To assess the impact of bottom trawls on benthic habitats, we need to understand the interaction between a fishing gear and the sediment. The seabed varies in its characteristics; as bottom trawls do vary in their designs and application. The intensity of bottom trawling impacts does, by consequence, also vary across a range of sediments. Fishers claim that they have reduced seabed impacts by changing their trawls. Whether or not, these changes are effective in reducing seabed impacts has not been scientifically evaluated. One way to assess how trawls impact the seabed is to measure the depth of the trawl tracks (bathymetry) and the changes in sediment backscatter as a measure of surface flattening (Depestele et al., 2016; Depestele et al., 2018).
In this internship, the student will learn how the seabed is mapped using multi-beam echosounders (MBES), and how bathymetrical and backscatter data change following the passage of a trawl track. The student will process MBES data and assist in providing insights to the impact of bottom trawls on the seabed.
References
Depestele, J., Degrendele, K., Esmaeili, M., Ivanović, A., Kröger, S., O’Neill, F. G., Parker, R., et al. 2018. Comparison of mechanical disturbance in soft sediments due to tickler-chain SumWing trawl vs. electro-fitted PulseWing trawl. ICES Journal of Marine Science: fsy124-fsy124. https://doi.org/10.1093/icesjms/fsy124
Depestele, J., Ivanovic, A., Degrendele, K., Esmaeili, M., Polet, H., Roche, M., Summerbell, K., et al. 2016. Measuring and assessing the physical impact of beam trawling. ICES Journal of Marine Science, 73: i15-i26. https://doi.org/10.1093/icesjms/fsv056
