Long‑term benthic monitoring shows amphipod declines and a contraction of historic gray whale feeding patches

A presenter identified as Jackie summarized multi‑decadal benthic time series from the Distributed Biological Observatory (DBO), focusing on DBO2 (the Chirikov/Cherikof basin) and adjacent lines. She said standardized sampling since about 2010 and earlier time series show a spatial contraction of amphipod‑dominated benthic patches that were historically abundant in the gray whale feeding grounds.

"Most of the amphipods that gray whales are feeding in on now are on the eastern part of the Cherikoff basin," Jackie said, describing time series and maps that show the historic feeding patch contracting eastward and shrinking in areal extent. She reported declines in both biomass and mean individual size of amphipods and other benthic invertebrates, which reduces the energy available per feeding event.

Jackie noted that the DBO time series also show regional increases in primary productivity in places but that changes in stratification and surface‑water dominance can reduce carbon export to sediments, lowering benthic food supply. She presented new caloric measurements and a per‑capita biomass/abundance index showing declines in the prey base in historic feeding areas.

Why it matters: amphipods and other benthic infauna historically provided a high‑energy prey base for suction‑feeding gray whales; declines in abundance and size reduce local carrying capacity and may force whales to shift foraging locations or rely more on pelagic prey such as krill. The presenter emphasized gray whales’ foraging flexibility but said a sustained loss of benthic prey poses a conservation and management concern.