A trophic cascade triggers collapse of a salt‐marsh ecosystem with intensive recreational fishing

Abstract

Overexploitation of predators has been linked to the collapse of a growing number of shallow-water marine ecosystems. However, salt-marsh ecosystems are often viewed and managed as systems controlled by physical processes, despite recent evidence for herbivore-driven die-off of marsh vegetation. Here we use field observations, experiments, and historical records at 14 sites to examine whether the recently reported die-off of northwestern Atlantic salt marshes is associated with the cascading effects of predator dynamics and intensive recreational fishing activity. We found that the localized depletion of top predators at sites accessible to recreational anglers has triggered the proliferation of herbivorous crabs, which in turn results in runaway consumption of marsh vegetation. This suggests that overfishing may be a general mechanism underlying the consumer-driven die-off of salt marshes spreading throughout the western Atlantic. Our findings support the emerging realization that consumers play a dominant role in regulating marine plant communities and can lead to ecosystem collapse when their impacts are amplified by human activities, including recreational fishing.

Landscape Estimates of Habitat Types, Plant Biomass, and Invertebrate Densities in a Georgia Salt Marsh

“…(Smith and Frey, 1985), and herbivory by Sesarma (Hughes et al, 2009;Altieri et al, 2012) will be most important in the tall Spartina zone.…”

Interactive effects of multiple climate change variables on trophic interactions: a meta-analysis

“…Our focus here is on the role of simultaneously (and rapidly) changing climate variables on trophic interactions, as these factors are among the major drivers of ecosystem structure and function [20]. Using established meta-analysis techniques, we determined the frequency of different interaction types (multiplicative, synergistic, antagonistic: see the "Effect size calculations" section) across different combinations of climate change variables and then elucidated the potential mechanisms underlying the interactions.…”

Fish community changes in Shoal Lake, Canada, following the overexploitation of a top predator

“…fewer yellow perch and cisco in the presence of high walleye abundance), and that the removal of a large, predatory fish often leads to a broader changes to the fish community (Carpenter et al 1985;Colby et al 1987;Lyons & Magnuson 1987;He & Kitchell 1990;Allan et al 2005;Baum & Worm 2009). These changes are also an important reminder to managers that fisheries collapses can affect communities in ways that are unpredictable and unfavorable (Link 2002;Daskalov et al 2007;Altieri et al 2012) and that capture fisheries can be slow to recover from exploitation (NeuBauer et al 2013). More broadly, this case study provides important insight into the structure and function in large-lake food webs (Shurin et al 2006), and the trophic ecology of top predators (Sergio et al 2014).…”