Lake Superior Tributaries Research Articles

Factors affecting recruitment dynamics of Great Lakes sea lamprey ( Petromyzon marinus) populations

Knowledge of stock–recruitment dynamics is as important for control of pest species such as the sea lamprey ( Petromyzon marinus) as it is for sustainable harvest management of exploited fish species. A better understanding of spatial and temporal variation in recruitment of pest populations may inform managers on where and when to effectively apply different control methods. Sea lamprey stock–recruitment data combined from streams across the Great Lakes basin into a Ricker stock–recruitment model indicated both compensation (density-dependent survival) and a large amount of density-independent recruitment variation. We evaluated the use of a mixed-effects model to look at common year effects and stream-level variables that could affect productivity and growing season length, with the objective of identifying factors that may explain this density-independent variation in recruitment. After selecting the “best model”, we tested factors that might affect recruitment variation, using a Great Lakes dataset comprising 97 stream–years. Lake Superior tributaries, streams with larger numbers of lamprey competitors, and streams regularly requiring lampricide treatment showed significantly higher recruitment. Alkalinity and thermal regulation did not affect the observed recruitment pattern among streams. In four long-term study streams we observed significant variation among streams, tested as a fixed effect, but no evidence suggested a common pattern of variation among years. Differences in recruitment among streams were consistent with evidence of quality of spawning and larval habitat among streams. Our findings suggest that management models should account for differences in recruitment dynamics among sea lamprey-producing streams, but not common year effects.

Summer Movements of Juvenile Coho Salmon under Variable Stream Flow Conditions

AbstractWe describe the distribution of juvenile (age‐0) coho salmon Oncorhynchus kisutch and the effects of summer flooding on their movements in a small Lake Superior tributary. We documented large fluctuations in fish abundance over a 60‐d survey period by conducting repeated snorkeling surveys within 16 reaches and 82 individual habitat units in a 2‐km segment of the Onion River, Wisconsin. Fish densities in reaches were more stable than those within individual habitat units. Moreover, temporal trends in fish abundance were correlated strongly with the physical features of reaches but not with those of individual habitat units. In focusing on fine‐scale changes in fish distribution, we uncovered three general patterns of movement within this stream. The first was associated with flood events, which caused the downstream displacement of large numbers of fish (up to 80% loss from individual pools). The second was the upstream recolonization of fish into depleted pools during the intervening periods of low flow, and the third was small‐scale movement within reaches. Three separate floods did not cause a decline in average pool densities over the study; however, there was a strong shift away from glide habitats and a concentration of fish in the middle reaches of the stream by the study's conclusion. Movement of the type and magnitude described here has clear implications for the association of fish with physical habitat conditions. We also speculate that such movement may have effects on social hierarchies and the relative fitness of individual coho salmon.

Migrations and Biological Characteristics of Adfluvial Coaster Brook Trout in a South Shore Lake Superior Tributary

AbstractWe used fish traps and electrofishing surveys to characterize the biology, life history traits, and potential biotic interactors important to the rehabilitation of native, adfluvial coaster brook trout Salvelinus fontinalis in Lake Superior. This study focused on the Salmon Trout River, Michigan, which is the site of the last known remnant population of adfluvial brook trout on the south shore of Lake Superior. The brook trout captured in passive traps (weirs) in the river ranged from 56 to 554 mm in total length (TL) and from 0 (young of the year) to 6 years of age. This population displayed a protracted 5‐month migration into the river but one that included relatively few fish. Coaster brook trout in this population appear to initiate adfluvial migrations near age 3 and 300 mm TL. Relative weight values increased with fish length and therefore reproductive life stage, possibly indicating the shift from river to lake habitats. This population of coaster brook trout is small and subject to potential biotic interactions with exotic species and population limitation because of an active fishery in the lake and river. Migratory runs of brook trout coincided with large runs of coho salmon Oncorhynchus kisutch, and the instream juvenile salmonid composition included proportionately high densities of coho salmon and rainbow trout O. mykiss. In addition, Floy tag return data indicated that exploitation of reproductive‐age Salmon Trout River coaster brook trout was at least 12% and may have been as high as 50% in the open waters of Lake Superior. A recent increase in the legal minimum length limit and reduction of the daily bag limit for recreational harvest may slow or reverse this trend.

Design of a Compound Inclined Screen Trap for Anadromous Salmonid Smolts

AbstractIn the late 1980s, Minnesota Department of Natural Resources fish managers became compelled to address the decline of wild steelhead Oncorhynchus mykiss in Lake Superior. Requisite to the development of stock–recruitment models, permanent smolt traps were designed and constructed on two Lake Superior tributaries. The design was engineered to function in a broad range of discharges with complete structural integrity, to keep itself free of debris, and to sample a large portion of the emigrating salmonid population. The first of these traps was built on the French River (discharge, from 3 to >1,840 ft3/s (cfs)) and began operation in 1994. After several years of very successful operation a second trap was built on the Knife River (discharge, from 5 to >9,000 cfs) that began operation in 1997. These structures employ fixed stainless steel dewatering screens permanently fixed at opposed compound inclines on each side of a channel that carries water to a catch–retention box, which is also fixed and above the level of the stream. Fish falling onto the screen are directed by gravity to the center channel, where they travel with the flowing water to the catch box. A stainless steel, overshot, rotating drum screen in the catch box has effectively retained fish with low mortality while expelling water‐borne debris. Both traps have operated continuously during open‐water periods since 1997 to sample emigrating salmonid smolts (primarily wild steelhead). Smolt capture efficiency has been estimated to be 94% with the French River trap and 85% with the Knife River trap. Fish managers may wish to examine and consider this design as a possibility for addressing their smolt monitoring needs.

Regional, watershed, and site-specific environmental influences on fish assemblage structure and function in western Lake Superior tributaries

The relative importance of regional, watershed, and in-stream environmental factors on fish assemblage structure and function was investigated in western Lake Superior tributaries. We selected 48 second- and third-order watersheds from two hydrogeomorphic regions to examine fish assemblage response to differences in forest fragmentation, watershed storage, and a number of other watershed, riparian, and in-stream habitat conditions. Although a variety of regional, fragmentation, and storage-related factors had significant influences on the fish assemblages, water temperature appeared to be the single most important environmental factor. We found lower water temperatures and trout–sculpin assemblages at lower fragmentation sites and higher temperatures and minnow–sucker–darter assemblages as storage increased. Factors related to riparian shading and flow separated brook trout streams from brown trout (Salmo trutta) – rainbow trout (Oncorhynchus mykiss) streams. Functionally, fish assemblages at lower fragmentation sites were dominated by cold-water fishes that had low silt tolerance and preferred moderate current speeds, while fishes with higher silt tolerances, warmer temperature preferences, and weaker sustained swimming capabilities were most common at higher storage sites. Our results suggest that site-specific environmental conditions are highly dependent on regional- and watershed-scale characters and that a combination of these factors operates in concert to influence the structure and function of stream fish assemblages.

Lower fitness of hatchery and hybrid rainbow trout compared to naturalized populations in Lake Superior tributaries.

We have documented an early life survival advantage by naturalized populations of anadromous rainbow trout Oncorhynchus mykiss over a more recently introduced hatchery population and outbreeding depression resulting from interbreeding between the two strains. We tested the hypothesis that offspring of naturalized and hatchery trout, and reciprocal hybrid crosses, survive equally from fry to age 1+ in isolated reaches of Lake Superior tributary streams in Minnesota. Over the first summer, offspring of naturalized females had significantly greater survival than offspring of hatchery females in three of four comparisons (two streams and 2 years of stocking). Having an entire naturalized genome, not just a naturalized mother, was important for survival over the first winter. Naturalized offspring outperformed all others in survival to age 1+ and hybrids had reduced, but intermediate, survival relative to the two pure crosses. Averaging over years and streams, survival relative to naturalized offspring was 0.59 for hybrids with naturalized females, 0.37 for the reciprocal hybrids, and 0.21 for hatchery offspring. Our results indicate that naturalized rainbow trout are better adapted to the conditions of Minnesota's tributaries to Lake Superior so that they outperform the hatchery-propagated strain in the same manner that many native populations of salmonids outperform hatchery or transplanted fish. Continued stocking of the hatchery fish may conflict with a management goal of sustaining the naturalized populations.

Mitochondrial DNA Analysis Indicates Sea Lampreys Are Indigenous to Lake Ontario

AbstractThe parasitic sea lamprey Petromyzon marinus occurs throughout North America's Great Lakes, where it has an immense economic impact on commercially and recreationally important fishes. Sea lampreys indisputably invaded Lake Erie and the upper Great Lakes from Lake Ontario in the mid‐1900s, but their official status as a nonnative species in Lake Ontario is based on circumstantial evidence and has long been subject to controversy. Presently, sea lampreys are considered by U.S. and Canadian government agencies to be an invasive species within the entire Great Lakes watershed, and millions of dollars are spent annually to suppress them. We sequenced 330 base pairs of the mitochondrial DNA control region of 224 sea lampreys collected from 10 locations (3 within the Lake Ontario drainage, 2 within the Lake Superior drainage, and 5 rivers between Quebec and New York that are tributary to the Atlantic Ocean). Eighteen haplotypes were revealed, of which 17 occurred in specimens from Atlantic coast rivers, 6 in specimens from Lake Ontario, and 2 in specimens from Lake Superior tributaries. Haplotype frequencies were not significantly different (P > 0.05) within regions, indicating low or no homing fidelity. But when haplotype frequencies were grouped within regions and compared along the hypothesized colonization pathway, significant differences were seen. Pronounced differences in haplotype frequency patterns between Atlantic coast and Lake Ontario drainage collections, together with arguments against the viability of canal passage, strongly support the idea of post‐Pleistocene natural colonization by one of at least three hypothesized zoogeographic pathways. If sea lampreys are indigenous to Lake Ontario, management policies aimed toward intense suppression might need reevaluation.

Examining primary producer–consumer interactions in a Lake Superior tributary using 15N-tracer, grazer-reduction, and nutrient-bioassay experiments

AbstractPrimary producer–consumer interactions and N dynamics were studied in a 3rd-order reach of Amity Creek, a Lake Superior tributary in northeastern Minnesota (mean discharge = 0.08 m3/s). A nutrient-limitation-bioassay experiment showed that primary production was co-limited by N and P. To evaluate the importance of grazers in controlling epilithic algal biomass, a grazer-reduction experiment was conducted using ceramic tile epilithon substrates (ambient grazing and low grazing treatments). Grazers significantly reduced epilithic biomass as measured by chlorophyll a, demonstrating that grazers constrain algal primary producers in this system. 15N-enriched NH4Cl was added to the stream for 6 wk, as a stable isotope tracer of N flow through producer and grazer compartments. A comparison of δ15N of tile epilithon, incubated for 4 wk during the 15N addition, to that of bulk epilithon collected from rock scrapings, showed that the thinner epilithon associated with tiles was much more enriched in 15N than...

Agreement Among Observers Classifying Larval Sea Lamprey ( Petromyzon marinus) Habitat

Estimates of larval sea lamprey ( Petromyzon marinus) abundance are used to rank Great Lakes tributaries for lampricide treatment. Observers subjectively stratify habitat into three categories: type I = preferred, type II = acceptable, type III = unacceptable. Agreement was evaluated among eight observers classifying habitats in small discrete plots in two Lake Superior tributaries, the Rock and Chocolay rivers, and among four observers classifying and measuring the amount of each habitat type along random transects in the Rock River. Agreement among the eight observers classifying habitat plots was high (Chocolay, κ = 0.742 and Rock, κ = 0.785). The amounts of types I, II, and III habitat estimated were statistically different among observers. However, the amount of variability found in the classification and measurement of habitat by observers had little effect on the ranking of 51 streams considered for lampricide treatment.

Reduction in Sea Lamprey Hatching Success Due to Release of Sterilized Males

Male sea lampreys ( Petromyzon marinus), sterilized by injection with bisazir, were released in Lake Superior tributaries from 1991 to 1996 and exclusively in the St. Marys River (the outflow from Lake Superior to Lake Huron) since 1997 as an alternative to chemical control. To determine effectiveness in reducing reproductive potential through the time of hatch, males were observed on nests and egg viability was determined in nests in selected Lake Superior tributaries and the St. Marys River. The proportions of sterilized males observed on nests were not significantly different than their estimated proportion in the population for all streams and years combined or for the St. Marys River alone. It was concluded that sterilized males survive, appear on the spawning grounds, and nest at near their estimated proportion in the population. There was a significant reduction in egg viability corresponding with release of sterilized males for all streams and years combined or for the St. Marys River alone. In the St. Marys River from 1993 to 2000, the percent reduction in egg viability was significantly correlated with the observed proportion of sterile males on nests. It was further concluded that sterilized males remain sterile through nesting and attract and mate with females. Reduction in reproductive potential in the St. Marys River due to both removal of females by traps and sterile-male-release ranged from 34 to 92% from 1993 to 2001 and averaged 64%. From 1999 to 2001, when the program stabilized, reductions ranged from 71 to 92% and averaged 81%. The current release of sterile males in the St. Marys River effectively reduced reproductive potential through the time of hatch and did so near theoretical levels based on numbers released, estimates of population size, and the assumptions of full sterility and competitiveness.

Passage of Four Teleost Species Prior to Sea Lamprey ( Petromyzon marinus) Migration in Eight Tributaries of Lake Superior, 1954 to 1979

Seasonally operated barriers in rivers are used by the Great Lakes Fishery Commission to block adult sea lamprey ( Petromyzon marinus) migrations, yet pass other fish during some part of the year. Knowledge of the overlap of spawning migrations of sea lampreys and other fish species are vital for the efficient operation of the Commission's barrier program. The migration of sea lamprey spawners was compared with the migration of four other fish species using trap captures at electric barriers on eight Lake Superior tributaries during 1954 to 1979. The passage of rainbow trout ( Oncorhynchus mykiss), rainbow smelt (Osmerus mordax), longnose suckers ( Catostomus catostomus), and white suckers ( Catostomus commersoni) prior to the capture of sea lampreys was quantified as the proportion of the annual catch of each species. Average passage over all streams and years was smallest (5%) for longnose sucker and largest (21%) for rainbow smelt. Passage prior to first sea lamprey catch was significantly different among rivers for all four species and significantly different among years for rainbow trout. Much of the variability in annual passage was unexplained by river or year effects. It is suggested that stream-specific information on run times of sea lampreys and other fishes be used to define timing of seasonal barrier operations. If barrier operations are timed to block the entire sea lamprey spawning run, then fish passage devices are needed to pass rainbow trout, rainbow smelt, longnose suckers, and white suckers.

Watershed influences on the transport, fate and bioavailability of mercury in Lake Superior: Field measurements and modelling approaches

AbstractThe issuance of fish consumption advisories in US states bordering Lake Superior has heightened the need for understanding the biogeochemical cycling and transformations of mercury in this great lake. Major routes of mercury (Hg) transport to lakes include atmospheric deposition (wet and dry), direct discharges and riverine (watershed) inputs. The specific objectives of this ongoing study are to: (i) determine the speciation and bioavailability of Hg transported to Lake Superior (ii) determine the importance of watershed‐specific characteristics that control physical and chemical forms of Hg; (iii) identify key mechanisms controlling Hg bioavailability and speciation in near‐shore zones relative to open lake regions; and (iv) provide process‐level information to compliment concurrent development of Hg fate and transport models of the Lake Superior ecosystem. Three tributaries of Lake Superior were chosen for detailed field study based on previous results and particular watershed characteristics. Mixing zones represent a potentially important zone of Hg entry into the food chain, and were sampled for biota, water and sediment in transects between the tributary mouth and the lake end member. Sampling of open‐water sites was conducted during Environmental Protection Agency‐sponsored cruises on the research vessel Lake Guardian. Results from our work on Lake Superior tributaries demonstrate that dissolved organic carbon and methylmercury (MeHg) export was greatest from watersheds containing wetlands. In Lake Superior, concentrations of Hg species were small at pelagic stations (total mercury (HgT) averaged 0.49 ng/L, MeHg averaged 6.4 pg/L). In contrast, MeHg concentrations in tributaries ranged from 100 to 250 pg/L. Watershed sites dominated by wetlands exhibited the greatest MeHg concentrations, occasionally in excess of 12 ng/L. Samples of bulk zooplankton ranged from 20 to 130 ng/g dry weight HgT and from 15 to 45 ng/g dry weight MeHg, and demonstrated typical bioacculmulation of mercury as well as distinct seasonality in concentrations.

Microhabitat Use and Behavior of Overwintering Juvenile Coho Salmon in a Lake Superior Tributary

Abstract Little is known about the behavior of coho salmon Oncorhynchus kisutch established in the Lake Superior drainage in the late 1960s. Unlike in their native range of the Pacific coast, Lake Superior coho salmon juveniles inhabit streams characterized by low winter flows and highly variable summer flows. Because high stream flows can profoundly affect fish behavior and distribution, we hypothesized that the winter ecology of coho salmon in Lake Superior streams would differ from patterns described for Pacific coast populations. Snorkeling surveys completed in winter 1998 examined the distribution and social organization of overwintering coho salmon in simple and complex pools of a Lake Superior tributary in Wisconsin. In both habitat types, coho salmon occupied focal positions in the main channel; however, fish were more tightly distributed and closer to the streambanks in simple pools. Aggressive interactions also were more common in simple pools. These results contrast sharply with research findin...

Emigration, Upstream Movement, and Habitat Use by Sterile and Fertile Sea Lampreys in Three Lake Superior Tributaries

Abstract To investigate upstream spawning migration behavior of fertile and sterilized sea lampreys Petromyzon marinus, we attached radio transmitters to 149 sea lampreys, released them in three tributaries of Lake Superior between 1993 and 1996, and followed their movements for up to 60 d. Emigration from spawning streams was variable between years and streams (10–50% of releases within a stream), appeared to be affected by the length of unimpeded stream, and was not affected by the sterilization procedure. Most sea lampreys that stayed in the streams moved upstream (64%), the majority moving between 2200 and 0300 hours. Total distance traveled, daily movement rates, and habitat selected by sea lampreys did not differ between fertile males and sterile males. In all streams, sea lampreys selected habitat with significantly reduced light levels and made use of habitat providing refugia—brush piles, overhanging banks, and boulders. Differences in emigration rates among streams implies that stocking rates of...

Seasonal Changes in Ruffe Abundance in Two Lake Superior Tributaries: Implications for Control

Abstract Since the discovery of ruffe Gymnocephalus cernuus in the St. Louis River in 1987, state, federal, and tribal management agencies have sought to slow its spread to areas outside the western end of Lake Superior. A debate over control strategies highlighted uncertainties about seasonal movements of this species between Lake Superior and its western tributaries. One strategy called for eliminating reproducing populations in tributaries on the periphery of the range using chemical piscicides. That strategy rested on the assumption that ruffe congregate in tributaries during a predictable time of year. This study was designed to explore that assumption. Ruffe collections from the Iron and Sand rivers during 1995 indicated that ruffe were present in those tributaries throughout the summer but that abundance was not highest at the predicted time: June 19–22. Maximum abundance in the Iron River did not coincide with that in the Sand River and did not occur during June 19–22 in either river. The timing o...

Over-winter Survival and Habitat Use by Juvenile Coho Salmon ( Oncorhynchus kisutch) in Two Lake Superior Tributaries

Dramatic declines in commercial and recreational fisheries for coho salmon ( Oncorhynchus kisutch) in Lake Superior have raised questions about the natural factors that limit their productivity. Snorkeling surveys were conducted during the winters of 1995–96 and 1996–97 to estimate over-winter mortality and determine winter habitat use by juvenile coho salmon in two spring-fed tributaries of Chequamagon Bay, Lake Superior. Results indicated high densities of juvenile coho salmon in pool habitats of the two streams ( x ¯ = 0.85 fish/m 2) and high over-winter survival (> 45%). Regression analyses revealed no significant relationships between fish distribution and physical habitat variables (large woody debris, overhead cover, and pool size). No shift in habitat use over the winter was found. These results contrast sharply with findings from the Pacific Northwest where juvenile coho salmon generally occupy complex pool habitats during the winter. Although streams of the Great Lakes region are similar in many respects to Pacific streams, differences, particularly in stream flow regimes, indicate that the early life history of coho salmon populations in these two regions differ dramatically. These observations may have important implications on the management of stream habitats in the Great Lakes.

Reproduction and Early Life History of Ruffe ( Gymnocephalus cernuus) in the St. Louis River, a Lake Superior Tributary

Reproduction and early life history of ruffe ( Gymnocephalus ceriums) was investigated during April to July in 1993 and 1994 in the St. Louis River, a western Lake Superior tributary. This study was conducted to assist fishery managers in determining possible interactions among the early life stages of ruffe and other North American percids, and in obtaining information useful in developing control methods targeted at the early life stages of ruffe. Ruffe had a prolonged spawning period that extended from late April to late June with peak spawning in mid to late May when water temperatures were between 12 and 14°C. The majority of ruffe protolarva were captured 1 to 2 weeks after egg deposition between mid May and late June and most were captured in water 0.5-m deep. Onshore-offshore movements were not observed, but diel vertical movements of larval ruffe were observed on several occasions. The greatest chance of ballast water transport of pelagic larval ruffe is between mid May and July. Information on reproduction and early life history in this report will assist fishery mangers in development of ruffe control methods, and assist Great Lakes shipping in ballast water management to prevent the spread of ruffe.

Downstream Movement of Leopard Frogs in a Lake Superior Tributary Exemplifies the Concept of a Lotic Macrodrift

ABSTRACT Over two field seasons, 319 downstream-moving leopard frogs (Rana pipiens) were captured and retained by a salmonid smolt trap operated in the Bois Brule River of northern Wisconsin. Most leopard frog movement occurred during late summer and autumn but was not conclusively correlated with any environmental factors. This movement was part of a macrodrift that included other larger taxa (e.g. Bufo and Orconectes) not typically retained by the drift nets used by aquatic ecologists to sample aquatic insects. Smolt traps, by virtue of the large volumes of water they strain, can be used to provide hard-to-obtain life history information for a variety of aquatic organisms.

Effect of Salmon Carcass Decomposition on Lake Superior Tributary Streams

We investigated the fate of organic matter and inorganic nutrients derived from spawning runs of chinook salmon in tributary streams to Lake Superior during fall and winter 1990. Upstream-downstream comparisons and experimental introduction of carcasses were used to determine how salmon carcass decomposition influenced several stream ecosystem components, including total phosphorus, total nitrogen, soluble reactive phosphorus (SRP), NO₃^-, NH₄⁺, periphyton biomass, and fine particulate organic matter (FPOM) in transport. Total phosphorus, SRP, and periphyton biomass were higher in a river reach that received a spawning run of an estimated 1200 fish than in an upstream reach that lacked spawning salmon. No upstream-downstream gradient in these components occurred in a river that did not receive a spawning run. Total phosphorus, SRP, and periphyton also were elevated where we experimentally introduced salmon carcasses, in the absence of a natural salmon run. Stable isotope analyses revealed that salmon-derived nitrogen was incorporated into grazing mayflies, and to a lesser extent into filter-feeding caddisflies. Salmon-derived carbon was not incorporated into these macroinvertebrates. These results show that salmon carcasses can be an important source of nutrients in streams even when runs are relatively small.

Effects of Lampricide Treatments, Relative to Environmental Conditions, on Abundance and Sizes of Salmonids in a Small Stream

Abstract We examined a 10-year set (spanning 1979–1991) of salmonid density, biomass, and length-at-age data from a first-order, soft-water, Lake Superior tributary that received three treatments of the Lampricide TFM (3-trifluoromethyl-4-nitrophenol) over the period studied. After a TFM treatment done during the first half of the 1986 growing season, reduced densities of three age-groups of brook trout Salvelinus fontinalis, and significantly reduced total biomass of brook trout, were observed. Mean lengths at age of most salmonid age-classes near the end of the 1986 growing season were small relative to those in other years, but for most groups this tendency was not statistically significant. Drought conditions during three of the study years were similarly associated with reduced growth of salmonids. There were no discernable, long-term effects of two TFM treatments in 1986 on salmonid abundances or mean lengths at age the following year. Similarly, a treatment near the end of the 1983 growing season h...