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Deep-pelagic fishes are among the most abundant vertebrates on Earth. They play a critical role in sequestering carbon, providing prey for harvestable fishing stocks and linking oceanic layers and trophic levels. However, knowledge of these fishes is scarce and fragmented, hampering the ability of both the scientific community and stakeholders to address them effectively. While modelling approaches incorporating these organisms have advanced, they often oversimplify their functional and ecological diversity, potentially leading to misconceptions. To address these gaps, this synthesis examines the biodiversity and ecology of global deep-pelagic fishes. We review pelagic ecosystem classifications and propose a new semantic framework for deep-pelagic fishes. We evaluate different sampling methods, detailing their strengths, limitations and complementarities. We provide an assessment of the world's deep-pelagic fishes comprising 1554 species, highlighting major groups and discussing regional variability. By describing their morphological, behavioural and ecological diversity, we show that these organisms are far from homogeneous. Building on this, we call for a more realistic approach to the ecology of deep-pelagic fishes transitioning between very different ecological niches during diel vertical migrations. To facilitate this, we introduce the concept of 'diel-modulated realised niche' and propose a conceptual model synthesising the multiple drivers responsible for such transitions., (© 2024 John Wiley & Sons Ltd.)

The yellowfin tuna is a very abundant tropical tuna species in the western equatorial Atlantic Ocean and an important fishery resource for the Brazilian tuna fleet. In this study we performed stable isotope analysis to better understand the spatial trophodynamics and dietary changes in yellowfin tuna around two insular marine protected areas in Brazil. A total of 65 yellowfin tuna specimens measuring between 47 and 138 cm LT (total length) were sampled around the archipelagos of Fernando de Noronha (FNA; n = 34) and Saint Peter and Saint Paul (SPSPA; n = 31) between July 2018 and September 2019. Bayesian mixing models and generalized additive models were used to investigate the contributions of four different prey items (zooplankton, cephalopods, fish larvae, and flying fish) to yellowfin tuna diet in each area and their potential changes in relation to predator growth. The four prey items were found to have different overall contributions between the two studied areas, with zooplankton being the most important prey in FNA, whereas flying fish was the most relevant prey to the species' diet in SPSPA. Significant changes in the species diet by size were also found, with fish smaller than 90 cm (TL) having a more generalist diet and larger animals relying more on consuming larger and more nutritious prey (i.e., flying fish). Our results suggest that these two marine protected areas play an important role in ocean dynamics, providing important and different foraging grounds for the development of this predator species., (© 2024 Fisheries Society of the British Isles.)

Here we report on new data on the occurrence and distribution of rare deep-sea fishes (Teleostei) collected from off north-eastern Brazil, including seamounts and oceanic islands of the Fernando de Noronha Ridge (Rocas Atoll and Fernando de Noronha Archipelago). Collections were made by the French RV Antea during the ABRACOS (Acoustics along the BRAzilian COaSt) expeditions between 29 September and 21 October 2015, and 9 April and 10 May 2017. Occurrences of Photostylus pycnopterus (Alepocephalidae), Gigantura chuni (Giganturidae), Ahliesaurus berryi (Notosudidae), Benthalbella infans, Rosenblattichthys hubbsi, Scopelarchoides danae (Scopelarchidae), Scopelengys tristis (Neoscopelidae), Zu cristatus (Trachipteridae), Stylephorus chordatus (Stylephoridae) and Pseudoscopelus cordilluminatus (Chiasmodontidae) are reported for the first time or confirmed in the Brazilian Exclusive Economic Zone. Photostylus pycnopterus and G. chuni are also recorded for the first time in the western South Atlantic, whereas records of P. cordilluminatus are the first in the western Atlantic. Other records of rare species of those families are also reported and discussed., (© 2022 Fisheries Society of the British Isles.)

This study reports on the first record of the intermediate scabbardfish Aphanopus intermedius in the western South Atlantic Ocean, based on a single specimen 725 mm standard length collected between 0 and 610 m depth around Rocas Atoll off north-eastern Brazil. Measurements and counts are provided and compared with those available in the literature., (© 2018 The Fisheries Society of the British Isles.)