Native Lake Trout Research Articles

Stable isotope analysis of western Lake Superior predatory fishes, part one: Trophic niche overlap

Characterizing food web interactions between introduced and native fish predators is important to quantify niche overlap, assess predator–prey balance, and support fisheries management. Lake Superior provides an ideal setting to investigate potential trophic overlap between native top predators, lake trout (Salvelinus namaycush) and walleye (Sander vitreus), and a diverse assemblage of introduced salmonids. Angler-caught fish were used to measure trophic position and niche overlap between predatory fishes in the western arm of Lake Superior based on carbon and nitrogen stable isotope ratios (δ13C, δ15N). Within a species, we did not find consistent differences in either δ13C or δ15N values by sex, collection year, capture location, or length. Among species, the range in δ15N values was >5 ‰, indicating that these species occupy ∼2 trophic positions, with dietary reliance ranging from primarily invertebrates to primarily fish, whereas the range in δ13C values indicated dietary reliance on a mix of pelagic and benthic prey. Combined, the δ13C and δ15N values revealed siscowet lake trout as the apex predator having a distinct trophic niche, while walleye and lean lake trout were intermediate trophic position predators with overlapping isotopic niches, and introduced salmonids were the lowest trophic position predators with overlapping trophic niches. Overlapping trophic niches indicated similar resource reliance and habitat occupancy among native lake trout and walleye, as well as among introduced salmonids, but less so between native and introduced predators.

Evaluation of fish spawning habitat at offshore reefs in southwest Lake Michigan using side‐scan sonar and underwater video

Abstract Offshore reefs in the Laurentian Great Lakes provide critical spawning habitats for native lake trout. Though many historic spawning reefs have been documented, thorough evaluation of the habitat they contain is rare. After decades of stocking, natural recruitment of lake trout has increased dramatically in the Illinois waters of Lake Michigan since 2010, reinforcing the need for information about the viability and distribution of spawning habitats. Using side‐scan sonar and underwater video, this study sought to map bottom substrates at Lake Bluff Reef and Gumby's Reef, offshore of the northern Illinois coast of Lake Michigan, to describe and quantify the availability of substrates suitable for lake trout spawning. Substrates were manually delineated in ArcGIS using side‐scan sonar imagery mosaics. Underwater video was used to verify substrate classifications through direct observation. Suitable spawning substrate consisting of fractured bedrock debris and piled boulder/cobble was observed at both reefs. Underwater video revealed the presence of lake trout at both reefs in the weeks leading up to the spawning season. The largest congregation of fish was observed in the vicinity of the shallowest points, steep slopes, and the largest patches of spawning substrate. The distribution, amount, and condition of spawning substrate available at each reef was in line with others studied in the region and their likely importance for lake trout spawning was reinforced by observed aggregations of mature fish. This study has expanded the inventory of well‐documented offshore reefs in the Illinois waters of Lake Michigan, enhancing appreciation of what is coming to be understood as the Illinois Reef Complex. Knowledge of the distribution and status of habitats critical to the life history of native fishes in the Great Lakes are necessary for managers to properly assess, manage, and conserve lake trout and other fish populations.

Past and Present Distribution and Identification of Extant Native Lake Trout (Salvelinus namaycush) Populations in the Canadian Maritime Provinces

Past and Present Distribution and Identification of Extant Native Lake Trout (Salvelinus namaycush) Populations in the Canadian Maritime Provinces

Genetic basis of thiaminase I activity in a vertebrate, zebrafish Danio rerio

Thiamine (vitamin B1) metabolism is an important driver of human and animal health and ecological functioning. Some organisms, including species of ferns, mollusks, and fish, contain thiamine-degrading enzymes known as thiaminases, and consumption of these organisms can lead to thiamine deficiency in the consumer. Consumption of fish containing thiaminase has led to elevated mortality and recruitment failure in farmed animals and wild salmonine populations around the world. In the North American Great Lakes, consumption of the non-native prey fish alewife (Alosa pseudoharengus) by native lake trout (Salvelinus namaycush) led to thiamine deficiency in the trout, contributed to elevated fry mortality, and impeded natural population recruitment. Several thiaminases have been genetically characterized in bacteria and unicellular eukaryotes, and the source of thiaminase in multicellular organisms has been hypothesized to be gut microflora. In an unexpected discovery, we identified thiaminase I genes in zebrafish (Danio rerio) with homology to bacterial tenA thiaminase II. The biochemical activity of zebrafish thiaminase I (GenBank NP_001314821.1) was confirmed in a recombinant system. Genes homologous to the zebrafish tenA-like thiaminase I were identified in many animals, including common carp (Cyprinus carpio), zebra mussel (Dreissena polymorpha) and alewife. Thus, the source of thiaminase I in alewife impacting lake trout populations is likely to be de novo synthesis.

Evidence of lake trout (Salvelinus namaycush) natural reproduction in Lake Erie

Native lake trout were extirpated from Lake Erie around 1965 and committed restoration efforts began in 1982. In 2021 and 2022, a total of six lake trout (Salvelinus namaycush) in the free embryo or post-embryo life stage were captured in lake trout embryo traps in Lake Erie offshore of Shorehaven Reef, NY. This represents the first conclusive evidence of successful natural reproduction since extirpation. Trapping locations were identified using the results of a fine-scale positioning acoustic telemetry array, visual observations of adult lake trout exhibiting spawning behavior, and underwater cameras to visually identify possible spawning locations. Lake trout utilized a very specific spawning habitat type—the eastern side of shallow offshore humps in 5–8 m of water. These sites were comprised of habitat typically associated with lake trout spawning with slopes of 5–14° and clean rubble-cobble sized rock with visible interstitial spaces. Genetic barcoding was used to identify the post-embryo stage salmonids to species, and microsatellite genotypes assigned strongly to the Seneca strain which comprises the majority of the adult population. These findings represent a significant milestone for lake trout rehabilitation efforts in Lake Erie, confirming that successful reproduction to the post-embryo stage is possible and supporting continued rehabilitation efforts by Lake Erie management agencies.

Can native species compete with valuable exotics? Valuing ecological changes in the Lake Michigan recreational fishery

The Chinook salmon population in Lake Michigan is declining precipitously due to ecological changes, and the impact on recreational fishing value is unknown. We estimate a conditional logit model to characterize how Wisconsin resident anglers react to changes in species-specific availability and catch rates. Using these results, we calculate the non-market value of access to the fishery that reflects current, historical, and potential future fishing conditions. We then predict whether native lake trout and walleye, which are more resilient to the changing conditions in the lake, can maintain the fishery’s value if non-native Chinook salmon collapses. Results show that while large losses would occur absent other improvements, a portion of the fishery’s value could be maintained if substitute species, particularly walleye, improved in quality and were readily accessible.

Spatiotemporal patterns in trophic niche overlap among five salmonines in Lake Michigan, USA

Native lake trout (Salvelinus namaycush) and introduced Chinook salmon (Oncorhynchus tshawytscha), coho salmon (Oncorhynchus kisutch), steelhead (Oncorhynchus mykiss), and brown trout (Salmo trutta) are major predators in Lake Michigan’s complex ecosystem and collectively support a valuable recreational fishery, but declines in their primary prey, alewife (Alosa pseudoharengus), have raised ecological and management concerns about competition and prey allocation. We applied niche overlap analysis to evaluate competition among salmonine predators during rapid forage base change in Lake Michigan. δ13C and δ15N stable isotope ratios indicated that lake trout had a unique trophic niche from inclusion of offshore and benthic prey, with <29% lake-wide niche overlap with Chinook salmon, coho salmon, and steelhead. Brown trout had moderate overlap with other species (45%–91%), while Chinook salmon, coho salmon, and steelhead had high overlap (71%–98%). Regional differences in isotopic signatures highlighted the potential importance of subsystem differences in fish diets in large aquatic systems. The uniqueness of the lake trout niche, and broadness of brown trout and steelhead niches, suggest these species may be resilient to forage base changes. This study further demonstrates how niche overlap analysis can be applied to tease apart competitive interactions and their response to ecosystem change.

Effects of vessel size and trawling on estimates of pelagic fish backscatter in Lake Huron

Integrated acoustic and netting surveys are conducted in marine and freshwater environments to assess the status of fisheries resources and study fish population dynamics. Vessel avoidance by fish, due to noise generated by the survey vessel or from simultaneous trawl operations, can bias acoustic estimates of fish density. Unlike in marine systems, few studies have assessed vessel avoidance in freshwaters, including the Laurentian Great Lakes. Annual acoustic and netting surveys have been conducted in Parry Sound, a coastal embayment of Georgian Bay, Lake Huron (Ontario, Canada). Parry Sound supports one of the lake’s few rehabilitated native lake trout Salvelinus namaycush populations, as well as abundant pelagic prey fish. In 2014–2017, night-time fisheries acoustic surveys were conducted with a 120 kHz transducer while intermittently deploying a pelagic trawl from an 18.9 m long vessel, a typical size of vessel used for acoustic surveying on the Laurentian Great Lakes. In 2017, a simultaneous acoustic survey was conducted from a 7 m long vessel with a 120 kHz transducer. To assess potential bias associated with trawling, fish backscatter was compared before, during, and after trawl operation. Furthermore, to assess potential bias associated with vessel size, fish backscatter was compared between the large and small vessel surveys. Fish backscatter was significantly lower and deeper during and after trawl deployment compared to immediately before, suggesting fish avoided the trawling vessel. In contrast, there was no significant difference in fish backscatter between the large and small vessel, although mean backscatter depth was slightly deeper from the large vessel. These results show bias from avoidance is possible in the fish density estimates obtained from hydroacoustic and trawling surveys in large freshwater ecosystems.

Pop‐off data storage tags reveal niche partitioning between native and non‐native predators in a novel ecosystem

Abstract Niche partitioning might be predicted to be particularly dynamic in ‘novel ecosystems’ characterized by human‐altered environmental conditions and biological invasions. Restoration efforts for native species in such systems can be informed by detailed characterization of niche partitioning. In Lake Ontario, fishery management agencies have been engaged in a long‐term struggle to restore native top predators including lake trout (Salvelinus namaycush). Meanwhile, management agencies continue to stock non‐native species like Chinook salmon (Oncorhynchus tshawytscha) into the lake to support a recreational fishery and to help control the abundance of a non‐native forage fish, the alewife (Alosa pseudoharengus). We used pop‐off data storage tags to study fine scale (9.1M lines of data from 22 animals) behaviour and habitat use by lake trout (native) and Chinook salmon (non‐native) in Lake Ontario in terms of depth and temperature, recorded at ≤70 s intervals for periods of up to 12 months. Chinook salmon occupied warmer and shallower waters during summer than did lake trout, and their niche breadth was wider. They achieved greater niche breadth in part because they were much more active vertically, cumulatively traveling 103 ± 1 m/hour during summer (model‐estimated median), whereas most lake trout were relatively inactive vertically (7 ± 1 m/hour). In each of our analyses, there was more inter‐individual variation among lake trout than among Chinook salmon, driven by some lake trout that spent considerable time making forays into warmer, shallower waters. Synthesis and applications. Our results illustrate the different foraging tactics used by two species in the Great Lakes and reflect their distinct life histories. Physical niche partitioning between Chinook salmon and lake trout helps to explain how these species can co‐exist in a multi‐species fishery even while having overlap in diet. The diversity of behaviours exhibited here by native lake trout have likely helped them persist during dramatic changes to the forage base in recent decades; that flexibility could help underlie their long‐term prospects for restoration during future changes to the ecosystem.

The Death and Life of the Great Lakes by Dan Egan

Book Reviews 129 profit from the HBC’s decision to downsize Fort William following the HBC’s merger in 1821 with the North West Company. The AFC’s venture at Grand Marais struggled from the outset. The HBC held a competitive advantage because of its extensive history of relations with the North Shore Anishinaabeg. The Indians, moreover, adeptly navigated this nascent trade rivalry to their advantage. The Anishinaabeg leader Espagnol, for instance, sagaciously waited until late spring to trade his furs, when he knew their value at each post. Chapman’s journal conveys great frustration at his post’s meager profits as well as the psychological struggles he endured during the winter of 1823-24. Johnston’s journal entries as clerk at Grand Marais the following winter describe a similar sentiment. Gichi Bitobig, Grand Marais provides a comprehensive examination of the North Shore fur trade during the early nineteenth century. Contrary to the title, this book is better situated as a borderlands study rather than a history of Grand Marais’s Anishinaabeg and fur-trading past. Cochrane, for instance, wrote that at the same time the AFC was establishing a trade presence at Grand Marais, commissioners from Britain and the United States were haggling over the location of the international border. That negotiation process factored into the AFC’s decision to compete with the HBC and set up a series of trading posts south of the border, including at Grand Marais. For the North Shore Anishinaabeg, on the other hand, the establishment of the international border not only did little to obstruct their traditional trading practices, they used it to their advantage when necessary. Cochrane furthermore characterizes Lake Superior’s North Shore during the early nineteenth century as a racially and culturally heterogeneous region, where identity was “not determined merely by descent, but by upbringing and culture” (p. 55). Wayne Ratzlaff Waubonsee Community College Dan Egan. The Death and Life of the Great Lakes. New York: W. W. Norton & Company, 2017. Pp. 364. Bibliography. Illustrations. Index. Notes. Paper: $17.95. In The Death and Life of the Great Lakes, Dan Egan chronicles the dramatic changes in the Great Lakes ecosystem wrought by human actions over the last roughly 250 years, focusing on the impacts of invasive species. He emphasizes that the Clean Water Act—as important 130 The Michigan Historical Review as it was in forcing cleanups of the massive pollution spewing from industry and urban wastewater—did very little to stem the tide of nonnative species that began with the opening of waterways connecting the Great Lakes to the Atlantic Ocean (the “front door”) and Mississippi River Basin (the “back door”). Many of these species have become infamously invasive, fundamentally changing the top, bottom, and middle of the food web. As Egan describes, multiple historic engineering feats combined to open these doorways, including the Erie Canal, the St. Lawrence Seaway, the Welland Canal, and the Chicago Sanitary and Shipping Canal. An early beneficiary of these connections, sea lamprey passed through the Erie Canal into Lake Ontario (by 1826) and the Welland Canal to Lake Erie (1920s), finding a virtually unlimited source of food in the native lake trout and other large fish. Even today, controlling this invader requires tens of millions of dollars per year. The book ends with a look to the future, and the most fascinating (and hopeful) aspect of this story is that native Great Lakes fish are responding to the massive changes in the food web, both through behavioral adaptation and morphological evolution. Lake trout are learning to root the invasive round gobies out of gravel shoals where they hide, as evidenced by their battered lips and full bellies. Whitefish, forced to feed on the omnipresent quagga mussels rather than their standard fare, suffered damage to their digestive and excretory tracts—and subsequently reduced weight at maturity—in the years following the quagga invasion. Their stomach muscles have become substantially larger and stronger, and though they are unable to crack mussel shells with their small jaws, they can grind them up in their stomachs and are gaining both size and numbers. Other native fish, including smallmouth bass and walleye, are cashing in on the over...

Factors Influencing Charter Fishing Effort Trends in Lake Huron

From 2002 to 2011, the number of charter fishing trips in Michigan waters of Lake Huron declined by 51%. Declines in catch rates, rising gasoline prices, and the economic downturn have been suggested as possible reasons for this decline. To better understand the relative importance of these factors, five catch‐based and six economic variables were evaluated using multiple regression, with charter effort from 1992 to 2011 as the response variable. Declining catch rate of introduced Chinook Salmon Oncorhynchus tshawytscha was more closely linked to declining effort than catch rate of native Lake Trout Salvelinus namaycush or Walleye Sander vitreus. The price of gasoline was a better predictor of effort than other economic variables. Although Chinook Salmon catch rate explained more variation in charter effort than any other variable, factors beyond the influence of fisheries management also influenced effort. Ecosystem changes that led to declines in salmon abundance created favorable conditions for Walleye, leading to some localized increases in charter effort.

Climate Change Expands the Spatial Extent and Duration of Preferred Thermal Habitat for Lake Superior Fishes

Climate change is expected to alter species distributions and habitat suitability across the globe. Understanding these shifting distributions is critical for adaptive resource management. The role of temperature in fish habitat and energetics is well established and can be used to evaluate climate change effects on habitat distributions and food web interactions. Lake Superior water temperatures are rising rapidly in response to climate change and this is likely influencing species distributions and interactions. We use a three-dimensional hydrodynamic model that captures temperature changes in Lake Superior over the last 3 decades to investigate shifts in habitat size and duration of preferred temperatures for four different fishes. We evaluated habitat changes in two native lake trout (Salvelinus namaycush) ecotypes, siscowet and lean lake trout, Chinook salmon (Oncorhynchus tshawytscha), and walleye (Sander vitreus). Between 1979 and 2006, days with available preferred thermal habitat increased at a mean rate of 6, 7, and 5 days per decade for lean lake trout, Chinook salmon, and walleye, respectively. Siscowet lake trout lost 3 days per decade. Consequently, preferred habitat spatial extents increased at a rate of 579, 495 and 419 km2 per year for the lean lake trout, Chinook salmon, and walleye while siscowet lost 161 km2 per year during the modeled period. Habitat increases could lead to increased growth and production for three of the four fishes. Consequently, greater habitat overlap may intensify interguild competition and food web interactions. Loss of cold-water habitat for siscowet, having the coldest thermal preference, could forecast potential changes from continued warming. Additionally, continued warming may render more suitable conditions for some invasive species.

Estimating wounding of lake trout by sea lamprey in the upper Great Lakes: Allowing for changing size-specific patterns

A primary fishery concern in the Laurentian Great Lakes is mitigating the persistent negative impact of parasitic sea lamprey (Petromyzon marinus) on native lake trout (Salvelinus namaycush). Wounds observed on surviving lake trout are commonly used by managers to assess damages associated with sea lamprey predation. We estimated the relationship between wounding rates and lake trout size, and how this varied spatially and temporally. We built upon previously published work by fitting wound rates as a logistic function of lake trout size. By using longer time series and data from three Great Lakes, our analysis harnessed substantially more contrast in host populations than previous work, and we also employed software advances for nonlinear mixed-effect models. Candidate models allowed logistic function parameters to be constant or to vary spatially, temporally, or both. Temporal effects were modeled as random walk processes. We also considered models that assumed either Poisson or negative binomial distributions for the number of wounds per fish at a given length. Models that allowed for both spatial and temporal effects in the shaping parameters and assumed a negative binomial wound distribution resulted in the best fit as indicated by Akaike's Information Criterion. Wounding rate estimates from models selected for each lake in this analysis are contrasted with those of wounding rate models currently used as components of lake trout population assessments. Although model fit was improved substantially, differences in wounding rates estimates are modest and estimates follow very similar temporal trends. However, as time series of wound data continue to grow, models that incorporate temporal variability in parameter estimation are expected to be increasingly favored. This research provides managers with an updated tool to obtain more reliable estimates of sea lamprey wounding.

Habitat use by fishes of Lake Superior. II. Consequences of diel habitat use for habitat linkages and habitat coupling in nearshore and offshore waters

Diel migration patterns of fishes in nearshore (15–80 m depth) and offshore (>80 m) waters of Lake Superior were examined to assess the potential for diel migration to link benthic and pelagic, and nearshore and offshore habitats. In our companion article, we described three types of diel migration: diel vertical migration (DVM), diel bank migration (DBM), and no diel migration. DVM was expressed by fishes migrating from benthopelagic to pelagic positions and DBM was expressed by fishes migrating horizontally from deep to shallow waters at night. Fishes not exhibiting diel migration typically showed increased activity by moving from benthic to benthopelagic positions within demersal habitat. The distribution and biomass of fishes in Lake Superior was characterized by examining 704 bottom trawl samples collected between 2001 and 2008 from four depth zones: ≤40, 41–80, 81–160, and >160 m. Diel migration behaviors of fishes described in our companion article were applied to estimates of areal biomass (kg ha−1) for each species by depth zone. The relative strength of diel migrations were assessed by applying lake area to areal biomass estimates for each species by depth zone to yield estimates of lake-wide biomass (metric tonnes). Overall, species expressing DVM accounted for 83%, DBM 6%, and non-migration 11% of the total lake-wide community biomass. In nearshore waters, species expressing DVM represented 74% of the biomass, DBM 25%, and non-migration 1%. In offshore waters, species expressing DVM represented 85%, DBM 1%, and non-migration 14% of the biomass. Of species expressing DVM, 83% of total biomass occurred in offshore waters. Similarly, 97% of biomass of non-migrators occurred in offshore waters while 83% of biomass of species expressing DBM occurred in nearshore waters. A high correlation (R2 = 0.996) between lake area and community biomass by depth zone resulted in 81% of the lake-wide biomass occurring in offshore waters. Accentuating this nearshore-offshore trend was one of increasing estimated total areal biomass of the fish community with depth zone, which ranged from 13.71 kg ha−1 at depths ≤40 m to 18.81 kg ha−1 at depths >160 m, emphasizing the importance of the offshore fish community to the lake ecosystem. The prevalence of diel migration expressed by Lake Superior fishes increases the potential of fish to link benthic and pelagic and shallow and deepwater habitats. These linkages enhance the potential for habitat coupling, a condition where habitats become interconnected and interdependent through transfers of energy and nutrients. Habitat coupling facilitates energy and nutrient flow through a lake ecosystem, thereby increasing productivity, especially in large lakes where benthic and pelagic, and nearshore and offshore habitats are often well separated. We propose that the application of biomass estimates to patterns of diel migration in fishes can serve as a useful metric for assessing the potential for habitat linkages and habitat coupling in lake ecosystems, and provide an important indicator of ecosystem health and function. The decline of native Lake Trout and ciscoes and recent declines in exotic Alewife and Rainbow Smelt populations in other Great Lakes have likely reduced the capacity for benthic-pelagic coupling in these systems compared to Lake Superior. We recommend comparing the levels and temporal changes in diel migration in other Great Lakes as a means to assess changes in the relative health and function of these ecosystems.

Paenibacillus thiaminolyticus is not the cause of thiamine deficiency impeding lake trout (Salvelinus namaycush) recruitment in the Great Lakes

Thiamine (vitamin B1) deficiency is a global concern affecting wildlife, livestock, and humans. In Great Lakes salmonines, thiamine deficiency causes embryo mortality and is an impediment to restoration of native lake trout ( Salvelinus namaycush ) stocks. Thiamine deficiency in fish may result from a diet of prey with high levels of thiaminase I. The discoveries that the bacterial species Paenibacillus thiaminolyticus produces thiaminase I, is found in viscera of thiaminase-containing prey fish, and causes mortality when fed to lake trout in the laboratory provided circumstantial evidence implicating P. thiaminolyticus. This study quantified the contribution of P. thiaminolyticus to the total thiaminase I activity in multiple trophic levels of Great Lakes food webs. Unexpectedly, no relationship between thiaminase activity and either the amount of P. thiaminolyticus thiaminase I protein or the abundance of P. thiaminolyticus cells was found. These results demonstrate that P. thiaminolyticus is not the primary source of thiaminase activity affecting Great Lakes salmonines and calls into question the long-standing assumption that P. thiaminolyticus is the source of thiaminase in other wild and domestic animals.

‘State of Lake Superior’: A review

‘State of Lake Superior’: A review

Quantifying the potential effects of climate change and the invasion of smallmouth bass on native lake trout populations across Canadian lakes

Climate change and invasive species are two stressors that should have large impacts on native species in aquatic and terrestrial ecosystems. We quantify and integrate the effects of climate change and the establishment of an invasive species (smallmouth bass Micropterusdolomieu) on native lake trout Salvelinus namaycush populations. We assembled a dataset of almost 22 000 Canadian lakes that contained information on fish communities, lake morphologies, and geography. We examined the pelagic‐benthic and littoral forage fish community available to lake trout populations across three lake size classes in these aquatic ecosystems. Due to the decreased presence of alternate prey resources, lake trout populations residing in smaller lakes are more vulnerable to the effects of smallmouth bass establishment. A detailed spatially and temporally explicit approach to assess smallmouth bass invasion risk in Ontario lakes suggests that the number of Ontario lakes with vulnerable lake trout populations could increase from 118 (~1%) to 1612 (~20%) by 2050 following projected climate warming. In addition, we identified nearly 9700 lake trout populations in Canada threatened by 2100, by the potential range expansion of smallmouth bass. Our study provides an integration of two major stressors of ecosystems, namely climate change and invasive species, by considering climate‐change scenarios, dispersal rates of invasive species, and inter‐specific biotic interactions.

A Synthesis of Cisco Recovery in Lake Superior: Implications for Native Fish Rehabilitation in the Laurentian Great Lakes

AbstractPopulations of cisco Coregonus artedi in the Laurentian Great Lakes supported large‐scale commercial fisheries and were the primary forage of piscivores during the first half of the 20th century. However, by 1970 populations had collapsed in all of the lakes. Since then, ciscoes have staged a recovery in Lake Superior. In this synthesis, we describe the status of ciscoes in Lake Superior during 1970–2006 and provide a comprehensive review of their ecology. Better understanding of age estimation techniques, application of hydroacoustic and midwater trawl sampling, and compilation of long‐term data sets have advanced our understanding of the species. Management agencies contemplating rehabilitation of cisco populations should recognize that (1) knowledge of cisco ecology and population dynamics is increasing; (2) ciscoes are long‐lived; (3) Great Lakes populations are probably composed of both shallow‐water and deepwater spawning forms; (4) large year‐classes can be produced from small adult stocks; (5) large variation in year‐class strength is probably intrinsic to Great Lakes populations; (6) despite the longevity and early maturity of ciscoes, stocks can be overfished because large year‐classes are produced infrequently; (7) regional environmental factors appear to play a large role in reproductive success; and (8) rainbow smelt Osmerus mordax are likely to have a negative effect on cisco recruitment under certain conditions. A top‐down approach for rehabilitating lake trout Salvelinus namaycush in Lake Superior probably benefited cisco recovery through lake trout predation on invasive rainbow smelt populations. We argue that managing for populations of exotic alewives Alosa pseudoharengus to support popular recreational fisheries of exotic Pacific salmonids in the other Great Lakes conflicts with stocking efforts to rehabilitate native lake trout in those lakes. If native fish rehabilitation is a serious and primary goal for management agencies in the Great Lakes basin, we propose that an ecosystem‐based approach to modifying the environment for the benefit of native fish species (i.e., decimation or eradication of invasive species) is required.

Potential Strategies for Recovery of Lake Whitefish and Lake Herring Stocks in Eastern Lake Erie

Lake Erie sustained large populations of ciscoes ( Salmonidae: Coregoninae) 120 years ago. By the end of the 19 th century, abundance of lake whitefish ( Coregonus clupeaformis) had declined drastically. By 1925, the lake herring (a cisco) population ( Coregonus artedii) had collapsed, although a limited lake herring fishery persisted in the eastern basin until the 1950s. In the latter part of the 20 th century, the composition of the fish community changed as oligotrophication proceeded. Since 1984, a limited recovery of lake whitefish has occurred, however no recovery was evident for lake herring. Current ecological conditions in Lake Erie probably will not inhibit recovery of the coregonine species. Recovery of walleye ( Sander vitreus) and efforts to rehabilitate the native lake trout ( Salvelinus namaycush) in Lake Erie will probably assist recovery because these piscivores reduce populations of alewife ( Alosa psuedoharengus) and rainbow smelt ( Osmerus mordax), which inhibit reproductive success of coregonines. Although there are considerable spawning substrates available to coregonine species in eastern Lake Erie, eggs and fry would probably be displaced by storm surge from most shoals. Site selection for stocking or seeding of eggs should consider the reproductive life cycle of the stocked fish and suitable protection from storm events. Two potential sites in the eastern basin have been identified. Recommended management rocedures, including commercial fisheries, are suggested to assist in recovery. Stocking in the eastern basin of Lake Erie is recommended for both species, as conditions are adequate and the native spawning population in the eastern basin is low. For lake herring, consideration should be given to match ecophenotypes as much as possible. Egg seeding is recommended. Egg seeding of lake whitefish should be considered initially, with fingerling or yearling stocking suggested if unsuccessful. Spawning stocks of whitefish in the western basin of Lake Erie could be utilized.

Editorial: Lakes in Crisis

Editorial: Lakes in Crisis