Recruitment and succession variability in oyster fouling communitiesin bahia san quintin, baja California, Mexico

摘要

Bahia San Quintin is a shallow bay on the Pacific coast of the Baja California peninsula, Mexico. Historically dominated by soft sediment systems, the bay currently supports a locally important oyster aquaculture industry. In this system, oysters (Crassostrea gigas) are cultivated on ropes and remain suspended in the water column for about one year, until they attain market size. These systems provide a significant amount of available substrate for the development of diverse fouling communities, which are dominated by ascidians, sponges, bryozoans, and hydrozoans. These fouling communities harbor non-indigenous species, one of which is the Australian ascidian, Microcosmus squamiger. This ascidian can attain pest-like densities, completely covering oyster ropes and likely limiting the amount of food and dissolved oxygen accessible to the oysters. Oyster farmers view fouling communities as a nuisance that both harm their oyster crop and increase their handling time in cleaning and packaging oysters. To investigate the impact of these fouling communities on the oyster crop I have been taking monthly recruitment and community succession samples at three sites within Bahia San Quintin for the past two years (2004-2005). I used oyster shells as substrate panels to look at the abundance and prevalence of fouling organisms after 1, 2, 3, 6, and 12 month soaking periods. Results from this study establish recruitment patterns and variability, and community development and succession trends following recruitment. These results, coupled with seasonal and water temperature information, will help develop management options to mitigate impacts of detrimental fouling species.