Little is known about recruitment in Olympia oysters Ostrea conchaphila, mainly owing to scarcity of well-established populations to study.  During peak years of harvesting in Puget Sound, Washington (1900-1928) apparently some 120 million individuals were removed each year along with loose shell cultch.  With the idea that loss of suitable substratum for settlement may have contributed to overall population demise, researchers at the University of Washington, Seattle set up experimental plots at the North Bay Oyster Reserve, one of the few remaining beds in Puget Sound.  Results show a small recruitment peak in late July, with tests of tidal elevation and substratum type showing trends towards better recruitment at lower levels on shell substrata (results for the 4 shell treatments could not be differentiated statistically).  Based on their results the authors recommend habitat restoration at low intertidal levels involving provision of O. lurida shell cultch.  White et al. 2009 J Shellf Res 28: 107. Photograph courtesy Monterey Fish Market, California.

NOTE  the tests involve establishment of 1m2 plots at 3 tidal elevations with 6 different substrata: bare, gravel, live O. lurida, shell of O. lurida, live Crassostrea gigas, and shell of same.  Plots are established in May and monitored after 5mo and 11mo

NOTE  of the 4 shell treatments, this is the only one that received significantly more recruits than the gravel or bare treatments

Olympia oysters Ostrea conchaphila 0.6X

A study by researchers at California State University, Fullerton on settlement/recruitment of Olympia oysters in 2 southern California estuaries shows peak appearance of spat in June.  A second, minor peak in August, as found by other investigators, is absent at both sites.  However, settlement in both estuaries is prolonged (May-Nov in Newport and Jun-Feb in Carlsbad).  Temperature records at either site do not correlate with either initiation or termination of settlement (see graph).  Seale & Zacherl 2009 J Shellf Res 28: 113.

NOTE  sites are Upper Newport Bay in Newport and Aqua Hedionda Lagoon in Carlsbad, California.  Settlement tiles are placed out at 2 locations in each estuary (see map).

NOTE  the graph shows recruitment (to spat size) for the "most-settled" site in Newport Bay.  Data for the most-settled site in Aqua Hedionda Lagoon show a similar pattern. The authors note that settlement varies greatly at the 2 locations within each estuary, even though separated by no more than about 600m