Predator decline leads to decreased stability in a coastal fish community

Abstract

Fisheries exploitation has caused widespread declines in marine predators. Theory predicts that predator depletion will destabilise lower trophic levels, making natural communities more vulnerable to environmental perturbations. However, empirical evidence has been limited. Using a community matrix model, we empirically assessed trends in the stability of a multispecies coastal fish community over the course of predator depletion. Three indices of community stability (resistance, resilience and reactivity) revealed significantly decreasing stability concurrent with declining predator abundance. The trophically downgraded community exhibited weaker top-down control, leading to predator-release processes in lower trophic levels and increased susceptibility to perturbation. At the community level, our results suggest that high predator abundance acts as a stabilising force to the naturally stochastic and highly autocorrelated dynamics in low trophic species. These findings have important implications for the conservation and management of predators in marine ecosystems and provide empirical support for the theory of predatory control.

Marine defaunation: Animal loss in the global ocean

“…Defaunation can reduce cross-system connectivity (54, 55), decrease ecosystem stability (56), and alter patterns of biogeochemical cycling (57). The ill effects of food web disarticulation can be further amplified when they occur in association with other marine disturbances.…”

Feeding and reproductive ecology of Cichla piquiti Kullander & Ferreira, 2006 within its native range, Lajeado reservoir, rio Tocantins basin

“…The lack of inspection in Lajeado reservoir, for example, has led to the use of predatory fishing methods (e.g., harpoons), which targeted large individuals and may have removed mega-spawners from the population (Froese, 2004). It must cause concern because extensive removal of top predators may affect food web structure and ecosystem functioning (Britten et al, 2014), with negative consequences for recruitment and fisheries. Management measures must, therefore, devote attention to C. piquiti as a means to maintain persistent stocks and ecosystem services (i.e.…”

Humans as a Hyperkeystone Species

“…The most convincing studies combine several of these approaches: for example, a now-classic study on the effects of large sharks on mesopredator and basal species off the US East Coast combined metaanalysis of fisheries monitoring time-series with experiments that manipulated mesopredator access to prey species, demonstrating an unsuspected interaction chain from sharks to shellfish [52]. Sharks [ 1 0 9 _ T D $ D I F F ] similarly emerged as keystone actors in food-web models [7,53] and long-term observational datasets [23,48,54], leading to a more robust case overall. Because humans are exploiting sharks in all ecosystems where they occur [23], and at rates that often greatly exceed their reproductive capacity [55,56], a more general case can be made with respect to the human hyperkeystone role.…”