon from the Oswegatchie River were of hatchery origin and whether natural reproduction was occurring in the river. Age data and genetic data from 12 microsatellite loci were collected from 38 individuals from the Oswegatchie River. The genetic data were used to reconstruct families by using COLONY and STRUCTURE statistical analysis programs. The genetic diversity of the Oswegatchie River population was also compared with other natural and introduced Lake Sturgeon populations in the region. The combination of family reconstruction and age data indicated that natural reproduction is occurring in the Oswegatchie River. Individuals that were presumed to be recruited had ages ranging from 6 to 12 years. It is often thought female Lake Sturgeon typically do not reach sexual maturity until about 20 years of age. Only 12–15 years had elapsed since the earliest times of stocking, suggesting the possibility that remnant native females remained in the system or stocked female Lake Sturgeon have reached early sexual maturity. The genetic diversity of the Lake Sturgeon population in the Oswegatchie River is comparable to that of other nearby natural populations. However, the effective population size (Ne) was lower than that of many natural populations. As natural reproduction continues in the Oswegatchie River, Ne will likely increase.

Effects of acclimation temperature on the thermal physiology in two geographically distinct populations of lake sturgeon (Acipenser fulvescens).

Temperature is one of the most important abiotic factors regulating development and biological processes in ectotherms. By 2050, climate change may result in temperature increases of 2.1-3.4°C in Manitoba, Canada. Lake sturgeon, Acipenser fulvescens, from both northern and southern populations in Manitoba were acclimated to 16, 20 and 24°C for 30days, after which critical thermal maximum (CTmax) trials were conducted to investigate their thermal plasticity. We also examined the effects of temperature on morphological and physiological indices. Acclimation temperature significantly influenced the CTmax, body mass, hepatosomatic index, metabolic rate and the mRNA expression of transcripts involved in the cellular response to heat shock and hypoxia (HSP70, HSP90a, HSP90b, HIF-1α) in the gill of lake sturgeon. Population significantly affected the above phenotypes, as well as the mRNA expression of Na+/K+ ATPase-α1 and the hepatic glutathione peroxidase enzyme activity. The southern population had an average CTmax that was 0.71 and 0.45°C higher than the northern population at 20 and 24°C, respectively. Immediately following CTmax trials, mRNA expression of HSP90a and HIF-1α was positively correlated with individual CTmax of lake sturgeon across acclimation treatments and populations (r = 0.7, r = 0.62, respectively; P < 0.0001). Lake sturgeon acclimated to 20 and 24°C had decreased hepatosomatic indices (93 and 244% reduction, respectively; P < 0.0001) and metabolic suppression (27.7 and 42.1% reduction, respectively; P < 0.05) when compared to sturgeon acclimated to 16°C, regardless of population. Glutathione peroxidase activity and mRNA expression Na+/K+ ATPase-α1 were elevated in the northern relative to the southern population. Acclimation to 24°C also induced mortality in both populations when compared to sturgeon acclimated to 16 and 20°C. Thus, increased temperatures have wide-ranging population-specific physiological consequences for lake sturgeon across biological levels of organization.

Population status and demographics of Lake Sturgeon in the Bad and White rivers, Wisconsin

Abstract Lake Sturgeon Acipenser fulvescens rehabilitation efforts in Lake Superior are guided by a rehabilitation plan that sets goals and criteria for a self-sustaining population, including a minimum of 1,500 mature adults, roughly equal sex ratio, and annual exploitation rates &amp;lt; 5%. The Bad and White rivers, Wisconsin host a genetically unique Lake Sturgeon population that is utilized by state-licensed recreational anglers and tribal subsistence fishers. Our objectives were to 1) determine if the Bad River population meets rehabilitation plan targets for a self-sustaining population, 2) assess harvest of Lake Sturgeon by recreational anglers and tribal subsistence fishers for compatibility with rehabilitation goals, 3) determine population trajectory from annual spawning runs, and 4) describe population demographics given the unique physical features of Lake Superior. We sampled Lake Sturgeon in the Bad and White rivers with gill nets over a 17-y period (2001 to 2017). The observed sex ratio in spawning runs was 2.2:1 (male : female), but calculated at 1.6:1 for the entire adult population on the basis of abundance estimates. Weight–length relationships converted to a standardized modified form factor indicated lower condition and possibly lower female fecundity compared with other large North American populations. Annual spawning run size estimates over time indicated that the population trajectory was stable to slightly increasing, and during 2016 was 739 and 241 individuals in the Bad and White rivers, respectively. Total population size (including nonspawners) exceeded 1,500 individuals, which met Lake Superior rehabilitation criteria for a self-sustaining population. Estimates of 1,426 males and 882 females were considered conservative because 472 unknown-sex fish could not be accounted for in return time and abundance models. Spawning return times were 2 or 3 y for males and 4 to 6 y for females, longer than many other populations. Exploitation by recreational anglers and tribal subsistence fishers was 1.3% or lower and met the rehabilitation plan target of &amp;lt; 5%, but we recommend exploitation not exceed 3.1% to maintain a self-sustaining population. These findings help gauge rehabilitation progress in Lake Superior and better describe the demographics of a remnant self-sustaining Lake Sturgeon population in Lake Superior.

Riverine characteristics and adult demography influence female lake sturgeon (Acipenser fulvescens) spawning behavior, reproductive success, and ovarian quality

Abiotic conditions and demographic factors can influence the timing of spawning. Behavioral plasticity allows females to select spawning conditions that are conducive to offspring development; however, reproductive costs associated with delaying spawning are not well understood. In this study, factors influencing timing of female spawning, residence time (RT), and reproductive success (RS) during two seasons were determined, and plasma testosterone concentrations were used to quantify atretic rates in a wild, lake sturgeon (Acipenser fulvescens) population. For the 123 females monitored, RT ranged from 1 to 23 days and was influenced by arrival date, temperature, discharge, and male number, with the latter having the largest influence. RS varied due to arrival date, temperature, discharge, male number, male length, and operational sex ratio. Two females had testosterone levels indicative of atresia and RS estimates lower than yearly means; however, most females had normal ovaries, suggesting little reproductive costs of plasticity in spawning ground residency time. Results demonstrate the multitude of factors influencing female reproductive behavior and RS, highlighting the importance of abiotic and demographic conditions to recruitment in wild populations.

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

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 (δ15N and δ13C) 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.

Strangers in their Own Streams: Restoring Lake Sturgeon Populations to the Lower Missouri River Basin

Strangers in their Own Streams: Restoring Lake Sturgeon Populations to the Lower Missouri River Basin

Diet characterization and a preliminary investigation into trophic niche placement for an endangered lake sturgeon (Acipenser fulvescens) population in the Saskatchewan River, SK, Canada.

All Canadian lake sturgeon (Acipenser fulvescens) populations are listed under the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) due to their complex life history, loss of habitat and negative interactions with anthropomorphic activities. Lake sturgeon diets vary considerably across their range and depend on the local benthic invertebrate fauna, substrata, and competition with congener species. Hence, determining population-specific prey assemblages is a vital contribution to effective conservation efforts. We used carbon and nitrogen stable isotopes to identify lake sturgeon prey preferences for juvenile (<100 cm) and adult (>100 cm) age classes and their trophic niche in the Saskatchewan River, SK, Canada. In this system, lake sturgeon were the top predator within the benthic food web with no direct competition for preferred prey items from congener species. Their diet was dominated by crayfish (49.1± 6.4%) and snails (36.3 ± 5.5%), with no significant differences between age classes. Furthermore, lake sturgeon favoured deep rocky pools throughout the river; a habitat where crayfish and snails are typically found. Therefore, conservation efforts should be directed at preserving these habitats for the residing benthic invertebrate community, and the lake sturgeon’s ability to access them.

Assessing off-target cytotoxicity of the field lampricide 3-trifluoromethyl-4-nitrophenol using novel lake sturgeon cell lines

Lampricides are currently being applied to streams and rivers to control the population of sea lamprey, an invasive species, in the Great Lakes. The most commonly used lampricide agent used in the field is 3-trifluoromethyl-4-nitrophenol (TFM), which targets larval sea lamprey in lamprey-infested rivers and streams. The specificity of TFM is due to the relative inability of sea lamprey to detoxify the agent relative to non-target fishes. There is increasing concern, however, about non-target effects on fishes, particularly threatened populations of juvenile lake sturgeon (LS; Acipenser fulvescens). There is therefore a need to develop models to better define lake sturgeon's response to TFM. Here we report the establishment of five LS cell lines derived from the liver, gill, skin and intestinal tract of juvenile LS and some of their cellular characteristics. All LS cell lines grew well at 25 °C in Leibovitz's (L)− 15 medium supplemented with 10% FBS. All cell lines demonstrated high senescence-associated β–galactosidase activity and varying levels of Periodic acid Schiff-positive polysaccharides, indicating substantial production of glycoproteins and mucosubstances by the cells. Comparative toxicity of TFM in the five LS cell lines was assessed by two fluorescent cell viability dyes, Alamar Blue and CFDA-AM, in conditions with and without serum and at 24 or 72 h exposure. Deduced EC50 values were compared between the cell lines and to the reported in vivo LC50s. Tissues sensitive to the effects of TFM in vivo correlated with cell lines from the same tissues being most sensitive to TFM in vitro. EC50 values for the LSliver-e cells was significantly lower than the EC50 for the rainbow trout (RBT) liver cells RTL-W1, reaffirming the in vivo observation that LS was generally more TFM-sensitive than rainbow trout. Our data suggests that whole-fish sensitivity of LS to TFM is likely attributable to sensitivity at the cellular level. Thus, LS cell lines, as well as those of RBT, can be used to screen and evaluate the toxicity of the next generation of lampricides on non-target fish such as lake sturgeon.

A reintroduced lake sturgeon population comes of age: A genetic evaluation of stocking success in the St. Louis River

A reintroduced lake sturgeon population comes of age: A genetic evaluation of stocking success in the St. Louis River