Effects of chronic bottom trawling disturbance on benthic biomass, production and size spectra in different habitats

Understanding how different drivers shape relationships between abundance and body mass (size spectra) is important for understanding trophic and competitive interactions in food webs and for predicting the effects of human pressures. Here, we sample seabed communities from small polychaetes (<0.001 g) to large fish (>1 kg) in the Celtic Sea and the western English Channel to examine how bottom trawling and primary production affect their size spectra and to compare these with predictions from a model that couples predator and detritivore communities. Size spectra were not well approximated by linear fits because of truncation of the size spectra of detritivores. Low primary production resulted in lower abundance of benthic fauna. Bottom trawling reduced the abundance of predators and large detritivores but allowed small detritivores to increase in abundance. These empirical size spectra were partly consistent with predictions from the size spectra model, showing that understanding the structuring of benthic communities requires a consideration of both size and functional group. The findings highlight the need for an ecosystem approach to understanding the effects of exploitation and climate change on marine ecosystems.

Download Full-text

Cumulative impacts of seabed trawl disturbance on benthic biomass, production, and species richness in different habitats

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f05-266 ◽

2006 ◽

Vol 63 (4) ◽

pp. 721-736 ◽

Cited By ~ 196

Author(s):

J G Hiddink ◽

S Jennings ◽

M J Kaiser ◽

A M Queirós ◽

D E Duplisea ◽

...

Keyword(s):

Species Richness ◽

Biomass Production ◽

North Sea ◽

Benthic Fauna ◽

Natural Disturbance ◽

Bottom Trawl ◽

The North ◽

Benthic Biomass ◽

The North Sea ◽

The Impact

Bottom trawling causes widespread disturbance of sediments in shelf seas and can have a negative impact on benthic fauna. We conducted a large-scale assessment of bottom trawl fishing of benthic fauna in different habitats, using a theoretical, size-based model that included habitat features. Species richness was estimated based on a generalized body mass versus species richness relationship. The model was validated by sampling 33 stations subject to a range of trawling intensities in four shallow, soft sediment areas in the North Sea. Both the model and the field data demonstrated that trawling reduced biomass, production, and species richness. The impacts of trawling were greatest in areas with low levels of natural disturbance, while the impact of trawling was small in areas with high rates of natural disturbance. For the North Sea, the model showed that the bottom trawl fleet reduced benthic biomass and production by 56% and 21%, respectively, compared with an unfished situation. Because of the many simplifications and assumptions required to synthesize these data, additional work is required to refine the model and evaluate applicability in other geographic areas. Our model enables managers to understand the consequences of altering the distribution of fishing activities on benthic production and hence on food web processes.

Download Full-text