REINTRODUCTION OF NATIVE FISHES TO THE GREAT LAKES PROPER: A RESEARCH THEME AREA

Great Lakes Fishery Commission

Board of Technical Experts

April 3, 2002

Randy L. Eshenroder¹ and Charles C. Krueger²

2100 Commonwealth Blvd., Suite 100

Ann Arbor, MI 48105 USA

Background

The indigenous fish fauna of the Great Lakes suffered well-documented losses (e.g., Bailey and Smith 1981) that varied among lakes. Originally, the fauna restricted to the lakes proper, i.e., the lakes themselves, was dominated by lake trout (Salvelinus namaycush), ciscoes (Coregonus spp.), and sculpins (Cottus and Myxocephalus). By the 1950s losses of these fishes were nearly complete in the lower lakes (Erie and Ontario) and severe in lakes Michigan and Huron; no species were lost from Lake Superior proper (Bailey and Smith 1981; Coon 1999). Past efforts to reintroduce extirpated lake-proper fishes have been confined to a single form of one species—the lean lake trout. Interest in reintroduction of other extirpated species, however, is emerging from management agencies and the public. For example, one species of deepwater cisco and one form of deepwater lake trout are being considered for reintroduction. These efforts, if they come to fruition, will likely stimulate enthusiasm for reintroducing other extirpated fishes. Such efforts will require a well-focused research agenda to help guide decision-making.

This paper describes a rationale and direction for research critical to the successful reintroduction of indigenous fishes of the Great Lakes proper. Such research will focus on the information needs associated with the transfer of fish from one Great Lake (where they are extant) to another (where they were extirpated). The Great Lakes Fishery Commission’s (GLFC) Board of Technical Experts has organized its Fishery Research Program into broad themes each described in a white paper such as this one. The specific objectives of this research theme are to 1) provide a forum for a coordinated and collaborative approach to research in support of the reintroduction of extirpated native Great Lakes fishes, 2) identify research needs for such reintroductions, and 3) provide funding opportunities for critical research that supports such reintroductions. This theme area will continue to dwell primarily on the successful reestablishment of the lean form of the lake trout. Other species will be added as scientific and/or management interest in their reintroduction materializes.

¹randye@glfc.org

²ckrueger@glfc.org

Source and Recipient Lakes

This research theme will focus on those fishes extirpated from the open waters of one or more of the Great Lakes and that are extant in at least one of the other Great Lakes. These fishes, various forms and species of lake trout, ciscoes, and sculpins, were important in Great Lakes food webs (e.g., Christie 1974). Their extirpation left vast areas of the Great Lakes, especially deep waters, depopulated (Eshenroder and Burnham-Curtis 1999). Not counting the lean form of the lake trout, an additional 12 reintroductions of extirpated deepwater lake trout, ciscoes, and sculpins are possible (Table 1).

Table 1. An X indicates a Great Lake where a lake-proper species of native fish has been extirpated with the stipulation that the form of the species still exists in another Great Lake.

	Great Lake
Species	Mich.	Huron	Erie	Ontario
Lean lake trout (Salvelinus namaycush)	X	X	X	X
Deepwater lake trout (S. namaycush subspecies)	X	X	X
Shortjaw cisco (Coregonus zenithicus)	X	X	X
Kiyi (C. kiyi)	X	X		X
Bloater (C. hoyi)				X
Deepwater sculpin (Myxocephalus thompsoni)				X
Spoonhead sculpin (Cottus ricei)			X

Lake Superior, with its deepwater fish fauna intact, is the major source for reintroductions to the other lakes (Table 2). It still contains seven distinct forms or species extirpated from the other lakes. Unfortunately, three deepwater ciscoes that occurred in the Great Lakes outside of Superior are extinct (Eshenroder and Burnham-Curtis 1999), and now no source for their reintroduction exists. Lakes Michigan and Huron, like Lake Superior, contain the bloater and deepwater and spoonhead sculpins and could serve as sources for these reintroductions. Lake Nipigon is another potential donor lake. Access from Lake Superior to Lake Nipigon was unimpeded until 8,000 B.P., and Nipigon supports a fish fauna similar to that of Lake Superior (Todd and Smith 1992).

Table 2. An X indicates a potential source lake for reintroduction of a fish species extirpated in one of the Great Lakes.

Species	Lake
Species	Superior	Mich.	Huron	Nipigon
Lean lake trout (Salvelinus namaycush)	X		X	X
Deepwater lake trout (S. namaycush subspecies)	X
Shortjaw cisco (Coregonus zenithicus)	X			X
Kiyi (C. kiyi)	X
Bloater (C. hoyi)	X	X	X	X
Deepwater sculpin (Myxocephalus thompsoni)	X			X
Spoonhead sculpin (Cottus ricei)	X	X		X

Empty Niches

Reintroduction from one Great Lake to another implies replacement at the population level with genotype(s) that are native to the basin but not to the lake. In most cases, the original genotypes were not saved in hatcheries or in refuge lakes. Speciation among lake trout and ciscoes was likely still underway within individual lakes in historical times. Whether the derived species arose independently in each lake or arose once from a single ancestor is conjectural (Eshenroder et al. 1999A). Eshenroder et al. (1999B) discussed the role of functional convergence in shaping the cisco species flock, and the same arguments regarding common selection pressures among the lakes would apply to lake trout (Eshenroder and Burnham-Curtis 1999). Therefore, a candidate genotype for reintroduction may not be a direct ancestor of the genotype that it is expected to replace. The primary goal of reintroduction should be to restore phenotypic variation (Krueger and Ihssen 1995)—not the original genotypes which in most cases are extinct. The challenge for lake trout and ciscoes is to match phenotypic expression in the donor lake with the desired functional role in the host lake.

Although deepwater lake trout were widely distributed in the Great Lakes (Krueger and Ihssen 1995), their reintroduction has been inhibited because of perceptions that they would not be economically or ecologically important. Deepwater lake trout were part of a species complex that evolved recently from the lean form of lake trout (Burnham-Curtis and Smith 1994). One of the deepwater forms, the banker (also called humper, terminology varies between Canada and the U.S.) is associated with deep offshore reefs and banks along islands in Superior. Bankers from the Klondike Reef, located in the southeastern waters of Lake Superior, are presently under culture in the U.S. and are proposed for reintroduction into the main basin of Lake Huron and into Lake Erie. The second widely recognized form of deepwater lake trout, the siscowet, has a high fat content and is common throughout the offshore waters of Lake Superior. Siscowets have the potential to reoccupy large areas of the Great Lakes that lean and humper lake trout are unlikely to use. Although scientific support exists for transplanting siscowets (e.g., Burnham-Curtis et al. 1995), they are not currently being considered for reintroduction.

Because of the ecological importance of deepwater lake trout and the need for a more experimental approach to lake trout rehabilitation (Eshenroder et al. 1999A), research relating to reintroducing deepwater lake trout will have a high priority in this theme area. As the inshore waters of the Great Lakes become enriched with introduced species, lake trout forms associated with deeper waters have an increased role to play. Unlike the lean form of lake trout, deepwater lake trout have never been transplanted. How their physiology and behavior will be expressed in a novel environment, even in an inland lake, is therefore conjectural, but such knowledge is potentially of great value to the lake trout rehabilitation program. The ability of deepwater lake trout when transplanted to aggregate on substrates favorable for spawning is especially important information. Making such a determination will be difficult indeed. Their spawning habitats in Lake Superior have not been described, and, moreover, the spawning habitats of siscowets have not even been located.

In keeping with Smith and Todd (1992), the six named species of deepwater ciscoes are considered to be true species for the purposes of this theme area. Of the three surviving species—the bloater, kiyi, and shortjaw—only the bloater is currently being considered for reintroduction. Bloaters from Lake Superior are being assessed for reintroduction into Lake Ontario (Baldwin 1999). The next step in this process will involve the creation, by the Province of Ontario, of a bloater brood stock expected to produce 0.5 million fingerlings per year. Stocking bloaters in Lake Ontario is expected to create more interest in reintroducing the shortjaw cisco in lakes Michigan, Huron, and Erie and the kiyi in Michigan, Huron, and Ontario (see Table 1).

The Great Lakes form of lake herring (Coregonus artedi), which is distinguished from the inland form (Todd and Smith 1992), is greatly depleted outside of Lake Superior (Eshenroder and Burnham-Curtis 1999). It was very diverse and included distinct morphological types in the Great Lakes (Koelz 1929). The most common of the Great Lakes forms was pelagic in the upper water column and tended to spawn in shallow waters. Spawning aggregations in Green and Saginaw bays were immense (Koelz 1929). This shallow form was not completely extirpated in any lake but is rare in lakes Michigan and Erie and very localized in Lake Huron’s main basin and in Lake Ontario. Although the shallow-water form of lake herring is not listed in Table 1, this species will also be included in this theme area because an infusion of diversity could be warranted, especially in lakes Michigan and Erie.

Two forms of lake herring existed in lakes Erie and Ontario: the widely distributed shallow-water form and a deep-bodied, chub-like form (deepwater ciscoes were marketed as chubs). The deep-bodied form was historically much-more valuable than the shallow-water form in commercial fisheries (Koelz 1929). The deep-bodied form is extirpated from Lake Erie and extremely rare in Lake Ontario. Deepwater (not deep-bodied) lake herring are common in Lake Superior out to depths of over 100 m, and the so-called shallow-water herring in this lake spawns as deep as 100 m. Either of these fishes, the true deepwater form or deep-spawning subpopulations of the shallow-water form, could potentially fill the niches vacated by losses of deep-bodied lake herring in lakes Erie and Ontario.

Several issues, however, need to be resolved first. The deepwater lake herring of Superior is fusiform and not deep bodied. One question is how good of an indicator is morphology for the ecological and functional characteristics of ciscoes. Is the deepwater (fusiform) lake herring of Lake Superior the best potential replacement for the deep-bodied lake herrings of lakes Erie and Ontario? Second, if Lake Superior’s deep-spawning subpopulations of shallow-water lake herring turn out to be the best candidates for a hypothetical reintroduction in either lake Erie or Ontario, what subpopulation(s) should be used? Lake herring are apparently still undergoing speciation in Lake Superior complicating their taxonomy. More knowledge regarding the ecological characteristics of various populations would be useful in planning reintroductions involving this enigmatic fish. Third, when, if ever, is it prudent to attempt to augment (or replace) a relict population such as the deep-bodied lake herring of Lake Ontario? Relict populations, so small that they avoided detection for decades, may be too genetically bottlenecked to proliferate.

Deepwater and spoonhead sculpins may be considered for reintroduction in the lower Great Lakes. The deepwater sculpin is abundant in the upper lakes and is absent from lakes Erie and Ontario. It was collected recently from Lake Erie, but these specimens may have originated from downstream movement of larvae from Lake Huron (Roseman et al. 1998). This sculpin appears on species lists for Lake Erie (Bailey and Smith 1981). Auer (1982) suspected, however, that these records were based on misidentifications of mottled sculpins. In Lake Ontario deepwater sculpins were thought extirpated for decades (Brandt 1986), but they have recently reappeared. They are apparently very rare—thus raising again the question of reintroducing on top of a very small population. Such populations either reestablished recently or, if ancestral, have likely suffered bottlenecks and associated genetic losses. What are the risks of transplanting deepwater sculpins from upstream populations to downstream populations? Were the downstream populations in times past regularly infused from upstream populations? These questions require resolution; the discovery of the relict population of deepwater sculpins in Lake Ontario has dampened enthusiasm for their reintroduction.

Spoonhead sculpins remain abundant in Lake Superior (Selgeby 1988), but are rare in Lake Michigan (Potter and Fleischer 1992), and are likely rare in Lake Huron. Spoonhead sculpins are not known from Lake Ontario; they certainly occurred in Lake Erie but have not been seen since 1950 (Trautman 1981). We are not aware of any discussions concerning reintroducing the spoonhead sculpin into Lake Erie. Not knowing what caused its extirpation makes reintroduction problematical. If the same causes remain, reintroduction efforts could be wasted.

Research Priorities

Restoration of phenotypic diversity, the ultimate goal of reintroduction, is seemingly a straightforward proposition. In the Great Lakes, however, the ecological characteristics of most of the extirpated forms and of their potential replacements are not well understood. Even in Lake Superior, where lake trout rehabilitation began in the 1950s, only one of three recognized forms has been stocked (Hansen et al. 1995). Although the general ecological characteristics of the other two forms are known (Krueger and Ihssen 1995), how these characteristics would be expressed in another Great Lake remains a mystery. This data gap is especially problematical for the endemic forms of lake trout and ciscoes, all recent species with limited distributions. In effect, the behavioral and physiological plasticity of these fishes will not be understood until they are transplanted into another lake. The ciscoes, in particular, are noted for plasticity (Todd et al. 1981); their reintroduction and that of the deepwater lake trout will of necessity be experimental.

Lake trout

The research priorities for lake trout recommended recently by Eshenroder et al. (1999A) remain current, and interested investigators should review this publication. This report identified two major issues: early-life bottlenecks and low genetic diversity. The first issue focuses on whether excessive mortality exists between egg deposition and the late-alevin stage and whether sufficient egg deposition occurs on appropriate spawning habitats. Low genetic diversity, the second issue, relates primarily to a failure to use more of the genetic diversity available in Lake Superior. Eshenroder et al. (1999A) believed that variations in reproductive success among life-history types could have been instrumental in revealing why the rehabilitation program has largely failed outside of Lake Superior. For example, stocked deepwater lake trout may not be as prone as stocked lean lake trout to aggregate for spawning on unstable substrates in high-energy zones along beaches (Eshenroder et al. 1995).

Although one stock of deepwater lake trout is being cultured, we believe that at least one other stock from a contrasting population should be employed in reintroduction attempts. Selection of source populations for a second reintroduction would be facilitated if an inventory of ecological characteristics and genetic profiles of potential source populations was available. A database containing morphological descriptions, including pictures; ecological characteristics, e.g., depth and thermal distributions, diets, maturity schedules, and spawning times and locations; and genetic profiles (as per Page 2001) is needed for Lake Superior populations. Such a database is an important first step in identifying the most appropriate source population for a particular reintroduction attempt. It would also provide insights on plasticity and relatedness of populations and help standardize the nomenclature for these populations.

Ciscoes

Research needs for ciscoes parallel those for lake trout. Lake Superior, in particular, contains a bewildering array of cisco phenotypes both within (Todd et al. 1980) and among species (Koelz 1929). Unlike for lake trout, however, endemic forms of ciscoes exist in other Great Lakes and in Lake Nipigon. Decision-making relevant to reintroduction of ciscoes would benefit if the plasticity in morphology and ecological characteristics and relatedness among forms were documented and made available in databases. Museum specimens may be helpful in exploring how much of the phenotypic diversity of ciscoes is genetic (Phillips and Ehlinger 1995). The relict populations in potential recipient lakes also need to be included in databases.

As with sculpin reintroduction, the question of whether relict populations are genetically bottlenecked becomes important. Moreover, why do locally abundant populations of shallow-water ciscoes, such as those in lakes Huron and Ontario, not expand their ranges? Reintroductions could seemingly be impeded by the same circumstances that currently block range expansion.

Todd (1986) reviewed coregonine propagation in the Great Lakes—he suggests that because fry stocking would require massive operations, fingerling or yearling life stages should be used instead. Research will be needed on culturing advanced life stages as virtually all coregonine stocking, even in Europe, has involved fry (Todd 1986). Many of the ciscoes spawn during winter, when collection is difficult, making knowledge of spawning times and locations especially important for cultural operations.

Sculpins

Lacking swim bladders, sculpins could conceivably be reintroduced by adult transfer in lieu of culture. Direct transfer can be tested, for instance, within a donor lake by mimicking the handling and transportation of sculpins live-captured, as if for a real transfer, and by releasing the captured fish back in the donor lake in cages or marked for recapture. Optimum times and locations for initiating adult transfers need also be resolved. The genetics of the relict deepwater sculpin population in Lake Ontario should also be compared to extant populations in the upper lakes. As with ciscoes, the conservation issue of reintroducing fish from another source on top of a relict population needs to be explored and resolved.

Examples of Relevant Work

Lake Trout

Question: Are Great Lakes deepwater morphotypes unique and endemic to the basin or do they occur elsewhere in North America?

Potential Approach: Conduct surveys in the largest, deepest inland lakes of North America to determine occurrence of non-lean forms.

Question: Assuming morphological diversity of lake trout occurs outside the basin, what process, parallel evolution or common ancestry, best accounts for its origin?

Potential Approach: Compare genetic relatedness of different morphotypes within a lake with relatedness of morphotypes across lakes and interpret the patterns in relation to plausible routes of post-glacial dispersal.

Question: How does morphological diversity of lake trout vary within Lake Superior?

Potential Approach: Develop an electronic repository to store existing morphological, ecological, and genetic data for deepwater lake trout as well as to provide for future collections. Compare morphology using color photographs and descriptions of distinguishing features of each form at each collection site. Photographic methods should be standardized to enhance opportunities for using imaging techniques to better define morphotypes.

Question: What are the spawning habitats of deepwater lake trout?

Potential Approach: Describe and compare spawning substrates of deepwater lake trout in Lake Superior or in other lakes where this form may occur or where it is transplanted for research purposes. Estimate egg deposition and fry production with traps or other devices (see Fitzsimons 1995).

Question: How do sympatric forms of lake trout differ in their use of thermal/depth niches? What habitats will deepwater lake trout from Lake Superior occupy when transplanted to another lake?

Potential Approach: Use archival tags, diet composition, and stable isotopes to assess habitat partitioning among morphotypes. Depth and thermal distributions, diets, growth and maturation schedules, spawning times and locations, and reproductive output should be compared among morphotypes.

Question: Are stocked lean lake trout depositing sufficient numbers of eggs at suitable spawning habitats and, if so, is there excessive mortality between spawning and the late-alevin life stage? Potential Approach: A comparative approach contrasting sites where natural recruitment is strong or increasing with sites where natural recruitment is inadequate is recommended.

Ciscoes

Question: Among endemic ciscoes, what is the relationship between morphotype, ecotype, and genotype?

Potential Approach: Phenotypic variation in gill-raker number and length, shape of mouth, length of paired fins, and depth of body—the key morphological traits—can be compared to ecological traits of major interest—diet and depth distribution—and to genotype (see Turgeon et al. 1999). Such comparisons should focus on juveniles as well as on adults and include experimental rearing.

Question: What extant cisco morphotypes are ecologically closest to those extirpated from a Great Lake such as Huron (Table 1) or to those that, like the deepwater form of Lake Ontario C. artedi, are very rare.

Potential Approach: The morphological traits of museum and agency-preserved specimens should be compared to contemporary specimens. Ecological data for extirpated and rare forms is scarce (e.g., Koelz 1929), but may be inferred from large data sets. As for lake trout, an electronic repository for ecological, morphological, and genetic data should be developed.

Sculpins

Question: Is live transfer of deepwater sculpins a realistic methodology for a reintroduction effort?

Potential Approach: Simulation of an actual transfer between a donor and recipient lake can be accomplished in the donor lake. Reintroduced sculpins can be held in cages to assess survival or survival can be estimated by mark and recapture. Mark and recapture can also measure dispersal and population density, demographics of interest in estimating a target number for transplantation.

Question: Does the relict population of deepwater sculpins in Lake Ontario have reduced genetic diversity relative to populations in the upper Great Lakes?

Potential Approach: Compare genetic variation of deepwater sculpin populations among the Great Lakes.

Products

Networking

A major feature of this theme area is sponsorship of an annual workshop where those working on reintroduction will be encouraged to report progress and plans. This type of workshop for lake trout began in 1986. Lake trout researchers from around the lakes expressed a strong interest in continuing these workshops, which typically had an attendance of from 35 to 40 persons. Presentations by graduate students were encouraged in the past and this practice will continue. Presentations by researchers from outside the basin will be given more emphasis than in the past. Workshops provide opportunities for collaboration and help keep researchers abreast of new methods and findings well before their availability in formal publications.

Special Products

Networking can be enhanced by special projects that emerge from discussions at workshops. For example, a project involving fishing of special traps to collect eggs on lake trout spawning reefs had its genesis in earlier meetings of the board’s lake trout task (Schreiner et al. 1995). A major published symposium also emerged from these earlier efforts (Selgeby et al. 1995). The now-ended task on early mortality syndrome also sponsored a symposium, which was held at the 1966 meeting of the American Fisheries Society (McDonald et al. 1998). All of these projects had a serendipitous origin in that they were not foreseen when this line of inquiry was begun by the board.

Schedule

This theme area will start on January 1, 2002, and continue for 5 years. The first of the annual coordination meetings will be held in June 2002. Progress reports will be submitted to the board at spring and fall meetings. A final report will be submitted within 3 months of the conclusion of the project.

Budget

A total of $6,000 per year is requested as follows: $1,500 for meeting costs; $2,500 for travel costs of out-of-basin presenters; and $2,000 travel for the PIs to consult on research priorities for ciscoes. Support for special projects such as symposia will be requested as needed. In addition, the board will support research that passes its peer review process.

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