Since the year 2000, the designation of remote, large‐scale marine protected areas (LSMPAs) has closed over 15 × 106 km2 of ocean to commercial fishing. Yet, while these mega‐reserves have collectively made a major contribution toward meeting global targets for marine conservation, their effectiveness for the protection of highly mobile, pelagic species remains largely unknown. This study reports on the spatial behavior and reproductive status of yellowfin tuna (Thunnus albacares) inhabiting a proposed LSMPA around Ascension Island (tropical Atlantic), with the aim of evaluating the conservation benefits for this economically important species. Using a combination of satellite archival tags and conventional mark–recapture it was shown that individual tuna can remain within Ascension Island waters for periods of between 100 and 200 days, with core residency areas (50% “utilization distributions”) generally extending <200 km from shore. The vast majority of activity occurred within 92.6 km (50 nmi) of the island and coincided with a “no‐take zone” established around the island in 2016. However, dispersive movements out of this zone were observed in some satellite‐tagged individuals, possibly marking the beginning of more extensive oceanic migrations. Gonad staging of 342 individuals sampled over a 32 month period found no evidence of reproductively active (ripe) individuals, strongly suggesting that tuna foraging around Ascension Island migrate elsewhere to breed. Study results provide further evidence of the importance of oceanic islands as residency areas for pelagic megafauna, helping to justify their inclusion within LSMPAs. In the absence of local recruitment, however, these individuals will remain susceptible to exploitation on spawning grounds located outside of reserves, ultimately limiting their effectiveness and thus calling for further research to identify and protect the areas where species are most vulnerable.

Recent studies have improved our understanding of nearshore marine ecosystems surrounding Ascension Island (central Atlantic Ocean), but little is known about Ascension's benthic environment beyond its shallow coastal waters. Here, we report the first detailed physical and biological examination of the seabed surrounding Ascension Island at 100 -1000 m depth. Multibeam swath data were used to map fine scale bathymetry and derive seabed slope and rugosity indices for the entire area. Water temperature and salinity profiles were obtained from five Conductivity, Temperature, Depth (CTD) deployments, revealing a spatially consistent thermocline at 80 m depth. A camera lander (Shelf Underwater Camera System; SUCS) provided nearly 400 images from 21 sites (100 m transects) at depths of 110 -1020 m, showing high variability in the structure of benthic habitats and biological communities. These surveys revealed a total of 95 faunal morphotypes (mean richness .14 per site), complemented by 213 voucher specimens constituting 60 morphotypes collected from seven targeted Agassiz trawl (AGT) deployments. While total faunal density (maximum .300 m 22 at 480 m depth) increased with rugosity, characteristic shifts in multivariate assemblage structure were driven by depth and substratum type. Shallow assemblages ( 100 m) were dominated by black coral (Antipatharia sp.) on rocky substrata, cup corals (Caryophyllia sp.) and sea urchins (Cidaris sp.) were abundant on fine sediment at intermediate depths (250 -500 m), and shrimps (Nematocarcinus spp.) were common at greater depths (.500 m). Other ubiquitous taxa included serpulid and sabellid polychaetes and brittle stars (Ophiocantha sp.). Cold-water corals (Lophelia cf. pertusa), indicative of Vulnerable Marine Ecosystems (VMEs) and representing substantial benthic carbon accumulation, occurred in particularly dense aggregations at ,350 m but were encountered as deep as 1020 m. In addition to enhancing marine biodiversity records at this locality, this study provides critical baseline data to support the future management of Ascension's marine environment.

Epinephelus adscensionis sampled from Ascension Island, South Atlantic Ocean, exhibits distinct life-history traits, including larger maximum size and size at sexual maturity than previous studies have demonstrated for this species in other locations. Otolith analysis yielded a maximum estimated age of 25 years, with calculated von Bertalanffy growth parameters of: L = 55·14, K = 0·19, t = -0·88. Monthly gonad staging and analysis of gonad-somatic index (I ) provide evidence for spawning from July to November with an I peak in August (austral winter), during which time somatic growth is also suppressed. Observed patterns of sexual development were supportive of protogyny, although further work is needed to confirm this. Mean size at sexual maturity for females was 28·9 cm total length (L ; 95% C.I. 27·1-30·7 cm) and no females were found >12 years and 48·0 cm L , whereas all confirmed males sampled were mature, >35·1 cm L with an age range from 3 to 18 years. The modelled size at which 50% of individuals were male was 41·8 cm (95% C.I. 40·4-43·2 cm). As far as is known, this study represents the first comprehensive investigation into the growth and reproduction of E. adscensionis at its type locality of Ascension Island and suggests that the population may be affected less by fisheries than elsewhere in its range. Nevertheless, improved regulation of the recreational fishery and sustained monitoring of abundance, length frequencies and life-history parameters are needed to inform long-term management measures, which could include the creation of marine reserves, size or temporal catch limits and stricter export controls.