title: Shifting elasmobranch community assemblage at Cocos Island--an isolated marine protected area.
abstract: Fishing pressure has increased the extinction risk of many elasmobranch (shark and ray) species. Although many countries have established no-take marine reserves, a paucity of monitoring data means it is still unclear if reserves are effectively protecting these species. We examined data collected by a small group of divers over the past 21 years at one of the world's oldest marine protected areas (MPAs), Cocos Island National Park, Costa Rica. We used mixed effects models to determine trends in relative abundance, or probability of occurrence, of 12 monitored elasmobranch species while accounting for variation among observers and from abiotic factors. Eight of 12 species declined significantly over the past 2 decades. We documented decreases in relative abundance for 6 species, including the iconic scalloped hammerhead shark (Sphyrna lewini) (-45%), whitetip reef shark (Triaenodon obesus) (-77%), mobula ray (Mobula spp.) (-78%), and manta ray (Manta birostris) (-89%), and decreases in the probability of occurrence for 2 other species. Several of these species have small home ranges and should be better protected by an MPA, which underscores the notion that declines of marine megafauna will continue unabated in MPAs unless there is adequate enforcement effort to control fishing. In addition, probability of occurrence at Cocos Island of tiger (Galeocerdo cuvier), Galapagos (Carcharhinus galapagensis), blacktip (Carcharhinus limbatus), and whale (Rhincodon typus) sharks increased significantly. The effectiveness of MPAs cannot be evaluated by examining single species because population responses can vary depending on life history traits and vulnerability to fishing pressure.
authors: Department of Biology, University of Victoria, P.O. Box 1700 STN CSC, Victoria, BC, V8W 2Y2, Canada.
authors: Easton R
authors: ER
authors: White
authors: Department of Biology, University of Northern Iowa, 144 McCollum Science Hall, Cedar Falls, IA, 50614-0421, U.S.A.
authors: Mark C
authors: MC
authors: Myers
authors: Department of Mathematics and Statistics, Dalhousie University, 6316 Coburg Road, P.O. Box 15000, Halifax, NS, B3H 4R2, Canada.
authors: Joanna Mills
authors: JM
authors: Flemming
authors: Department of Biology, University of Victoria, P.O. Box 1700 STN CSC, Victoria, BC, V8W 2Y2, Canada.
authors: Julia K
authors: JK
authors: Baum
mesh_terms: D000818:Animals; D044822:Biodiversity; D003247:Conservation of Natural Resources; D003364:Costa Rica; D008954:Models, Biological; D010140:Pacific Ocean; D011157:Population Dynamics; D012754:Sharks / Q000502:physiology*; D012860:Skates, Fish / Q000502:physiology*
keywords: AMP; MPA; Pacífico oriental tropical; cero inflación; ciencia ciudadana; citizen science; eastern tropical Pacific; fisheries; generalized linear mixed models; marine reserve; modelos lineales mixtos generalizados; reserva marina; sharks; tiburones; zero-inflated