title: Squidpops: A Simple Tool to Crowdsource a Global Map of Marine Predation Intensity.
abstract: We present a simple, standardized assay, the squidpop, for measuring the relative feeding intensity of generalist predators in aquatic systems. The assay consists of a 1.3-cm diameter disk of dried squid mantle tethered to a rod, which is either inserted in the sediment in soft-bottom habitats or secured to existing structure. Each replicate squidpop is scored as present or absent after 1 and 24 hours, and the data for analysis are proportions of replicate units consumed at each time. Tests in several habitats of the temperate southeastern USA (Virginia and North Carolina) and tropical Central America (Belize) confirmed the assay's utility for measuring variation in predation intensity among habitats, among seasons, and along environmental gradients. In Belize, predation intensity varied strongly among habitats, with reef > seagrass = mangrove > unvegetated bare sand. Quantitative visual surveys confirmed that assayed feeding intensity increased with abundance and species richness of fishes across sites, with fish abundance and richness explaining up to 45% and 70% of the variation in bait loss respectively. In the southeastern USA, predation intensity varied seasonally, being highest during summer and declining in late autumn. Deployments in marsh habitats generally revealed a decline in mean predation intensity from fully marine to tidal freshwater sites. The simplicity, economy, and standardization of the squidpop assay should facilitate engagement of scientists and citizens alike, with the goal of constructing high-resolution maps of how top-down control varies through space and time in aquatic ecosystems, and addressing a broad array of long-standing hypotheses in macro- and community ecology.
authors.affiliation: Tennenbaum Marine Observatories Network, Smithsonian Institution, Washington, DC, United States of America.|Virginia Institute of Marine Science, The College of William and Mary, Gloucester Point, Virginia, United States of America.
authors.forename: J Emmett
authors.initials: JE
authors.lastname: Duffy
authors.affiliation: Virginia Institute of Marine Science, The College of William and Mary, Gloucester Point, Virginia, United States of America.
authors.forename: Shelby L
authors.initials: SL
authors.lastname: Ziegler
authors.affiliation: Smithsonian Marine Station, Fort Pierce, Florida, United States of America.
authors.forename: Justin E
authors.initials: JE
authors.lastname: Campbell
authors.affiliation: College of Charleston, Charleston, South Carolina, United States of America.
authors.forename: Paige M
authors.initials: PM
authors.lastname: Bippus
authors.affiliation: Virginia Institute of Marine Science, The College of William and Mary, Gloucester Point, Virginia, United States of America.
authors.forename: Jonathan S
authors.initials: JS
authors.lastname: Lefcheck
mesh_terms: D000818:Animals; D001531:Belize; D057894:Coral Reefs; D017753:Ecosystem; D005399:Fishes / Q000502:physiology*; D009657:North Carolina; D011235:Predatory Behavior; D012621:Seasons; D014768:Virginia