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.

The roughbar frogfish, Fowlerichthys avalonis, is one of the largest frogfish residents of rocky bottoms, at depths of 10 to 300 m, inhabiting the eastern Pacific. It is an endemic species with a geographic range along the continental shelf from the southern United States to Chile. This study provides evidence for the occurrence of the species at Socorro Island (18°46′19″N 110°53′43″W), Revillagigedo Archipelago, Mexico, obtained from videos taken in a submersible at a depth of 66 m. This report extends the known distribution of F. avalonis to 400 km off the mainland coast of the Americas, and represents the fourth species of the family Antennariidae to be reported for the Revillagigedo Archipelago.

The basket star Gorgonocephalus eucnemis is a common ophiuroid resident of rocky bottoms and artificial substrata at depths of 8 to 1,850 m, and in the eastern Pacific is distributed from the Bering Sea to San Diego, USA. This paper presents a new record of this species obtained with a submersible at Guadalupe Island, Mexico (29.10976°N, −118.25417°W), which extends its distribution range over 400 km, and corresponds to the southernmost site of occurrence of this ophiuroid in the eastern Pacific.

During a series of submersible surveys of the Shiribeshi Seamount, northern Sea of Japan, by the remotely-operated vehicle (ROV) ‘Dolphin 3K’ and the human-occupied vehicle (HOV) ‘Shinkai 2000’ in July 2001, dense patches of golden skate eggs were observed. Given the lack of information for this species, an analysis was performed to estimate the abundance of the eggs and to ascertain if any patterns could be determined from the distribution of eggs on the sea-floor as recorded by the ROV and HOV video cameras. Eggs, including some with viable embryos, were found on only one of four ROV benthic transect surveys and one crewed submersible dive in the same location. The site where eggs were laid was relatively small and appeared to have been revisited through time. This work is part of an ongoing collaborative effort between East Stroudsburg University and the Marine Biodiversity Research Programme at the Japan Agency for Marine–Earth Science and Technology to characterize the midwater and benthic deep-sea faunas around Japan.

Modern in situ survey technologies such as crewed submersibles, remotely-operated vehicles (ROVs), towed camera arrays, and visual/video plankton recorders (VPRs) were used to characterize the dominant anthomedusan species off the eastern seaboard of Japan. Notes on the taxonomy, distribution, behaviour and interspecies interactions are presented for the four observed species: Euphysa japonica, E. flammea, Calycopsis nematophora and Pandea rubra. A new generic definition for the genus Calycopsis is proposed. The possibility of run-on, cascading detrimental effects of oceanic acidification on midwater ecosystems was identified from observations made during the present study.