Abstracts - Oral Presentations

Habitat Use and Juvenile Ecology -

Mike Friday (Ontario MNR Upper Great Lakes Management Unit) - Spawning Habitat Enhancement through Flow Manipulation [full presentation (1.46 MB pdf)]

Description: From 2004 to 2006 Ontario Power Generation provided flow over Kakabeka Falls (on the Kaministiquia River, ON) to allow adult sturgeon access to traditional spawning grounds and facilitate successful spawning, hatch and larval drift (23 m3/sec was provided in 2004 and 2005; 17 m3/sec was provided in 2006). This area is often dewatered during the period of spawning for power production and scenic flows for Kakabeka Falls Provincial Park. To monitor sturgeon movements into the spawning area radio telemetry was utilized. Adult sturgeon were tagged in the lower river (with external radio transmitters) when they were known to be migrating upstream to spawn. Their movement into the spawning area and migration back downstream was monitored using an ATS data logger. Larval drift netting was carried out to document spawning success under these flow regimes.

Stephan Peake (University of New Brunswick) - The effect of water velocity on adhesion and survival of lake sturgeon eggs in an experimental raceway [full presentation (438 KB pdf)]

Description: This study examined the effect of water velocity (range: ~ 8 to 26 cm/s) on adhesion and development of lake sturgeon eggs in a 10-m long Plexiglas raceway. Eight groups of 25 fertilized eggs were deposited along a velocity gradient in the raceway and monitored during development. Most eggs adhered initially; however, those in the 3 fastest areas began to break off in a time dependent manner during the first 24 h, after which the numbers of eggs failing to adhere stabilized. By day three, fungal infections were apparent in the 4 groups exposed to the slowest moving water, and deaths due to fungal infections increased in a time dependent manner throughout the rest of the study. By day six, all lake sturgeon eggs in the slowest 2 velocities were dead, and adhesion failure began in those remaining in the 4 fastest areas. By day eight, no eggs were left attached in the 2 fastest areas. In summary, the number of lake sturgeon eggs that hatched relative to water velocity approximated a normal distribution, with the peak located at approximately 16 cm/s, and lake sturgeon eggs exposed to lower velocities tended to die of fungal infections, while those at higher speeds became dislodged. As such, water velocities around 16 cm/s may be optimal for lake sturgeon eggs distributed on smooth surfaces (e.g. bedrock), Furthermore, the capture of large numbers of drifting eggs at spawning sites may indicate reproductive activity; however, it may also be indicative of less than ideal habitat.

David C. Caroffino (Purdue University) - Abundance and mortality of early-life stages of lake sturgeon in the Peshtigo River, Wisconsin [full presentation (2.33 MB pdf)]

Description: If lake sturgeon Acipenser fulvescens restoration is to be successful, a requirement is the thorough understanding of recruitment barriers, such as early life stage mortality. The objectives of this study were to estimate egg, larval, and age-0 juvenile abundance, and to identify and quantify sources of predation for these early life stages. Eggs, larvae, and age-0 juveniles were captured using egg mats, drift nets, and wading surveys, respectively, from April through August 2006. Potential predators were captured using gill nets and electrofishing from May through August 2006. Three distinct spawning events were observed, and the combined estimate of egg deposition was 714,399 (95%CI: 432,100 – 997,221). Catches of larvae during the drift period totaled 190 individuals, yielding an estimate of 3,260 drifting larvae (95% CI: 829 – 6,776). Fifty age-0 juveniles were marked in the lower river, with 27 subsequently recaptured, yielding an absolute abundance of 75 fish (95%CI: 54-126). Stomach contents were examined from 357 potential predators. Sturgeon eggs were present in only one predator (northern hog sucker Hypentelium nigricans), and no evidence of either larval or age-0 juvenile life stage consumption was found. These results suggest that early life predation may not be a significant barrier to sturgeon recruitment; however, more intensive sampling must occur to ensure that predation is simply not being detected.

Patrick S. Forsythe (Michigan State University) - Vulnerability of larval lake sturgeon to predation and evaluation of the bigger is better hypothesis [full presentation (3.28 MB pdf)]

Description: Lake sturgeon (Acipenser fulvescens) have experienced dramatic declines in abundance and distribution. Though conservation plans have been implemented, many populations have not recovered numerically, suggesting unknown barriers to recruitment, likely during early life history stages. Restoration planning has been hampered by the paucity of information regarding inter-annual variation in natural reproduction and of abiotic or biotic factors underlying recruitment. Much of the work dedicated to explain recruitment variation of fish species has focused on the larval stage because of high suspected rates of mortality. Predation is suspected to be a significant source of mortality in lake sturgeon. However, larval or juvenile fish have not been found in the stomachs of predators and mortality rates remain unknown. Our primary objectives were to determine the initial abundance of larval lake sturgeon drifting from spawning areas over consecutive evenings, describe the drifting behavior of individuals as they move down-stream, estimate the magnitude of mortality of individuals dispersing from the spawning areas, and demonstrate the vulnerability of larvae to different candidate predators in a laboratory setting. Laboratory and field data are also used to provide an empirical test of the “bigger is better hypothesis”. We are interested in determining if directional selection favors the survival of larger offspring dispersing from the spawning grounds. Preliminary results indicate that mortality was extensive during out-migration and that larvae were extremely vulnerable to predation by fish. It is possible that recruitment is most limited by extremely high rates of mortality immediately following hatch and through initial drift.

Cameron Barth (University of Manitoba) - Ecology and habitat use of juvenile lake sturgeon downstream of a hydroelectric generating station on the Winnipeg River [full presentation (2.94 MB pdf)]

Description: Information related to the general ecology of juvenile lake sturgeon in a large impounded river is relatively scarce. As such, we studied habitat use, movements and feeding in a population of fish downstream of a hydroelectric generating station on the Winnipeg River. We found a large population of juvenile fish that inhabited deep, flat-bottomed areas with a detectable current, from the face of the dam to approximately 14 km downstream. Depth appeared to be the strongest habitat variable. Fish were concentrated in these areas and appeared to segregate themselves from other sympatric species. During spring, most fish stomachs contained large amounts of Dipterans; however, as summer progressed, gut contents became more diverse and stomach fullness declined. Recapture information suggests that juvenile growth is relatively slow (2 to 5 cm from spring to fall). Preliminary age analyses indicate that 1+ lake sturgeon were between 18 and 23 cm long by the end of their second summer. As we caught very few fish smaller than 18 cm, it is unlikely that any age-0 fish were caught, and as such the ecology of this group remains largely unknown. Nevertheless, preliminary results of this study indicate that riverine areas immediately downstream of a hydroelectric generating station can contain suitable spawning and nursery habitat for lake sturgeon.

Katie Lord Donald (University of Michigan) - Movements and habitat use of juvenile lake sturgeon in the North Channel of the St. Clair River

Description:
- Movement patterns of juvenile sturgeon in the North Channel of the St. Clair River
- General habitat characteristics
- Trends found during study
- Using information as a predictor in other systems

Dan Daugherty (Purdue University) - Determination of lake sturgeon habitat availability in northern Lake Michigan tributaries: applications to the restoration process [full presentation (1.78 MB pdf)]

Description: Lake sturgeon Acipenser fulvescens have experienced a decline in abundance, distribution, and loss or fragmentation of crucial habitats since the early 1800s. Assessments of remnant lake sturgeon spawning populations in Great Lakes tributaries over the last two decades have focused on the estimation of population-based parameters such as abundance, survival, growth, and habitat use. However, few studies have determined the availability and distribution of habitats for lake sturgeon in these systems. Without this information, determination of the most appropriate management and restoration strategies in each system is difficult. The objective of our study was to characterize and quantify habitats for all riverine life stages of lake sturgeon (i.e., egg, larval, juvenile, and staging/spawning adult) in ten northern Lake Michigan tributaries. Georeferenced habitat sampling was conducted during 2004 and 2005 to develop spatially-explicit habitat models in a geographic information system based on lake sturgeon habitat suitability indices for each life-history stage. The resulting habitat models were then used to determine quality, quantity, distribution, and current and potential accessibility to habitats upstream of dam locations. The habitat-based information collected from these models, coupled with our understanding of current population status in these systems, were utilized to determine appropriate lake sturgeon restoration strategies within each system.

Genetics and Management Implications -

Andrea Drauch (UC Davis) - Evaluating the usefulness of a remnant lake sturgeon population as a possible source for reintroductions into the Ohio River drainage [full presentation (1.17 MB pdf)]

Description: Lake sturgeon were once a common species in the Ohio River drainage; however, impoundment, pollution, habitat destruction, and overharvest have contributed to massive population declines in this system. Currently, the White River lake sturgeon population is thought to be the last remaining lake sturgeon population in the Ohio River drainage. Several agencies have proposed reintroducing lake sturgeon from the White River to appropriate areas in the Ohio River system. In order to assess the genetic suitability of the remnant White River lake sturgeon population as a source for reintroductions into the Ohio River drainage, we used nuclear and mitochondrial markers to evaluate its genetic diversity, genetic distinctiveness, and genetic integrity. The White River population exhibited slightly lower levels of genetic diversity than other lake sturgeon populations. However, the population’s two private microsatellite alleles and three private haplotypes suggest a unique evolutionary trajectory. Significant genetic structure was identified between the White River and seven additional lake sturgeon populations, suggesting its genetic distinctiveness from other stocks. Population assignment tests revealed a single putative migrant in the White River, indicating the population has almost completely maintained its genetic integrity. These data indicate that the White River population may be the most suitable source population for future lake sturgeon reintroductions throughout the Ohio River drainage. Furthermore, the White River population appears to be a reservoir of unique genetic information and reintroduction may become a necessary strategy to ensure the persistence of this important lineage.

Kim T. Scribner (MSU) - Reproductive ecology and conservation status of lake sturgeon, Acipenser fulvescens: Inferences based on genetic determination of parentage

Description: Molecular genetic markers have been used widely to provide valuable insights into mating systems and to estimate reproductive success for many fish species, including species of conservation concern. We used microsatellite markers to determine parentage for a remnant population of lake sturgeon in the Black River system in Michigan. Parentage data were used to estimate phenotypic, demographic, and ecological correlates of male and female reproductive success. Polygyny and polyandry were common, with males and females mating with an average of 3.10 and 1.93 mates, respectively. Despite recent reductions in population size, and recruitment of hatchery fish into the adult reproductive population, we did not observe evidence of inbreeding (matings of related individuals). Variance in reproductive success was high in both males and females. On average, adults whose offspring migrated downstream during a more constrained time period produced fewer offspring than individuals whose offspring migrated downstream over a more protracted time period. Body size (and thus age) was not correlated with reproductive success. We observed a significant relationship between mate number and the number of offspring produced, suggesting that adults increase their reproductive success by distributing gametes among multiple mates and by spawning during multiple or more protracted periods of time. Estimates of the effective number of breeders were 44% and 47% of the census number of breeders when Nb was estimated from parentage data and temporal changes in allele frequencies, respectively. We discuss the implications of the species reproductive ecology in light of alternative supplementation strategies under consideration and in the context of aspects of species’ early larval life history.

Kristin Bott (Michigan State University) - Analyses of lake sturgeon recruitment over multiple spatial and temporal scales using genetic and phenotypic data

Description: Lake sturgeon population numbers have declined dramatically due to anthropogenic disturbance in open-waters of the Great Lakes and in stream spawning habitats. The effects of disturbance have likely varied in both magnitude and duration among populations, which has significant implications for basin-wide recovery efforts, particularly when individuals from different natal streams readily cross management boundaries. Estimation of temporal and spatial variation in stock recruitment is exceedingly difficult for lake sturgeon because individuals spend much of an extended pre-reproductive period in open waters, geographically removed from natal rivers. Because sturgeon from different rivers across Lake Michigan are highly differentiated genetically, and based on the availability of established size-age relationships, we provide estimates both age and population of origin for individuals, including those collected from different open-water habitats. We utilize estimates of uncertainty in age and river assignments to establish cohorts for individual rivers, allowing estimates and comparisons of recruitment among and within rivers over time. Analyses indicate that individuals from different tributaries of Lake Michigan are not uniformly distributed across open-water habitats of the basin. We observed similarities in year to year patterns of recruitment among populations that may be tied to inter-annual variation in weather or other environmental regimes. Estimates of recruitment and differential occupancy of lake habitats will be discussed relative to temporal and spatial variation in environmental quality and relative to future restoration goals.

James A. Crossman (Michigan State University) - Quantification of genetic and environmental factors on variation among early life history traits in lake sturgeon [full presentation (2.52 MB pdf)]

Description: Variation in early life history traits of larval fish can be attributed to both genetic and environmental factors. Quantification of causal factors underlying variation in these traits at important transition periods in life is critical to forecasting stock recruitment and to designs of management programs for imperiled species, including lake sturgeon. It is essential that we determine the magnitude and direction of covariation among these traits. Studies on lake sturgeon depicting contributions of genetic or environmental sources to variation among traits and how these sources relate to growth and survival are lacking. Accordingly, we examined major factors governing both embryonic and yolk-sac larvae growth and survival under known genetic and environmental sources using a streamside rearing facility on the Upper Black River, Michigan. Genetic sources included the known relatedness, biological attributes, and reproductive success of adult lake sturgeon used in artificial crosses while environmental sources included temperature, dissolved oxygen, and refuge and resource availability. Specific objectives were to, (1) determine if variation in development at the egg and larval stages were influenced by genetic or environmental factors, (2) determine the influence of individual female size and condition on variability in egg and larval size at hatch, yolk-sac volume at hatch, yolk-sac absorption rate, and egg and larval mortality, and (3) determine the effects of refuge and resource availability on yolk-sac absorption and growth within and among half-sib family groups. Conclusions from this work will provide insight into the magnitude of genetic and environmental contributions to individual survival and stock recruitment.

Amy M. Schueller (Michigan State University) - Evaluation of lake sturgeon stocking strategies using an individual-based model [full presentation (655 KB pdf)]

Description: Lake sturgeon restoration is a priority throughout the Great Lakes basin, where sturgeon have been reduced to less than 1% of historic levels due to habitat degradation, over-harvest, and fragmentation of spawning populations. Stocking has generally been embraced as a component of rehabilitation, but difficulty has arisen when prioritizing the number of lake sturgeon to stock and parentage of those fish. We determined stocking strategies for lake sturgeon that maintain population growth across a range of initial population sizes, and we determined implications of stocking strategies on the accrual of inbreeding. An individual based modeling approach was developed that represented the demographics and genetics of lake sturgeon. We ran the model across a range of initial population sizes to determine stocking strategies that achieve positive population growth and best maintain genetic integrity. Higher stocking rates are required at smaller initial population sizes to avoid population extinction and inbreeding, and larger numbers of parents for stocking purposes are needed to reduce the risk of inbreeding. Stocking strategies need to be specific to population size. This research will help to ensure the sustainability of the lake sturgeon within the Great Lakes basin by developing optimal stocking strategies to maximize population growth rate while incorporating concerns about inbreeding.

Amy Welsh (SUNY) - Development of Lake Sturgeon Genetic Stocking Guidelines [full presentation (338 KB pdf)]

Stocking of lake sturgeon in various regions of the Great Lakes is becoming an increasingly popular management strategy. However, several genetic risks are inherent in stocking, including outbreeding depression, loss of genetic diversity, and artificial selection. A draft set of guidelines for stocking has been developed to minimize these risks and support lake sturgeon rehabilitation in the Great Lakes. The guidelines are relevant to the entire Great Lakes and will provide guidance to the development of lake-specific management plans. We developed microsatellite markers and standardized data, protocols which enabled us to combine genetic data from multiple laboratories. This dataset was used to identify genetic stocking units (GSUs). Eight GSUs were identified throughout the Great Lakes. Criteria for the identification of priority populations for genetic preservation were established such as high levels of genetic differentiation. A decision tree was created, incorporating the above information, to foster selection of appropriate stocking sites and to assist managers in choosing appropriate donor populations. Finally, we included recommendations for the design and implementation of stocking programs. Recommendations are provided for the number of consecutive years stocking should occur, the number of adults to use for gamete collection, rearing procedures in the hatchery, number of individuals to be stocked, and post-stocking monitoring procedures.

Stream Side Rearing -

Marty Holtgren (Little River Band of Ottawa Indians) - Operation and evaluation of a streamside rearing facility for lake sturgeon in the Manistee River, MI [full presentation (2.29 MB pdf)]

Description: The Little River Band of Ottawa Indians has operated a streamside rearing facility on the Manistee River for lake sturgeon since 2004. The facility has been upgraded each year with modified rearing protocols and new equipment. In 2006 we implemented preventative disease treatments, 24 h feeding of sturgeon with brine shrimp and bloodworms, and increased filtration and clarifying of incoming river water. Throughout fish rearing we collected measurements of growth, determined condition factors, and recorded mortality. Growth rates and condition factors were compared between wild and reared fish. Growth of streamside reared fish was also compared against hatchery reared fish. External radio-transmitters were attached to 10 streamside reared fish and 2 wild-captured to compare habitat use and river retention. The results will be the topic of this presentation.

Ed Baker (Michigan DNR) - Lake Sturgeon Restoration Using Streamside Rearing Facilities on Four Lake Michigan Tributaries [full presentation (2.16 MB pdf)]

Marc White (Riveredge Nature Center) - Use of volunteers in the daily operation of a lake sturgeon streamside rearing facility on the Milwaukee River, WI [full presentation (5.91 MB pdf)]

Description: In the spring of 2006, Riveredge Nature Center undertook a partnership with the USFWS, WDNR, The Little River Band of Ottawa Indians and UWSP to operate a streamside rearing facility on the Milwaukee River, WI with the goal of rearing, imprinting and releasing 1000-1500 Lake Sturgeon/year over the next 25 years. Although grant funds are expected to cover the initial three years of this effort, funding for the remaining 22 years of operation has not been secured. Given the uncertainty of long-term project funding, Riveredge Nature Center has implemented a staff-supported, volunteer based model for the daily operation of the SRF. During the 2006 rearing season, Riveredge staff has recruited, trained and supported a group of 26 volunteers in the daily operation of the Milwaukee River Lake Sturgeon SRF. This presentation will highlight the challenges and opportunities that come with volunteer operation of Lake Sturgeon Streamside Rearing Facilities.

Sturgeon Legal Issues -

Fred Hnytka (DFO Winnipeg) - Species at Risk Act and Recovery of the lake sturgeon in Canada [full presentation (852 KB pdf)]

Greg Drogowski (Michigan DNR) - Poaching prevention and the Citizen Watch Program on the Black River, MI

Todd Schaller (Wisconsin DNR) - Lake Winnebago sturgeon spearing, spring spawning and the Wolf River Enforcement Program [full presentation (2.33 MB pdf)]

Description: Overview of Lake Sturgeon law enforcement efforts on the Lake Winnebago System (East Central Wisconsin). A very unique resource that creates some very unique enforcement challenges. Focusing on enforcement efforts related to the Lake Winnebago and Upriver Lakes Sturgeon Spearing Season and the Sturgeon Guard program on the Wolf River system.

Mike Kitt (Wisconsin DNR) - Menominee River Fishery Enforcement Program [full presentation (1.22 MB pdf)]

Mary Burnham Curtis (USFWS Forensics)
a) ID of caviars in trade - at the species, river system, and individual levels
b) Distinguishing between caviars from aquaculture raised and wild caught fish
c) Establishing genetic registries for brood stock in aquaculture operations

Assessment Technologies -

Larry Hildebrand (Golder Associates Ltd.) - White sturgeon research and recovery in the Upper Columbia River

Description: In the last decade, white sturgeon (Acipenser transmontanus) populations in the upper Columbia River basin have been the subject of intensive research and recovery efforts. These populations experience frequent recruitment failures and as a result, the species was recently listed as endangered under the Canadian Species at Risk Act. This talk provides an overview of research methods and findings to date, describes the recovery process, and discusses potential causes of recruitment failure.

Chris Pullen and Rob Mellow (Golder Associates Ltd.) - Use of a stream side flow-through holding system as part of a lake sturgeon (Acipenser fulvescens) larval survival study [full presentation (2.70 MB pdf)]

Description: As part of a lake sturgeon (Acipenser fulvescens) annual monitoring program on the Groundhog River, located 75 km northwest of Timmins, ON Golder Associates Ltd. has conducted a sturgeon egg incubation and survival study annually since 2004. . The purpose of the egg incubation and survival study component is to evaluate the potential for exposure impacts on fertilized eggs by treated mine water effluent from the Montcalm Mine, operated by Xstrata Nickel (formerly Falconbridge Limited).

As an addition to the 2006 monitoring program, post-hatch larvae were held for 48 hours in reference and exposure conditions both in the river and in a stream side flow though system to assist in quantifying effluent effects on yolk sac larvae. The study was conducted in situ to account for synergistic environmental effects.

The intent of the parallel flow through holding system was to act as a controlled environment to in-situ riverine larval holding conditions. We feel that in addition to the data gathered, the design, construction and operation of the system may prove to be a practical methodology for other lake sturgeon egg incubation and larval fish studies at remote sites.

Nancy Auer (Michigan Technological University) - Rapid assessment of lake sturgeon spawning stocks using fixed-location, split-beam sonar technology

Description: Accurate assessment of lake sturgeon stocks can be compromised by weather, water level fluctuations, availability of personnel and the unique biology and habits of the species.
Fixed-location, split-beam sonar technology was successfully applied to identify number of adult lake sturgeon moving upstream and downstream for spawning in the Sturgeon River, Michigan May to June 2004. We used a Hydroacoustic Technology Inc. model 241 split-beam echo-sounder operating at 200 kHz and a single 4.0 x 10º elliptical-beam transducer with a near field range of 0.1 m set perpendicular to the river flow. Data collected from migrating lake sturgeon included swimming speed, range from transducer, time and date of passage, and target strength. The spawning population of lake sturgeon was estimated to be at 350 to 400 fish with almost equal numbers of fish being seen moving upstream as downstream. Most fish were recorded moving within the mid-section of the river, 1.5 – 1.65 m deep, and swimming speeds upstream were slower than those for downstream moving fish. Our results show that spilt-beam sonar can be applied to lake sturgeon assessments, without the stress of actually handling these large, pre-spawning fish and with greater coverage of population.

Lisa O’Connor (DFO Sault Ste. Marie, ON) - Additional potential for PIT technology in lake sturgeon management [full presentation (1.29 MB pdf)]

Description: While tagging lake sturgeon with passive integrated transponder (PIT) tags for individual identification has become part of the standardized protocol for agencies around the Great Lakes, there remains the potential for a much wider application of the technology. Remote detector stations and instream antennae could provide valuable basic life history information (frequency of spawning, stream fidelity, mortality), data on the timing of spawning and other movements, population estimates (when used in combination with a capture program), and a long-term population monitoring tool. We will describe a different PIT tag and antennae system that we use for other species, and provide examples of the data that we collect with minimal effort.

Henry Quinlan (USFWS Ashland) - PIT tagging standardization, gear demonstration and distribution, and web based PIT tagging data base [full presentation (654 KB pdf)]

Description: Efforts to rehabilitate lake sturgeon in the Great Lakes can be greatly enhanced by agency cooperation basinwide. Fishery biologists throughout the Great Lakes collect data on lake sturgeon to assist efforts to restore sturgeon populations to their wide range of former habitats. Individual lake sturgeons are known to utilize multiple Great Lakes, making cooperation and communication among biologists from different states and countries paramount to increasing our knowledge about their status and habits. Over the last half dozen years, biologists have increasingly used Passive Integrated Transponder (PIT) tags to individually mark lake sturgeon captured and released. When a tagged sturgeon is recaptured, biologists can learn from its movement and how much is has grown since it was initially tagged.

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