Many coastal fish species undergo ontogenetic shifts, but comparable knowledge for most exploited deep-sea fishes and their habitat use is lacking. We use otolith stable isotope analysis (SIA) to hindcast experienced temperature, depth, and field metabolic rate of 3 ecologically and commercially important deep-sea fishes from the Azores, mid-north Atlantic. Otoliths of bluemouth rockfish Helicolenus dactylopterus, Atlantic wreckfish Polyprion americanus, and blackspot seabream Pagellus bogaraveo were analysed to determine the stable isotope composition of carbon and oxygen in aragonite at core, mid and edge of otoliths. Oxygen SIA thermometry was used to infer water temperatures and depths, and carbon isotopes were used to derive individual field metabolic rate at each section. We identified sharp ontogenetic and interspecific differences in temperature, depth, and metabolism: juvenile rockfish inhabited intermediate depths before shifting to deeper waters as sub-adults; wreckfish occupied shallow waters before an abrupt ontogenetic shift to deep waters at maturity; juvenile seabream recorded the warmest temperatures, before gradually shifting to deeper waters as they grow. The mass-specific metabolic rates declined expectedly across all 3 species as individuals grew and occupied deeper and colder environments. Rockfish revealed the highest metabolic rates at low temperatures while in wreckfish, allometric scaling exponents for the whole organism field metabolic rate were comparatively low, potentially associated with changes in activity levels associated with ontogenetic depth changes. The thermal and metabolic differences throughout the ontogeny between the species illustrate the diversity of life cycles in deep-sea fishes and the relevance of integrating these into multispecies fisheries management.

After hatching, sea turtles leave the nest and disperse into the ocean. Many years later, they return to their natal coastlines. The period between their leaving and their returning to natal areas, known as the “Lost Years”, is poorly understood. Satellite tracking studies aimed at studying the “Lost Years” are challenging due to the small size and prolonged dispersal phases of young individuals. Here, we summarize preliminary findings about the performance of prototype microsatellite tags deployed over a three-year period on 160 neonate to small juvenile sea turtles from four species released in the North Atlantic Ocean. We provide an overview of results analyzing tag performance with metrics to investigate transmission characteristics and causes of tag failure. Our results reveal that, despite certain unfavorable transmission features, overall tag performance was satisfactory. However, most track durations were shorter than those observed on individuals of similar size in other studies and did not allow for detailed analyses of trajectories and turtle behavior. Our study further suggests that tracking durations are correlated with the targeted species, highlighting a lack of robustness against some neritic behaviors. Unprecedented diving data obtained for neonate sea turtles in this study suggest that the vertical behaviors of early juveniles are already too strenuous for these miniaturized tags. Our findings will help to inform the biologging research community, showcasing recent technological advances for the species and life stages within our study.

The increased risk of local extinction becomes critical for sharks depending on the narrow and isolated coastal habitats of oceanic islands. This includes large pelagic oceanic sharks that use such habitats as nurseries, as previously hypothesized for the smooth hammerhead Sphyrna zygaena, the least known of cosmopolitan large hammerhead sharks. We used a combination of acoustic and satellite telemetry in a juvenile population of Faial and Pico islands, Azores, mid-north Atlantic, to confirm if this isolated archipelago holds nurseries, and to answer questions related to their function and spatial–temporal stability. Our long-term acoustic tracking data showed a cluster of individual core home ranges in specific areas of north shore Faial, and surface positions from five Argos-linked tagged individuals also showed a clustering overlap in those areas for up to 1 year. These patterns seem to reveal a true habitat preference within the Faial-Pico island (sub) population of juvenile smooth hammerhead shark, and thus constitute strong evidence for this area to be considered a nursery. Some individuals remained in this nursery for up to 4 years, especially during summers. Sharks also showed a strong diel behavior, typically using the inshore nurseries during the day and moving further offshore during the night, during which they increased activity and dove deeper, most possibly to feed. We speculate that a combination of increased feeding opportunities, expanded trophic niche, and reduced predatory pressure may be a key evolutionary driver for the existence, prolonged use, and even preference of coastal nurseries at oceanic islands by juvenile smooth hammerhead shark. Given that these nurseries may constitute essential fish habitat for this species, they should be explicitly included in spatial management measures at the local and regional scales, as they may also play a role of greater importance to the north Atlantic population of this oceanic species.

In this paper, we cover 4 years of live fish transports that ranged from 14 to 200 h (8 days), and bioloads from 3.8 to 76.9 kg/m(3). The key ingredients for success in all trips, where virtually no mortality occurred, was atributed to (1) pre-buffering the water with sodium bicarbonate and sodium carbonate at 50 g/m(3) (each)-and/or ATM Alka-Haul(TM) at 25 g/m(3)-and applying additional (partial or full) doses throughout each transport, whenever the tanks were accessible; (2) pre-quenching ammonia with ATM Triage(TM) at 32 g/m(3), and applying additional (partial or full) doses throughout each transport, whenever the tanks were accessible; (3) keeping the dissolved oxygen saturation rate above 100%, ideally above 150%; (4) Keeping temperature on the lower limit of each species' tolerance range; (5) Using foam fractionators to effectively eliminate organic matter from the water and (6) Using pure sine wave inverters, which allows for a steady supply of electrical current throughout the transport. The use of a 'preventive' versus 'corrective' pH buffering philosophy is also discussed.

A holistic understanding of the life-history strategies of marine populations is often hindered by complex population dynamics, exacerbated by an intricate movement ecology across their life histor...

Concentrations of V, Cr, Mn, Co, Ni, Cu, Zn, As, Se, Cd and Pb were determined in muscle, liver and gonads of two ecologically contrasting fishes, Helicolenus dactylopterus (benthic) and Pagellus bogaraveo (benthopelagic). Elevated concentrations of As, Se and Cd found in tissues of both species appear to mirror the contribution of volcanic activity to the natural inputs of elements to Azorean waters. Results showed different element accumulation between the two species. Whereas higher concentrations were found in the liver of P. bogaraveo, elevated values were observed in the muscle of H. dactylopterus. Differences in accumulation are most likely related to metabolic rates, diet specificities and habitat. Concentrations in gonads varied up to four orders of magnitude, being higher and more variable in P. bogaraveo than H. dactylopterus. Elevated values of Cd were detected in gonads of both species despite its non-essential role on metabolic functions, presumably related to elimination.

It has been speculated that some deep-sea fishes can display large vertical migrations and likely doing so to explore the full suite of benthopelagic food resources, especially the pelagic organisms of the deep scattering layer (DSL). This would help explain the success of fishes residing at seamounts and the increased biodiversity found in these features of the open ocean. We combined active plus passive acoustic telemetry of blackspot seabream with in situ environmental and biological (backscattering) data collection at a seamount to verify if its behaviour is dominated by vertical movements as a response to temporal changes in environmental conditions and pelagic prey availability. We found that seabream extensively migrate up and down the water column, that these patterns are cyclic both in short-term (tidal, diel) as well as long-term (seasonal) scales, and that they partially match the availability of potential DSL prey components. Furthermore, the emerging pattern points to a more complex spatial behaviour than previously anticipated, suggesting a seasonal switch in the diel behaviour mode (benthic vs. pelagic) of seabream, which may reflect an adaptation to differences in prey availability. This study is the first to document the fine scale three-dimensional behaviour of a deep-sea fish residing at seamounts.

The application of the “ecosystem approach” to fisheries management demands knowledge of the patterns of habitat use of target species but in the case of seamounts, this information is still very limited or, for most species, simply unavailable. Novel approaches, such as the use of acoustic biotelemetry in deep sea environments can potentially elucidate the spatial behaviour of seamount associated fishes. We tested the use of passive acoustic telemetry to study the residency of sub-adult and adult blackspot seabream (Pagellus bogaraveo) at the Condor seamount, Azores, mid-north Atlantic. Twenty‐eight fish tagged with acoustic transmitters were monitored by two receivers moored at the summit of the seamount (ca. 200m depth) over two and a half years. Twenty‐two of these fish were detected by the receivers but only twelve fish (43%) were detected beyond the two initial days after release. This sub-group of fish was detected at the seamount summit for an average 25% of the days monitored and up to 829days, with a predicted 50% chance of detection at the seamount 278days after release. While at the summit, fish were typically site attached to one side of the seamount summit, particularly at night. Our data indicate that 1) there is high individual variability in the residency at the seamount, ranging from short interspersed visits to year-long residency and 2) the fine-scale movements of blackspot seabream at the Condor seamount could well be characterised by horizontal displacements smaller than previously thought and by frequent diel vertical migrations. This work demonstrates the great potential of acoustic telemetry as a tool to study the habitat use of seamount fishes and to provide information relevant for the spatial management and conservation of these species and habitats. Concurrently, it also highlights the problems and methodological challenges with post-release mortality, particularly in larger individuals, and appropriate receiver coverage, that need to be addressed in future studies.