Discovery of a large offshore population of the northeast Pacific burrowing shrimp Neotrypaea sp. (Decapoda: Axiidea)

The burrowing ghost shrimp Neotrypaea californiensis and Neotrypaea gigas, are recognized primarily from soft-sediment intertidal mudflats of estuaries and coastal lagoons in the northeastern Pacific from southern Alaska to Baja California. Individual records, however, are also known from occasional deep-water offshore collections. In previous offshore grab samples from California to Washington, USA, Neotrypaea spp. were present in about 14% of stations between 20 and 130 m depth. We assumed these usually low density (1–2 per core) small individuals were errant settlers from estuarine sources until summer 2019 when we found the first known large multi-year class population in an area 58–77 m deep 12 km offshore of Newport, Oregon, USA. The newly discovered Neotrypaea population, that we tentatively identify as Neotrypaea gigas, occurred at 35 of 52 stations (67%) in densities up to 26 individuals per 0.1 m² box core and included multiple size classes. Plan view camera samples indicate burrow densities of over 400 openings m⁻². This is the first report of a major burrowing shrimp population on the continental northeast Pacific coastal ocean.

• We found a large population of Neotrypaea burrowing shrimp in ∼70 m water depth.

• The number and extent of offshore Neotrypaea exceed that of the nearby estuary.

• Offshore shrimp may be a substantial new benthic food source.

• Burrowing and hydraulic activities are likely to have significant ecosystem consequences.