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Background: Many ecologically and commercially important species occur in the epipelagic marine environment and have been observed to spend a considerable amount of time associating with surface structure. The bottom depth of this habitat often exceeds transmission (~ 500-1000 m) and receiver (500–750 m) range specifications for commonly used acoustic telemetry methods that rely on an array of receivers deployed on the seafloor with overlapping fields of detection to provide positioning of acoustically tagged individuals. This poses logistical challenges for tracking the fine-scale movements, behaviors, and associations to moored and free-floating structure of these species. Acoustic telemetry can provide high resolution positioning data for tagged animals within an array of receivers with overlapping fields of detection; however, this technique has not been applied in deep open-ocean environments off the benthos. Results: Herein, we detail the development of a novel vertical acoustic telemetry array that can be mounted on, or suspended from, various moored and free-floating structures in the open ocean, thus facilitating high resolution tracking of structure-associated epipelagic animals. This new 'vertical acoustic array' (VAR) allows for the calculation of a transmitter's distance from the array and depth with average error around these metrics ranging from 16.2 to 54.8 m (distance error) and 8.6 to 61.5 m (depth error) within the tested range (~ 500 m radius around the array, ~ 300 m deep). We also validated the ability of the VAR to inform the association of an epipelagic species to surface structure by calculating fine-scale positioning for a great barracuda around a fish aggregating device (FAD), which on average was 27.9 ± 2.9 m away at a depth of 9.3 ± 0.4 m over a 9-day tracking period, demonstrating high association with the structure. Conclusions: This new array is able to provide two-dimensional (distance away and depth) animal behavior data around natural and anthropogenic moored and free-floating structures in open-ocean environments where bottom depths often exceed transmission (~ 1000 m) and receiver (~ 500 m) range specifications of traditional bottom moored positioning arrays. This array can also be used to quantitatively assess associations of epipelagic species beyond presence/absence using a single receiver, advancing the potential to improve understanding of the interactions between pelagic fauna and anthropogenic structures such as wind turbines, oil rigs, and fish aggregation devices. [ABSTRACT FROM AUTHOR]

The pelagic zone of the ocean can be a challenging environment in which to conduct research and as a result we lack the robust baseline abundance and diversity data, compared to what is available in more accessible coastal habitats, to be able to track changes or stressors to the biota in this environment. Many large‐scale fisheries target pelagic fish, and much of the information available on these species is based on fisheries‐dependent data that may be biased towards hotspots and commercially valuable fishes. Here, a long‐term video and visual fish survey was conducted on two subsurface moored fish aggregating devices (FADs) in the pelagic waters of the central Bahamas to determine the feasibility of using moored pelagic FADs as tools for collecting fish abundance and diversity data. A wide range of species was documented, including large migratory fish that are the focus of commercial and recreational fisheries, and smaller often overlooked species on which little abundance or seasonality information exists. We found that FADs colonize quickly and reach a peak stable (albeit seasonally cyclical) abundance and diversity within the first several months after deployment. Species richness was higher in video surveys, but abundance was higher in visual surveys, except for sharks. Our results highlight the need to tailor survey methods to fit the context and study objective, and provide further evidence for the importance of fisheries‐independent data in monitoring pelagic species. [ABSTRACT FROM AUTHOR]

Fisheries-independent data on the diversity, relative abundance, and demographic structure of poorly studied, threatened oceanic sharks are absent from much of the western North Atlantic Ocean, where multiple oceanic shark species have experienced significant population declines. Resource-limited management approaches require the identification of critical habitats or aggregation sites worthy of protection and enforcement. Data were collected on oceanic sharks using pelagic longline surveys, targeted baiting, and opportunistic encounters in oligotrophic open-ocean habitats of north-eastern Exuma Sound (NES), The Bahamas. The oceanic epipelagic shark community was also characterized using targeted baiting off Columbus Point, Cat Island (CI), a seamount north of San Salvador (SSSM), and the northwestern tip of Mayaguana. Pelagic longline surveys suggested that the relative abundance of sharks at NES was low (shark catch-per-unit-effort: 0.0007 sharks hook−1 h−1; 2.3 sharks per 1000 hooks). Silky sharks Carcharhinus falciformis, particularly juveniles (134 ± 39 cm stretched total length; mean ± SD STL), were the most common. Targeted baiting suggested oceanic whitetip sharks C. longimanus were abundant at CI, where large adults (245 ± 23 cm STL), most of which were females (83.8%, n = 98 of 117) that were gravid (65.7%; n = 46 of 70 assessed for pregnancy), dominated the aggregation. Many (20.5–26.5%, n = 24–31 of 117 depending on assumptions regarding tag loss) were recaptured or resighted at CI for up to five years. Silky sharks dominated catches at SSSM. Oceanic sharks, particularly adults, were sometimes caught or observed alongside short-finned pilot whales Globicephala macrorhynchus or tunas. Although The Bahamas offers threatened oceanic sharks refuge from fishing across its entire jurisdiction, these data suggest that some fixed features, including sites such as CI and potentially SSSM, are important aggregation sites with high regional conservation value and should be prioritized by fisheries managers and enforcement officials. [ABSTRACT FROM AUTHOR]

Near‐future climate change projections predict an increase in sea surface temperature that is expected to have significant and rapid effects on marine ectotherms, potentially affecting a number of critical life processes. Some habitats also undergo more thermal variability than others, and the inhabitants therefore must be more tolerant to acute periods of extreme temperatures. Mitigation of these outcomes may occur through acclimation, plasticity or adaptation, although the rate and extent of a species' ability to adjust to warmer temperatures is largely unknown, specifically as it pertains to effects on various performance metrics in fishes that inhabit multiple habitats throughout ontogenetic stages. Here, the thermal tolerance and aerobic performance of schoolmaster snapper (Lutjanus apodus Walbaum, 1792) collected from two different habitats were experimentally assessed under different warming scenarios (temperature treatments = 30, 33, 35, 36°C) to assess vulnerability to an imminently changing thermal habitat. Larger subadult and adult fish collected from a 12 m deep coral reef exhibited a lower critical thermal maximum (CTmax) compared to smaller juvenile fish collected from a 1 m deep mangrove creek. However, the CTmax of the creek‐sampled fish was only 2°C above the maximum water temperature measured in the habitat from which they were collected, compared to a CTmax that was 8°C higher in the reef‐sampled fish, resulting in a wider thermal safety margin at the reef site. A generalized linear model showed a marginally significant effect of temperature treatment on resting metabolic rate (RMR), but there were no effects of any of the tested factors on maximum metabolic rate or absolute aerobic scope. Post hoc tests revealed that RMR was significantly higher for creek‐collected fish at the 36°C treatment and significantly higher for reef‐collected fish at 35°C. Swimming performance [measured by critical swimming speed] was significantly lower at the highest temperature treatment for creek‐collected fish and trended down with each successive increase in temperature treatment for reef‐collected fish. These results show that metabolic rate and swimming performance responses to thermal challenges are somewhat consistent across collection habitats, and this species may be susceptible to unique types of thermal risk depending on its habitat. We show the importance of intraspecific studies that couple habitat profiles and performance metrics to better understand possible outcomes under thermal stress. [ABSTRACT FROM AUTHOR]

The isotopic composition of tooth‐bound collagen has long been used to reconstruct dietary patterns of animals in extant and palaeoecological systems. For sharks that replace teeth rapidly in a conveyor‐like system, stable isotopes of tooth collagen (δ13CTeeth & δ15NTeeth) are poorly understood and lacking in ecological context relative to other non‐lethally sampled tissues. This tissue holds promise, because shark jaws may preserve isotopic chronologies from which to infer individual‐level ecological patterns across a range of temporal resolutions.Carbon and nitrogen stable isotope values were measured and compared between extracted tooth collagen and four other non‐lethally sampled tissues of varying isotopic turnover rates: blood plasma, red blood cells, fin and muscle, from eight species of sharks. Individual‐level isotopic variability of shark tooth collagen was evaluated by profiling teeth of different ages across whole jaws for the shortfin mako shark Isurus oxyrinchus and sandbar shark Carcharhinus plumbeus.Measurements of δ13CTeeth and δ15NTeeth were positively correlated with isotopic values from the four other tissues. Collagen δ13C was consistently 13C‐enriched relative to all other tissues. Patterns for δ15N were slightly less uniform; tooth collagen was generally 15N‐enriched relative to muscle and red blood cells, but congruent with fin and blood plasma (values clustered around a 1:1 relationship).Significant within‐individual variability was observed across whole shortfin mako shark (δ13C range = 1.4‰, δ15N range = 3.6‰) and sandbar shark (δ13C range = 1.2‰–2.4‰, δ15N range = 1.7‰–2.4‰) jaws, which trended with tooth age.We conclude that amino acid composition and associated patterns of isotopic fractionation result in predictable isotopic offsets between tissues. Within‐individual variability of tooth collagen stable isotope values suggests teeth of different ages may serve as ecological chronologies, that could be applied to studies on migration and individual‐level diet variation across diverse time‐scales. Greater understanding of tooth replacement rates, isotopic turnover and associated fractionation of tooth collagen will help refine potential ecological inferences, outlining clear goals for future scientific inquiry. [ABSTRACT FROM AUTHOR]

As on land, oceans exhibit high temporal and spatial temperature variation. This "ocean weather" contributes to the physiological and ecological processes that ultimately determine the patterns of species distribution and abundance, yet is often unrecognized, especially in tropical oceans. Here, we tested the paradigm of temperature stability in shallow waters (<12.5 m) across different zones of latitude. We collated hundreds of in situ, high temporal-frequency ocean temperature time series globally to produce an intuitive measure of temperature variability, ranging in scale from quarter-diurnal to annual time spans. To estimate organismal sensitivity of ectotherms (i.e. microbes, algae, and animals whose body temperatures depend upon ocean temperature), we computed the corresponding range of biological rates (such as metabolic rate or photosynthesis) for each time span, assuming an exponential relationship. We found that subtropical regions had the broadest temperature ranges at time spans equal to or shorter than a month, while temperate and tropical systems both exhibited narrow (i.e. stable) short-term temperature range estimates. However, temperature-dependent biological rates in tropical regions displayed greater ranges than in temperate systems. Hence, our results suggest that tropical ectotherms may be relatively more sensitive to short-term thermal variability. We also highlight previously unexplained macroecological patterns that may be underpinned by short-term temperature variability., (© The Author(s) 2024. Published by Oxford University Press on behalf of National Academy of Sciences.)

Booralana nickorum sp. nov. is described from the deep-water slope of the Exuma Sound, The Bahamas, from depths of 540 to 560 metres. It is the fourth species to be assigned to the genus and the second species described from the Western North Atlantic. The species can be distinguished from Booralana tricarinata Camp and Heard, 1988 and the other species by the sub-triangular pleotelson and the uropodal exopod of mature males being far longer than endopod, with both rami extending well beyond the posterior margin of the pleotelson. Additionally, pleopods 3 and 4 lack a prominent angle at midpoint of ramus.