How Fishes Create Connections in Pelagic Ecosystems: Lanternfishes (Myctophidae) in the Gulf of Mexico

Lanternfishes are a highly diverse and globally-important family of fishes, forming a ubiquitous part of the deep-pelagic micronekton. The majority of lanternfish species conduct diel vertical migrations (DVMs) from the mesopelagic (200 – 1000 m) to the epipelagic (0 – 200 m), where they feed at night. As voracious zooplanktivores and an important food source for commercially-important fishes, seabirds, and deep-living predators, lanternfishes create important trophic linkages between coastal, upperocean, and deep-ocean ecosystems, and form an important part of the biological pump. Nonetheless, relatively little is known about the variability of lanternfish biodiversity, assemblage structure, and species distribution patterns, or of their DVM behaviours over spatial and temporal scales. In this study, we present a synthesis of recent research findings examining the vertical and horizontal distribution patterns of the myctophid assemblage in the Gulf of Mexico, including temporal and spatial (relative to mesoscale oceanographic features) variability. The analyses were conducted using depth-stratified data (spanning 0 – 1500 m), collected between 2011 and 2017 across a 200 x 700 km region. Biodiversity analyses suggest that the myctophid assemblage is well-mixed through the northern Gulf of Mexico with a relatively stable species composition over time. However, abundance data show greater variability across spatial and temporal scales. We discuss the implications of these findings for ecosystem structuring and carbon transfer between the surface and deep oceans.