Larval production, dispersal, and growth in a fjord: a case study on larvae of the sand dollar Dendraster excentricus

In a small shallow fjord with predominantly wind-driven circulation, larvae of the sand dollar Dendraster excentricus (Eschscholtz) do not persist for longer than 2 wk after a local population in the fjord spawns. Changes in distnbuhon and abundance of larval cohorts indicate that larvae are advected out of the fiord and thus contribute to a regional larval pool. A series of plankton samples at the start of 2 reproductive seasons showed that cohorts of larvae are produced during spring tides that expose the intertidal adult population to air. Growth rates of 1 to 3 wk old larvae of D. excentricus and Strongylocentrotus franciscanus in the fjord are comparable to those reared in the laboratory. Later in the season, advanced-stage larvae of D. excentricus are found in surface waters in the fjord; this may enhance their chances of locating suitable habitat for settlement. Many of these advanced-stage larvae have shortened larval arms that may indicate delayed metamorphosis.