PhD defence on the use of hydrodynamics to improve the selectivity of towed fishing gear

Improved selectivity of demersal trawl fishing gear is a common research topic. The aim is to improve the catch rate of the target species and minimize unwanted bycatch. Trials include, e.g., changes in mesh size and shape, escape routes for unwanted species, and scaring methods. 

In her PhD project, Karen Baastrup Burgaard has investigated yet another parameter from the toolbox: the hydrodynamics around the fishing gear. The project has studied how this flow of water can be used to increase catch efficiency, while also reducing bycatch of unwanted species. 

Karen Baastrup Burgaard, who conducted her PhD study at DTU Aqua and DTU Construct, used the sea star fishery as a case study. Sea stars are increasingly abundant in coastal areas, where they eat a lot of shellfish. Bottom trawling is among the most common methods used to reduce the population of sea stars as well as to catch sea stars for animal feed production. 

Karen Baastrup Burgaard has investigated the hydrodynamics around fishing gear experimentally in a current flume and by using theoretical models. She has also participated in fishing trials on a commercial fishing vessel to test the hypotheses.

The results consistently show that the sea stars are ejected from the seabed when an upward near-bed flow is created, leading to their subsequent catch in a trailing net. Thus, by making targeted use of hydrodynamics, the fisheries will be able to get a "cleaner" catch of sea stars with only a small bycatch of mussels. In addition, the effect on the seabed will decrease, when the starfish do not have to be mechanically scraped from the bottom.

Karen Baastrup Burgaard expects that the method, she has developed, can be used in other fisheries, and that a better understanding of the hydrodynamics of towed fishing gear can lead to the design and development of gear with improved selectivity and a lower impact on the marine environment.

About the PhD defence

Karen Baastrup Burgaard will defend her PhD thesis "Using hydrodynamics to improve the selectivity of towed fishing gears” on Thursday 29 June 2023, 13:00 on Teams and at DTU Lyngby Campus, building 303A, auditorium 41, 2800 Kgs. Lyngby.  

Supervisors

• Principal supervisor: Professor Barry O’Neill, DTU Aqua
• Co-supervisor: Professor David R. Fuhrman, DTU Construct
• Co-supervisor: Associate Professor Stefan Carstensen, DTU Construct

Examiners

• Senior Researcher Asbjørn Christensen, DTU Aqua (Chair)
• Professor Muk Chen Ong, University of Stavanger, Norway
• Flume Tank Site Manager Jens Peter Kofoed, SINTEF, Denmark

Chairperson at defence

• Senior Researcher Camille Saurel, DTU Aqua

Learn more

A copy of the thesis is available by e-mail on request. Please contact Karen Baastrup Burgaard, kbur@aqua.dtu.dk