Ambitious global targets for mangrove and seagrass recovery.

There is an urgent need to halt and reverse loss of mangroves and seagrass to protect and increase the ecosystem services they provide to coastal communities, such as enhancing coastal resilience and contributing to climate stability.1,2 Ambitious targets for their recovery can inspire public and private investment in conservation,3 but the expected outcomes of different protection and restoration strategies are unclear. We estimated potential recovery of mangroves and seagrass through gains in ecosystem extent to the year 2070 under a range of protection and restoration strategies implemented until the year 2050. Under a protection-only scenario, the current trajectories of net mangrove loss slowed, and a minor net gain in global seagrass extent (∼1%) was estimated. Protection alone is therefore unlikely to drive sufficient recovery. However, if action is taken to both protect and restore, net gains of up to 5% and 35% of mangroves and seagrasses, respectively, could be achieved by 2050. Further, protection and restoration can be complementary, as protection prevents losses that would otherwise occur post-2050, highlighting the importance of implementing protection measures. Our findings provide the scientific evidence required for setting strategic and ambitious targets to inspire significant global investment and effort in mangrove and seagrass conservation.

Relative influence of environmental factors and fishing on coral reef fish assemblages.

Understanding whether assemblages of species respond more strongly to bottom-up (availability of trophic resources or habitats) or top-down (predation pressure) processes is important for effective management of resources and ecosystems. We determined the relative influence of environmental factors and predation by humans in shaping the density, biomass, and species richness of 4 medium-bodied (10-40 cm total length [TL]) coral reef fish groups targeted by fishers (mesopredators, planktivores, grazer and detritivores, and scrapers) and the density of 2 groups not targeted by fishers (invertivores, small fish ≤10 cm TL) in the central Philippines. Boosted regression trees were used to model the response of each fish group to 21 predictor variables: 13 habitat variables, 5 island variables, and 3 fishing variables (no-take marine reserve [NTMR] presence or absence, NTMR size, and NTMR age). Targeted and nontargeted fish groups responded most strongly to habitat variables, then island variables. Fishing (NTMR) variables generally had less influence on fish groups. Of the habitat variables, live hard coral cover, structural complexity or habitat complexity index, and depth had the greatest effects on density, biomass, and species richness of targeted fish groups and on the density of nontargeted fishes. Of the island variables, proximity to the nearest river and island elevation had the most influence on fish groups. The NTMRs affected only fishes targeted by fishers; NTMR size positively correlated with density, biomass, and species richness of targeted fishes, particularly mesopredatory, and grazing and detritivorous fishes. Importantly, NTMRs as small as 15 ha positively affected medium-bodied fishes. This finding provides reassurance for regions that have invested in small-scale community-managed NTMRs. However, management strategies that integrate sound coastal land-use practices to conserve adjacent reef fish habitat, strategic NTMR placement, and establishment of larger NTMRs will be crucial for maintaining biodiversity and fisheries.

Influencia Relativa de los Factores Ambientales y la Pesca sobre el Ensamblaje de Peces en los Arrecifes de Coral Resumen Es importante entender si el ensamblaje de especies responde con mayor fuerza al proceso de abajo-arriba (disponibilidad de recursos tróficos o hábitats) o al de arriba-abajo (presión de depredadores) para el manejo efectivo de los recursos y los ecosistemas. Determinamos la influencia relativa de los factores ambientales y la depredación humana en la configuración de la densidad, la biomasa y la riqueza de especies de cuatro peces de arrecife de coral con un tamaño corporal mediano (10-40 cm de longitud total [LT]) que son preferidos por los pescadores (mesodepredadores, planctívoros, forrajeros y detritívoros, y raspadores) y también determinamos la densidad de dos grupos que no son blanco de los pescadores (invertívoros y peces de talla pequeña ≤10 cm LT) en la región central de las Filipinas. Usamos árboles de regresión amplificados para modelar la respuesta de cada grupo de peces a 21 variables de predicción: trece variables de hábitat, cinco variables de isla y tres variables de pesca (ausencia o presencia de una reserva marina vedada [RMV], tamaño y antigüedad de la NTMR). Los grupos de peces preferidos y no preferidos por los pescadores respondieron con mayor fuerza a las variables de hábitat que a las variables de isla. Las variables de pesca (RMV) en general tuvieron una menor influencia sobre los grupos de peces. De las variables de hábitat, la cobertura de coral duro vivo, la complejidad estructural o el índice de complejidad del hábitat y la profundidad tuvieron el mayor efecto sobre la densidad, la biomasa y la riqueza de especies de los peces preferidos por los pescadores y sobre la densidad de los peces no preferidos por los pescadores. De las variables de isla, la proximidad al río más cercano y la elevación de la isla tuvieron la mayor influencia sobre los grupos de peces. Las RMVs afectaron sólo a los peces preferidos por los pescadores; el tamaño de la NTMR tuvo una correlación positiva con la densidad, la biomasa y la riqueza de especies de los peces preferidos por los pescadores, particularmente los peces mesodepredadores, forrajeros y detritívoros. De manera importante, las RMVs con un tamaño mínimo de 15 ha afectaron positivamente a los peces de talla mediana. Este hallazgo proporciona seguridad para las regiones que han invertido en RMVs de pequeña escala y manejadas por la comunidad. Sin embargo, las estrategias de manejo que integran prácticas firmes de uso de suelo costero para conservar el hábitat adyacente de peces, la ubicación estratégica de RMV y el establecimiento de RMVs más grandes serán cruciales para el mantenimiento de la biodiversidad y las pesquerías.

Artificial Intelligence Meets Citizen Science to Supercharge Ecological Monitoring.

The development and uptake of citizen science and artificial intelligence (AI) techniques for ecological monitoring is increasing rapidly. Citizen science and AI allow scientists to create and process larger volumes of data than possible with conventional methods. However, managers of large ecological monitoring projects have little guidance on whether citizen science, AI, or both, best suit their resource capacity and objectives. To highlight the benefits of integrating the two techniques and guide future implementation by managers, we explore the opportunities, challenges, and complementarities of using citizen science and AI for ecological monitoring. We identify project attributes to consider when implementing these techniques and suggest that financial resources, engagement, participant training, technical expertise, and subject charisma and identification are important project considerations. Ultimately, we highlight that integration can supercharge outcomes for ecological monitoring, enhancing cost-efficiency, accuracy, and multi-sector engagement.

Parasite infection directly impacts escape response and stress levels in fish.

Parasites can account for a substantial proportion of the biomass in marine communities. As such, parasites play a significant ecological role in ecosystem functioning via host interactions. Unlike macropredators, such as large piscivores, micropredators, such as parasites, rarely cause direct mortality. Rather, micropredators impose an energetic tax, thus significantly affecting host physiology and behaviour via sublethal effects. Recent research suggests that infection by gnathiid isopods (Crustacea) causes significant physiological stress and increased mortality rates. However, it is unclear whether infection causes changes in the behaviours that underpin escape responses or changes in routine activity levels. Moreover, it is poorly understood whether the cost of gnathiid infection manifests as an increase in cortisol. To investigate this, we examined the effect of experimental gnathiid infection on the swimming and escape performance of a newly settled coral reef fish and whether infection led to increased cortisol levels. We found that micropredation by a single gnathiid caused fast-start escape performance and swimming behaviour to significantly decrease and cortisol levels to double. Fast-start escape performance is an important predictor of recruit survival in the wild. As such, altered fitness-related traits and short-term stress, perhaps especially during early life stages, may result in large scale changes in the number of fish that successfully recruit to adult populations.

Practical methods for culturing parasitic gnathiid isopods.

The reliance of parasites on their hosts makes host-parasite interactions ideal models for exploring ecological and evolutionary processes. By providing a consistent supply of parasites, in vivo monocultures offer the opportunity to conduct experiments on a scale that is generally not otherwise possible. Gnathiid isopods are common ectoparasites of marine fishes, and are becoming an increasing focus of research attention due to their experimental amenability and ecological importance as ubiquitous, harmful, blood-feeding "mosquito-like" organisms. They feed on hosts once during each of their three juvenile stages, and after each feeding event they return to the benthos to digest and moult to the next stage. Adults do not feed and remain in the benthos, where they reproduce and give birth. Here, we provide methods of culturing gnathiids, and highlight ways in which gnathiids can be used to examine parasite-host-environment interactions. Captive-raised gnathiid juveniles are increasingly being used in parasitological research; however, the methodology for establishing gnathiid monocultures is still not widely known. Information to obtain in vivo monocultures on teleost fish is detailed for a Great Barrier Reef (Australia) and a Caribbean Sea (US Virgin Islands) gnathiid species, and gnathiid information gained over two decades of successfully maintaining continuous cultures is summarised. Providing a suitable benthic habitat for the predominantly benthic free-living stage of this parasite is paramount. Maintenance comprises provision of adequate benthic shelter, managing parasite populations, and sustaining host health. For the first time, we also measured gnathiids' apparent attack speed (maximum 24.5 cm sec-1; 6.9, 4.9/17.0, median, 25th/75th quantiles) and illustrate how to collect such fast moving ectoparasites in captivity for experiments. In addition to providing details pertaining to culture maintenance, we review research using gnathiid cultures that have enabled detailed scientific understanding of host and parasite biology, behaviour and ecology on coral reefs.

Non-reef habitats in a tropical seascape affect density and biomass of fishes on coral reefs.

Nonreef habitats such as mangroves, seagrass, and macroalgal beds are important for foraging, spawning, and as nursery habitat for some coral reef fishes. The spatial configuration of nonreef habitats adjacent to coral reefs can therefore have a substantial influence on the distribution and composition of reef fish. We investigate how different habitats in a tropical seascape in the Philippines influence the presence, density, and biomass of coral reef fishes to understand the relative importance of different habitats across various spatial scales. A detailed seascape map generated from satellite imagery was combined with field surveys of fish and benthic habitat on coral reefs. We then compared the relative importance of local reef (within coral reef) and adjacent habitat (habitats in the surrounding seascape) variables for coral reef fishes. Overall, adjacent habitat variables were as important as local reef variables in explaining reef fish density and biomass, despite being fewer in number in final models. For adult and juvenile wrasses (Labridae), and juveniles of some parrotfish taxa (Chlorurus), adjacent habitat was more important in explaining fish density and biomass. Notably, wrasses were positively influenced by the amount of sand and macroalgae in the adjacent seascape. Adjacent habitat metrics with the highest relative importance were sand (positive), macroalgae (positive), and mangrove habitats (negative), and fish responses to these metrics were consistent across fish groups evaluated. The 500-m spatial scale was selected most often in models for seascape variables. Local coral reef variables with the greatest importance were percent cover of live coral (positive), sand (negative), and macroalgae (mixed). Incorporating spatial metrics that describe the surrounding seascape will capture more holistic patterns of fish-habitat relationships on reefs. This is important in regions where protection of reef fish habitat is an integral part of fisheries management but where protection of nonreef habitats is often overlooked.

Shoaling reduces metabolic rate in a gregarious coral reef fish species.

Many animals live in groups because of the potential benefits associated with defense and foraging. Group living may also induce a 'calming effect' on individuals, reducing overall metabolic demand. This effect could occur by minimising the need for individual vigilance and reducing stress through social buffering. However, this effect has proved difficult to quantify. We examined the effect of shoaling on metabolism and body condition in the gregarious damselfish Chromis viridis Using a novel respirometry methodology for social species, we found that the presence of shoal-mate visual and olfactory cues led to a reduction in the minimum metabolic rate of individuals. Fish held in isolation for 1 week also exhibited a reduction in body condition when compared with those held in shoals. These results indicate that social isolation as a result of environmental disturbance could have physiological consequences for gregarious species.

Phenotypic plasticity confers multiple fitness benefits to a mimic.

Animal communication is often deceptive; however, such dishonesty can become ineffective if it is used too often, is used out of context, or is too easy to detect [1-3]. Mimicry is a common form of deception, and most mimics gain the greatest fitness benefits when they are rare compared to their models [3, 4]. If mimics are encountered too frequently or if their model is absent, avoidance learning of noxious models is disrupted (Batesian mimicry [3]), or receivers become more vigilant and learn to avoid perilous mimics (aggressive mimicry [4]). Mimics can moderate this selective constraint by imperfectly resembling multiple models [5], through polymorphisms [6], or by opportunistically deploying mimetic signals [1, 7]. Here we uncover a novel mechanism to escape the constraints of deceptive signaling: phenotypic plasticity allows mimics to deceive targets using multiple guises. Using a combination of behavioral, cell histological, and molecular methods, we show that a coral reef fish, the dusky dottyback (Pseudochromis fuscus), flexibly adapts its body coloration to mimic differently colored reef fishes and in doing so gains multiple fitness benefits. We find that by matching the color of other reef fish, dottybacks increase their success of predation upon juvenile fish prey and are therefore able to deceive their victims by resembling multiple models. Furthermore, we demonstrate that changing color also increases habitat-associated crypsis that decreases the risk of being detected by predators. Hence, when mimics and models share common selective pressures, flexible imitation of models might inherently confer secondary benefits to mimics. Our results show that phenotypic plasticity can act as a mechanism to ease constraints that are typically associated with deception. VIDEO ABSTRACT.

Colour vision and response bias in a coral reef fish.

Animals use coloured signals for a variety of communication purposes, including to attract potential mates, recognize individuals, defend territories and warn predators of secondary defences (aposematism). To understand the mechanisms that drive the evolution and design of such visual signals, it is important to understand the visual systems and potential response biases of signal receivers. Here, we provide raw data on the spectral capabilities of a coral reef fish, the Picasso triggerfish Rhinecanthus aculeatus, which is potentially trichromatic with three cone sensitivities of 413 nm (single cone), 480 nm (double cone, medium sensitivity) and 528 nm (double cone, long sensitivity), and a rod sensitivity of 498 nm. The ocular media have a 50% transmission cut off at 405 nm. Behavioural experiments confirmed colour vision over their spectral range; triggerfish were significantly more likely to choose coloured stimuli over grey distractors, irrespective of luminance. We then examined whether response biases existed towards coloured and patterned stimuli to provide insight into how visual signals - in particular, aposematic colouration - may evolve. Triggerfish showed a preferential foraging response bias to red and green stimuli, in contrast to blue and yellow, irrespective of pattern. There was no response bias to patterned over monochromatic non-patterned stimuli. A foraging response bias towards red in fish differs from that of avian predators, who often avoid red food items. Red is frequently associated with warning colouration in terrestrial environments (ladybirds, snakes, frogs), whilst blue is used in aquatic environments (blue-ringed octopus, nudibranchs); whether the design of warning (aposematic) displays is a cause or consequence of response biases is unclear.