USGS - science for a changing world

U.S. Geological Survey - Great Lakes Science Center

Population Restoration

Modification of Great Lakes environments has adversely affected native biodiversity through dramatic reductions in abundance and local extinction of many native species. To remediate past effects on native biodiversity, the USGS-GLSC is restoring populations of multiple native species in the Great Lakes. Restoration efforts are focusing on native fish in the Great Lakes, such as lake sturgeon (threatened in Michigan and Ontario), lake trout, Atlantic salmon, deepwater cisco, lake herring, and brook trout, as well as native species in connecting habitats to the Great Lakes, such as Karner blue butterflies (endangered status), Pitcher’s thistle (threatened status), and American bittersweet (declining rangewide).


Problem Statement
As part of an ongoing program to restore lake sturgeon (Acipenser fulvescens) in New York, hatchery-produced juveniles have been stocked into Oneida (8,127) and Cayuga (3,752) lakes, 1995-2004. Release of juveniles as a restoration strategy assumes movement into available suitable habitat. These lakes are connected to the New York Canal system consists largely of rivers altered into a barge canal. Migration of these fish into the Seneca and Oswego Rivers (Oswego and Erie Canals) has been documented. Measurable local populations appear to be present in the system upstream and downstream of barriers (lock/dam complexes). In typical canals the majority habitat consists of relatively homogenous depths and substrates maintained by regular dredging and have degraded water quality. The canal system offers a suite of human impacted habitat conditions that are unfortunately not so rare within the lake sturgeon’s native range. These habitat conditions likely affect use of, movements within, and possible spawning in, the system. Whether a population of lake sturgeon can be sustained in this system will ultimately depend on the quality, quantity, distribution, and availability of essential habitats. Also, knowledge of population parameters such as population size, growth rate, and size distribution, are critical to the evaluation of population stability and persistence. In order to evaluate the potential of the Oswego River basin to support a self-sustaining lake sturgeon population, a comprehensive examination of current distribution and abundance, delineation of critical habitats for all life stages, documentation of spawning activity and habitat, and the effects of river channelization and barriers on all of these, is necessary. The results of this project status assessment will aid tribal, state, and federal managers efforts to more completely understand the restoration ecology of this native species and help to formulate a more effective sturgeon management plan for New York.

In the Oswego, Oneida and Seneca rivers:

  1. Determine the distribution, relative abundance and migratory movements of lake sturgeon in the Western New York Canal system.
  2. Examine age specific growth rates of lake sturgeon and compare to other NY waters with wild and stocked populations.
  3. Identify areas suitable for lake sturgeon spawning and evaluate use of those areas by adult sturgeon.
Principal Investigator: Dawn E. Dittman

Problem Statement
This research has three primary objectives: 1) locate populations of rare, threatened, and endangered species within the US Lake Ontario-St. Lawrence basin and Akwesasne territory with the aid of new tools and data to provide the most efficient surveys, 2) estimate their relative abundances and identify the associated optimal habitat conditions, and 3) use those findings to clarify threats and population status and assist with ranking priority areas for protection and possible restoration (where appropriate). This work will also support the State Wildlife Action Plan and enhance our understanding of the condition and character of SGCN throughout New York, but with a focus on the area of Akwesasne and other sections of the upper St. Lawrence River Basin. The results will be made available as an aid to future fish (and other species) management and planning efforts.


  • SGCN species distributions are not uniform throughout Great Lakes-St. Lawrence waterways and optimal SGCN habitat can be identified and distinguished from other habitats (and thus mapped).
  • Empirical species-habitat models developed for SGCN can effectively predict the habitats capable of supporting those species – This effort helps to validate GLGap model development methods for rare and uncommon species and establishes a means of more efficiently locating and assessing SGCN in lotic habitat.
  • Fish community structure is influenced by the presence of SGCN species.
  • Manageable threats to SGCN can be identified and characterized.

Background & Description
There is a biodiversity crisis in general for aquatic systems. Globally, approximately ¼ - ½ of vertebrate diversity is found within the tiny amount (~0.01%) of water in lakes and rivers (Sowa et al. 2007) and aquatic fauna are disproportionately imperiled (Master 1991, Williams et al. 1989, NRC 1992). Projected aquatic extinction rates are five times higher than those for terrestrial species (Sowa et al. 2007). Ten percent of all freshwater fish species are found in the US. However, 31% of freshwater fish in North America are considered vulnerable to extinction (Williams et al. 1989, 1993). Recent work by the American Fisheries Society’s Endangered Species Committee shows a substantial increase in imperilment of North American freshwater and diadromous fishes (Jelks et al. 2008).

Rare species are, of course the most vulnerable and yet much of what constitutes biodiversity within any given habitat is comprised of rare and uncommon species (Fisher et al. 194??). These species are an essential component of complete species lists, which are among the most basic information needed for understanding natural multi-species communities. Rare species also have important roles in providing ecological services (Lyons et al. 2005). They may function as keystone species and, as a group, can serve as a reserve of ecological capabilities, helping communities respond to disturbances. The difficulty of working with rare, poorly known species and the great need to evaluate those species, has lead to the “rare species modeling paradox” (Lomba et al. 2010), where few successful species distribution models have been developed to address the pressing rare species assessment needs.

The FEMRF Committee, as well as State and Federal agencies, tribes, and NGOs, recognize that Threatened and Endangered (T&E) species are important and more information is needed to effectively manage them and their supporting ecosystems throughout the Lake Ontario and St. Lawrence drainage. By definition, T&E species are in serious decline or nearing extinction. Thus, they are most sensitive to habitat loss or degradation, or any other threat that increases mortality or reduces production. In addition to T&E species, are species which are somewhat more common, but are declining in abundance and/or distribution, or whose population status is unknown. These are collectively classified as Species of Greatest Conservation Need (SGCN). The New York State Comprehensive Wildlife Conservation Strategy identifies a number of threats to these species (Anonymous 2006, WAP), including habitat loss and fragmentation, various types of water and air pollution, and invasive species. Better assessment of the status and distributions of SGCN species is needed within the Great Lakes system in reference to these threats (LaPan et al. 2002).
The spatial distribution of fish assemblages is a basic ecological question that helps us determine if distinct ecological communities are maintained by unique habitat conditions, biological interaction, or (more likely) some combination of both. This question has been addressed by many local-scale studies (Daniels 1993) and has contributed to development of practical indices, like the IBI (Karr 1981, Daniels et al. 2002). A few such studies have been conducted in New York State. However, few have been conducted at larger scales (e.g., watershed scale) (Browne 1981, McKenna 2001, 2003a, McKenna and Castiglione 2011, McKenna and Johnson in press).

Lake Ontario is the last lake in the chain of flow through the Great Lakes and it is drained by the St. Lawrence River, the second largest river on the continent. The St. Lawrence River receives all of the water from the Great Lakes, as well as direct input from many rivers and streams in New York and Canada. As cited in the WAP and other documents, there is a suite of threats to aquatic organisms and their associated habitats in this region. Of the 19 fish species currently listed as Endangered or Threatened in New York State waters, four occur within the St. Lawrence drainage within Lake Ontario and its local watersheds. One, the Pugnose Shiner (Notropis anogenus) is classified as Endangered. The Lake Sturgeon (Acipenser fulvescens), Mooneye (Hiodon tergisus), and Eastern Sand Darter (Ammocrypta pellucida) are considered threatened. In addition, some of the other species found in the area are locally or globally declining. Uncommon species, not yet listed, but in decline are those that may benefit most from evaluation of their distributions, population abundances, and habitat requirements. Some of those species of concern include, Blackchin Shiner (Notropis heterodon), Iowa Darter (Etheostoma exile), and Ninespine Stickleback (Pungitius pungitius).

While T&E species are rare by definition, other SGCN species may or may not be rare, but are becoming less common (or suspected of declining). Collecting information on rare species is inherently difficult, because of that rarity. This is compounded if a species is also difficult to detect, where it does occur – an obvious problem for aquatic organisms. As a result, there are few data on rare fishes in the Lake Ontario-St. Lawrence basin and their status and distribution are poorly known or essentially unknown (Carlson 2001). In addition, diversity is scale dependent. The larger the area of consideration, the richer the community is and, typically, the greater the diversity supported. The behavior of species diversity and implications for natural communities at large scales requires larger sample sizes and involves more species and individuals. Study at these larger scales becomes more difficult because of the greater complexity and effort required, but is necessary for planning and management on the scales most effective for rare and uncommon species and general biodiversity conservation.

New analytical tools and data now make these larger-scale studies feasible (Hughes et al. 2006, McKenna et al. 2006). Recent work in the Great Lakes region provides us with new ways to survey for SGCN. For example, recent work in the Akwesasne wetland collected 42 fish species (and several herps), and identified three distinct fish habitat zones associated with the river and its tributaries (McKenna et al. 2005). These new data included records of uncommon species. Also, advances in data and tools that characterize fish-habitat relationships and predictive capabilities produced by the Great Lakes Regional Aquatic Gap Analysis Project (GLGap) provide a unique opportunity to combine data-derived estimates of fish occurrences and efficient field sampling to locate and evaluate rare and uncommon species. Success using similar Aquatic Gap Analysis data and methods to study rare species has been demonstrated by Hayer et al. (2008) in South Dakota.

The present research includes two major components. The first is an extensive evaluation of fish resources in the St. Lawrence River and its tributaries, supported by selected species distribution models from the GLGap project. This component will be carried out as a joint effort with the St. Regis Mohawk Tribe Environment Division and collaboration among other TLAS scientists (Johnson and Dittman). The second component is development of a predictive modeling process, designed to effectively identify rare species habitats. The rare species modeling extends the GLGap development process to include rare species and makes use of a variety of independent data to test and validate those models.

Principal Investigator: James E. McKenna, Jr.

Problem Statement
Native fish conservation, restoration, and rehabilitation programs are a key activity for natural resource agencies. Lake sturgeon (Acipenser fulvescens) is a native fish species that is considered integral to healthy fish communities across the Great Lakes Region. In 1993 the New York State Department of Environmental Conservation (NYSDEC) initiated a project to restore Lake Sturgeon as a viable self-sustaining component of the fish community in St. Lawrence River tributaries and the St. Lawrence River itself. Several historic sturgeon waters were selected for restoration stocking. One of these systems was the Oswegatchie River / Black Lake / Indian River system. From 1994 through 2004 fingerling Lake Sturgeon were released into the Oswegatchie River and into Black Lake /Indian River to reestablish the species in the watershed. Assessment of the results of management actions is a critical component of restoration ecology. Some the ultimate goals of the sturgeon restoration management in New York include the detection of a minimum number of adult sturgeon, the detection of spawning sturgeon in the target waters, and successful recruitment in a minimum of 3 years. The females from the early years of stocking, have reached the minimum age of first reproduction. An identified critical information need for ongoing Lake Sturgeon management in New York is spawning population delineation and quantification of natural recruitment. Analysis will allow determination of whether some of the endpoint goals of sturgeon restoration in New York have the potential to be reached in the Oswegatchie River and Black Lake System.

The released sturgeon are reaching maturity and will start to use currently unquantified available spawning habitat. The available spawning habitat will vary in quality, resulting in a range of habitat use intensity and potential natural production. Quantification and multifactor analysis of key habitat characters and habitat use with a comparison with the key characters of currently productive sturgeon spawning habitat will allow the determination of how well the available spawning habitat will support sturgeon reproduction, or if that habitat will need enhancement to meet the goal of natural recruitment.


  • Identification and mapping of potential spawning habitat sites for Lake Sturgeon in the stocked sections of the Oswegatchie River and Black Lake system.
    • Locate sites that potentially have the key habitat characters of sturgeon spawning grounds integral to habitat suitability index models.
    • Measure key habitat characters to quantify the habitat quality of identified potential spawning sites.
  • Quantify use by sturgeon at identified potential spawning sites by measuring egg deposition and index larval drift from the sites.
  • Model habitat quality and the potential larval production of the identified spawning habitat based on habitat assessment and comparison with known productive spawning areas in similar nearby rivers. Identify the best of the best available spawning sites.
  • Determine how well the available spawning habitat will support sturgeon reproduction, or if that habitat will need enhancement to meet the goal of population sustaining natural reproduction.

Background & Description
Lake sturgeon (Acipenser fulvescens) were once a common component of the native fish community, but have undergone a widespread decline throughout the Great Lakes primarily due to overfishing and degradation of spawning areas, including reduced access to historic spawning areas. Lake sturgeon are considered rare, threatened, or of special conservation concern by Great Lakes fisheries management agencies. The goals for Lake Sturgeon across the Great Lakes Basin are to ensure populations are documented, protected, managed and, when needed and feasible, enhanced (Peterson et al. 2007, Elliott et al. 2009).

Lake Sturgeon was classified as threatened in New York State in 1976. Declines were due to overfishing, construction of dams that cut off key upstream spawning grounds, and pollution. The New York State Comprehensive Wildlife Conservation Strategy (Anonymous 2006) included lake sturgeon as a species of greatest conservation need within the St. Lawrence River region. The in the early 1990’s New York State Department of Environmental Conservation (NYSDEC) initiated a project to restore lake sturgeon as a viable self-sustaining component of the fish community in St. Lawrence River tributaries. One endpoint goal of the NYSDEC sturgeon restoration management is detection of a minimum number of adult sturgeon and of spawning sturgeon in the restoration waters (Carlson 2005). This project will provide information to measure progress toward attaining that goal. This work will also complement another TLAS project “Evaluation of aquatic species of greatest conservation need in St. Lawrence River Tributaries.” This includes Lake Sturgeon as one of those species of greatest conservation need.

The Oswegatchie River (105 rkm) / Black Lake (4,593 acres) were identified as historic sturgeon water in which sturgeon were severely reduced (Carlson 1995). A major component of the Lake Sturgeon recovery plan in New York is based on population restoration by stocking of hatchery reared fish. In 1993 and 1994 20,100 small (25-55mm) sturgeon were released in the Oswegatchie River. From 1994 through 2004, a total of 13,517 larger (160-200mm) fingerling sturgeon were released in the Oswegatchie River and 9,090 were released in Black Lake (Carlson 2005). Figure 1. shows the primary stocking locations and the numbers of fingerlings released at each site.

This project will complement a previous Oswegatchie River Lake Sturgeon project conducted by Scott Schlueter of the USFWS and the State University of New York - College of Environmental Science and Forestry. He analyzed the distribution, movement, and habitat utilization, and river retention of the newly stocked juvenile Lake Sturgeon in the Oswegatchie River in 1998 and 1999 (Schlueter 2000). He found some of the sturgeon stayed near the stocking sites and appeared to be healthy, as others migrated far downstream.

Research work during the 2009-2010 and the current complementary TLAS studies on species of concern in the system found ripe males were present in 2010 downstream of major barriers, including near the stocking site downstream of the Huevelton dam. The females from the earliest years of stocking are approaching the standard age of first reproduction (18-25) for Lake Sturgeon (Bruch and Binkowski 2002). In 2012 one female with eggs was captured at one of the natural upstream barriers in the Indian River, 2km upstream from Black Lake. The age of first reproduction for the oldest stocked females has been reached.

Principal Investigator: Dawn E. Dittman

Problem Statement
Anthropogenic activities have greatly impacted fish populations in the Great Lakes. Of all the Great Lakes, fish populations in Lake Ontario have been impacted the most severely, including the extirpation of Atlantic Salmon (Salmo salar) and deepwater coregonids such as bloater (Coregonus hoyi) and major declines in lake sturgeon (Acipenser fulvescens), deepwater sculpin (Myoxocephalus quadricornis), lake herring (C. artedi) and American eel (Anguilla rostrata). Loss of spawning habitat and perhaps overfishing are thought to be the major causes for the loss of Atlantic salmon and lake sturgeon, whereas invasive species such as alewife (Alosa pseudoharengus) and rainbow smelt (Osmerus mordox) are considered to have led to the decline of coregonids, and deepwater sculpin. Because of the complexities associated with the extirpation or decline of native fish species in the Great Lakes there is no single remedy suitable for the restoration of all species. The restoration of deepwater coregonids, as well as extirpated Atlantic salmon, must at least initially rely on hatchery reared fish.

This effort will consist of three separate thrusts geared at restoring Atlantic salmon, bloater, and lake herring in Lake Ontario and the St. Lawrence River.

  1. Atlantic salmon: Facilitate restoration of Atlantic salmon in Lake Ontario and the St. Lawrence River through the development of new and innovative restoration techniques and the evaluation of multiple salmon strains to determine their suitability for restoration.
  2. Coregonids: Facilitate coregonid restoration in the lower Great Lakes through the development of new and innovative restoration techniques while following proper disease protocols when transferring eggs to isolation facilities and the evaluation of the suitability and current use of historic spawning sites.
Principal Investigator: Jim H. Johnson

Problem Statement
Migrating fish are known to move into the Black River at spawning time and successful Walleye (Sander vitreus, Mitchell, 1818) spawning is suspected, but has not been documented. Enhancement of Walleye, and potentially Lake Sturgeon (Acipenser fulvescens), spawning habitat in this area may significantly contribute to production of these native species in Eastern Lake Ontario. We hypothesize that the production of Walleye and/or Lake Sturgeon will be enhanced by improving spawning habitat in the mouth of the Black River downstream of the first river barrier.


  • Evaluate existing benthic habitat / substrate of the Black River between Dexter, New York and the head of Black River Bay, with special emphasis on conditions appropriate for Walleye or Lake Sturgeon spawning.
  • Assess present Walleye and Lake Sturgeon production within the study area.
  • Develop and evaluate scenarios for Walleye spawning bed enhancement (and for Lake Sturgeon, if possible), identifying the best locations, engineering needs, logistics, and post-placement success measures.
  • Work with engineers to install appropriate and durable spawning beds.
  • Conduct post-construction evaluation of the effects of enhanced spawning beds on Walleye and Lake Sturgeon (if any).

Background & Description
This study is a high priority for the New York State Department of Environmental Conservation (NYSDEC) Lake Ontario Program and Region 6 Fisheries Management. Walleye is a popular native sport fish and Lake Sturgeon is a New York State Threatened species that once supported a commercial fishery. Also, the Black River Lake Sturgeon population is known to have a relatively high level of genetic differentiation (Welsh et al. 2010). Production of both of these native species (and other associated species) may be substantially enhanced in the Eastern Basin of Lake Ontario with successful completion of this work (Stewart et al. 2012). This is a large project that will be supported by several different agencies and funding sources.

This research will enhance the ecological function of the watershed by increasing productivity (and hopefully population size) of several fish species that are part of the native migratory community. These fishes are responsible for flux of mass and energy between the riverine system and Lake Ontario. Enhancing these populations (and associated species) should enhance the ecological coupling between the lake and the watershed. The focus species are considered game fish and historically supported commercial fisheries. Thus, these species are valuable and important to local economies. What we will learn from this work may be applied to other sections of the watershed and may improve our ability to develop future fish enhancement projects.

Walleye is one of the most valuable game fish in North America and Lake Sturgeon is of great interest due to its rarity, game value, and the fact that it once supported commercial fisheries. Both of these species have been studied extensively and their life histories are well known, although those characteristics can vary among different aquatic systems (Scott and Crossman 1973, Smith 1985, Werner 2004, for example). Populations of Walleye and other native lithophilic spawners that require fast water are high priority targets for enhancement and restoration in the Great Lakes Region. NYSDEC Biologists report that Walleye and Lake Sturgeon are present in small numbers in the Black River below the dam at Dexter, New York during migration, and some appropriate spawning habitat exists. However, surveys by the NYSDEC (Klindt and Adams 2005) have found that the available fast-water habitat (regulated by the dam) is dominated by bedrock with a relatively small area of suitable spawning substrate (gravel-cobble-boulder). This is largely due to intense scouring by spring floods (flow ranges from 55,500 ft3/s to 10 ft3/s). Low summer flows expose some of the potential spawning areas.

Walleye and sturgeon overlap in their spawning requirements, although spawning times and substrate preferences differ (Threader et al. 1998, Lyttle 2008). Spawning bed enhancement would benefit Walleye, Lake Sturgeon, and several other high value sport and native species. Enhancement of spawning habitat in this area has great potential to produce Walleye, and possibly Lake Sturgeon, by natural means and significantly contribute to production of these species in eastern Lake Ontario.
Walleye ecology: Habitat requirements, spawning, and other life stages

Walleye are large members of the perch family (Percidae) growing as large as 91cm (2.2 kg) (Page and Burr 1991, Werner 2004). They are a large lake and river species, rarely found in lakes smaller than 100 acres in size. Walleye migrate up tributaries from Lake Ontario shortly after winter thaw, when flows are highest; in the Black River these flows can be dangerously fast. The fish seek areas of appropriate gravel-cobble substratum in less than 2m of water to spawn and deposit their eggs (Smith 1985). The eggs develop and hatch into larvae within a time period dictated by water temperature, typically 7 - 30 days. These larvae are quite small and leave the gravel soon after hatching, at night, drifting down river to nursery areas. The larvae tend to swim up into the water column and may drift near the surface, but are at the mercy of river currents and could be collected at any depth near the spawning areas. Little is known about the development in the nursery areas, but Walleye switch from planktivory to piscivory at a young age (~7.5 cm total length) (Colby et al. 1994, Geiling et al 1996).

Lake sturgeon ecology: Habitat requirements, spawning, and other life stages
The Lake Sturgeon is a primitive, long-lived, late-maturing, bottom feeding fish species (Harkness and Dymond 1961, Auer 1999) that prefers waters above 10°C and 5 to 10 meters deep for spawning (Bemis and Kynard 2002). Lake Sturgeon are found in rivers and nearshore areas of the Great Lakes and engage in extensive migrations for feeding and spawning (Auer 1999, Bruch and Binkowski 2002). Lake Sturgeon is New York’s largest freshwater fish, averaging 75 to 198 cm in length and up to 45 kg; the maximum recorded size is 274 cm and 125 kg. Females mature between 14 and 33 years of age, males between 8 and 12. Spawning is in stream rapids in the spring, with each female spawning at 4 to 9 year intervals and males every 2 to 7 years (Harkness and Dymond 1961, Nilo et al. 1996, Threader et al. 1998). The diet of Lake Sturgeon consists of invertebrates (aquatic insect larvae and mollusks) and some fish (Harkness and Dymond 1961, Kempinger 1996). This species is a classic example of an easily threatened species, vulnerable to overfishing, habitat fragmentation, degradation of spawning and feeding habitat quality, and restricted access to spawning areas. As a consequence of interrupted spawning cycles, only 10-20% of adult Lake Sturgeon within a population are sexually active and spawn during a given season. Among others, this necessitates a larger minimum population size than that needed to sustain other more synchronous spawners (Peterson et al. 2007).

Known Black River habitats, spawning, and production
The Black River is among the four largest tributaries to Lake Ontario and drains a watershed nearly 5,000 km2 in area. Our study area is located at the mouth of this river below the lowest dam, which is located at Dexter, NY (Fig. 1). The study area is approximately 2.25 Km long and initial estimates of enhanced spawning beds may cover a total of 1 ha (Fig. 2); enhancement may effectively double the area of suitable spawning habitat in this river system. The extremely high spring flows are powerful and highly variable, easily moving even large boulders; most of the river channel below the dam is scoured to the limestone bedrock underlying this area. At low water conditions, some sections of the river that are flooded in spring are de-watered. Natural variability of the flow in this part of the river is exacerbated by flow manipulation for hydropower. As a result, a poorly sorted collection of gravel, cobble, and boulders is retained in only a few off-channel areas. The largest is associated with a small cove between the hydropower facility and the NY Route 180 bridge (Fig. 2). Smaller areas where material is deposited are located between the hydropower spillways and some of the islands downstream of the bridge.

Migrating Walleye and Lake Sturgeon are known to move into the study area at spawning time. A popular Walleye sport fishery exists in this part of the river and Lake Sturgeon have been caught there. However, it is unclear whether the fishery is supported strictly by hatchery augmentation or if some natural production is contributing. Successful spawning by both of these species is suspected, but has not been documented.

Identification of potentially suitable spawning areas: Flow, depth, substratum (type and depth), and temperature measurements
Walleye and Lake Sturgeon spawning habitat suitability depends upon a combination of flow and substrate conditions, in association with appropriate water temperature (Walleye: 6° - 11° C; Lake Sturgeon: 13° - 18° C, Scott and Crossman 1973). Acoustic survey and visual inspection of bottom substratum with SCUBA diving expeditions during the summer of 2012 identified two areas of the river that have appropriate bottom substrate (Fig. 2), both located above the Route 180 bridge. Preliminary measures of river flow immediately below the dam in Dexter, NY were made in the spring of 2012. Despite spring 2012 being an exceptionally dry year, with unusual timing of the spring flood, measurements showed sufficient flows in the potential Walleye spawning areas (Fig. 3).
Appropriate water temperatures and high flows coincide during a brief time period near ice-out for Walleye and a few weeks later for Lake Sturgeon. Initial sampling for Walleye and Lake Sturgeon eggs and drifting larvae was also conducted in the spring of 2012; a few walleye eggs, but no larvae were collected.

Estimates of spawning and production
Walleye and Lake Sturgeon are broadcast spawners. Fertilized eggs are carried a short distance by the current before falling into the substrate interstices, where they incubate. Hatched larvae leave the substrate and drift down stream to more appropriate nursery areas. We will use a variety of sampling gear (e.g., egg traps and drift samplers) to measure present spawning activity and fish production within the study area. The same or comparable methods will be used to measure spawning and production after new spawning beds have been installed (Geiling et al. 1996, D’Amours et al. 2001). Comparison of these production estimates before and after spawning bed enhancement will provide a measure of the efficacy of river habitat modifications (Dumont et al. 2011).

Principal Investigator: James E. McKenna, Jr.

Lake trout Salvelinus namaycush historically were the keystone predator and supported a valuable commercial fishery in the Laurentian Great Lakes until the extirpation of most populations by the 1950s. Lake trout have been stocked throughout the Great Lakes since the 1970s, but aside from local progress in restoration in Lake Huron, rehabilitation has occurred only in Lake Superior. Recently, ecosystem changes in Lake Huron have resulted in the lakewide recruitment of wild adult lake trout. The USGS GLSC works cooperatively with a variety of agencies (MDNR, OMNR, CORA, USFWS) to conduct long-term gill net surveys to assess the population status of lake trout in Lake Huron. Assessment of long-lived fish such as lake trout can only be achieved through long-term population surveys.

Principal Investigator: Stephen Riley

Lake trout and burbot are the two top native coldwater piscivores in the main basin of Lake Michigan.  The lake trout population in Lake Michigan was extirpated during the 1950s due to the combined effects of sea lamprey (Petromyzon marinus) predation and overfishing.  Since the early 1960s, state and federal fish management agencies have conducted an active fisheries program to rehabilitate the lake trout population.  The goal of the program has been to re-establish a self-sustaining lake trout population capable of supporting a fishing harvest.  The principal tools used have been a large-scale sea lamprey control program and the massive stocking of hatchery-reared lake trout.  Lakewide plants of lake trout (mainly yearlings) averaged between 2 and 3 million fish annually between 1965 and 1994. 

Although stocked lake trout have survived reasonably well in Lake Michigan, natural reproduction has been extremely limited.  Only a few naturally-produced lake trout fry have been caught in Lake Michigan since 1965.  Several suggested causes for the reproductive failure include EMS, the predation of eggs and fry, insufficient spawning stock size, inadequate stocking methods, and an inappropriate genetic background in hatchery-reared lake trout. 

Almost all of the stocking of lake trout in Lake Michigan occurred nearshore between 1965 and 1980.  During the mid 1980s, two offshore refuges were created to encompass what were believed to be the most productive native lake trout spawning reef areas in Lake Michigan.  These two refuges have been closed to fishing.  The Northern Refuge covers more than 1,550 km2 in the Beaver Island area and contains a large complex of shallow-water (0-20 m) spawning reefs.  Three specific offshore reef sites, Boulder Reef, Richard's Reef, and Gull Island Shoal were chosen, based on historical records and habitat surveys to receive all the lake trout stocked in the Northern Refuge.  Stocking at Richard=s Reef was discontinued in 2003.  The Southern or Midlake Refuge, in the south-central portion of the lake, encompasses 2,859 km2 and includes a complex of four large deep-water reefs.  Stocking of lake trout on the Midlake Refuge has been directed at Sheboygan, Northeast, East, and Milwaukee reefs.  A third refuge area was established inshore in the Clay Banks region of Wisconsin waters in 1986; again fishing was prohibited within this refuge.  The stocking of various lake trout strains in Lake Michigan was designed to correspond with the habitat in which the trout were planted.  In the shallow-water reefs of the Northern Refuge, shallow-water strains, such as the Marquette, Wyoming, and Marquette X Gull Island Shoal (Lake Superior) Hybrid strains, were planted.  In the deep-water reefs of the Southern Refuge, deep-water strains, such as the Seneca and Green strains, were planted.

It is paramount to the lake trout rehabilitation effort in Lake Michigan that the various stocking sites be monitored each year to determine whether natural reproduction has occurred.  If naturally-reproduced lake trout fry or juvenile lake trout are caught, it may also be important to determine which strain is represented by these young lake trout.  Identification of the locations in Lake Michigan and the lake trout strains which correspond to successful natural reproduction could then be used to formulate future stocking strategies for Lake Michigan.  For example, if naturally reproduced fry of several different strains were recovered from the three reefs in the Northern Refuge, the indication would be that the Northern Refuge was a desirable site for stocking and that strain was not an important factor for lake trout rehabilitation at the Northern Refuge.  If inshore locations along the Michigan coast yielded the first naturally-reproduced lake trout in Lake Michigan, then fishery managers would want to consider shifting stocking emphasis to this region of the lake.

The burbot recovery in Lake Michigan coincided with a decline in the abundance of deepwater sculpin (Myoxocephalus thompsonii).  As burbot abundance leveled off during the 1990s, so too did deepwater sculpin abundance.  Thus, the Great Lakes Science Center bottom trawl survey data suggested a predator-prey link between the burbot and deepwater sculpin populations.  However, bioenergetics modeling has not been applied to the burbot population in Lake Michigan to estimate annual consumption of deepwater sculpins by burbot.  In addition, the round goby (Neogobius melanostomus) is slowly spreading into the main basin of Lake Michigan.  Bioenergetics model applications to the burbot population would be useful in estimating annual consumption of round gobies by burbot.  In this way, the role of burbot within the Lake Michigan food web becomes better defined.

Specifically, the objectives of this study are to: (1) compare diet, growth, maturity, fecundity, thiamine levels in eggs, annual survival, and sea lamprey mortality of lake trout at various stocking sites in Lake Michigan, (2) compare growth and survival of various strains of lake trout stocked into Lake Michigan, (3) use the above-mentioned research findings to improve the lake trout rehabilitation effort in Lake Michigan, (4) survey the lake trout population in Lake Michigan for evidence of natural reproduction, (5) use the results of this surveillance for management recommendations concerning lake trout rehabilitation in Lake Michigan, (6) use the spring LWAP survey results to characterize the population dynamics of burbot in Lake Michigan, and (7) apply bioenergetics modeling to the burbot population to estimate annual consumption of various prey fishes.

Principal Investigator: Charles Madenjian

Cisco (Coregonus artedi) is important to ecosystem function in the Great Lakes and historically supported productive fisheries.  Cisco populations in Lake Erie crashed in the mid-1920s due to the impacts of over-exploitation and habitat loss, but in the last 15 years there have been small but consistent catches by commercial fishermen.  Restoration of cisco in Lake Erie would facilitate restoration of ecosystem function by increasing the diversity and stability of the prey fish community and by providing a thiaminase-free prey for lake trout.  To date, genetic analyses of contemporary Lake Erie cisco collections has indicated that they are most similar to cisco from historical (1950s) Lake Erie collections and thus represent a remnant population and not migrants from Lake Huron.  However, the sample size of the historical collections was relatively small and not geographically representative of lakes Erie and Huron.  A larger historical sample of cisco is required to help improve confidence in the genetic assessment of contemporary samples and to provide a benchmark of historical diversity estimates that might be used to assess the resurging and eventually rehabilitated populations.  In addition, more extensive contemporary sample collections are needed from Lake Huron to assess its suitability as a source of broodstock (if needed).  Therefore we propose to analyze the genetic population structure of historical cisco samples from lakes Erie and Huron.  We will test the hypothesis that cisco from lakes Huron and Erie existed as a single population.  Secondary hypotheses will test the status of contemporary collections to provide further insight about their origins and suitability of Lake Huron as a source for broodstock.  Results of this study will provide information that can be used to guide creation and assessment of rehabilitation strategies that will enable progress toward meeting the goals and objectives laid out in the rehabilitation plan. 

Principal Investigator: Wendylee Stott

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