Jorge Fontes

Extreme diving behaviour in devil rays links surface waters and the deep ocean

Ecological connections between surface waters and the deep ocean remain poorly studied despite the high biomass of fishes and squids residing at depths beyond the euphotic zone. These animals likely support pelagic food webs containing a suite of predators that include commercially important fishes and marine mammals. Here we deploy pop-up satellite archival transmitting tags on 15 Chilean devil rays (Mobula tarapacana) in the central North Atlantic Ocean, which provide movement patterns of individuals for up to 9 months. Devil rays were considered surface dwellers but our data reveal individuals descending at speeds up to 6.0 m s−1 to depths of almost 2,000 m and water temperatures <4 °C. The shape of the dive profiles suggests that the rays are foraging at these depths in deep scattering layers. Our results provide evidence of an important link between predators in the surface ocean and forage species occupying pelagic habitats below the euphotic zone in ocean ecosystems.

New and rare coastal fishes in the Azores islands: occasional events or tropicalization process?

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.

Vertical migrations of a deep-sea fish and its prey.

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.

Multi-scale recruitment patterns and effects on local population size of a temperate reef fish

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.

A Multi-Scale Study of Red Porgy Movements and Habitat Use, and Its Application to the Design of Marine Reserve Networks

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.

Rapid Environmental Picture Atlantic exercise 2015: A field report

The paper describes the sixth edition of Rapid Environmental Picture Atlantic exercise (REPIS-Atlantic) which took place in July 2015 off the Portuguese islands of Azores to demonstrate coordinated operations of unmanned underwater, surface, and air vehicles contributed by participants coming from Europe and the United States of America. REP-Atlantic is a yearly demonstration exercise targeted at advancing the state of art in networked vehicle systems through large scale experimentation in real-life operational scenarios.

Ocean Productivity May Predict Recruitment of the Rainbow Wrasse (Coris julis)

Predicting recruitment fluctuations of fish populations remains the Holy Grail of fisheries science. While previous work has linked recruitment of reef fish to environmental variables including temperature, the demonstration of a robust relationship with productivity remains elusive. Despite decades of research, empirical evidence to support this critical link remains limited. Here we identify a consistent and strong relationship between recruitment of a temperate wrasse Coris julis, from temperate reefs in the mid-Atlantic region, with Chlorophyll, over contrasting scales, across multiple years. Additionally, we find that the correlation between Chlorophyll and recruitment is not simply masking a temperature-recruitment relationship. Understanding the potential mechanisms underlying recruitment variability, particularly as it relates to changing climate and ocean regimes, is a critical first step towards characterizing species’ vulnerability to mismatches between pulsed planktonic production and early pelagic life stages.

Automated species counting using a hierarchical classification approach with Haar cascades and multi-descriptor random forests

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 frameworks 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.

Elemental composition of two ecologically contrasting seamount fishes, the bluemouth (Helicolenus dactylopterus) and blackspot seabream (Pagellus bogaraveo).

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.

‘Solo datasets’: unexpected behavioural patterns uncovered by acoustic monitoring of single individuals

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 history (Nathan et al. 2008; Parsons et al. 2008; Jeltsch et al. 2013). Movement patterns and spatial ecology can vary spatially and temporally for different reasons, mainly related to the organism’s life history and environmental variability (Abecasis et al. 2009, 2013; Afonso et al. 2009). Changes in spatial use and movement can occur daily when visiting feeding grounds or avoiding predators, or seasonally, when sexually mature individuals migrate to spawning/breeding grounds (Kozakiewicz 1995; Sundström et al. 2001). However, observed shifts in spatial use and movement patterns, as a result of behavioural plasticity, may also vary greatly from one individual to another of the same species and/or population (Afonso et al. 2009). Further, ontogeny can also play an important role and explain a possible change in individual spatial variation. Noticeable differences in the behaviour and movements of mature and immature individuals have been documented in various marine organisms (Lowe et al. 1996; Lecchini and Galzin 2005). Permanent habitat shifts have been associated with ontogenesis in pigeye sharks (Carcharhinus amboinensis), moving from inshore to offshore areas after reaching maturity (Knip et al. 2011). Hence, a relevant debate lies in the implications of ‘solo datasets’ and the potential pertinence of the patterns an individual dataset could uncover. Data deficiency can be the primary barrier to efficient marine conservation and management, and while longterm species-specific data are often lacking (Broderick 2015), it appears worthwhile to investigate patterns exhibited by single individuals as a baseline to address further research projects more thoroughly. Relatively, long-term monitoring of a unique specimen can reveal extraordinary, previously unexpected behaviours. For instance, using a ‘solo dataset’ from a scalloped hammerhead shark, Sphyrna lewini, Spaet et al. (2017)