Asynchrony in the inter-annual recruitment of lake whitefish Coregonus clupeaformis in the Great Lakes region

Spatially separated fish populations may display synchrony in annual recruitment if the factors that drive recruitment success, particularly abiotic factors such as temperature, are synchronised across broad spatial scales. We examined inter-annual variation in recruitment among lake whitefish (Coregonus clupeaformis) populations in lakes Huron, Michigan and Superior using fishery-dependent and -independent data from 1971 to 2014. Relative year-class strength (RYCS) was calculated from catch-curve residuals for each year class across multiple sampling years. Pairwise comparison of RYCS among datasets revealed no significant associations either within or between lakes, suggesting that recruitment of lake whitefish is spatially asynchronous. There was no consistent correlation between pairwise agreement and the distance between datasets, and models to estimate the spatial scale of recruitment synchrony did not fit well to these data. This suggests that inter-annual recruitment variation of lake whitefish is asynchronous across broad spatial scales in the Great Lakes. While our method primarily evaluated year-to-year recruitment variation, it is plausible that recruitment of lake whitefish varies at coarser temporal scales (e.g. decadal). Nonetheless, our findings differ from research on some other Coregonus species and suggest that local biotic or density-dependent factors may contribute strongly to lake whitefish recruitment rather than inter-annual variability in broad-scale abiotic factors.

Recruitment dynchrony of Yellow Perch (Perca flavescens, Percidae) in the Great Lakes Region, 1966-2008

Population-level reproductive success (recruitment) of many fish populations is characterized by high inter-annual variation and related to annual variation in key environmental factors (e.g., climate). When such environmental factors are annually correlated across broad spatial scales, spatially separated populations may display recruitment synchrony (i.e., the Moran effect). We investigated inter-annual (1966–2008) variation in yellow perch (Perca flavescens, Percidae) recruitment using 16 datasets describing populations located in four of the five Laurentian Great Lakes (Erie, Huron, Michigan, and Ontario) and Lake St. Clair. We indexed relative year class strength using catch-curve residuals for each year-class across 2–4 years and compared relative year-class strength among sampling locations. Results indicate that perch recruitment is positively synchronized across the region. In addition, the spatial scale of this synchrony appears to be broader than previous estimates for both yellow perch and freshwater fish in general. To investigate potential factors influencing relative year-class strength, we related year-class strength to regional indices of annual climatic conditions (spring-summer air temperature, winter air temperature, and spring precipitation) using data from 14 weather stations across the Great Lakes region. We found that mean spring-summer temperature is significantly positively related to recruitment success among Great Lakes yellow perch populations.

Why this flip wasn’t a flop: What the numbers don’t tell you about flipped classes

This paper details the conversion of a large, required Civil Engineering fluid mechanics course into a more student-centered, active learning-oriented course through the flipping of one lecture per week. In the flipped class, students collaboratively solve homework problems in groups while receiving “expert” feedback from instructors and TAs. To offset the lost lectures, some course material that has been delivered in traditional lectures has been placed online in the form of short videos and textbook readings, with low-stakes quizzes for assessment.

Student learning gains were quantitatively assessed by comparing quiz and final exam scores for three semesters (1 pre-flip and 2 post-flip). To maintain some element of consistency across the course transformation, a comprehensive, multiple-choice final exam has served to provide quantitative metrics on which the course improvement can be gaged. In addition, quiz questions remained relatively similar across semesters. One-way ANOVAs revealed a statically significant difference on quiz performance, with post-flip students performing better than those in pre-flip semesters. In addition, students in the final iteration of the course transformation significantly outperformed previous students on final exams by about 7%.

Taken together, the numbers suggest that the process of flipping a large fluid mechanics course is associated with small but positive improvements to quiz and final exam performance. However, it is best to rely on other indicators beyond course performance in order to more accurately depict the impact of a course transformation. To supplement the results of the quantitative analyses, student comments about the course and instructor observations of the transformation implementation were assessed. Students found the work sessions to be very effective, enjoyed collaborating with peers and the instructor, and thought the online videos were helpful. The instructor indicated that the benefits of the flipped class include the following: heightened student engagement during class periods; greatly increased instructor awareness of student perceptions, challenges, personal issues, and conceptual bottlenecks; eventual reduction in instructor preparation time; improved instructor-student relationships; and a better focus on more important course objectives.

Challenges and opportunities for recruiting students to undergraduate civil engineering programs

Society needs more civil engineers, with the projected near-term need for civil engineers greater than any other engineering discipline. Ailing national infrastructure and projected retirement rates have led to job projections suggesting that the near-term need for civil engineering graduates is almost double that of any other engineering discipline. This need, combined with other attractive attributes of civil engineering, should make civil engineering a top engineering major at many undergraduate universities. In spite of the career opportunities readily available to graduating civil engineers, and in spite of the general increasing trend in the number of total undergraduate engineering students, undergraduate civil engineering programs, taken as a whole, have struggled to maintain and grow their numbers. Individually, many undergraduate programs struggle to recruit students to civil engineering, and this poses a major problem not only to individual programs but to the profession itself.

We analyzed a set of civil engineering student surveys to determine the factors, attitudes, and experiences that typically lead students to select careers in civil engineering and found several common responses, many of which can be leveraged to promote the discipline. The data suggest that about one half of our students pre-select civil engineering prior to beginning as first-year engineering students, and that the top reasons for their selection of civil engineering include: a passion for building things; a desire to make a difference; flexible career options; and a love for math and science (which presumably is shared by young engineers of all disciplines).

We present data from another survey carried out with undergraduate students in other engineering majors, as to why students select other disciplines and how civil engineering is perceived. This survey highlights several perceptions about civil engineering among first year engineers. These include the misperception of civil engineering as a narrow field focused only around bridges, buildings, and roads, as well as the perception of civil engineers earning low salaries.

These student perceptions pose challenges to civil engineering recruiters, but also afford opportunities for clarification and improved recruitment, especially for programs that allow students to select their engineering discipline during their first year of college. We conclude this paper with a set of talking points we have deployed at our own university that directly address the above challenges and opportunities.

Engineering faculty on writing: What they think and what they want

Writing has been identified as an important skill for engineers, and while faculty generally agree that writing should be included in the engineering classroom, there are many barriers that may discourage faculty to do so. This survey explored how faculty are including writing in their classes, what barriers they face, and also asks faculty what resources they would like so that the inclusion of writing could be more realistic and feasible.

In terms of their approaches to incorporating writing in their courses, a majority of respondents reported sometimes or frequently assigning writing in the following types of assignments: project documentation, written explanations of homework, and short-answer questions on tests and quizzes. A majority of respondents also reported frequent use of grading rubrics for writing, as well as specifying the audiences for whom students should target their writing.

Respondents identified their top challenges to including writing in their courses, including large enrollments, lack of time, and lack of teaching assistants competent to assess writing. To address these challenges, the most favored suggestion was having teaching assistants trained to assess writing, followed by expanding the availability of writing resources for faculty and students. Additionally, the issue of student preparation was brought up on numerous occasions; faculty stated that previous negative experiences with student writing hindered faculty from including writing assignments in their courses.

In a perfect world, all faculty would have teaching assistants that were trained in teaching engineering writing. However, other more realistic resources include providing rubrics and sample work on an accessible and easy to use website. This paper reports on the faculty survey about writing and also how it relates the larger project that includes providing these important resources to faculty.

Writing to learn engineering: Identifying effective techniques for the integration of written communication into engineering classes and curricula (NSF RIGEE project)

The inclusion of writing-based exercises in technical courses has multiple learning benefits to students. Writing exercises not only serve to improve students’ written communication skills (i.e., “learn to write”), but can also be leveraged to develop critical thinking skills and promote deeper understanding of technical concepts (i.e., “write to learn”). Nevertheless, while writing-intensive assignments are relatively common in upper-level technical courses, especially in the form of laboratory and project reports, writing is often absent in the larger, required core courses that are taken by large numbers of engineering students. This is a missed opportunity to both enhance student learning of technical content as well as missed chance for students to have more writing practice. This NSF RIGEE project aims to investigate, support, and promote the inclusion of writing in technical courses, particularly introductory and core courses. Analysis of an engineering instructor survey carried out as part of the project revealed concerns about assessment and feedback on students’ written work. Additionally, writing instructors were interested in the creation of guides designed to aid instructors in the creation and tailoring of writing prompts for use in their existing technical courses. This paper introduces preliminary resources we have created in response to these stated needs, in order to help instructors develop, implement, and assess writing assignments in their courses. Current resources include a decision tree to help instructors create writing assignments within their classrooms and assessment rubrics that can easily be adapted to specific writing assignment needs. Resources will continue to be developed during the remainder of the project, culminating in a writing website geared towards instructors.

Testing for synchrony in recruitment among four Lake Michigan fish species

In the Great Lakes region, multiple fish species display intraspecific spatial synchrony in recruitment success, with interannual climate variation hypothesized as the most likely driver. In Lake Michigan, we evaluated whether climatic or other physical variables could also induce spatial synchrony across multiple species, including bloater (Coregonus hoyi), rainbow smelt (Osmerus mordax), yellow perch (Perca flavescens), and alewife (Alosa pseudoharengus). The residuals from stock–recruitment relationships revealed yellow perch recruitment to be correlated with recruitment of both rainbow smelt (r = 0.37) and alewife (r = 0.36). Across all four species, higher than expected recruitment occurred in 5 years between 1978 and 1987 and then switched to lower than expected recruitment in 5 years between 1996 and 2004. Generalized additive models revealed warmer spring and summer water temperatures and lower wind speeds corresponded to higher than expected recruitment for the nearshore-spawning species, and overall variance explained ranged from 14% (yellow perch) to 61% (alewife). For all species but rainbow smelt, higher recruitment also occurred in extremely high or low years of the North Atlantic Oscillation index. Future development of indices that describe the physical Great Lakes environment could improve understanding of how climate can synchronize fish populations within and across species.

Logarithmic velocity structure in the deep hypolimnetic waters of Lake Michigan

The characteristics of the bottom boundary layer are reported from a Lake Michigan field study carried out in deep hypolimnetic waters (55 m depth) during the stratified period (June–September 2012). The sandy substrate at the measurement site was densely covered with invasive quagga mussels (mean size: 1.6 cm; mean density: 10,000 mussels m−2). The measurements reveal a sluggish, compact bottom boundary layer, with flow speeds at 1 mab less than 5 cm s−1 for most of the period, and a dominance of subinertial energy. A downwelling event caused the largest currents observed during the deployment (10 cm s−1 at 1 mab) and a logarithmic layer thickness of 15 m. In spite of the weak flow, logarithmic profile fitting carried out on high-resolution, near-bed velocity profiles show consistent logarithmic structure (90% of profiles). Flow was dominated by subinertial energy but strong modified by near-inertial waves. Fitted drag coefficients and roughness values are Cd1m = 0.004 and Z0 = 0.12 cm, respectively. These values increase with decreasing flow speed, but approach canonical values for 1 mab flow speeds exceeding 4 cm s−1. The estimated vertical extent of the logarithmic region was compact, with a mean value of 1.2 m and temporal variation that is reasonably described by Ekman scaling, 0.07 u*/f, and the estimated overall Ekman layer thickness was generally less than 10 m. Near-bed dissipation rates inferred from the law of the wall were 10−8−10−7 W kg−1 and turbulent diffusivities were 10−4−10−3 m2s−1.

Water quality estimation of river plumes in southern Lake Michigan using hyperion

This study focuses on the calibration of an existing bio-geo-optical model for studying the spatial variability of water quality parameters including chlorophyll (CHL), non-algal particles (NAP), and colored dissolved organic matter (CDOM) in episodic river plumes. The geographic focus is the St. Joseph River plume in southern Lake Michigan. One set of EO-1 Hyperion imagery and one set of boat-based spectrometer measurements were successfully acquired to capture episodic plume events. Coincident water quality measurements were also collected during these plume events. In this study, a database of inherent optical properties (IOPs) measurements and spectral signatures was generated and used to calibrate the bio-geo-optical model. Field measured concentrations of NAP and CDOM at 67% of the sampled sites fall within one standard deviation of the retrieved means using the spectrometer measurements. The percentage of sites, 88%, is higher for the estimation of CHL concentrations. Despite the dynamic nature of the observed plume and the time lag during field sampling, 77% of the sampled sites show field measured CHL and NAP concentrations falling within one standard deviation of the Hyperion derived values. The spatial maps of water quality parameters generated from the Hyperion image provided a synoptic view of water quality conditions. Results show that concentrations of NAP, CHL, and CDOM were more than three times higher in conjunction with river outflow, and inside the river plumes, than in ambient water. It is concluded that the storm-initiated plume is a significant source of sediments, carbon and chlorophyll to Lake Michigan.

Shear dispersion from near‐inertial internal Poincaré waves in large lakes

In this work, we study mixed layer lateral dispersion that is enhanced by near-inertial internal Poincaré waves in the offshore region of a large stratified lake, Lake Michigan. We examine the hypothesis that the vertical shear created by near-inertial internal Poincaré waves is not only an energy source for vertical mixing in the thermocline and mixed layer, but also enhances horizontal dispersion via an unsteady shear flow dispersion mechanism. Complex empirical orthogonal function analysis reveals that the dominant shear structure is observed to mirror the thermal structure, with the location of maximum shear gradually lowered as the mixed layer deepens. This changing structure of shear and vertical mixing produces different characteristics in shear flow dispersion between the early and later stratified periods. The estimated depth-averaged surface layer vertical turbulent diffusivity grows from 10-5 m2s-1 to 10-3 m2s-1 over the stratified period, and the associated lateral dispersion coefficients are estimated as 0.1 – 40 m2s-1. The Poincaré waves are found to enhance greatly lateral dispersion for times less than the inertial period following release. In contrast, sub-inertial shear is the dominant mechanism responsible for shear dispersion for times greater than the inertial period. A simple approximation of the dispersion coefficient for lateral dispersion is developed, which scales as the product of surface current velocity (or wind friction velocity) and mixed layer depth. The calculated dispersion coefficients agree well with Okubo’s diffusion diagram for times up to a week, which suggests that unsteady shear dispersion is a plausible mechanism to explain observed dispersion rates in the mixed layer for early times after release.