River Restoration Effects on Steelhead Populations in the Manistee River, Michigan: Analysis Using an Individual‐Based Model

The Manistee River, Michigan, watershed includes two dams as well as residential and agricultural development, and the river itself contains a sizeable population of steelhead Oncorhynchus mykiss that supports a valuable recreational fishery. Restoration of the Manistee River and its flow regime may improve steelhead habitat and the fishery. We developed an individual‐based model of steelhead in the Manistee River to assess the population effects of changes in the number of spawners, water discharge from Tippy Dam, and water temperature. The model follows steelhead from spring spawning to the end of the growing season in early fall and depicts the river environment as a series of cells that vary in dimension, water velocity, and substrate. Simulated water discharge, temperature, and prey availability changed daily based on observations from Tippy Dam. Empirically based models describe individual steelhead fry and parr foraging and growth. In the model, steelhead select habitats and maximize individual fitness while accounting for dominance and the availability of feeding territories. We calibrated the model to replicate fish growth, mortality, and population size. Simulation experiments manipulated the number of spawning females, water discharge, and water temperature. The results suggest that Manistee River steelhead incur density limitations in the fry and parr stages and that water discharge and temperature changes affect the number and biomass of parr. Increasing river discharge negatively affected parr numbers and weight. Decreasing maximum midsummer temperature increased parr numbers and weight when the change was large, but otherwise had little effect. These results indicate that restoration of the natural flow regime in the Manistee River will probably increase the quality of the habitat for steelhead but that density limitations in the fry and parr stages may ultimately limit population growth.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141355/1/tafs1654.pd

The geometry of reaction norms yields insights on classical fitness functions for Great Lakes salmon.

Life history theory examines how characteristics of organisms, such as age and size at maturity, may vary through natural selection as evolutionary responses that optimize fitness. Here we ask how predictions of age and size at maturity differ for the three classical fitness functions-intrinsic rate of natural increase r, net reproductive rate R0, and reproductive value Vx-for semelparous species. We show that different choices of fitness functions can lead to very different predictions of species behavior. In one's efforts to understand an organism's behavior and to develop effective conservation and management policies, the choice of fitness function matters. The central ingredient of our approach is the maturation reaction norm (MRN), which describes how optimal age and size at maturation vary with growth rate or mortality rate. We develop a practical geometric construction of MRNs that allows us to include different growth functions (linear growth and nonlinear von Bertalanffy growth in length) and develop two-dimensional MRNs useful for quantifying growth-mortality trade-offs. We relate our approach to Beverton-Holt life history invariants and to the Stearns-Koella categorization of MRNs. We conclude with a detailed discussion of life history parameters for Great Lakes Chinook Salmon and demonstrate that age and size at maturity are consistent with predictions using R0 (but not r or Vx) as the underlying fitness function

Impacts of Adfluvial Fish on the Ecology of Two Great Lakes Tributaries

Anadromous and adfluvial fish can transport high concentrations of nutrients and energy into streams during spawning runs. While the ecological effects of their spawning migrations are variable, in some instances these fish contribute to increased nutrient concentrations, primary productivity, invertebrate biomass, and resident fish growth and survival in the nutrient‐poor streams of the Pacific Northwest. In tributaries of the Great Lakes, the effects of introduced salmonid and native adfluvial fish are poorly documented. We conducted field experiments to determine the effects of a semelparous fall fish, Chinook salmon Oncorhynchus tshawytscha, and an iteroparous spring fish, steelhead O. mykiss, on the ecology and productivity of two tributaries to the Muskegon River, Michigan, a Lake Michigan tributary. We sampled stream biota and water chemistry before and after the introduction of Chinook salmon carcasses and eggs in the fall and steelhead eggs in the spring in a tributary stream with natural spawning runs and in another tributary stream without runs but with carcass and egg additions. There was no response in terms of invertebrate density or water chemistry to spawning migrations or salmon carcass introductions in either tributary. The density of resident brown trout Salmo trutta increased in both stream types after the introduction of salmon carcasses in the fall, and energy consumption increased after the addition of salmon eggs in the fall and spring in the manipulated stream. Based on stomach content analysis, fish that had eggs in their stomachs also consumed more energy than fish that did not consume eggs. The results suggest that adfluvial fish may affect some tributaries of the Great Lakes by providing high‐energy food sources to resident stream fish, but the potential effect of this egg consumption on resident fish growth and survival requires more research.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141037/1/tafs1670.pd

Influence of Predation Mortality on Survival of Chinook Salmon Parr in a Lake Michigan Tributary

Predation mortality among Chinook salmon Oncorhynchus tshawytscha parr can act at small spatiotemporal scales and cause variability in parr survival and potential recruitment. We analyzed predator diets and multiplied per capita consumption rates by predator population estimates to evaluate the relative effect of predation by stocked sport fishes on the variability in survival of Chinook salmon parr in the Muskegon River, Michigan, from 2004 to 2007. Brown trout Salmo trutta were a major predator of Chinook salmon parr, consuming from 15% to 34% of the total number available, while walleyes Sander vitreus consumed from 0.2% to 15%. Walleyes also consumed large quantities of brown trout and rainbow trout O. mykiss. Brown trout predation on Chinook salmon parr was largely dependent on parr size, while walleye predation was buffered by the availability of rainbow trout and brown trout. Predation mortality appeared to be responsible for a more than three‐fold difference in the survival of Chinook salmon parr in the Muskegon River. The vulnerability of Chinook salmon parr to predation appeared to be controlled by parr growth rates, brown trout stocking dates, and the number of brown trout stocked. Fishery regulations to manipulate piscivore abundance may lead to higher survival and lower variability in the survival of Chinook salmon parr.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141027/1/tafs0147.pd

Hatch Dates, Growth, Survival, and Overwinter Mortality of Age‐0 Alewives in Lake Michigan: Implications for Habitat‐Specific Recruitment Success

Alewives Alosa pseudoharengus are key components of Laurentian Great Lakes ecosystems and spawn in multiple habitat types. Exploration of alewife early life history dynamics within these different habitats should help identify important recruitment processes. During 2001‐2003, we quantified physical (temperature, transparency) and biotic (chlorophyll a, zooplankton densities) habitat factors and collected age‐0 alewives (using ichthyoplankton nets and trawls) in a nearshore region of Lake Michigan and Muskegon Lake, Michigan (a drowned river mouth lake connected to Lake Michigan). We characterized alewife hatch dates, individual condition, growth, mortality, and size‐dependent overwinter survival to infer differences in habitat‐specific recruitment success. Temperature, turbidity, chlorophyll‐a concentrations, and densities of zooplankton prey were consistently higher in Muskegon Lake than in nearshore Lake Michigan. On average, young alewives in Muskegon Lake hatched earlier, grew faster, were in better condition (based on a biphasic length‐weight relationship), and had greater survival than alewives in Lake Michigan. By the end of the growing season, young alewives in Muskegon Lake obtained a larger size than those residing in nearshore Lake Michigan, suggesting that they were more likely to survive through winter (a period of intense size‐selective mortality) and ultimately recruit to the adult population.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141621/1/tafs1298.pd

Methodological Bias in Estimates of Strain Composition and Straying of Hatchery‐Produced Steelhead in Lake Michigan Tributaries

Steelhead Oncorhynchus mykiss were first introduced into the Great Lakes in the late 1800s. Subsequently, natural recruitment of steelhead from spawning runs in streams across the basin has been regularly supplemented by hatchery production of strains derived from widely dispersed locales within the species’ native range. Estimates of hatchery contributions to the spawning runs of naturalized populations may be underrepresented by observations of marked fish, as not all hatchery fish are marked prior to release. To assess the potential bias in estimates of the hatchery contribution to steelhead spawning runs in four major rivers in Michigan, we used scale pattern analysis (SPA) to identify nonmarked hatchery fish and multilocus genotypes to estimate the proportional contributions of each hatchery strain to spawning runs. The four hatchery strains currently stocked are significantly genetically distinct (mean FST = 0.077), making it possible to identify specific strains by use of likelihood‐based assignment tests. The differences between direct (mark observations) and indirect (SPA and genetic analysis) estimates of hatchery contribution were mainly due to variations in the percentage of hatchery fish marked by states prior to release and the potential for confusion between certain marks and injuries. By combining direct and indirect assessment methodologies, we estimated that the percentage of hatchery fish returning to the four rivers ranged from 13% to 31% of total spawning runs. The large contribution of hatchery fish to nonstocked rivers differed significantly from expectations of strain‐specific stocking rates across the Lake Michigan basin and for individual streams, indicating high amounts of straying into Michigan streams.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141020/1/nafm1288.pd

Development of a risk assessment framework to predict invasive species establishment for multiple taxonomic groups and vectors of introduction

A thorough assessment of aquatic nonindigenous species’ risk facilitates successful monitoring and prevention activities. However, species- and vector-specific information is often limited and difficult to synthesize across a single risk framework. To address this need, we developed an assessment framework capable of estimating the potential for introduction, establishment, and impact by aquatic nonindigenous species from diverse spatial origins and taxonomic classification, in novel environments. Our model builds on previous approaches, while taking on a new perspective for evaluation across species, vectors and stages to overcome the limitations imposed by single species and single vector assessments. We applied this globally-relevant framework to the Laurentian Great Lakes to determine its ability to evaluate risk across multiple taxa and vectors. This case study included 67 aquatic species, identified as “watchlist species” in NOAA’s Great Lakes Aquatic Nonindigenous Species Information System (GLANSIS). Vectors included shipping, hitchhiking/fouling, unauthorized intentional release, escape from recreational or commercial culture, and natural dispersal. We identified potential invaders from every continent but Africa and Antarctica. Of the 67 species, more than a fifth (21%) had a high potential for introduction and greater than 60% had a moderate potential for introduction. Shipping (72%) was the most common potential vector of introduction, followed by unauthorized intentional release (25%), hitchhiking/fouling (21%), dispersal (19%), stocking/planting/escape from recreational culture (13%), and escape from commercial culture. The ability to assess a variety of aquatic nonindigenous species from an array of potential vectors using a consistent methodology is essential for comparing likelihoods of introduction, establishment, and impact. The straightforward design of this framework will allow its application and modification according to policy priorities by natural resource managers. The ability to use a variety of information sources facilitates completion of assessments despite the paucity of data that often plagues aquatic nonindigenous species management

Estimating Seasonal Movements of Chinook Salmon in Lake Huron from Efficiency Analysis of Coded Wire Tag Recoveries in Recreational Fisheries

The decline of hatchery‐reared Chinook salmon Oncorhynchus tshawytscha stocks in Lakes Huron and Michigan during the 1980s prompted mass‐tagging programs to investigate reproduction, poststocking survival, and movements. In Lake Huron, millions of smolts implanted with coded wire tags (CWTs) were released in Michigan waters and recovered from charter and noncharter fisheries, surveys, and weirs. Using generalized linear models (GLMs), we investigated Chinook salmon seasonal movements based on the spatial and temporal distributions of recoveries by fishing trips in U.S. recreational fisheries and recovery efficiency. We used models incorporating area, month, year, and recovery source; creel‐clerk and “headhunter” (CWT collection specialist) samples; and charter captain reports. We implemented models for recoveries regardless of release area and from one particular area. All model predictors and interactions between month and area were significant. The variation in recovery levels among recovery sources was larger than temporal or spatial variation. Headhunters were 7 times more efficient than captains in recovering CWTs from charter‐boat catch and 11 times more efficient than clerks in recovering CWTs from non‐charter‐boat catch; this was due to the higher catches experienced in charter than in noncharter trips and to different recovery program goals. The spatial and temporal distribution of GLM‐standardized recovery levels suggested that Chinook salmon released along the western coast of Lake Huron moved near shore during early spring and north during summer, returning mostly to nearby stocking areas in summer and fall. To complement our GLM analysis, we evaluated the distributions of CWT salmon released and recovered in U.S. and Canadian waters by all sources. Data supported previous conclusions on longitudinal movements and indicated that in spring fish moved from eastern locations to near shore in western Lake Huron then back to overwinter locations in autumn. These movement patterns coincided with seasonal prey species concentrations and favorable temperatures. The implications of our results for salmon fisheries management and the design of future tagging studies are discussed.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142006/1/nafm0792.pd

Relationship between Surface Water Temperature and Steelhead Distributions in Lake Michigan

Salmonines support valuable recreational fisheries and are the predominant predators in the open waters of the Great Lakes, yet the spatial distributions of salmonines in these systems have not been fully documented. We analyzed the horizontal distributions of steelhead Oncorhynchus mykiss in Lake Michigan from 1992 to 1997 and related these distributions to mean surface temperature and temperature variation. We used angler catch rate data from Lake Michigan natural resources agencies to index the spatial and temporal distributions of steelhead and obtained surface water temperature data from advanced very‐high‐resolution radiometer satellite imagery through the National Oceanic and Atmospheric Administration’s CoastWatch Program. During most months, steelhead catch rates were negatively related to surface temperature and were highest in areas of high temperature variation (i.e., vertical thermal fronts and upwelling zones) where thermal conditions and prey densities may have been optimal for growth. Our results demonstrate how remotely sensed and creel survey data can be integrated to allow for more effective exploitation and management of lakewide fish stocks while enabling researchers to generate and test hypotheses regarding the spatial distributions of fish populations.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141241/1/nafm0211.pd