Trends in the Abundance of Megafauna in Marine Protected Areas of the Tropical Eastern Pacific

Many species of marine megafauna, including sharks, rays, and turtles, are experiencing severe global declines, which will have major consequences for marine ecosystems given the important roles these species play. Marine protected areas (MPAs) are a widely used method for conserving species, but there is uncertainty whether these areas are more than just paper parks. Malpelo and Cocos are two small islands in an important marine corridor in the tropical eastern Pacific that have both been designated as MPAs. A single dive company recorded counts of Scalloped Hammerhead Sharks (Sphyrna lewini), Whitetip Reef Sharks (Triaenodon obesus), and Spotted Eagle Rays (Aetobatus narinari) on every dive between 1999 and 2009 at Malpelo. The same company also counted sea turtles sighted while diving between 1992 and 2014. For the elasmobranchs, the MPA at Malpelo seems to be working because, based on generalized linear mixed models, the major trends in abundance are with seasonality and environmental variables rather than year. In contrast, sea turtle abundance appears to be declining at Cocos. This dataset will also allow for the study of spatial trends in this important corridor, particularly for migratory hammerheads. Sensitivity analyses will guide minimum effort recommendations for effective monitoring.