METHYLMERCURY ACCUMULATION IN MESO- AND BATHYPELAGIC FISH OF THE NORTHERN GULF OF MEXICO

Humans are exposed to toxic methylmercury (MeHg) mostly from the consumption of seafood, particularly top-predator fish (e.g., tuna, swordfish, king mackerel) that that can accumulate high levels of MeHg. A recent investigation has shown that MeHg concentrations in predatory fish of the subtropical North Pacific Ocean increase with greater foraging depth. However, little is known about the MeHg content of small prey fish inhabiting meso- and bathypelagic zones of the ocean. We are sampling dragonfish, lanternfish, bristlemouths, and hatchetfish with vertical net trawls at multiple locations in the northern Gulf of Mexico as part of the ongoing DEEPEND project. Preliminary results suggest that MeHg concentrations vary widely within and among these fish species. The three species of Myctophiformes fishes that migrate to shallower depths to feed at night have lower concentrations of MeHg than four of the five Stomiiformes species that do not migrate from depth. Differences of MeHg concentrations in prey fish as a function of vertical migration and foraging depth in the ocean provide a mechanism to explain how concentrations in predatory fish increase with greater foraging depth.