LONG-TERM INCREASE IN MESOPELAGIC FISH LARVAE IN THE SUBTROPICAL NORTH ATLANTIC OCEAN AND WESTERN ANTARCTIC PENINSULA

The high global biomass, broad distribution, and diel vertical migration behavior of mesopelagic fishes suggest they are important mediators of deep-sea carbon storage and open-ocean food webs. However, their abundance patterns and sensitivity to environmental change remain poorly understood. We investigated long-term patterns in the abundance of mesopelagic fish larvae incidentally collected in epipelagic zooplankton net tows from two long-term biogeochemical and ecological time series: the Bermuda Atlantic Time-series Study (BATS) in the North Atlantic subtropical gyre and the Palmer Long-Term Ecological Research (PAL LTER) program in the western Antarctic Peninsula (WAP) from 1994-2021 and 1993-2024, respectively. For the first time, we report long-term increases in the abundance of mesopelagic fish larvae in both regions. At BATS, we posit long-term change in the structure of the plankton food web has led to enhanced zooplankton biomass and increased abundance of fish larvae (e.g., bristlemouths Cyclothone spp.). Along the WAP, warming and changing physical dynamics could lead to habitat expansion for pelagic species, explaining recent increases in mesopelagic fish larvae (e.g., lanternfish Electrona antarctica) abundance at slope stations and modest increases at inshore (coastal) stations.  Because these earliest stages of pelagic fishes are thought to represent an index of adult spawning biomass, long-term increases in fish larvae may signal changes in micronekton communities in these ecosystems, with implications for pelagic food web dynamics and carbon cycling.

Presentation Preference: Oral

Primary Presenter: Tor Mowatt-Larssen, Virginia Institute of Marine Science (tmowattlarssen@vims.edu)

Authors:

Tor Mowatt-Larssen, Virginia Institute of Marine Science, William & Mary  (tmowattlarssen@vims.edu)

Deborah Steinberg, Virginia Institute of Marine Science, William & Mary  (debbies@vims.edu)