title: Effects of predation and habitat structure on the abundance and population structure of the rock shrimpRhynchocinetes typus(Caridea) on temperate rocky reefs.
abstract: Human disturbances, such as overfishing, may disrupt predator-prey interactions and modify food webs. Underwater surveys were carried out at six shallow-water reef barrens in temperate waters of northern-central Chile from October to December 2010 to describe the effects of predation, habitat complexity (low, medium and high) and refuge availability on the abundance and population structure of the rock shrimpRhynchocinetes typus(Rhynchocinetidae), an important mesoconsumer on subtidal hard substrata. Three sites were within managed (restricted access) areas for fishermen, and three were unmanaged (open-access). Field observations and tethering experiments were conducted to examine the relationship between fish and shrimp abundances, and the relative predation rates on shrimps. Direct effects of predation onR. typusbody-size distribution were examined from shrimps collected in the field and fish stomachs. The presence and the abundance ofR. typusincreased with habitat reef complexity and refuge availability. Shrimp abundance was negatively related to fish abundance in managed areas, but not in open-access areas, where shrimp densities were the highest. Also, predation rates and body-size distribution of shrimps were unrelated, although fish consumed more large shrimps than should be expected from their distribution in the field.R. typusoccurred most often in shelters with wide openings, offering limited protection against predators, but providing potential aggregation sites for shrimps. Overall, direct effects of predation on shrimp densities and population structure were weak, but indirect effects on shrimp distribution within reefs appear to have been mediated through behavioural responses. Our study highlights the need to assess both numerical and behavioural responses of prey to determine the effects of predator loss on mesoconsumer populations.
authors.affiliation: The Swire Institute of Marine Science, The University of Hong Kong, Pokfulam Rd, Hong Kong, People's Republic of China ; School of Biological Sciences, The University of Hong Kong, Pokfulam Rd, Hong Kong, People's Republic of China.
authors.forename: Nicolas C
authors.initials: NC
authors.lastname: Ory
authors.affiliation: School of Biological Sciences, The University of Hong Kong, Pokfulam Rd, Hong Kong, People's Republic of China.
authors.forename: D
authors.initials: D
authors.lastname: Dudgeon
authors.affiliation: The Swire Institute of Marine Science, The University of Hong Kong, Pokfulam Rd, Hong Kong, People's Republic of China ; School of Biological Sciences, The University of Hong Kong, Pokfulam Rd, Hong Kong, People's Republic of China.
authors.forename: C P
authors.initials: CP
authors.lastname: Dumont
authors.affiliation: Facultad Ciencias del Mar, Universidad Católica del Norte, Larrondo 1281, Coquimbo, Chile.
authors.forename: L
authors.initials: L
authors.lastname: Miranda
authors.affiliation: Facultad Ciencias del Mar, Universidad Católica del Norte, Larrondo 1281, Coquimbo, Chile ; Centro de Estudios Avanzados en Zonas Áridas (CEAZA), Coquimbo, Chile.
authors.forename: M
authors.initials: M
authors.lastname: Thiel