Examples of bottom living organisms in Limfjorden and Kattegat. Photo: Ciaran McLaverty.

PhD defence on effects of trawling on bottom living fauna

Tuesday 25 Feb 20


Ole Ritzau Eigaard
Senior Researcher
DTU Aqua
+45 35 88 33 74


Ciaran McLaverty
DTU Aqua
+45 35 88 34 19

On 28 February 2020, Ciaran McLaverty will defend his PhD thesis at DTU, Lyngby.

PhD student Ciaran McLaverty, DTU Aqua has investigated which bottom living (benthic) organisms are most sensitive to fishing with gears being dragged over the seafloor. His studies include shellfish dredging in shallow coastal waters and otter trawling for Norway lobster in the inner Danish waters.

Marine sediments constitute one of the largest ecosystems on earth and the animal life which inhabit these environments represent a remarkable range of biodiversity and important functions in the ecosystem.

Benthic fauna is widely used as indicators in environmental and fisheries management to track and monitor the state of the marine environment and the ecological effects of trawling. Benthic indicators typically focus on the number of species and abundance of individuals within each species, but these methods have shown ineffective in the detection of bottom trawling impacts.

Therefore, Ciaran McLaverty has taken a different approach. Instead of focusing on species, he has investigated the effect of bottom trawling on different sizes and biomass of benthic fauna, as well as several other key life-history traits. The results show that larger individuals (4 mm or more) are very sensitive to trawling, while smaller individuals are more affected by other environmental factors than fisheries. This indicates that the use of larger organisms as indicators potentially can improve the monitoring and assessment of effects of bottom trawling.

About the thesis defence

Ciaran McLaverty will defend his PhD thesis "Effects of chronic bottom trawling on benthic macrofaunal communities" on Friday 28 February 2020 at 13.00 at DTU, building 303A, auditorium 41, 2800 Lyngby. 


  • Principal supervisor: Senior Researcher Ole Ritzau Eigaard, DTU Aqua
  • Co supervisor: Senior Consultant Grete E. Dinesen, DTU Aqua
  • Co supervisor: Professor Jens Kjerulf Petersen, DTU Aqua


  • Senior Researcher Martin Lindegren, DTU Aqua
  • Dr. Hilmar Hinz, IMEDEA, Spain
  • Professor Jan Geert Hiddink, Bangor University, UK

Chairperson at defence

  • Senior Researcher Karin Hüssy, DTU Aqua

The thesis

A copy of the thesis “Effects of chronic bottom trawling on benthic macrofaunal communities" is available for reading at DTU Aqua. Contact Rikke Hansen, rikh@aqua.dtu.dk.