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Archived – Feasibility of Pacific Oyster and California Sea Cucumber Polyculture
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Growth and production of California sea cucumbers (Parastichopus californicus), co-cultured with suspended Pacific oysters (Crassostrea gigas), were investigated in a 12-month study conducted at two sites of deep-water, suspended oyster culture in British Columbia. Rates of oyster biodeposition (faeces and pseudofaeces), and the utilization of this particulate material as a food source by P. californicus, were also examined.
Peaks in sedimentation rates (93.6 g dry wt m-2 d-1) through 8.5 m water depth were observed in April and July 2004. At the two study sites, maximum mean fluxes of total organic carbon in sediment traps at 8.5 m depth occurred in July 2004 and amounted to 3,123 and 4,150 mg dry wt C m-2 d-1. Maximum mean fluxes of total nitrogen at the two sites were 633 and 441 mg dry wt N m-2 d-1 which occurred in July and November 2004, respectively. Mean C/N ratios of particulate material in the sediment trap samples collected at the two sites ranged between 5.93 and 8.39 and may be classified as being of high nutritional value.
Sea cucumbers grown in trays at both sites successfully utilized biodeposits from the cultured oysters and showed a mean weight increase of 42.9 g in approximately 12 months (average growth rates for both sites ranged from 0.061 to 0.158 g d-1). Overall growth was affected by the absence of visceral organs and the cessation of feeding activity in the November 2004 sampling period. Mean values for organic content were significantly higher in the foregut of the sea cucumbers (233.0 mg g dry sediment-1) than in the sediment (64.3 mg g dry sediment-1) or in the hindgut (142.8 mg g dry sediment-1), showing both active selection of organic material from the sediments and digestion/assimilation of these organics in the gut. Organic material deposited in the trays was assimilated by P. californicus with an average efficiency of 48.4%.
The successful utilization of the naturally- available biodeposits from the cultured oysters by sea cucumbers suggest the feasibility of developing a commercial-scale co-culture system that would both reduce the amount of organic deposition underneath shellfish farms and produce a secondary cash crop.
Research team: Chris Pearce (DFO), Debbie Paltzat (UBC), Penny Barnes (CSR), Scott McKinley (UBC). For information contact Chris Pearce (E-mail: PearceC@pac.dfo-mpo.gc.ca). Submitted by DFO (ACRDP).
Apr. '04-Jun '05
Debbie Paltzat examines trays in which oysters and sea cucumbers are being cultured together
