Weber, S. B. | bioRxiv Science

bioRxiv2026

Migratory connectivity of pelagic predators between tropical Atlantic islands and seamounts revealed through passive acoustic telemetry

BACKGROUNDOceanic islands and seamounts are recognised as hotspots of abundance and diversity for marine top predators, such as sharks and large teleosts, and are hypothesised to function as migratory stepping stones for mobile, pelagic species. However, while movements of pelagic predators between such features have been documented in some oceans, evidence from the tropical Atlantic remains limited. RESULTSHere, we report on long-distance migrations of three species of pelagic predator between oceanic islands and seamounts in the tropical south Atlantic recorded via independent passive acoustic telemetry arrays. These include the first recorded trans-Atlantic migration of a Galapagos shark (Carcharhinus galapagensis) from Ascension Island (UK) to the Sao Pedro and Sao Paul Archipelago (Brazil) (minimum distance 1,930 km); the longest documented oceanic migration of an Almaco jack (Seriola rivoliana) from St Helena (UK) to Ascension Island (minimum 1,300 km); and multiple movements of Galapagos and silky sharks (C. falciformis) between two Mid-Atlantic Ridge seamounts and Ascension Island (minimum 265-325 km). These detections are notable given the limited duration, sample sizes, and temporal overlap of acoustic tracking studies in the region, suggesting substantial connectivity across large spatial scales. CONCLUSIONSOur findings provide empirical support for the role of oceanic islands and seamounts as connectivity hubs for pelagic predators in the tropical Atlantic, underscoring their importance as key nodes in marine protected area networks. More broadly, this study demonstrates the value of collaborative regional tracking networks in resolving large-scale movement patterns and informing marine management at ecologically relevant scales.

ecology↗

bioRxiv2024

Distinct functional roles of distributed cortical representations for working memory storage

While distributed cortical areas represent working memory contents, their necessity for memory maintenance has been questioned. We examined the differential effects of maintaining multiple items on the neural information across cortical regions. In each trial of the fMRI experiment, participants (n=81) had to memorize two items, each either an orientation or a pure pitch, for 13.8s and continuously recalled the target after the delay. We kept the overall working memory load constant, but varied the sensory modality of each item to vary the effective visual load. We show that increasing visual load decreased behavioural recall performance for orientations and continuous orientation-specific decodable information in visual cortex but less so infrontoparietal areas. Simulations show that this drop in decodable information is best interpreted as a drop in mnemonic information represented by patterns of visual cortex activity. Our results provide evidence for shared labour of visual cortices, where maintaining two versus one orientation leads to a loss in representational fidelity, and anterior cortices, where multiple items could be represented in a more robust but less precise format.

neuroscience↗