Growth rates of the venus clam Ruditapes largillierti grown under experimental culture conditions in New Zealand

The growth rates and survivorship of juvenile and adult Ruditapes largillierti grown in mesh bags on two commercial oyster farm leases were assessed from March 1997 to January 1998. Clams in Okiwi Bay grew faster than those in the Mahurangi Harbour. Subtidal clams in Okiwi Bay grew faster than intertidal clams (1.6 and 1.2 mm month^-1, respectively). However, in the Mahurangi Harbour, clams grew faster in the intertidal: growth rates ranged from 1 to 1.2 mm month^-1. This was attributed to increased siltation occurring in the subtidal regions around the oyster farms in the Mahurangi Harbour. No growth was recorded for adult clams ongrown in the Mahurangi Harbour. Survivorship of both juvenile and adult clams was generally high; initial mortalities (∼ 10%) in the Mahurangi Harbour were attributed to the stress of transportation. However, intertidal claros in Okiwi Bay experienced 20% mortality in January 1998, probably resulting from desiccation due to the high temperatures that occurred during this period. The results presented here suggest that R. largillierti may be suitable for commercial culture.