Food web feedbacks drive the response of benthic macrofauna to bottom trawling

Abstract

Bottom trawl fisheries have significant effects on benthic habitats and communities, and these effects have been studied intensively in the last decades. Most of these studies have related the changes in benthic community composition to direct effect of trawl gears on benthos, through imposed mortality. This line of argumentation ignores the fact that benthic organisms themselves form a complex food web and that bottom trawling may trigger secondary effects through this food web. We studied the potential consequences of such food web effects using a model of benthic predators, filter feeders, deposit feeders and fish. Our analysis shows how inclusion of ecological interactions complicates the relationship between bottom trawling intensity and the state of the benthic community and causes a non‐linear and non‐monotonic response of the benthic community to trawling. This shows that indirect food web effects can fundamentally alter the response of a benthic ecosystem to bottom trawling, compared to the direct effects of mortality. In light of our results, we argue that indicators of fishing impact on benthos need to account for positive as well as negative effects of bottom trawling, in order to accurately quantify the impact. Our findings highlight that understanding the food web ecology of the benthic ecosystem is crucial for understanding and predicting the effects of trawling on the seafloor. Work that promotes such understanding of the food web ecology seems a more productive research strategy than conducting ever more empirical trawling effect measurements.

Effects of bottom trawling and hypoxia on benthic invertebrate communities

“…The declining trend of S. entomon with trawling may itself also be driven by predation, since cod, an important predator on S. entomon (Neuenfeldt et al 2020), may be found at higher abundances in areas of high fishing. Although the importance of these feeding interactions is speculative and largely hypothetical, it highlights how indirect food web effects can complicate relationships between bottom trawling and benthic communities (Sköld et al 2018, van de Wolfshaar et al 2020.…”

A General-Purpose Biotic Index to Measure Changes in Benthic Habitat Quality across Several Pressure Gradients

“…In GPBI, it is assumed that species lose individuals (and may disappear) between the reference and the tested station because they are sensitive to a disturbance, but without any a priori statements about this sensitivity. In fact, some of these species could be collateral victims of changes in bioturbation disturbance, facilitation disappearance, competition for food resources, or predation [56]. Consequently, by taking all species in the community into account (i.e., sampled species), GPBI captures a part of the consequences of the (negative) interactions between species which are not detected by other indices.…”

Beoordeling van ecologische effecten van garnalenvisserij op bodem en biota : Mate van wetenschappelijke onderbouwing

“…,,(Van Denderen et al 2016),(Van de Wolfshaar et al 2020)). Tenslotte kunnen ook positieve relaties (facilitatie) tussen soorten verstoord raken.Met name biobouwende soorten zoals zeegras, kokerwormen en bankvormende schelpdieren zoals oesters en mosselen bouwen een omgeving waar veel andere soorten van profiteren, door golven en stroming te remmen, sediment te stabiliseren en fysieke aanhechtingsmogelijkheden te creëren.…”