<p>The shallow waters around Isla del Coco, Costa Rica, have the highest density of apex predators within the Eastern Tropical Pacific. This represents a unique opportunity to assess the structure of predatory interactions in a community relatively unimpacted by fishing. Facilitation of predation has commonly been observed in shallow reef systems, limited in depth by observations via scuba divers. Here we present a preliminary catalog of facilitative behavioral interactions between 12 taxa of deepwater piscivores at Isla del Coco and Las Gemelas Seamount in the Eastern Tropical Pacific, collected via video from submersible vehicles to depths of approximately 311 m from 2002-2012. Observations were ad hoc and likely represent only a portion of the web of interactions that occur in this ecological setting. That such interactions can be observed to 300 m during the narrow time frame of submersible dives suggests that direct behavioral facilitation of piscivory may play a significant role in the apex predator guild of deepwater fishes. Investigating the extent and population-community consequences of such interactions will provide valuable insight into patterns and processes that occur in communities protected from direct fisheries as well as focus conservation actions. Rev. Biol. Trop. 64 (Suppl. 1): S187-S196. Epub 2016 February 01.</p><p> </p>

Background: The diverse feeding habits of sea anemones have led them to be classified as opportunistic polyphagous predators. However, most studies have focused on the diet of temperate sea anemones, and little is known about the trophic ecology of tropical species and their role in tropical ecosystems. We studied the diet of the intertidal sea anemone Anthopleura nigrescens by examining the gut contents of specimens collected at two sites on Costa Rica's Pacific coast, testing for differences in prey items captured between daytime and nighttime high tides. Results: We found 25 prey items including: mollusks, crustaceans, annelids, insects and eggs. Juvenile bivalves, barnacle cyprids, and copepods were the main prey items. The anemones at Playa Dominical captured significantly more juvenile bivalves during nighttime high tides, and those at Mata de Limón captured more cyprids during daytime high tides. Conclusions: This study shows that A. nigrescens is an opportunistic polyphagous predator, like most of its temperate counterparts.

From 2006 to date the submersible DeepSee has been used to study the deep waters in and around Isla del Coco National Park, Costa Rica. Over these years, images and samples have been collected at depths between 50 and 450 m. Here we present a catalogue of bony fishes recorded by the submersible in deep waters of Isla del Coco, 500 km south-southwest of mainland Costa Rica, and at Las Gemelas Seamount within the designated Seamounts Management Area, 50 km southwest of Isla del Coco. A database with video-images of bony fishes was created from videos taken by the submersible’s high-definition digital camera from 2006 to 2015. Additional information on the distribution of fishes was obtained from 11 dives (24.3 hrs) using the remotely operated vehicle Hela at Las Gemelas Seamount during February 2012. Images of bony fishes were obtained during 376 dives (365 DeepSee dives plus 11 Hela dives) in 18 different locations, and here we report on a total of 85 taxa (i.e. putative species). In this catalogue we present images that are the first color photographs published for some species. In other cases, identifications were possible only to the level of genus (11), family (5) or order (1); hence the information is presented in terms of putative taxa. Four new records are reported for Isla del Coco: Leptenchelys vermiformis (Ophichthidae), Hyporthodus mystacinus (Serranidae), Kathetostoma averruncus (Uranoscopidae), and Symphurus diabolicus (Cynoglossidae). Depth ranges of twenty-six species are expanded beyond previously published records; three were observed in shallower water, twenty-two in deeper water and one was observed both shallower and deeper than in previous reports. As might be expected, increased bottom time with the submersible resulted in additions to the list of documented species. This highlights the importance of maintaining systematic research efforts in the deep waters around Isla del Coco, both for scientific purposes as well as conservation.

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Gelatinous zooplankton are an abundant and diverse group of animals in the pelagic environment. However, knowledge of species diversity and spatial distributions, as well as their ecological role, is scarce. We present information of epi- and mesopelagic gelatinous zooplankton recorded by the ‘DeepSee’ submersible between 2006 and 2012 at Isla del Coco (Cocos Island), Costa Rica, an oceanic island in the Eastern Tropical Pacific. Two species of scyphomedusae, three species of hydromedusae, two genera of siphonophores, and two species of ctenophores were observed in the videos, at depths between 50 and 400 m. None of these species had been previously recorded in the waters around the island. Furthermore, except for the jellyfish Pelagia noctiluca and a siphonophore in the genus Praya, all are new records for Costa Rican waters. This study also includes the first record of the cnidarians Modeeria rotunda, Solmissus sp., Halitrephes maasi and Apolemia spp., and the ctenophore Thalassocalyce inconstans in the Eastern Tropical Pacific. We show that surveys in regions with little information about gelatinous zooplankton may broaden our knowledge of their natural history and may result in new records of gelatinous species.