Lake sturgeon were the special focus theme of a portion of the 2007 Lake Committee Meetings Common Session held in Ypsilanti, MI in March.  The objective of the session was to highlight a few new initiatives and studies that have particular application to rehabilitation efforts for lake sturgeon in the Great Lakes. 

Rob Elliott, Fish Biologist with the Green Bay FRO was asked to organize and moderate the symposium.  Eight presentations were invited and featured the following topics:

• Introduction to theme topic and current distribution, abundance and status of lake sturgeon populations across the Great lakes – R. Elliott (USFWS)
• Genetic structuring of remnant lake sturgeon populations and related conservation and stocking guidelines – A. Welsh (SUNY-Oswego)
• Genetic analyses of lake sturgeon stock composition in open water habitats: applications to questions of habitat occupancy, harvest, and recruitment – K. Scribner (MSU)
• Implementation and evaluation of streamside rearing techniques for lake sturgeon rehabilitation – M. Holtgren (Little River Band of Ottawa Indians)
• Variation in survival and recruitment of lake sturgeon – J. Crossman (MSU)
• Host-size selection and lethality of sea lamprey on lake sturgeon – H. Patrick and T. Sutton (Purdue University)
• Law enforcement concerns and updates on the sturgeon caviar trade within the Great Lakes region – R. Gibson (OMNR)
• Synthesis of theme presentations – R. Elliott (USFWS)

These topics provide good examples of both the opportunity and complexity of effectively implementing lake sturgeon rehabilitation and restoration throughout the Great Lakes.  About 200 professionals from state, federal and tribal agencies were in attendance during the session.  Following the symposium, Elliott prepared a written summary of the proceedings for the Council of Lake Committees annual meeting in April, 2007.  The following provides additional detail on these topics.  Contact: Rob Elliott, USFWS, Green Bay FRO, robert_elliott@fws.gov.

Further Detail:

Through the mid 1800s, lake sturgeon were a dominant component of the nearshore benthivore fish community throughout most of the Great Lakes basin.  Their decline was rapid and commensurate with habitat loss, degraded water quality, and intensive fishing associated with European settlement and development of the region.  Today, relatively large populations (>1000 spawning individuals/yr) remain only in the Lake Winnebago system, in Lake Nipissing, in the St. Lawrence River, and in the area around Lake St. Claire.  Additional smaller self sustaining populations have persisted in several Great Lakes tributaries scattered across each of the Great Lakes, but in most areas and rivers where they were found historically, they have been reduced to very low abundance or have been extirpated.

Genetic analysis using standardized microsatellite and mitochondrial DNR markers has been completed for most of the remnant populations throughout the Great Lakes basin.  A high degree of population structure has been observed, indicating that most populations are reproductively isolated, likely due to spawning site fidelity.  This information has provided the rational and basis for developing basin-wide guidelines that would minimize the genetic risks of stocking and would support lake sturgeon rehabilitation in the Great Lakes.  Criteria for the identification of priority populations for genetic preservation were established and 8 genetic stocking units (GSUs) were identified throughout the Great Lakes that would reduce the risk of outbreeding depression.  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, recommendations are included for the design and implementation of stocking programs including recommendations for the number of consecutive years stocking should occur, for the number of adults to use for gamete collection, for gamete collection and rearing procedures, for the number of individuals to be stocked, and for post-stocking monitoring procedures.  The guidelines are relevant to the entire Great Lakes and provide guidance for the development of lake-specific management plans and for the implementation of ongoing rehabilitation.

The availability of genetic data capable of identifying population of origin for individuals and groups of fish from all habitats now provides the opportunity to examine critical information pertaining to movements and habitat occupancy in open-water habitats, rates of straying between spawning populations, population-specific levels of directed or incidental exploitation, and inter-annual variation in population recruitment.  Lake sturgeon spend the vast majority of extended life times, including prolonged pre-reproductive periods, in open water habitats of the Great Lakes that are separated geographically from natal rivers.  Evidence suggests that individuals from different tributaries of Lake Michigan are not uniformly distributed across open-water habitats of the basin, even at micro-geographic scales within Green Bay.  Movements between eastern and western portions of the basin were asymmetrical, with sturgeon from eastern Lake Michigan comprising a significant proportion of fish occurring in central and northern areas of Green Bay, but sturgeon originating from Green Bay tributaries were not found in significant abundance in eastern waters of Lake Michigan.  Estimated population composition of fall angling harvest for one Lake Michigan tributary shows that harvests included significant representation from non-target and numerically depressed populations.  Non-target populations at greatest risk were in close geographic proximity to the harvest locale.  Collectively, these examples from Lake Michigan highlight numerous novel applications of a valuable basin-wide genetics database such as the ability to estimate differential habitat occupancy, recruitment, straying and exploitation relative to landscape-level variation in degree of anthropogenic disturbance, habitat quality and distribution, and in the context of future species restoration goals.

A significant aspect of rehabilitation efforts for lake sturgeon in the Great Lakes is the need to rehabilitate existing remnant populations and the desire to reintroduce the species back into waters where they have been extirpated, using techniques that are acceptable to all management agencies involved.  Towards this end, a portable streamside rearing facility was designed and used by the Little River Band of Ottawa Indians for rehabilitation efforts of a remnant population of lake sturgeon in the Manistee River, Michigan beginning in 2004.  The streamside rearing facility facilitates rearing of wild caught sturgeon larvae in their natal water.  This rearing approach provides a cost effective technique for small batch rearing, incorporates aspects of genetic conservation, and addresses concerns regarding imprinting and spawning site fidelity.  Successful rearing of sturgeon during the first three years of operation indicates this portable design may be adapted and modified for other locations and fish species.  Other management agencies in the Great Lakes Basin including Michigan DNR and Wisconsin DNR have begun to use this technology to rear lake sturgeon for reintroduction stocking.  This rearing method may be an important management tool for both restoring remnant populations and for reintroductions in a manner consistent with existing rehabilitation guidelines and management plans.

Understanding factors influencing survival of all life stages of lake sturgeon continues to be a critical need for effectively addressing Fish Community Objectives for this species.  Studies on the Black River tributary to Black Lake, MI have allowed for the detailed examination of trends in survival, sources of mortality, and recruitment dynamics during egg, hatching, and juvenile stages through the first year of age. A high degree of within year and between year variation in different recruitment parameters and life history traits during this period is evident. Analyses have revealed heterogeneity in egg deposition, high rates of egg loss due to microbial infection and predation, and high levels of larval predation. Furthermore, significant differences in incubation time, size, growth, and yolk-sac utilization efficiency between larvae from early and late spawning adults suggests that tradeoffs in expression and covariation in early life history traits are important when predicting recruitment dynamics of lake sturgeon populations. It also has been demonstrated that fish reared at a streamside hatchery up to 13 weeks of age survived better after release than those reared in a non-natal water source.  All of these findings have direct application to the implementation of rehabilitation efforts and provide additional information that further supports the importance of careful and comprehensive consideration of all factors potentially affecting the success of both remnant populations and of reintroduction efforts.

The control of lamprey in the Great Lakes is another factor that may have significant implications for lake sturgeon sustainability.  Predation effects of lamprey on adult lake sturgeon survival are not well understood.  Adult lake sturgeon survival must remain high if populations are to be self sustaining, so any negative effect of parasitism by sea lampreys may contribute to limited sustainability or recovery of lake sturgeon populations in the Great Lakes.  Current studies indicate that lake sturgeon survival following sea lamprey parasitism was strongly dependent on sturgeon body size and the location of lamprey attachment.  Direct mortality of lake sturgeon, resulting from acute anemia following an attack, and indirect mortalities resulting from secondary fungal infection were greatest for smaller size classes of lake sturgeon (11-31% for <650 mm FL) than for larger sturgeon (0-8% for >650 mm FL).  Greater than 50% of sea lamprey attacks occurred on the ventral surface of the rostrum or pectoral fin axils, and attachment at these locations typically resulted in sturgeon mortality.  Declines in lake sturgeon growth and condition also were significant for smaller size lake sturgeon.  Though these studies are just a first step in understanding the full effects of lamprey parasitism on lake sturgeon in the wild, they indicate the need to better understand this potential source of mortality and incorporate it into management decisions for both lamprey control and for sturgeon rehabilitation across the basin.

Integral to any comprehensive rehabilitation strategy for lake sturgeon is the need for effective compliance with carefully considered regulations in order to insure populations are protected from over-harvest.  The harvest and sale of sturgeon products in the Great Lakes is susceptible to pressures from a world market. Open sources documents, such as CITES reports, show that only 10-20 % of traditional caviar on the world-wide market was legally acquired.  Caviar is regarded as the world’s most valuable wildlife resource.  Eestimated annual worth of the legal and black market world caviar trade is approx. $100 million and $500 million respectively.  While the natural (wild) supply is diminishing, demand continues to rise which can lead to increased illegal activity.  The lake sturgeon is a commercial species in parts of Canada and recreational fisheries exist in both the US and Canada.  Unfortunately different mandates may create problems with protecting Sturgeon.  Because regulations vary among jurisdictions and not all areas require tagging of harvested fish, laundering capabilities exist.  In many places, quotas are not gender specific and fishers are not prohibited from targeting females. In addition, catch reports require reporting of landed weight of fish, not eggs.  Although agencies typically have a suite of legislative and regulatory tools to track the harvest and movement of fish, the enforcement workforce is limited.  Unless specific objectives are communicated clearly between all federal, state, provincial, tribal and first nation governments for a particular species, they may not be monitored closely.  Iindividuals involved in illegal activities are often well educated on local regulations, and they understand the loopholes and know about the burden of proof.  They also are well aware that multi-agency and/or multi jurisdictional investigations are difficult to undertake.  As demand continues to increase for sturgeon products worldwide, it becomes increasingly important to consider the role of regulation compliance in ensuring the sustainability of lake sturgeon populations in the Great Lakes.