Quantifying Pelagic Habitat Use by Myctophids in the Northern Gulf of Mexico

Deep pelagic ecosystems are some of the largest on Earth but are amongst the least understood. As human impacts on the deep oceans continue to increase, there is an urgent need to understand the processes that influence pelagic fauna, particularly in deep waters. One of the most globally-important taxa are the Myctophidae, which are a ubiquitous component of the deep-pelagic micronekton and play key roles in the vertical and horizontal transfer of energy between ecosystems. In the present study, quantitative, depth-stratified trawl data were analysed to assess the distributions of the dominant myctophid species in relation to physical and chemical environmental variables in the northern Gulf of Mexico (GoM) during summer 2011. The data were collected through the NOAA-supported Offshore Nekton Sampling and Analysis Program. Significant correlations to meso-scale features associated with the Loop Current were observed at depths to 1000 m, but the effects were weak and only explained 6 - 11% of the observed variance in assemblage composition. These results indicate that myctophid assemblages were well-mixed in 2011 and suggest high dispersal rates across the study region (>500 km). These findings have implications for understanding the sensitivity of myctophid populations following different forms of disturbance.