Seabirds, Herring and the Razor's Edge—To Finesse or Forgo When Facing Ecological Extirpation

Migrant juvenile Atlantic herring ( Clupea harengus ) from across the greater Gulf of Maine (GoM) provide pelagic forage in the Grand Manan Island region, a major trophic hub. A centuries‐old weir fishery for herring juveniles, never monitored, has collapsed from chronic GoM overfishing. Razorbills ( Alca torda ) and Atlantic puffins ( Fratercula arctica ) nest on nearby Machias Seal Island, feeding their chicks with these herring. Using published data, this study demonstrates probabilistic relationships between weir‐fishery landings of juvenile herring (~availability) and relative portions of young herring fed to both razorbill and puffin chicks. Herring‐diet differences for razorbills suggest nuanced forecasting of prospective imminent fishery collapses. Facing collapse, razorbills are more likely to capture herring in addition to less‐pelagic alternate species (hake, sand lance), while puffins make more use of the alternates. Previous research, based on exploratory correlation and regression, did not demonstrate these connections for the Grand Manan region. As indicator “units,” the probabilistic herring‐seabird relationships raise the potential of interspecific corroboration in herring recruitment forecasts. For example, when landings are low, razorbill use is greater than puffin use, and razorbill herring biomass use remains moderate‐to‐high, fisheries for juveniles could place increased multiyear limits on prospective catches system‐wide. Such relationships could be of considerable precautionary use, since systemic fishing‐induced forage deficiencies have become the norm. With the erosion of resilience, ecosystem components are now at high risk of extirpation in the northeastern GoM. The concepts should increase understanding of Anthropocene challenges and the actions required of humans to prevent depletion of natural resilience in ecosystems.