Understanding large‐scale migratory behaviours, local movement patterns and population connectivity are critical to determining the natural processes and anthropogenic stressors that influence population dynamics and for developing effective conservation plans. Atlantic tarpon occur over a broad geographic range in the Atlantic Ocean where they support valuable subsistence, commercial and recreational fisheries. From 2001 through 2018, we deployed 292 satellite telemetry tags on Atlantic tarpon in coastal waters off three continents to document: (a) seasonal migrations and regional population connectivity; (b) freshwater and estuarine habitat utilization; (c) spawning locations; and (d) shark predation across the south‐eastern United States, Gulf of Mexico and northern Caribbean Sea. These results showed that some mature tarpon make long seasonal migrations over thousands of kilometres crossing state and national jurisdictional borders. Others showed more local movements and habitat use. The tag data also revealed potential spawning locations consistent with those inferred in other studies from observations of early life stage tarpon leptocephalus larvae. Our analyses indicated that shark predation mortality on released tarpon is higher than previously estimated, especially at ocean passes, river mouths and inlets to bays. To date, there has been no formal stock assessment of Atlantic tarpon, and regional fishery management plans do not exist. Our findings will provide critical input to these important efforts and assist the multinational community in the development of a stock‐wide management information system to support informed decision‐making for sustaining Atlantic tarpon fisheries.

Within oligotrophic ecosystems, resource limitations coupled with interspecific variation in morphology, physiology, and life history traits may lead to niche partitioning among species. How generalist predators partition resources and their mechanisms, however, remain unclear across many ecosystems. We quantified niche partitioning among upper trophic level coastal and estuarine species: American alligators (Alligator mississippiensis), bull sharks (Carcharhinus leucas), common bottlenose dolphins (Tursiops truncatus), common snook (Centropomus undecimalis), and Atlantic tarpon (Megalops atlanticus) in the Shark River Estuary of the Florida Coastal Everglades, USA using acoustic telemetry, stable isotope analysis, and visual surveys, combined with published diet and life history demographic information. Spatial and isotopic niche overlap occurred among most species, with variability in partitioning among interspecific interactions. However, seasonal variability in habitat use, movements patterns, and trophic interactions may promote coexistence within this resource-limited estuary. Beyond guild-level niche partitioning, predators within the Shark River Estuary also exhibit partitioning within species through individual specializations and divergent phenotypes, which may lead to intraspecific variability in niche overlap with other predators. Niche differentiation expressed across multiple organizational levels (i.e., populations and communities) coupled with behavioral plasticity among predators in oligotrophic ecosystems may promote high species diversity despite resource limitations, which may be important when species respond to natural and human-driven environmental change.

Summary The southeastern coast of Florida, USA supports a substantial recreational fishery, yet little is known of the coral reef ecosystem or fisheries resources past 50 m depth. Fish assemblages associated with low‐relief substrate and three vessel reefs between 50 and 120 m depth off southeast Florida were surveyed by remotely operated vehicles providing the first characterization of the mesophotic fish assemblages in the region. Two distinct assemblages were observed on low‐relief substrate and high‐relief vessel reefs. A total of 560 fishes of 42 species was recorded on 27 dives on low‐relief substrate, and 50 152 fishes of 65 species were recorded on 24 dives on three vessel reefs. Small planktivorous Anthiinae fishes and several economically valuable species were common on vessel reefs but rare on low‐relief substrate. Fish assemblages on vessel reefs more closely resembled those found at similar depths in high‐relief natural areas off east‐central Florida and the Gulf of Mexico than those associated with adjacent low‐relief habitat or nearby coral reef tracts. From a fisheries perspective, these results provide limited support to the hypothesis that in deep‐water regions with limited relief, vessel reefs may provide an opportunity to increase fish diversity and abundance by creating high‐relief habitat without compromising adjacent fish assemblages.

Queen triggerfish Balistes vetula are an ecologically and economically important species associated with coral reefs throughout the tropical Atlantic Ocean. To better understand spatial and temporal movement patterns and help determine the effectiveness of a no-take marine reserve (Buck Island Reef National Monument, BIRNM), 55 queen triggerfish were surgically implanted with acoustic transmitters and tracked for 434.6 ± 27.3 d (mean ± SE) within a large acoustic array in St. Croix, US Virgin Islands. Queen triggerfish displayed high site fidelity within the reserve during non-spawning months. Home range sizes, as measured by 95% minimum convex polygons and kernel utilization distributions, averaged 2.44 ± 0.30 and 3.34 ± 0.17 km 2 , respectively. High site fidelity was interrupted briefly during full moons from November to March (2015March ( -2017, when 22% of the tagged population (n = 12) undertook repeated migrations to a nesting area located approximately 12 km from BIRNM. During the same-season spawning periods, 5 other fish were exclusively detected at a receiver station within the reserve, indicating a possible local nesting area and resident (non-migratory) contingent of queen triggerfish. The high site fidelity of queen triggerfish during non-spawning months coupled with the discovery of a resident spawning population highlights the importance of BIRNM as a potential refuge from local fishing pressures. This study provides improved understanding of queen triggerfish movement ecology, an extremely valuable asset for the development of spatial management strategies throughout their range.