News & Press Releases

Department of Fisheries Oceanography "Application of optical and acoustic technologies to improve the understanding of fish behavior, ecology, and stock assessment." By: Christopher Rillahan Advisor: Dr. Pingguo He Committee Members Dr. Kevin D. E. Stokesbury, Dr. Steven X. Cadrin, Dr. Theodore Castro-Santos, and Dr. Kresimir Williams Tuesday January 7th, 2025 11:00 AM SMAST West 204 706 S. Rodney French Blvd, New Bedford and via Zoom Abstract: Marine species inhabit an extensive underwater environment that is largely inaccessible to humans. Consequently, we have relied on various technologies to study and manage the commercial and recreational species we depend on. Over the past century, there have been rapid advancements in optical and acoustic technology, which have coincided with an increased need for effective fisheries management. The ability to observe fish during the capture process has shed light on the role of fish behavior and the potential bias it introduces into fisheries data. Due to insufficient knowledge of most systems, scientific surveys and stock assessment models have traditionally relied on simplified assumptions about fish behavior. While it has been understood that fish have well-developed sensory systems, mobility, and complex life histories, the lack of information has limited their use in gear catchability, survey design, and assumptions about spatial and temporal population dynamics. This dissertation examines the use of optical and acoustic technology to address these limitations, improving the interpretative power of survey data and reducing potential bias. Baited remote underwater video systems (BRUVS) were employed in Chapter II to examine the role of a species' life history in the performance of traditional survey gears (e.g., fish pots and demersal otter trawls). The spatial distribution of black sea bass (Centropristis striata), a structure-oriented species, in Buzzards Bay was observed to vary depending on the survey gear. Conversely, scup (Stenotomus chrysops), a habitat-agnostic species, exhibited similar patterns across survey methods. Video observations of black sea bass documented an increasing affinity for structured habitats during the summer and fall. This shift in the spatial distribution of black sea bass dramatically affected the trawl survey data. Catch data from the spring trawl survey generally corresponded to the video and pot data with respect to the spatial distribution and population structure of both black sea bass and scup. Conversely, the fall trawl survey data starkly contrasted with the two other surveys, with few adult black sea bass catches. The lack of catch is presumably due to the shifting residence of black sea bass to rocky habitats, which are not sampled by the trawl and, therefore, unavailable to the survey. The shifting availability between the spring and fall trawl surveys presents an inaccurate picture of black sea bass abundance in Buzzards Bay....... ************ Join Zoom Meeting https://umassd.zoom.us/j/91787205979 Note: Meeting passcode required, email contact below to receive ************** To request the full abstract, Zoom passcode, or for any other questions, please email Callie Rumbut at c.rumbut@umassd.edu

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Financial Aid Services wants to remind all students to file their FAFSA! Join Financial Aid Services for FAFSA Help Labs in Foster 105 Jan 8, 2025, 3-4pm Contact Mark Yanni myanni@umassd.edu

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Department of Fisheries Oceanography "Portfolio Theory: an Important Tool For Ecosystem-Based Fisheries Management" By: Fiona Edwards Advisor: Steven X. Cadrin (University of Massachusetts Dartmouth) Committee Members Gavin Fay (University of Massachusetts Dartmouth), Lauran Brewster (University of Massachusetts Dartmouth), Jason Link (National Marine Fisheries Service) Thursday January 9th, 2025 1pm SMAST East 101-103 836 S. Rodney French Blvd, New Bedford and via Zoom Abstract: Traditional single-species fisheries management does not account for multi-species interactions and has not always performed well for avoiding overfishing or rebuilding many fisheries. Considering these interactions has become increasingly important for effectively managing fisheries because of climate change and divergent stock trends. Ecosystem-based fishery management (EBFM) is a more holistic approach to fisheries management which has gained traction over the last several decades. EBFM considers the biological, physical, and social-economic components which may influence fisheries. Implementing EBFM requires new tactics that can be informed by interdisciplinary research. One way risk associated with achieving a target reward has been analyzed in the finance field analysis is through portfolio optimization whereby the financial risk of a portfolio is minimized for given levels of return based on portfolio covariance. A set of fishery stocks landing values can be analyzed similarly to a set of financial assets in an investment portfolio. In this study, a candidate fisheries portfolio is analyzed for New England demersal species caught in the same fisheries. The sensitivity of this portfolio to data decisions such as species composition and time series length is investigated by developing efficient frontiers for different sets of fishery stocks and different time periods. Efficient frontiers were developed using portfolio optimization techniques from the finance field and adding harvest constraints to account for limits on harvesting in fisheries. Sensitivity analyses showed that risk estimates were sensitive to both species exclusion and time series selection. Examination of the changes in the frontiers to different periods of the time series characterized by regional shifts in management strategy allowed for evaluation of the degree of flexibility afforded to fishers during these times. Efficient frontier analyses based upon historic landings data indicated that the same target revenue could have been achieved with less or similar risk had a portfolio approach to management been taken for these species. Portfolio effects as applied to fisheries management can provide additional catch stability through increased diversification of multispecies fisheries and can reduce the risk of foregone revenue, all of which make it an important tool to consider for implementing EBFM. Join Zoom Meeting https://umassd.zoom.us/j/94065204146 Note: Meeting passcode required. To request the Zoom passcode or for any other questions, please email Callie Rumbut at c.rumbut@umassd.edu

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Financial Aid Services wants to remind all students to file their FAFSA! Join Financial Aid Services for FAFSA Help Labs in Foster 105 Jan 10, 2025, 3-4pm Contact Mark Yanni myanni@umassd.edu

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A virtual information session on the graduate business programs at UMass Dartmouth. - Explore various business graduate programs - Find out how you can complete your degree at your pace - Discover how you can concentrate in a field that meets your interests and career goals - Learn about Charlton's more flexible GMAT waivers - Understand the value of Charlton College of Business degree - Hear about the next steps to enrollment This event designed to answer questions you may have about the various degree and certificate programs.

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Topic: Experimental Study on Fluid-Structure Interactions of Highly Flexible High Aspect Ratio Wings Location: SENG 110 (Materials Science Lab) Abstract: High aspect-ratio wings have garnered substantial interest due to their aerodynamic benefits, particularly their ability to reduce undesirable tip vortex effects, thereby achieving a superior lift-to-drag ratio compared to lower aspect-ratio wings. However, this structural configuration inherently results in increased flexibility, which can lead to aeroelastic instabilities such as flutter, divergence, and control reversal. Flutter instability, in particular, poses a critical design challenge due to its potential to cause catastrophic failure. While extensive research has addressed both linear and nonlinear dynamics related to the onset of flutter in high aspect-ratio wings, few studies have systematically investigated the post-flutter behavior. Understanding this post-flutter response is essential for predicting and managing complex flutter phenomena, thereby enhancing design safety and resilience. The objective of this study is to fill the gap by conducting a thorough experimental study of the interaction between fluid and structure in highly flexible wings during the post-critical phase. When studying the performance of high aspect-ratio wings, it's crucial to recognize the Fluid-Structure Interaction (FSI) at play. This involves a full coupling between the fluid dynamics and structural mechanics. Therefore, a comprehensive understanding demands a simultaneous exploration of both the structural and flow aspects, allowing for a full understanding of the interaction dynamics. The majority of studies focusing on flow visualization around airfoils have been conducted on either stationary airfoils or those with limited degrees of freedom. While the study of flow around rigid airfoils has contributed to our fundamental understanding, the dynamics of flow around rigid wings differ significantly from the complex, three-dimensional dynamics seen in flexible wings. Recent efforts have offered insights into how wing flexibility influences surrounding flow; however, the complexity of 3-D flow physics and its interaction with flexible wing structures remains unexplored, and this gap is further compounded by a shortage of integrated studies that concurrently examine both structural and fluid dynamics. Additionally, the lack of comprehensive experimental data limits the ability of numerical models to accurately capture the three-dimensional flow behavior around flexible wings. This research presents a detailed experimental investigation of the flow-induced vibration characteristics of a highly flexible wing, focusing on parameters such as vibration amplitude, dominant frequencies, mode shapes, and mean deflection, with special attention to the post-flutter phase. A modal analysis-based method, along with digital image correlation (DIC) technique, was employed to measure the wings structural response. Concurrently, flow behavior around the wing was analyzed quantitatively using time-resolved volumetric particle tracking velocimetry (TR-PTV) and two-dimensional particle image velocimetry (TR-2D-PIV) techniques. The study examines a wide range of angles of attack and flow velocities to provide a comprehensive view of fluid-structure interactions in high aspect-ratio wings under varied operational conditions. Our preliminary results show that changes in the angle of attack significantly affect the onset of limit cycle oscillations, as well as the dominant oscillation frequencies and mode shapes. At higher flow velocities and angles of attack, a significant increase in tip deflection was observed, while minimal deflection occurred at lower or zero angles of attack. By employing the Q-criterion, we identified and visualized the coherent structure of vortices, uncovering the substantial influence of angle of attack and flow velocity on their behavior. At lower angles of attack, the leading edge and trailing edge vortices were almost vertical, with minimal interaction with the tip vortex. As the angle of attack increased, these vortices tilted to follow the wing's curvature and became larger and stronger, interacting more with the tip vortex. Our results show that at low-amplitude oscillations, the vortices dissipated quickly, whereas at high-amplitude oscillations, they were able to sustain their coherence for a longer duration, influencing the downstream flow pattern. ADVISOR(S): Dr. Banafsheh Seyed-aghazadeh, Department of Mechanical Engineering (b.aghazadeh@umassd.edu) COMMITTEE MEMBERS: Dr. Mehdi Raessi, Department of Mechanical Engineering and Dr. Hangjian Ling, Department of Mechanical Engineering and Dr. Geoffrey Cowles, SMAST Department of Fisheries Oceanography All EAS Students are ENCOURAGED to attend.

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