The impact of bottom trawling on epifauna in the North Sea

Boer, Niek (2019) The impact of bottom trawling on epifauna in the North Sea. Research Project, Science Education and Communication.

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Abstract

Introduction The North Sea is one of the most intensively fished seas in the world. Fishing here often happens by the means of bottom trawling, making it one of the most widespread forms of anthropogenic seabed disturbance. Because of various life-history traits, benthic epifauna is particularly vulnerable for this form of fishing. Various studies have shown that chronic trawl disturbance leads to changes in species composition, decreased biodiversity and decreased abundance of various epifaunal species. In this research, I have examined bottom trawling impact on epifauna in the North Sea. I have first looked at the impact of bottom trawling on the community level by looking at biotic indicators such as biodiversity and species composition. For the species level, I looked at various life-history traits of individual species like size, body type and mobility. I hypothesized that bottom trawling will, in general, have a negative impact on epifauna in terms of i.e. biodiversity, while it also alters the species composition. As hydrodynamic forces (i.e. natural disturbance) have a similar impact on benthic epifauna, I expect to find the same changes here. Methods The study area is located in the southern part of the North Sea. A total of 10 variables have been used to explain species abundance, species composition and biodiversity. As a proxy for natural hydrodynamics I have taken the tidal-induced bed shear stress and the (maximum) wind driven bed shear stress (wave-induced bed shear stress). For fishing intensity, an average value was calculated for the years 2008 to 2015. Other variables are temperature, salinity, sediment type and depth. Species were taxonomically and functionally classified. For each species, physical characters such as size and morphology have been identified. Data analysis was conducted by the means of constructing generalized linear models (GLMs) Results The results show that fishing intensity significantly correlates with altered benthic communities in terms of species composition and biodiversity. The relative proportion of arthropods increases with higher fishing intensity, while the relative proportion of echinoderms decreases. Also, species with exoskeletons are more prevalent in benthic communities that are intensively fished. At last, there’s also an increased proportion of small animals in communities with high fishing intensities. Implications With the recent ban on pulse fishing, a method of bottom trawling that is thought to be better for benthic communities, in the European Union, it is expected that many fishermen will go back to traditional fishing methods such as beam trawling. This is something to think about, as traditional beam trawling has a significant negative impact on benthic communities. Countries surrounding the North Sea have pledged to protect benthic communities and other sea life in the North Sea. It is therefore necessary to keep looking for sustainable alternatives that won’t impact benthic communities.

Item Type:	Thesis (Research Project)
Supervisor name:	Reijden, K.J. van der
Degree programme:	Science Education and Communication
Thesis type:	Research Project
Language:	English
Date Deposited:	16 Jul 2019
Last Modified:	17 Jul 2019 09:54
URI:	https://fse.studenttheses.ub.rug.nl/id/eprint/20269

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