October 21, 2026 — Following the Deepwater Horizon oil spill, scientists across the region jumped into action to monitor its impacts. One particular effort focused on pelagic nekton—the small critters like fish, shrimp, and cephalopods that swim freely in the ocean and serve as the base of pelagic food webs. The Deep-Pelagic Nekton Dynamics of the Gulf (DEEPEND) Consortium led this project to quantify long-term trends in the offshore fauna of the Gulf. While observed declines in these critical prey groups can’t be tied directly to the spill, scientists have not identified another likely explanation.
Tracking the Shift: A Decade of Deepwater Science
The first pelagic nekton sampling effort took place as soon as possible following the spill, with sampling occurring almost continuously for 9 months in 2011. These data represent the benchmark of pelagic nekton to which past and future numbers can be compared. The numbers were also similar to data collected during the 1980s and 1990s.
The next sampling involved six efforts across four consecutive years (2015–2018), followed by three more in 2021–2023. Overall, these efforts comprise more than a decade of abundance and composition data for pelagic nekton in the Gulf of America.
During each of these events, the project team sampled discrete depths from 0 to 1,500 meters in the Gulf using a 10-square-meter Multiple Opening/Closing Net and Environmental Sensing System, or MOCNESS, with 3 millimeter mesh. Once net tows were complete, the science teams identified and counted each of the animals collected in each sample.
In addition to traditional net-sampling methods, the team also used echosounders to measure acoustic backscatter in the water column during the day and at night. This allowed them to independently estimate relative abundance of animals in fine spatial detail. Scientists also collected tissue samples from three dominant lanternfish species to monitor changes in genetic diversity.