Mechanisms Affecting Recruitment of Yellow Perch in Lake Michigan

Report issued on: August 2001INHS Technical Report prepared for Great Lakes Fishery Trus

Integration of technologies for understanding the functional relationship between reef habitat and fish growth and production

Functional linkage between reef habitat quality and fish growth and production has remained elusive. Most current research is focused on correlative relationships between a general habitat type and presence/absence of a species, an index of species abundance, or species diversity. Such descriptive information largely ignores how reef attributes regulate reef fish abundance (density-dependent habitat selection), trophic interactions, and physiological performance (growth and condition). To determine the functional relationship between habitat quality, fish abundance, trophic interactions, and physiological performance, we are using an experimental reef system in the northeastern Gulf of Mexico where we apply advanced sensor and biochemical technologies. Our study site controls for reef attributes (size, cavity space, and reef mosaics) and focuses on the processes that regulate gag grouper (Mycteroperca microlepis) abundance, behavior and performance (growth and condition), and the availability of their pelagic prey. We combine mobile and fixed-active (fisheries) acoustics, passive acoustics, video cameras, and advanced biochemical techniques. Fisheries acoustics quantifies the abundance of pelagic prey fishes associated with the reefs and their behavior. Passive acoustics and video allow direct observation of gag and prey fish behavior and the acoustic environment, and provide a direct visual for the interpretation of fixed fisheries acoustics measurements. New application of biochemical techniques, such as Electron Transport System (ETS) assay, allow the in situ measurement of metabolic expenditure of gag and relates this back to reef attributes, gag behavior, and prey fish availability. Here, we provide an overview of our integrated technological approach for understanding and quantifying the functional relationship between reef habitat quality and one element of production – gag grouper growth on shallow coastal reefs

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

Alewife planktivory controls the abundance of two invasive predatory cladocerans in Lake Michigan

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74873/1/j.1365-2427.2007.01728.x.pd

Lake Michigan’s suitability for bigheaded carp: The importance of diet flexibility and subsurface habitat

As bighead (Hypophthalmichthys nobilis) and silver carp (Hypophthalmichthys molitrix)—collectively bigheaded carp (BHC)—arrive at Lake Michigan’s doorstep, questions remain as to whether there is sufficient food to support these invasive filter‐feeding fishes in the upper Laurentian Great Lakes. Previous studies suggest that suitable BHC habitat is limited to a few productive, nearshore areas. However, those studies did not consider the influence of BHC’s diet plasticity or the presence of spatially‐discrete subsurface prey resources. This study aimed to characterise Lake Michigan’s suitability for BHC and evaluate the importance of these considerations in habitat suitability assessments.We used simulated outputs of prey biomass (phytoplankton, zooplankton, and detritus) and water temperature from a three‐dimensional biophysical model of Lake Michigan to evaluate growth rate potential (GRP, quantitative index of habitat suitability) of adult BHC throughout the entire volume of the lake. Our GRP model applied a foraging model and a bioenergetics model to translate prey concentrations and water temperatures into habitat quality indexed by individual fish growth rate. We defined suitable habitat as habitats that can support GRP ≥ 0 g g−1 day−1. We developed six feeding scenarios to evaluate the impact of diet flexibility and subsurface prey resources on suitable habitat quantity. Scenarios were defined by the number of prey types the fish could consume and the depths at which they could feed (surface or whole water column).Consistent with previous studies, we found that habitats with the highest quality were concentrated near river mouths and in eutrophic areas of Green Bay. However, in contrast to previous studies, we found suitable offshore habitat for bighead carp owing to our added considerations of diet plasticity and subsurface prey resources. For silver carp, these considerations extended suitable habitat within Green Bay and in some tributary‐influenced nearshore areas, but offshore areas remained predominantly unsuitable in all feeding scenarios. Differences in simulated habitat suitability between these two species probably reflect differences in energy density and mass of the specific fishes we used in our model. However, reports of these two species in environments where they coexist indicate that bighead carp grow at faster rates than silver carp, as our model simulated.Our vertical analysis at Muskegon, MI, U.S.A. indicates that subsurface temperature and prey biomass are not only sufficient to support bighead carp growth but provide maximum habitat quality during late summer stratification.Overall, our study demonstrates that BHC are capable of surviving and growing in much larger areas of Lake Michigan than predicted by previous studies, and thus suggests that the risk of establishment is not sufficiently reduced by low plankton concentrations. Maps generated by our model identified the potential for cross‐lake migration corridors that may facilitate and accelerate lake‐wide movements. We believe these maps could be used to prioritise surveillance protocols by identifying areas to which BHC might spread upon entering the lake. More broadly, this research demonstrates how the physiology and trophic ecology of BHC contributes to their high invasive capacity and can permit their survival in novel environments.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/151968/1/fwb13382_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/151968/2/fwb13382.pd

Forecasting the Impacts of Silver and Bighead Carp on the Lake Erie Food Web

Nonindigenous bigheaded carps (Bighead Carp Hypophthalmichthys nobilis and Silver Carp H. molitrix; hereafter, “Asian carps” [AC]) threaten to invade and disrupt food webs and fisheries in the Laurentian Great Lakes through their high consumption of plankton. To quantify the potential effects of AC on the food web in Lake Erie, we developed an Ecopath with Ecosim (EwE) food web model and simulated four AC diet composition scenarios (high, low, and no detritus and low detritus with Walleye Sander vitreus and Yellow Perch Perca flavescens larvae) and two nutrient load scenarios (the 1999 baseline load and 2× the baseline [HP]). We quantified the uncertainty of the potential AC effects by coupling the EwE model with estimates of parameter uncertainty in AC production, consumption, and predator diets obtained using structured expert judgment. Our model projected mean ± SD AC equilibrium biomass ranging from 52 ± 34 to 104 ± 75 kg/ha under the different scenarios. Relative to baseline simulations without AC, AC invasion under all detrital diet scenarios decreased the biomass of most fish and zooplankton groups. The effects of AC in the HP scenario were similar to those in the detrital diet scenarios except that the biomasses of most Walleye and Yellow Perch groups were greater under HP because these fishes were buffered from competition with AC by increased productivity at lower trophic levels. Asian carp predation on Walleye and Yellow Perch larvae caused biomass declines among all Walleye and Yellow Perch groups. Large food web impacts of AC occurred in only 2% of the simulations, where AC biomass exceeded 200 kg/ha, resulting in biomass declines of zooplankton and planktivorous fish near the levels observed in the Illinois River. Our findings suggest that AC would affect Lake Erie's food web by competing with other planktivorous fishes and by providing additional prey for piscivores. Our methods provide a novel approach for including uncertainty into forecasts of invasive species' impacts on aquatic food webs. Received December 6, 2014; accepted July 15, 201

Non-linear Structure Formation in Cosmologies with Early Dark Energy

We argue that a few per cent of "Early Dark Energy" can be detected by the statistics of nonlinear structures. The presence of Dark Energy during linear structure formation is natural in models where the present tiny Dark-Energy density is related to the age of the Universe rather than a new fundamental small parameter. Generalisation of the spherical collapse model shows that the linear collapse parameter delta_c is lowered. The corresponding relative enhancement of weak gravitational lensing on arc-minute scales lowers the value of sigma_8 inferred from a given lensing amplitude as compared to Lambda-CDM. In presence of Early Dark Energy, structures grow slower, such that for given sigma_8 the number of galaxies and galaxy clusters is substantially increased at moderate and high redshift. For realistic models, the number of clusters detectable through their thermal Sunyaev-Zel'dovich effect at redshift unity and above, e.g. with the Planck satellite, can be an order of magnitude larger than for Lambda-CDM.Comment: 10 pages, 12 figure