When mesophotic meets shallow: First records of deep‐associated reef fishes in a well‐studied tropical bay under the influence of spring–summer upwelling

We document the first records of reef fishes typically associated with mesophotic environments on shallow (<10 m) coral reefs inside a well-studied tropical bay. The vermilion snapper Rhomboplites aurorubens and the pygmy angelfish Centropyge aurantonotus, usually restricted to deeper (>40 m) shelf habitats along the Brazilian coast, were recorded inside Baía de Todos os Santos (BTS). Integrating long-term ecological and oceanographic monitoring, fisheries information and underwater visual records, we show that these occurrences coincided with coastal upwelling and the advection of cooler shelf waters. We propose that cold-water intrusions act as thermal corridors enabling cross-shelf movements.