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Adfluvial brook trout in Lake Superior, commonly referred to as coasters, were once widely distributed among tributaries and supported trophy fisheries. The Minnesota Department of Natural Resources recently enhanced efforts to rehabilitate brook trout in Minnesota waters by imposing restrictive harvest regulations intended to produce more large individuals adopting a coaster life-history. The agency evaluated effects of the regulation changes by conducting electrofishing stream surveys concurrently with changes and three additional times over the next 16 years. Catch per unit effort of brook trout across all streams was similar among sampling periods. Generalized linear mixed models indicated a greater proportional size structure (number ≥ 330 mm/number ≥ 200 mm) and proportion of older fish (≥ age 3) after the regulation change. Genetic analyses indicated that individuals from coaster hatchery strains, which were stocked in nearby jurisdictions, made up only 5.6% of all individuals in Minnesota streams and 12% of individuals ≥ 330 mm, although the two largest fish were hatchery strain. Our results indicated that conservative regulations can contribute to rehabilitation of coaster populations and that stocked coasters could not account for the improved size and age structure. [ABSTRACT FROM AUTHOR]

Reduced reproductive success of hatchery fish spawning in the natural environment will reduce the ability of stocking programs to enhance wild populations. We used DNA-based parentage assignment to compare the reproductive success of wild fish and first-generation hatchery fish from a smolt stocking program that used broodstock from within the naturalized steelhead Oncorhynchus mykiss population in a Minnesota tributary to Lake Superior. The reproductive success of hatchery females was significantly lower than that of wild females (approximately 60%) in all three study years; however, the reproductive success of hatchery males was only significantly lower in one year. Higher reproductive success of wild fish was attributed to greater probability of success (i.e., having at least one offspring) and not differences in numbers of offspring among successful parents. Generalized linear models indicated that run timing was associated with probability of success although this did not explain differences between hatchery and wild fish. Despite runs that extended 7-9 weeks, most successful adults arrived in the first three weeks of the run (85-98% of all successful females, 98-100% of successful males). The early part of the run corresponded to periods of high flow, which likely increased access to quality spawning and rearing habitat higher upstream in the system. Relationships between fish length and reproductive success were inconsistent. Managers may minimize potential environmental and genetic contributors to reduced performance by hatchery fish, but continued reliance on hatchery supplementation may hinder achievement of the long-term goal of a fishery supported largely by naturally reproducing populations. [ABSTRACT FROM AUTHOR]

Historically, less than 2% of steelheadOncorhynchus mykissstocked in river mouths on Minnesota tributaries to Lake Superior returned as adults. To investigate the influence of stocking location on adult return rates, similar proportions of age-1 steelhead were stocked in the mouth and throughout upstream reaches of the Knife River. A subset of steelhead stocked upstream were implanted with coded wire tags (CWT), which resulted in 18% of all fish stocked, regardless of location, possessing a CWT. A fish trap near the mouth of the river was used to sample emigrating age-0 through age-3 juveniles and returning adults. Of the steelhead stocked upstream 45% survived to emigrate. Electrofishing surveys and trap results indicated no steelhead remained in the river past age 2. No evidence was found that larger age-1 stocked steelhead displaced smaller age-1 wild steelhead. Only 12% of returning adults possessed CWTs, 6% less than the percentage stocked with CWTs (18%). Adult return rates for those stocked in the river mouth were 1.0% compared with 0.5% for those stocked upstream. Overall, stocking in the river mouth contributed 69% of the returning adults. Given these results, Minnesota fishery managers should continue to look for alternate ways to increase steelhead return rates if greater adult numbers are desired. Received February 12, 2013; accepted July 3, 2013 [ABSTRACT FROM PUBLISHER]

Abstract: Hatchery augmentation of steelhead Oncorhynchus mykiss was evaluated over 20years in Minnesota tributaries of Lake Superior using three approaches — stocking fry or yearlings of a naturalized strain (STT), and yearlings of a domesticated strain (KAM). The STT strain was introduced over 100years ago and became naturalized to Lake Superior and its tributaries, unlike KAM, which has not been shown to reproduce successfully in streams. We compared smolt–adult return rates to anglers and in-river traps, and production costs per adult for these three programs in the French and Knife rivers. STT smolts derived from stocked fry in the French River resulted in the highest smolt–adult return rates to traps and anglers (13.3%), and lowest cost per returning adult ($46). STT stocked as yearling smolts produced the lowest return rate (1.5%) and highest cost per returning adult ($192) for both rivers combined. KAM stocked as yearling smolts were intermediate in return rate (2.6%) and cost per adult ($90). Differences in return rates of the three strains were attributable to the extent of domestication selection, size at stocking, season of stocking, and summer lake temperatures. Smolts derived from fry-stocked STT were strongly influenced by summer lake temperatures in their first lake year. Yearling-stocked STT were influenced by size at stocking and summer lake temperatures. KAM yearlings benefitted from summer stocking at larger sizes. Based on poor survival and fiscal constraints, the STT yearling program was discontinued. Stocking programs will continue to evolve according to changing biological, financial, social, and political pressures. [Copyright &y& Elsevier]

Populations 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. [ABSTRACT FROM AUTHOR]

Lake Superior's fish community continues to change as a result of the recovery of populations of lake trout Salvelinus namaycush, the naturalization of introduced salmonids Oncorhynchus spp. and Salmo spp., declines in the populations of rainbow smelt Osmerus mordax, and the fluctuating recruitment of cisco Coregonus artedi. This study used bioenergetics modeling of the dominant predator fish in the western arm of Lake Superior in 2004 to provide a comprehensive picture of the relationship between predator demand and prey fish availability. The results, presented for nearshore and offshore areas and three geographically distinct ecoregions, indicate that the western arm is at or near its carrying capacity for predators. Estimated predator demand was about one-half the annual biomass plus production of coregonines but exceeded the biomass plus production of rainbow smelt, possibly because of underestimates of this species in shallow areas and recent shifts in predator diets. Lean lake trout were responsible for most Of the consumption of these prey fish, while the deepwater siscowet form ranked second. The commercial harvest of prey fish biomass was trivial compared with the consumption by predator fish. Chinook salmon Oncorhynchus tshawytscha, along with other nearshore potamodromous species, played minor roles in total consumption. Chinook salmon are an indicator of forage status, as they have responded to declines in the rainbow smelt biomass with a dramatic diet shift to ciscoes and a decline in weight at age since the early 1990s. Slightly reduced lean lake trout growth and density-dependent survival in some areas also indicate that competition for prey is intense. Because most of the predators in the western arm are wild fish, stocked predators no longer have a great impact on prey populations. Bioenergetics modeling of predator demand combined with hydroacoustic estimates of prey supply can be valuable for managing the fisheries of large lakes, allocating resources to various interest groups, and increasing basic understanding of lake production and community dynamics. [ABSTRACT FROM AUTHOR]

Rehabilitation of Lake Superior's coaster brook trout Salvelinus fontinalis hinges not only on resolving critical ecological challenges but also on addressing key human dimensions challenges. This article addresses the key issues of values, agency coordination, stakeholder engagement, and public awareness and outreach and makes relevant recommendations. First, agencies should continue to improve coordination by expanding the scope and membership of the Lake Superior Brook Trout Committee and other forums. The size of the basin and the large number of partners involved requires consistent communication and transparent coordination mechanisms. Second, the range of values currently associated with brook trout and their rehabilitation must be expanded beyond the current focus on fishery interests by incorporating a more diverse array of groups and interests. Third, the number of groups engaged in native brook trout restoration efforts should be enlarged by reaching out to new groups, particularly watershed organizations, local governments, and environmental groups, as the comprehensive nature of the restoration efforts will require the cooperation and support of a broader array of groups. Finally, the level of general public awareness and support for the activities necessary to rehabilitate coasters needs to be increased. An outreach program should engage all stakeholders early in the planning process and provide science-based information to establish reasonable expectations. Fishery managers and their partners should look for opportunities to bring positive attention to ongoing rehabilitation and habitat management activities. [ABSTRACT FROM AUTHOR]

Coaster brook trout are a migratory form of brook trout Salvelinus fontinalis that spend part of their lives in the Great Lakes. Over the last century the abundance of coaster brook trout in Lake Superior has declined dramatically, and only remnant stocks remain. Recently, the rehabilitation of coaster brook trout in Lake Superior has become a goal of fish management agencies. The specific goal agreed upon by all of the agencies involved is to maintain widely distributed, self-sustaining populations in as many of the historical habitats as practical. We discuss realistic expectations for rehabilitation and emphasize the need for management agencies, academia, and angling organizations to work cooperatively. We first present a brief history of coaster brook trout in Lake Superior, then discuss habitat requirements and protection, the regulations required for rehabilitation, stocking, species interactions, and the role that human dimensions play in rehabilitation. The management issues that must be addressed are implementation of a basinwide survey to identify remnant stocks and critical habitat, restrictive harvest regulations, watershed rehabilitation, critical biological review, and the formulation of expectations before experimental stocking programs are initiated, along with coordinated, basinwide information sharing and cooperative management among agencies similar to that undertaken during the rehabilitation of lake trout Salvelinus namaycush in Lake Superior. Future research needs include basic coaster biology and life history, habitat use in streams and the lake, interaction with other species in the Lake Superior fish community, and interaction between stream-resident and coaster brook trout. Successful rehabilitation will require a shift from a harvest fishery to one with minimal or no harvest of coaster brook trout in the Lake Superior basin. Coaster brook trout rehabilitation will take time and will proceed at different rates at different locations, depending on the presence of remnant stocks, quality of habitat, angling pressure, and political will. [ABSTRACT FROM AUTHOR]

Stocks of lake trout Salvelinus namaycush in Lake Superior are recovering from historical collapse. Stocking, control of sea lampreys Petromyzon marinus, and harvest restrictions have aided lake trout recovery, but the contribution of stocked lake trout to contemporary recruitment has not been quantified in western Lake Superior. Using variants of the Ricker stock-recruit model, we evaluated the production of age-7 lake trout (recruits) by examining age-8 and older wild and stocked parental lake trout (spawners). We found that density of wild lake trout spawners and recruits increased during 1980-2003, whereas the density of stocked spawners decreased in all management areas. Two competing models best described recruit density of the 1988-2003 year-classes: (1) wild and stocked parents each contributed to recruitment but stocked parents contributed negatively and (2) only wild parents contributed to recruitment. Recruitment rates declined significantly with increasing spawner density in four of five management areas, which suggests that recruitment is density dependent in much of western Lake Superior. We conclude that stocked lake trout did not contribute significantly to lake trout rehabilitation in western Lake Superior during 1980-1995. [ABSTRACT FROM AUTHOR]

We describe the diet and prey selectivity of lean (Salvelinus namaycush namaycush) and siscowet lake trout (S. n. siscowet) collected during spring (April-June)from Lake Superior during 1986-2001. We estimated prey selectivity by comparing prey numerical abundance estimates from spring bottom trawl surveys and lake trout diet information in similar areas from spring gill net surveys conducted annually in Lake Superior. Rainbow smelt (Osmerus mordax) was the most common prey and was positively selected by both lean and siscowet lake trout throughout the study. Selection by lean lake trout for coregonine (Coregonus spp.) prey increased after 1991 and corresponded with a slight decrease in selection for rainbow smelt. Siscowet positively selected for rainbow smelt after 1998, a change that was coincident with the decrease in selection for this prey item by lean lake trout. However, diet overlap between lean and siscowet lake trout was not strong and did not change significantly over the study period. Rainbow smelt remains an important prey species for lake trout in Lake Superior despite declines in abundance. [ABSTRACT FROM AUTHOR]

Lake herring (Coregonus artedi) and rainbow smelt (Osmerus mordax) are a valuable prey resource for the recovering lake trout (Salvelinus namaycush) in Lake Superior. However, prey biomass may be insufficient to support the current predator demand. In August 1997, we assessed the abundance and spatial distribution of pelagic core gonines and rainbow smelt in western Lake Superior by combining a 120 kHz split beam acoustics system with midwater trawls. Core gonines comprised the majority of the midwater trawl catches and the length distributions for trawl caught fish coincided with estimated sizes of acoustic targets. Overall mean pelagic prey fish biomass was 15.56 kg ha-1 with the greatest fish biomass occurring in the Apostle Is lands region (27.98 kg ha-1), followed by the Duluth Minnesota region (20.22 kg ha-1), and with the lowest biomass occurring in the open waters of western Lake Superior (9.46 kg ha-1). Biomass estimates from hydroacoustics were typically 2-134 times greater than estimates derived from spring bottom trawl surveys. Prey fish biomass for Lake Superior is about order of magnitude less than acoustic estimates for Lakes Michigan and Ontario. Discrepancies observed between bioenergetics-based estimates of predator consumption of core gonines and earlier coregonine biomass estimates may be accounted for by our hydroacoustic estimates. [ABSTRACT FROM AUTHOR]

We assessed abundance, size, and species composition of forage fish and zooplankton communities of western Lake Superior during August 1996 and July 1997. Data were analyzed for three ecoregions (Duluth-Superior, Apostle Islands, and the open lake) differing in bathymetry and limnological and biological patterns. Zooplankton abundance was three times higher in the Duluth-Superior and Apostle Islands regions than in the open lake due to the large numbers of rotifers. Copepods were far more abundant than Cladocera in all ecoregions. Mean zooplankton size was larger in the open lake due to dominance by large calanoid copepods although size of individual taxa was similar among ecoregions. Forage fish abundance and biomass was highest in the Apostle Islands region and lowest in the open lake ecoregion. Lake herring (Coregonus artedi), rainbow smelt (Osmerus mordax) and deepwater ciscoes (Coregonus spp.) comprised over 90% of the abundance and biomass of fishes caught in midwater trawls and recorded with hydroacoustics. Growth and condition offish was good, suggesting they were not resource limited. Fish and zooplankton assemblages differed among the three ecoregions of western Lake Superior, due to a combination of physical and limnological factors related to bathymetry and landscape position. [ABSTRACT FROM AUTHOR]

Survival of the 1963-1982 year-classes of stocked yearling lake trout Salvelinus namaycush declined significantly over time in Lake Superior. To investigate possible causes of this decline, a Ricker model of stock-recruitment was used to describe the catch per effort (CPE) of age-7 stocked lake trout in the Michigan, Minnesota, and Wisconsin waters of Lake Superior as functions of the numbers of yearlings stocked 6 years earlier (an index of density dependence), the density (CPE) of wild adult lake trout (an index of predation), and large-mesh (≥114-mm stretch-measure) gill-net fishing effort (an index of fishing mortality). Declining CPE of stocked lake trout in Michigan and Wisconsin was significantly associated with increasing large-mesh gill-net fishing effort. Declining CPE of stocked lake trout in Minnesota was significantly associated with increasing density of wild lake trout. Declining survival of stocked lake trout may therefore have been caused by increased mortality in large-mesh gill-net fisheries in Michigan and Wisconsin, and by predation by wild lake trout that recently recolonized the Minnesota area. We recommend that experimental management be pursued to determine the relative importance of large-mesh gill-net fishing effort and of predation by wild lake trout on the survival of stocked lake trout in U.S. waters of Lake Superior. [ABSTRACT FROM AUTHOR]

An introduction to papers published within the issue is presented, including the genetic issues relates to coaster brook trout rehabilitation and another on the combination of techniques used to document important aspects of coaster brook trout behavior.