College of Engineering at UMass Dartmouth

Department of Fisheries Oceanography

"An Overview of the U.S. Lobster Stock Assessment Process "

Tracy Pugh, Invertebrate Fisheries Project Leader, Mass Division of Marine Fisheries

Wednesday, March 19, 2025
3pm-4pm
SMAST E 101-102 and via Zoom

Abstract:

American lobster (Homarus americanus) is managed in the U.S. by the Atlantic States Marine Fisheries Commission (ASMFC) under the authority of the Atlantic Coastal Fisheries Cooperative Management Act (ACFCMA), along with 27 other nearshore species of commercial or recreational importance. Each species (or group of species) has at least a management board and one or more advisory and/or technical committees. The US Lobster Stock Assessment is conducted by the Lobster Stock Assessment Subcommittee (SAS), which is comprised of species experts and stock assessment specialists. The assessment occurs roughly every 4-5 years, and the SAS is currently working on the 2025 assessment, which will be submitted to an external peer review this summer then finalized and presented to the Board this fall. The lobster assessment focuses on population change over time and stock status is determined using trend-based reference points. The assessment is primarily driven by a length-based model which operates in quarterly time steps. Data provided to the model include basic life history information, multiple fishery-independent surveys, and fishery-dependent landings data as well as sex ratio and length composition data collected by at-sea samplers. The SAS also compiles empirical stock indicators which are independent of the model and provide additional information on the health of each stock. This presentation will provide an overview of the US lobster stock assessment process, some details on the types of data included and how they are used, and will describe assessment outputs and stock status as of the previous (2020) assessment. .

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EAS PhD Dissertation Defense by Cory Hoi (CSE Option/Mechanical Engineering)

Date: March 20, 2025
Time: Noon-2pm

Topic: Advancing Surfactant Replacement Therapy: Novel Computational Simulations of Multi-Phase Flow of Non-Newtonian and Newtonian Fluids

Location: SENG 110
Zoom link: Please contact Dr. Raessi (mraessi@umassd.edu).

Abstract:

Prematurely born infants are at risk of developing respiratory distress syndrome (RDS) due to a deficiency of pulmonary surfactant. Without this surface tension reducing molecule, large pressure gradients in the lung can lead to atelectasis and increase mortality risk. Medical practitioners treat RDS with surfactant replacement therapy (SRT), a procedure which reintroduces exogenous surfactant into the airway. However, SRT has a 35% non-response rate, largely due to the challenges of delivering the surfactant uniformly, and reaching the distal regions of the lung.

Current research has focused on understanding the physics of Newtonian surfactant delivery, specifically how the plug propagates along the airway, deposits its mass onto the airway wall, and splits at each airway bifurcation. However, in practice, many of the surfactants used exhibit non-Newtonian shear thinning behavior. Additionally, the mucus in the lung forms a bilayer of periciliary fluid, composed of mostly Newtonian fluid. This complexity introduces additional challenges for computational simulations, as no established methods currently exist for simulating non-Newtonian liquid interactions, with Newtonian liquid, and gas.

This thesis addresses the current gap in research by developing a novel numerical method using the volume-of-fluid (VOF) approach. This method enables computational simulations that accurately capture interactions between a non-Newtonian shear-thinning liquid, a Newtonian liquid, and gas in the presence of a rigid body. To validate its accuracy, semi-analytical solutions are derived for multiphase Poiseuille ow of non-Newtonian and Newtonian fluids. Additionally, numerical simulations are conducted for canonical cases, such as bubbles rising in shear-thinning fluids.

Finally, the numerical method is applied to simulate non-Newtonian surfactant plugs propagating through straight capillary tubes and a bifurcating airway model. The interplay between non-Newtonian plugs and the pre-existing film is analyzed, highlighting its potential implications for improving SRT.

Acknowledgment: The research support from the National Science Foundation (NSF) under CBET grant 1904204 and partial support from NSF-DMS 2012011 grant are gratefully acknowledged.

Advisor:
(508-999-8496), Dept of Mechanical Engineering

Committee Members:
Dr. Geoffrey Cowles, SMAST
Dr. Alfa Heryudono, Dept. of Mathematics
Dr. Hangjian Ling, Dept. of Mechanical Engineering

Open to the public.  All MNE and EAS students are encouraged to attend.

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