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Effect of ration on gonad development of the Pacific geoduck clam, Panopea generosa (Gould, 1850)

Authors

  • R. Marshall,

    1. Pacific Biological Station, Fisheries and Oceans Canada, Nanaimo, BC, Canada
    2. Faculty of Land and Food Systems, The University of British Columbia, Vancouver, BC, Canada
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  • R.S. McKinley,

    1. Faculty of Land and Food Systems, The University of British Columbia, Vancouver, BC, Canada
    2. Centre for Aquaculture and Environmental Research, The University of British Columbia/Fisheries and Oceans Canada, Vancouver, BC, Canada
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  • C.M. Pearce

    Corresponding author
    1. Pacific Biological Station, Fisheries and Oceans Canada, Nanaimo, BC, Canada
    2. Fisheries and Aquaculture Department, Vancouver Island University, Nanaimo, BC, Canada
    • Correspondence: C.M. Pearce, Pacific Biological Station, Fisheries and Oceans Canada, 3190 Hammond Bay Road, Nanaimo, British Columbia, Canada V9T 6N7. E-mail: Chris.Pearce@dfo-mpo.gc.ca

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  • Reproduced with the permission of the Minister of Fisheries and Oceans Canada.

Abstract

The effect of ration on Panopea generosa gonad development was tested over 52 days. Clams were fed Isochrysis sp. and Chaetoceros muelleri (50 : 50 cell count) at rations of 0.8 × 109, 2.4 × 109, 4.0 × 109, 5.6 × 109, 7.2 × 109 and 10.0 × 109 cells clam−1 day−1 (R1, R2, R3, R4, R5 and R6, respectively). The highest ration (R6) caused a 25% die-off within 3 days and was discontinued. Ration did not significantly affect condition index, gonadosomatic index, connective tissue occupation index or oocyte diameter. Clams fed the R5 ration (85% of which spawned from day 26 to 52) were more spent than clams in any other treatment with significantly fewer oocytes mm−2 than those fed the R1, R2 and R3 rations and significantly lower levels of sperm occupation than clams fed any other ration. Spawn percentages were low from day 26 to 52 in R1, R2 and R4 (15, 0 and 0%, respectively). Clams in the R3 treatment had a similar spawn percentage (100% from day 26 to 52) to those in the R5 treatment yet maintained gonads in a more ripened condition with higher levels of gamete occupation, making R3 the most likely ration to maximize gamete output over time.

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