Development of seabed friendly bottom trawls

• Main Author: Nguyen, Truong X.
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 2016
• Subjects: Newfoundland; Canada; Snow crab
• Online Access: https://research.library.mun.ca/12222/; https://research.library.mun.ca/12222/1/thesis.pdf

Concerns over the impacts of fishing practices, especially bottom trawling, on the ocean environment have been expressed at the local, national and international scale. While physical alterations of the seabed by bottom trawling are known to occur, the biological effects on benthic communities and their recovery rates depend on substrate types, depth, and natural disturbance in the fishing area, as well as how trawl gears are designed and operated. In this thesis, I investigate different key research aspects regarding the subject of development of seabed friendly bottom trawls, in particular shrimp trawling in Newfoundland and Labrador, Canada. The complementary use of different research approaches (e.g., underwater video observations, numerical modeling and simulation, flume tank testing, and at-sea experiments) were applied for each of the research questions. First, I investigated the behavioural interactions of individual snow crab in response to the rockhopper footgear of a traditional inshore shrimp trawl used in Newfoundland and Labrador, Canada. I found that snow crab were quickly overtaken under the footgear of the approaching trawl and over half of the snow crab (i.e., 54%) observed experienced an encounter with the rockhopper footgear components. The majority of the snow crab observed appeared to be aware of the trawl and were actively responding and/or reacting to the approaching threat. Second, the strengths and limitations of different commercially available trawl simulation software (i.e., DynamiT, SimuTrawl, and Trawl Vision PRO) in terms of design capability, simulation capability, and reliability of results, were investigated and interpreted. The study provides valuable knowledge and reference for stakeholders (e.g., gear designers, researchers, and educators) who are considering using numerical simulation methods to optimize their gear design concepts during the early stages of development of seabed friendly bottom trawls (e.g., predict expected mechanical stresses of trawl components on the ...