Ecological role of large benthic decapods in marine ecosystems: a review

Large benthic decapods play an increasingly important role in commercial fisheries worldwide, yet their roles in the marine ecosystem are less well understood. A synthesis of existing evidence for 4 infraorders of large benthic marine decapods, Brachyura (true crabs), Anomura (king crabs), Astacidea (clawed lobsters) and Achelata (clawless lobsters), is presented here to gain insight into their ecological roles and possible ecosystem effects of decapod fisheries. The reviewed species are prey items for a wide range of invertebrates and vertebrates. They are omnivorous but prefer molluscs and crustaceans as prey. Experimental studies have shown that decapods influence the structuring of benthic habitat, occasionally playing a keystone role by suppressing herbivores or space competitors. Indirectly, via trophic cascades, they can contribute to the maintenance of kelp forest, marsh grass, and algal turf habitats. Changes in the abundance of their predators can strongly affect decapod population trends. Commonly documented non-consumptive interactions include interference-competition for food or shelter, as well as habitat provision for other invertebrates. Anthropogenic factors such as exploitation, the creation of protected areas, and species introductions influence these ecosystem roles by decreasing or increasing decapod densities, often with measurable effects on prey communities. Many studies have investigated particular ecosystem effects of decapods, but few species were comprehensively studied in an ecosystem context. A simplified synthetic framework for interpreting ecosystem roles of decapods was derived from the available evidence; however, more experimental and long-term observational studies are needed to elucidate mechanisms and shed light on the long-term consequences of decapod fisheries.