'Set net' of Great Blue Heron (Ardea herodias)

Tom Okey observed:

On Island View Beach at 6:15 in the morning 14 great blue heron were lined up along a sandbar to a small tidal lagoon embayment and they were spaced evenly along that stand bar apparently waiting for fish to try to exit, as they were all facing towards shore. Their apparent 'set net' hunting configuration gave the impression that they were cooperating to catch almost-stranded forage fish in the intertidal zone as the tide ebbed.

Pacific hearing (Clupea pallasii) and possibly other nearshore forage fish have become unusually abundant this year in 2018. This is the very beach at which we have recently discovered the presence of sea otters after being absent for over a century (see other LEO observations a, b, and c).

Simulations that I conducted with the Prince William sound ecosystem model indicate the likelihood of a trophic cascade in soft sediment environments controlled by the presence of sea otters where sea otters would decrease the biomass of filter feeders such as clams and thus enable higher biomass of forage fishes and other near-shore commercial fishes through increases in available primary and secondary production (plankton). The presence of this 'set net' of blue heron, if a new occurrence, might indicate an increase in forage fishes, potentially due in part to the presence of sea otters.

.