Our Marine Invertebrate Zoology 2016 students first noticed the Pacific sand crab, Emerita analoga, on Keeha Beach, a wave-exposed sandy beach on Vancouver Island, British Columbia (48°47’05”, 125°11’09”). These animals are a dominant member of the wave-exposed sandy beach macrofauna of California and Oregon, with occasional records from Washington to Alaska suggested to correspond to El Niño Southern Oscillation (ENSO) events. E. analoga were observed on the west coast of Vancouver Island, serendipitously during haphazard exploration by the Marine Invertebrate Zoology students. Although this same section of beach had been explored at the same time of year in annual field trips (2006 and 2008–2015), with similarly unstructured but wide-ranging intertidal meanderings by a group of 15–22 students, we had not previously seen this species here.
Given that in California, E. analoga accumulates harmful algal bloom toxins, is consumed by crabs, fish, birds, and marine and terrestrial mammals, and serves as the intermediate host for a variety of parasites, including the peritonitis-inducing acanthocephalan implicated in sea otter mortalities, the implications of this range expansion are complex. As coastal waters warm, we predict that E. analoga will colonize sandy beaches north of its current range, where it may serve as an abundant prey item and as a vector for the trophic transfer of toxins and parasites.
Wonham, M.J. & M.W. Hart. 2018. El Niño Range Extensions of Pacific Sand Crab (Emerita analoga) in the Northeastern Pacific. 2018. Northwest Science, 92 (1): 53-60. https://doi.org/10.3955/046.092.0106