Larval dynamics of the sand crab, Emerita analoga, off the central Oregon coast during a strong El Nino period

Populations of the sand crab, Emerita analoga, are well establishedon the California coast. However, populations in Oregon occursporadically and appear to be restocked by larvae drifting northfrom California. Due to increased northward transport in winterduring El Niño events, we would expect that larval recruitmentto northern populations should be higher during these periods.This hypothesis was tested by comparing larval abundances betweennon-El Niño and El Niño years, 1997 and 1998,respectively. In 1997, larval abundances and seasonality weresimilar to historical data from 1969–71. First zoeal (Z1)stage larvae were present during these summers, but in low numbers,indicating that E.analoga spawned off the coast of Oregon. In1998, strong larval recruitment from the south occurred, demonstratedby a large number of fifth zoeal stage (Z5) larvae collectedoff Oregon in April and May. The large numbers of Z1 found insummer 1998 indicate that the Z5, which arrived from Californiaearlier that spring, successfully recruited to adulthood andreproduced. These data indicate that Oregon E.analoga populationsare probably dependent on larvae travelling from Californiain the Davidson Current. It follows that this species couldbe used as an indicator of coastal current fluctuations suchas those seen during El Niño events.