Jennifer E. Caselle

Reef manta rays Mobula alfredi are large, filter-feeding elasmobranchs known to aggregate in coastal areas and island archipelagos. Effective spatial conservation strategies, such as marine protected areas (MPAs), for this mobile marine species rely on a comprehensive understanding of movement behavior. To better understand movement patterns, we externally deployed 58 acoustic tags on reef mantas at the Palmyra Atoll National Wildlife Refuge and monitored the presence of mantas on an extensive array of acoustic receivers (n = 85) for close to a decade. We documented an average maximum residency rate of 88% as well as consistent use of all 4 primary habitat types at Palmyra—the lagoon system, reef terrace, forereef, and channel. Notably, the highest rates of detection were recorded in the nutrient rich lagoon habitats (69% of detections). Manta movements displayed a diel structure, with a preference for the forereef, reef terrace, and channel during daylight hours, and the lagoon at night. We also found bimodal peaks of activity during new and full moons. In addition, detections around the atoll increased during the cooler periods of fall and winter. Our findings demonstrate that the no-fishing regulations at Palmyra Atoll are an effective spatial management strategy for this resident population of reef mantas and indicate that reef ecosystems in remote locations may be well-suited for designation as MPAs, offering protection for threatened elasmobranch species.

Large‐scale marine protected areas (LSMPAs; > 1000 km²) provide important refuge for large mobile species, but most do not encompass species' ranges. To better understand current and future LSMPA value, we concurrently tracked nine species (seabirds, cetaceans, pelagic fishes, manta rays, reef sharks) at Palmyra Atoll and Kingman Reef (PKMPA) in the U.S. Pacific Islands Heritage Marine National Monument. PKMPA and the U.S. Exclusive Economic Zone encompassed 39% and 54% of species movements (n = 83; tracking duration range: 0.5–350 days), respectively. Species distribution models indicated 73% of PKMPA contained highly suitable habitat. Under two projected future scenarios (SSP 1–2.6, “Sustainability”; SSP 3–7.0, “Rocky Road”), strong sea surface temperature gradients initially could cause abrupt oceanic change resulting in predicted habitat loss in 2040–2050, followed by an equilibrium response and regained habitat by 2090–2100. Current and future suitable habitats were available adjacent to PKMPA, suggesting that increased MPA size could enhance protection. Our three‐tiered approach combining animal tracking with publicly available remote sensing data and future projected environmental scenarios could be used to design, study, and monitor protected areas throughout the world. Holistic approaches that encompass diverse species and habitat use can enhance assessments of protected area designs. Animal telemetry and remote sensing may be helpful for ascertaining the extent to which other MPAs protect large mobile species in the future.

Most platforms for collecting images to characterise marine benthic habitats involve a downward or forward‐facing field of view that is relatively constrained (~70°), covering a relatively small area of benthos (downward ~1 m², forward ~25 m²). Here we propose the use of a four‐camera platform having a wide combined field of view (~280°), covering a much greater area (up to 100 m²). We also present a stereo‐camera configuration that has the added benefit of being able to accurately measure sample area and dimensions of benthic biota. The design proposed is robust and self‐righting, facilitating rapid deployment and retrieval from a range of vessels, depths and environments. We present an exemplar workflow to generate a habitat map (~100 km²) within a no‐take National Park Zone within the South‐west Corner Marine Park, Australia and demonstrate the benefit of increasing the field of view to estimate habitat heterogeneity. The relatively broad sample unit of this wide‐field drop camera is well suited to estimating coverage (e.g. of a seagrass bed) and habitat mapping. It is time‐efficient in the field, enabling spatially balanced sampling designs to acquire ground‐truthing data for medium‐ to large‐scale habitat mapping projects. This platform is a practical tool to monitor change in marine environments and assess the environmental impact (e.g. sea bed alteration) of activities such as offshore energy or fishing gears.

Marine protected areas (MPAs) are widely implemented tools for long‐term ocean conservation and resource management. Assessments of MPA performance have largely focused on specific ecosystems individually and have rarely evaluated performance across multiple ecosystems either in an individual MPA or across an MPA network. We evaluated the conservation performance of 59 MPAs in California's large MPA network, which encompasses 4 primary ecosystems (surf zone, kelp forest, shallow reef, deep reef) and 4 bioregions, and identified MPA attributes that best explain performance. Using a meta‐analytic framework, we evaluated the ability of MPAs to conserve fish biomass, richness, and diversity. At the scale of the network and for 3 of 4 regions, the biomass of species targeted by fishing was positively associated with the level of regulatory protection and was greater inside no‐take MPAs, whereas species not targeted by fishing had similar biomass in MPAs and areas open to fishing. In contrast, species richness and diversity were not as strongly enhanced by MPA protection. The key features of conservation effectiveness included MPA age, preimplementation fisheries pressure, and habitat diversity. Important drivers of MPA effectiveness for single MPAs were consistent across MPAs in the network, spanning regions and ecosystems. With international targets aimed at protecting 30% of the world's oceans by 2030, MPA design and assessment frameworks should consider conservation performance at multiple ecologically relevant scales, from individual MPAs to MPA networks.

Animal consumers excrete dissolved inorganic nitrogen, an essential nutrient for regulating primary production and macroalgal growth in the ocean. Often overlooked in attempts to explain kelp forest productivity, relatively little is known about the role of consumers in nutrient cycling in temperate systems, such as the magnitude of nutrients excreted and the factors that influence spatial and temporal variability in consumer‐derived nutrients. To investigate the supply of ammonium (NH₄⁺) excreted by the dominant members of the nearshore rocky reef fish community, we combined empirically‐measured relationships between excretion rate and body mass with data on fish density and size structure from visual SCUBA surveys conducted from 2005 to 2018 in the northern Channel Islands, California, USA. The fish community excreted a substantial amount of ammonium to the kelp forest (mean: 95.5–131.3 μmol·m⁻²·h⁻¹), however excretion varied substantially among sites and over time (range: 23.1–247.9 μmol·m⁻²·h⁻¹). The ammonium supply was influenced by the establishment of marine protected areas (MPAs) that restricted fishing activities and environmental characteristics that influenced geographic and temporal shifts in the overarching fish community structure. Fish‐derived ammonium excretion rates were 50%–80% greater inside MPAs compared to areas open to fishing, while environmental and habitat characteristics (e.g. habitat vertical relief, kelp biomass, wave exposure, chlorophyll a) explained 85% of the spatial variation in community excretion rates. In contrast, large‐scale oceanographic phenomena (e.g. North Pacific Gyre Oscillation index) and past patterns of fish recruitment explained 57% of the temporal variation in nutrient excretion over the 14‐year time series. Results suggest that fish‐derived ammonium may provide an important and underappreciated nutrient source to kelp beds, particularly during low‐nutrient periods (e.g. seasonal reductions in upwelling or El Niño‐Southern Oscillation events), and that fishing disrupts these nutrient cycling pathways. Fishes likely play a critical role in supporting the resiliency of kelp forest ecosystems by supplying a relatively constant source of reduced nitrogen that can be utilized by giant kelp and other macroalgae to fuel primary production of biogenic habitat. Read the free Plain Language Summary for this article on the Journal blog.

The amount of ocean protected from fishing and other human impacts has often been used as a metric of conservation progress. However, protection efforts have highly variable outcomes that depend on local conditions, which makes it difficult to quantify what coral reef protection efforts to date have actually achieved at a global scale. Here, we develop a predictive model of how local conditions influence conservation outcomes on ~2,600 coral reef sites across 44 ecoregions, which we used to quantify how much more fish biomass there is on coral reefs compared to a modeled scenario with no protection. Under the assumptions of our model, our study reveals that without existing protection efforts there would be ~10% less fish biomass on coral reefs. Thus, we estimate that coral reef protection efforts have led to approximately 1 in every 10 kg of existing fish biomass.

The Tropical Indo-Pacific (TIP) includes about two thirds of the world’s tropical oceans and harbors an enormous number of marine species. The distributions of those species within the region is affected by habitat discontinuities and oceanographic features. As well as many smaller ones, the TIP contains seven large recognized biogeographic barriers that separate the Red Sea and Indian Ocean, the Indian from the Pacific Ocean, the central and eastern Pacific, the Hawaiian archipelago, the Marquesas and Easter Islands. We examined the genetic structuring of populations of Cirrhitichthys oxycephalus, a small cryptic species of reef fish, across its geographic range, which spans the longitudinal limits of the TIP. We assessed geographic variation in the mitochondrial cytb gene and the nuclear RAG1 gene, using 166 samples collected in 46 localities from the western to eastern edges of the TIP. Sequences from cytb show three well-structured groups that are separated by large genetic distances (1.58–2.96%): two in the Tropical Eastern Pacific (TEP), one at Clipperton Atoll another occupying the rest of that region and the third that ranges across the remainder of the TIP, from the central Pacific to the Red Sea and South Africa. These results indicate that the ~4,000 km wide Eastern Pacific Barrier between the central and eastern Pacific is an efficient barrier separating the two main groups. Further, the ~950 km of open ocean that isolates Clipperton Atoll from the rest of the TEP is also an effective barrier. Contrary to many other cases, various major and minor barriers from the Central Indo-Pacific to the Red Sea are not effective against dispersal by C. oxycephalus, although this species has not colonized the Hawiian islands and Easter Island. The nuclear gene partially supports the genetic structure evident in cytb, although all haplotypes are geographically mixed.

In ecosystems, sharks can be predators, competitors, facilitators, nutrient transporters, and food. However, overfishing and other threats have greatly reduced shark populations, altering their roles and effects on ecosystems. We review these changes and implications for ecosystem function and management. Macropredatory sharks are often disproportionately affected by humans but can influence prey and coastal ecosystems, including facilitating carbon sequestration. Like terrestrial predators, sharks may be crucial to ecosystem functioning under climate change. However, large ecosystem effects of sharks are not ubiquitous. Increasing human uses of oceans are changing shark roles, necessitating management consideration. Rebuilding key populations and incorporating shark ecological roles, including less obvious ones, into management efforts are critical for retaining sharks’ functional value. Coupled social-ecological frameworks can facilitate these efforts.

Marine Protected Areas (MPAs) have been implemented globally as a conservation tool to improve the health and function of marine ecosystems. Research has focused on assessing MPA effectiveness, however certain habitats and communities are often avoided because they are difficult or expensive to monitor. Mesophotic (30-100m) rocky reef fish communities are a valuable commercial and recreational resource that is highly targeted but often overlooked in monitoring due to depth restricted sampling. We used two MPAs in California’s statewide protection network, along with parried reference sites, to test how protection status along with environmental conditions influenced the abundance and biomass of three highly targeted species with varying life histories and habitat preferences. Depth and habitat were strong predictors for all groups; ocean whitefish ( Caulolatilus princeps ), California sheephead ( Semicossyphus pulcher ), and targeted rockfish ( Sebastes spp ). The pattern of these effects however, differed between the species groups and the influence of protection was mixed. This work highlights how species with high habitat affinities benefit differently from protection, as a function of depth and habitat representation within the MPA/reference pair. To accurately evaluate MPAs, and the network as a whole, researchers must recognize organism-habitat relationships and incorporate them when assessing conservation efforts.