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The spatial dynamics of marine populations are shaped by habitat availability, environmental variability and individual interactions, particularly when multiple species share limited habitat such as patchy offshore reefs. The yellowmouth barracuda Sphyraena viridensis and the almaco jack Seriola rivoliana are the 2 most abundant bentho-pelagic reef predators in the Azores archipelago (central North Atlantic). They aggregate at shallow offshore seamounts, and largely share diet preferences, but very little is known about how habitat and resources are shared by these predators intra- and inter-specifically. Here we use long-term (over 3 yr) passive acoustic telemetry to investigate the patterns of activity, space use and associative behaviour at an isolated, small shallow seamount. By quantifying fine-scale spatiotemporal overlaps and performing null model randomization tests, we found evidence of non-random associations, mostly between conspecifics of both species, as well as shifts in diel and seasonal patterns of space occupancy. Both species were detected more often during spring, and appear to be more active during daytime, suggesting the absence of fine-scale temporal habitat partitioning. Additionally, we found evidence of size-dependent spatial behaviour in almaco jack, with similarly sized individuals co-occurring more often and larger specimens being more infrequently detected. This study quantitatively assesses individual associations using solely presence-absence data collected through passive acoustic telemetry, showing the potential of this approach in a broader application to a significant number of past and ongoing studies, even if many were not originally designed to study this important aspect of fish ecology.

Many large marine predators make excursions from surface waters to the deep ocean below 200 m. Moreover, the ability to access meso- and bathypelagic habitats has evolved independently across marine mammals, reptiles, birds, teleost fishes, and elasmobranchs. Theoretical and empirical evidence suggests a number of plausible functional hypotheses for deep-diving behavior. Developing ways to test among these hypotheses will, however, require new ways to quantify animal behavior and biophysical oceanographic processes at coherent spatiotemporal scales. Current knowledge gaps include quantifying ecological links between surface waters and mesopelagic habitats and the value of ecosystem services provided by biomass in the ocean twilight zone. Growing pressure for ocean twilight zone fisheries creates an urgent need to understand the importance of the deep pelagic ocean to large marine predators. Expected final online publication date for the Annual Review of Marine Science, Volume 14 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

REPLYING TO H. Murua et al. Nature https://doi.org/10.1038/s41586-021-03396-4 (2021) Our previously published paper1 provided global fine-scale spatiotemporal estimates (1° × 1°; monthly) of overlap and fishing exposure risk (FEI) between satellite-tracked shark space use and automatic identification system (AIS) longline fishing effort. We did not assess shark mortality directly, but in addition to replying to the Comment by Murua et al.2, we confirm—using regression analysis of spatially matched data—that fishing-induced pelagic shark mortality (catch per unit effort (CPUE)) is greater where FEI is higher. We focused on assessing shark horizontal spatiotemporal overlap and exposure risk with fisheries because spatial overlap is a major driver of fishing capture susceptibility and previous shark ecological risk assessments (ERAs) assumed a homogenous shark density within species-range distributions3,4,5 or used coarse-scale modelled occurrence data, rather than more ecologically realistic risk estimates in heterogeneous habitats that were selected by sharks over time. Furthermore, our shark spatial exposure risk implicitly accounts for other susceptibility factors with equal or similar probabilities to those commonly used in shark ERAs3,5.

REPLYING TO A. V. Harry & J. M. Braccini Nature https://doi.org/10.1038/s41586-021-03463-w (2021) Our global analysis1 estimated the overlap and fishing exposure risk (FEI) using the space use of satellite-tracked sharks and longline fishing effort monitored by the automatic identification system (AIS). In the accompanying Comment, Harry and Braccini2 draw attention to two localized shark–longline vessel overlap hotspots in Australian waters, stating that 47 fishing vessels were misclassified as longline and purse seine vessels in the Global Fishing Watch (GFW)3 2012–2016 AIS fishing effort data product that we used. This, they propose2, results in misidentifications that highlight fishing exposure hotspots that are subject to an unexpected level of sensitivity in the analysis and they suggest that misidentifications could broadly affect the calculations of fishing exposure and the central conclusions of our study1. We acknowledged in our previously published paper1 that gear reclassifications were likely to occur for a small percentage of the more than 70,000 vessels studied, however, here we demonstrate that even using much larger numbers of vessel reclassifications than those proposed by Harry and Braccini2, the central results and conclusions of our paper1 do not change.

Marine reserves across different eco-regions and habitats have proven to benefit exploited fish populations within their borders. There is also mounting evidence, mostly from continental shelf regions, that such positive effects will depend on the species ecological traits (e.g. mobility) and on the characteristics of the reserves (e.g. design, age and enforcement). This study examines the effects of protection on commercial coastal fishes with different ecological traits from three marine reserves with distinct habitats (coastal vs. offshore reefs), protection regime (legal vs. voluntary, partial vs. total protection) and age (8, 15 and 26 years old) across the oceanic archipelago of the Azores, mid North Atlantic. Overall, positive effects of protection on fish abundance or individual size were limited to species of larger maximum size and lower mobility in reserves with higher compliance levels. This result agrees with many studies elsewhere showing that reserves of small size and/or insufficient compliance do not provide adequate protection to the entire fish community, limiting their contribution to manage fisheries and conserve biodiversity. That might very well be the case of Azorean marine reserves but a more conclusive result will require testing the effects of protection on larger, well enforced reserves, which still do not exist in the region. There was also a clear influence of depth in commercial fish distribution and a common preference for substrates of higher complexity across ecological traits. Combined, these results highlight the need to include complex reef structures, diverse coastal habitats and larger areas when designing multispecies marine reserves and stress that an appropriate management regime is crucial for the success of the reserve, in particular to promote compliance.

Postsettlement spillover from marine protected areas (MPAs) can support adjacent fished populations and has been subject of many scientific studies. The larval subsidy effect, on the contrary, is more challenging to study and less demonstrated, although it, arguably, provides key benefits for fisheries. We modeled and predicted the spatial distribution of fish spawning biomass and fecundity across a temperate insular MPA network (Azores archipelago, Northeast Atlantic) and identified potential single- and multispecies reproductive habitats (RHs) in shallow reefs. Reproductive strategies or skewed sex ratios influenced spatial patterns of potential spawning biomass and fecundity. Predicted multispecies RHs covered 5%–20% of the studied reef habitat. Given their potentially high reproductive output, we argue that such sites should be considered in marine conservation planning to increase chances of achieving fisheries and conservation benefits. Spatial patterns of the reproductive output may function as surrogates for larval subsidy when limited or no larval connectivity information is available and also may assist in identifying potential larval sources and priority sites for conservation.

Effective ocean management and the conservation of highly migratory species depend on resolving the overlap between animal movements and distributions, and fishing effort. However, this information is lacking at a global scale. Here we show, using a big-data approach that combines satellite-tracked movements of pelagic sharks and global fishing fleets, that 24% of the mean monthly space used by sharks falls under the footprint of pelagic longline fisheries. Space-use hotspots of commercially valuable sharks and of internationally protected species had the highest overlap with longlines (up to 76% and 64%, respectively), and were also associated with significant increases in fishing effort. We conclude that pelagic sharks have limited spatial refuge from current levels of fishing effort in marine areas beyond national jurisdictions (the high seas). Our results demonstrate an urgent need for conservation and management measures at high-seas hotspots of shark space use, and highlight the potential of simultaneous satellite surveillance of megafauna and fishers as a tool for near-real-time, dynamic management., Data analysis was funded in part by the Marine Biological Association (MBA) and the UK Natural Environment Research Council (NERC) (NE/R00997X/1) (to D.W.S.) with additional research support from the Save Our Seas Foundation and the NERC Oceans 2025 Strategic Research Programme, in which D.W.S. was a principal investigator. D.W.S. was supported by an MBA Senior Research Fellowship, N.Q. by European Regional Development Fund (FEDER) via the Programa Operacional Competitividade e Internacionalização (COMPETE), National Funds via Fundação para a Ciência e a Tecnologia (FCT) under PTDC/MAR/100345/2008 and COMPETE FCOMP-01-0124-FEDER-010580 (to N.Q. and D.W.S.), and Norte Portugal Regional Operational Programme (NORTE 2020) under the PORTUGAL 2020 Partnership Agreement through the European Regional Development Fund (ERDF) in project MarInfo (NORTE-01-0145-FEDER-000031). Additional support was provided by an FCT Investigator Fellowship IF/01611/2013 (N.Q.), FCT Doctoral Fellowship PD/BD/52603/2014 (M.V.), PTDC/MAR-BIO/4458/2012, Xunta de Galicia - Isabel Barreto Program 2009-2012 (G.M.), Australian Research Council (ARC) grant DE170100841 and operational funds from the Australian Institute for Marine Science (AIMS) (both to A.M.M.S.).

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.

The common dolphinfish (Coryphaena hippurus) is an epipelagic, mid-trophic level, highly migratory species distributed throughout the world’s tropical and subtropical oceans in waters greater than 20°C. Life-history variables, migratory behaviour, and genetic markers have been used to define major stocks in the central Atlantic Ocean and Mediterranean Sea. Here, we used the mitochondrial DNA gene NADH subunit 1 (688 bp) to test for differences between population groups. A total of 103 haplotypes were detected among 203 fish. Gene diversities in samples were large and similar among populations (mean h = 0.932; range 0.894–0.987), but nucleotide diversities varied widely among samples (range π = 0.004–0.034) and appear to reflect population histories. Principal component analysis revealed two large populations groups, and the analysis of molecular variation and pairwise values of ΦST resolved population structure within these groups. Populations in the eastern Atlantic and Mediterranean showed the largest amounts of divergence from one another (ΦCT = 0.331). Adult movement and biophysical barriers to larval dispersal may explain contemporary differences between stocks, but the divergent populations in the Mediterranean Sea are likely due to isolations by cold temperature barriers during Pleistocene glaciations. The geographically large stock groupings require international cooperation in the harvest management and conservation of local dolphinfish populations.

The effectiveness of marine reserves for highly mobile reef fishes such as jacks and trevallies is normally assumed to be small, even though we generally lack the understanding of their long-term movement patterns. In this work, we combined the analysis of multi-year landings and underwater visual census with acoustic telemetry to investigate the long-term movement patterns (up to 4 years) of almaco jack, Seriola rivoliana, a large reef top predator, in one protected and one unprotected offshore shallow seamount in the Azores, central North Atlantic. Although the analysis of visual census and landing data suggests a pronounced seasonal pattern of occurrence, we found that tagged fish were almost continuously detected at the seamounts for up to four consecutive years. Some individuals showed a few long periods of undetection of 1–2 months in the Formigas reserve, mostly in the fall and winter. Mobility within this seamount increased during spring and summer, and geostrophic current speed was negatively correlated with detection probability. Overall, the acoustic telemetry results showed that adult almaco jacks were resident year-round, refuting the traditional view that these fish are essentially migratory and a seasonal occurrence in the Azores. Given the intrinsic vulnerability of resident fish to fishing, our results highlight the importance of protecting these sites in order to preserve these mature fish aggregations with high reproductive potential.

Seven coastal fish species are newly reported for the remote north Atlantic archipelago of the Azores: Mediterranean sand eel Gymnammodytes cicerelus, bar jack Caranx ruber, two-banded seabream Diplodus vulgaris, bastard grunt Pomadasys incisus, unicorn leatherjacket filefish Aluterus scriptus and longspined porcupinefish Diodon holacanthus. The occurrence is also confirmed for 19 species that had been hitherto cited occasionally for the region, totalling a list of two elasmobranchs and 23 teleosts. Diplodus vulgaris, which appears to have recently colonized the islands, as well as roughtail stingray Dasyatis centroura and golden grey mullet Liza aurata, re-cited based on new records, are frequent or common coastal species in the Azores. The remaining 22 species, exceptional or rare in the region, are of tropical or subtropical affinity and find their northernmost distribution limit within the central and north-east Atlantic Ocean precisely in the Azores. This biogeographical pattern contrasts with that of the Azorean coastal fish community and suggests a tropicalization process in the region in line with previous findings of similar patterns across the north-east Atlantic Ocean and the Mediterranean Sea. These novel data from the most isolated archipelago of the North Atlantic Ocean, located in a biogeographic boundary area where colonization opportunities are reduced, reinforce the need for long-term monitoring programmes of coastal fish communities and, in particular, of indicator species groups to improve understanding of the effects of climate change on marine communities.

The yellowmouth barracuda Sphyraena viridensis, a highly mobile predator, is considered a migratory seasonal visitor to the Azores Islands by local fishers. This perception is challenged here through a combined analysis of multi-annual commercial landings, underwater visual census and telemetry data from acoustically tagged fish to investigate the long-term movement patterns and residency (up to 4 years) in a seamount marine reserve. Although the landing patterns suggested a strong seasonal variation in abundance, the visual census and the telemetry experiment results were consistent with year-round residency in the Azores. Barracudas occurred consistently in underwater census throughout the year, and most tagged fish were almost continuously detected at the seamounts for up to four consecutive years. Detection probability did, however, decrease over time and showed seasonal variability as tagged fish were less mobile with longer absences during summer and fall. Given the intrinsic vulnerability of fish aggregations to exploitation, our results highlight the need to protect shallow seamount habitats and preserve sexually mature fish aggregations and their reproductive potential, contributing to the sustainable management and conservation of these vulnerable ecosystems.

We present a classification framework to detect underwater terrain deformations commonly caused by marine species in real time during AUV surveys. The method uses two classifiers in a hierarchical manner to overcome the fact that there are no substantial datasets in the literature about underwater terrain and the creation of one would involve a great consumption of human and technological resources. The first classifier based on Haar cascades, scans the image from an AUV stereo camera and detects all possible candidates of interest. Then, a Multi-Descriptor Random Forest is used to classify these candidates according to which species is more likely to have caused the associated terrain deformation. This classifier is able to integrate multiple descriptors to ensure the robustness of the system despite the vast amount of image distortions that happen underwater. The performance of the method is shown during a multiple AUV survey mission, where the Camera Vehicles follow the underwater ground up close. A comparison of the framework's output with the one from marine biologists exemplifies the accuracy of the system and its usefulness while supporting activities such as marine population monitoring to preserve nursery areas.

article i nfo 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 envi- ronments 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. 200 m 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 829 days, with a predicted 50% chance of detection at the seamount 278 days 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.

Recruitment of the temperate reef fish Coris julis was studied across the Azores Archipelago (central North Atlantic), over four consecutive recruitment seasons and at three spatial scales: between islands (separated by 100s of km), sites within islands (separated by 10s of km) and transects within sites (separated by 10s of m). At the largest scale (i.e. between islands) spatial recruitment patterns were highly variable, suggesting the influence of stochastic processes. Recruitment was spatially consistent within islands, even though magnitude was unpredictable between years, indicating that processes at meso-scales are probably more deterministic. Recruits settled randomly at the transect scale, probably reflecting habitat homogeneity. It was proposed that large and island-scale patterns reflect larval availability, driven by physical and biological processes occurring in the plankton. No evidence was found for a density-dependent relationship between newly settled and 2 week settled C. julis nor between cumulative recruitment and young-of-the-year. It appears that adult density is limited by larval supply (pre-settlement regulation) at low recruitment sites, and determined by post-settlement, density-dependent processes at high recruitment sites. This work is one of few to investigate multiple spatial and temporal scales of recruitment for a coastal fish species inhabiting isolated, temperate oceanic islands and hence, provides a novel comparison to the many studies of recruitment on coral reefs and other, more connected systems.

To estimate connectivity between populations, we used trace-element composition in otoliths of the temperate wrasse Coris julis as a proxy for the environmental conditions experienced from hatch to settlement. Recruits collected at different sites in the Azores archipelago (northeastern Atlantic) differed significantly in their natal chemical signatures, and were sufficiently diverse to be separated into in 4 distinct natal types. Types 1 and 4 were both low in Mg and Ba, although Mg was dominant in Type 1, and Type 4 was more Ba enriched. Type 2 had high Ba and intermediate Mg con- centrations, while Type 3 showed the highest Mg and intermediate Ba concentrations. We identified at least 2 natal types present in recruits at each site, which suggests multiple larval sources per site. Recruits from 3 sites did not differ greatly in their natal type composition, suggesting a common set of sources, but also limiting our ability to describe meaningful connectivity and dispersal scenarios. In contrast, we found that the prevalent Natal Type 4 was absent at 1 site, suggesting that the source characterized by Natal Type 4 does not contribute to the replenishment of C. julis populations at the site. The most striking difference was observed at the smallest scale (10s of kilometers), where we found distinct natal type compositions between north and south shores on the same island, suggest- ing that these 2 sites have consistent differences in the contribution of specific natal sources. Further, the south shore site had recruits with elevated Mg:Ca concentrations from the otolith core to edge, which suggests that these larvae developed in inshore areas and experienced local retention.

The fisheries benefits of marine reserves are hard to achieve for highly vagile fish species. An alternative is to protect essential habitats, such as spawning grounds, especially if these are stable over time. We studied the movements and habitat use patterns of white trevally Pseudo- caranx dentex (Carangidae), a commercially important species, to assist in the design of marine reserves. Diel, seasonal and inter-annual movements of trevally were studied using active acoustic tracking, passive acoustic monitoring and standard tag-release in the Faial Channel, Azores Islands. White trevally were captured at inshore and offshore reefs. Inshore trevally moved daily alongshore, using large activity spaces, while the short-term movements of offshore trevally were restricted to the reef summits. During the summer spawning season, both groups displayed frequent migrations of up to several kilometres, but inshore fish remained inshore, whereas offshore reef fish expanded their range to include visits to inshore sites. This behaviour eventually resulted in low long-term residence within the study area, especially that of inshore fish. During the spawning season, one inshore site was visited by most of the fish. However, instead of gathering in large aggregations at a single location, it appears that the trevally adopted a multiple-site visiting behaviour, which may increase mating opportunities through mixing between inshore and offshore fish that are otherwise segre- gated for most of the year. Protection of spawning biomass and sites for this species seems potentially feasible, but this would require protecting a suite of sites per island. Furthermore, because fish would not be fully protected under this scenario, we argue that such spatial management measures need to be accompanied by conventional fishing-effort control measures applied to all local populations.

Marine reserves should work most effectively for exploited species that are strongly site attached to small home ranges (HRs) contained within reserve boundaries. However, to benefit local fisheries through spillover, the species in the reserves must also be able to migrate to unprotected areas. We evaluated the optimal design of marine reserves for protecting and promoting spillover of a commercially important parrotfish, Sparisoma cretense (Linnaeus, 1758), by empirically quantify- ing short- and long-term movements of individuals originally captured inside and outside a small reserve in the Azores Islands (mid-Atlantic). Movements were quantified using active tracking, passive acoustic monitoring and standard tag-recapture. We found that the dual social organization of the species determined the individuals' movements and habitat use. Haremic fish occupied small HRs associated with permanently established male territories in high energy reef areas. Group (schooling) fish spent most of their time in sheltered reefs but expanded their HRs during the spawning season with daily migrations to the 'territorial' areas. S. cretense HR sizes were consider- ably larger than those previously reported for tropical parrotfishes. Passive acoustic monitoring indicated very high site fidelity and minimal dispersion for up to 30 mo. This study demonstrates that residency of adult parrotfish can last for years. Several individuals emigrated to the reserve from neighbouring areas and some of them relocated thereafter. We suggest that a network of adequately enforced marine reserves of small to medium size (ca. 1 to 5 km 2 ) containing suitable habitat diver- sity can effectively protect core populations of S. cretense, but benefits to adjacent fisheries through spillover will be limited to the areas adjacent to the reserve boundaries.

Background The Azores archipelago lies at the limit of whale shark (WS) distribution in the North Atlantic, where sporadic sightings of “pintado” (local name) date back to the early tuna fishing operation from the mid XX century. From 1998 and 2008, only nine adult whale shark sightings had been confirmed by the Azores Fisheries Observer Program. However, from 2008 onwards there has been a dramatic increase in the numbers of reported adult individuals around the most southern island of Santa Maria. A recent study found that this increase in sighting frequency was related to an increase in local SST (above 22.5°C), and decrease in chlorophyll-a, with local variation around the large seamounts in the area. While whale sharks and tuna have long been known to associate, the nature and motivation of these associations remains unclear. Moreover the WS-tuna associations in the region remain to be characterized as well as the potential impact of fishing these associations. Approach In this study, we analysed a 13-year observer dataset (1998–2011) from the pole-and-line tuna fisheries from the Azores EEZ to investigate the regional behaviour (distribution in catch abundance and composition) of three tuna species, skipjack, bigeye and albacore during this period. We also examined how these patterns have responded to the environmental drivers, the distribution and abundance of whale sharks and compared whale shark associated fishing events and events targeting free swimming schools. We also detailed an elaborate protocol to guide future research to investigate the impact of fishing the WS-tuna associations and test the “functional bycatch” theory by combining state of the art electronic tracking and behaviour technology with physiological proxies of stress and condition of both whale shark and tuna. Results Changes in the distribution the tuna species were evident with the centre of gravity found closest to the whale shark aggregations in the latter years (2008 in particular) and was independent of fishing effort. Between 2008 and 2011 for the areas where whale sharks have been found we find the associated whale shark fishing events have significantly more individuals of skipjack and bigeye tuna and the area surrounding the eastern islands (Santa Maria etc.) also yielded the highest catches per fishing event. The albacore did not show any significant variation in CPUE for either predictor. Overall, catch rates of tuna were higher and multi-species aggregations were more likely when associated with whale sharks. Conclusions Preliminary results suggest that the presence of WS during the tuna fishing season may have an effect on fishing yields and tuna species composition of catches. It is also apparent that the fishing fleet behaviour could be responding to WS distribution and abundance. Our results support the need to investigate the potential detrimental effects that fishing WS-tuna associations may have on both the WS and tuna.

The MORPH project (FP 7, 2012-2016) aims at the development of efficient methods and tools to map the underwater environment in situations that defy existing technology. Namely, missions that involve underwater surveying and marine habitat mapping of rugged terrain and structures with full 3D complexity, including near-vertical cliffs. Potential applications include the study of cold water coral reefs or ecosystems in underwater canyons. For mapping purposes, the project advances the novel concept of an underwater robotic sensor carrier consisting of a number of spatially separated mobile robotic modules, each of them carrying complementary sensors. The modules are connected virtually via wireless communication links. Free from the constraints of rigid links, the modules can reconfigure themselves spatially and position their sensors optimally as a function of the shape of the terrain, which may include walls with a negative slope. In the scope of the project, a final demonstration on a vertical cliff will validate the efficacy of the methods developed.

Understanding the movements of marine organisms in space and time has become a key area of research in support of management and conservation decision-making processes. This includes the optimal design of networks of marine reserves, as movements of fish are a major determinant for the reserve effect (increase in size and number inside reserves) and spillover effect (emigration from reserves). The increasing use of acoustic telemetry techniques, particularly passive acoustic arrays, is providing much of that information, but studies have typically used one specific approach at a specific spatial-temporal scale. We studied movement patterns, habitat use and dispersal in the red porgy, Pagrus pagrus (a commercially important species) in the Azores islands, mid-north Atlantic, with the aim of supporting the design of marine reserves that would protect local populations while enhancing fisheries. Movements were quantified using: (1) short-term active acoustic tracking; (2) multi-year passive acoustic monitoring; and (3) standard tag-release experiments in the Faial Channel. We found the short-term home ranges of red porgy to be quite large for a reef fish – up to 50 ha. Furthermore, frequent short-term displacements of up to 9 km and periodic absences from main core activity areas indicate that HR varies considerably in size and location throughout the year. Home range expansion occurred mostly during the protracted period of spawning activity, but we saw no evidence for spawning aggregations. We found evidence that individuals of smaller size utilize larger home ranges and are less site-specific, supporting the hypothesis that dispersal in the red porgy is largely determined by ontogenic changes. Large individual variability in both short-term and long-term movement patterns accounted for some emigrations from tagging sites and for one documented relocation. These findings indicate that adequate protection of subpopulations of red porgy will not be achieved using small, isolated reserves (1 to 5 km2), but reserves of size in the order of tens of km2 and spaced a few kilometers apart should provide protection while promoting emigration (spillover) of red porgy from reserves to neighboring grounds. This study shows that the combination of spatial and temporal scales and approaches is needed to capture a realistic picture of the full suite of spatial behaviors used throughout a species’ life history.

Reproductive biology and habitat preferences of the white trevally, Pseudocaranx dentex (Carangidae), were studied in the Azores islands, central north Atlantic, to determine the spatial and seasonal dynamics of habitat use of immature and mature fish. The sex ratio was close to 1:1 and fish matured at about 30 cm fork length. There were no differences in the maturation or length-weight relationships between sexes. The spawning season lasts from June to September. Underwater visual censuses showed that schools of mature individuals preferentially aggregate around the summits of offshore reefs during the spawning season. In contrast, schools of smaller, immature fish use inshore habitats all year round. Our data support the hypothesis that offshore reefs are a preferential spawning habitat of larger white trevally, and most possibly for a number of visitor pelagic predators as well. Inverse relationships between exploitation levels, abundance and size composition at the two different islands suggest that the summer fishery targeting trevally schools around offshore reefs has negatively impacted the population. These findings bring additional ecological and management relevance to offshore reefs.

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 increasing public perception that marine megafauna is under threat is an outstanding incentive to investigate their essential habitats (EMH), their responses to human and climate change pressures, and to better understand their largely unexplained behaviors and physiology. Yet, this poses serious challenges such as the elusiveness and remoteness of marine megafauna, the growing scrutiny and legal impositions on their study, and difficulties in disentangling environmental drivers from human disturbance. We argue that advancing our knowledge and conservation on marine megafauna can and should be capitalized in regions where exceptional access to multiple species (i.e., megafauna ‘hotspots’) combines with the adequate legal framework, sustainable practices, and research capacity. The wider Azores region, hosting EMHs of all key groups of vulnerable or endangered vertebrate marine megafauna, is a singular EMH hotspot on a migratory crossroads, linking eastern and western Atlantic margins and productive boreal waters to tropical seas. It benefits from a sustainable development model based on artisanal fisheries with zero or minor megafauna bycatch, and one of the largest marine protected area networks in the Atlantic covering coastal, oceanic and deepsea habitats. Developing this model can largely ensure the future integrity of this EMH hotspot while fostering cutting-edge science and technological development on megafauna behavior, biologging and increased ocean observation, with potential major impacts on the Blue Growth agenda. An action plan is proposed.