Culture environment and hatchery of origin influence growth, condition and feeding organ morphology in the Pacific oyster Crassostrea gigas in South Africa

  • A Nel
  • G Pitcher
  • NB Richoux
  • S Jackson

Abstract

South Africa lacks a commercial oyster hatchery. To inform the sourcing of seed for future hatchery establishments, we compared half-sib Pacific oyster Crassostrea gigas cohorts from hatcheries in Namibia and Chile. We measured oyster growth, mortality, condition and feeding organ morphology in Algoa Bay (AB, Eastern Cape) and Saldanha Bay (SB, Western Cape), South Africa, from July 2011 to June 2012. Within SB, 14.3% of mean daily sea temperatures exceeded this species’ thermal optimum of 19 °C, compared to 50.5% in AB. Food abundance (mean daily chlorophyll a concentration) in SB (7.8 mg m–3) was double that in AB (3.9 mg m–3) where, presumably to increase particle clearance rates in a relatively phytoplankton-poor environment, oysters had larger gill:palp surface area ratios. Plankton fatty acid profiles (indicators of food quality) differed between locations. In AB, instantaneous growth rates differed between cohorts, and trends varied seasonally. Within both locations, condition index was usually higher in Chilean oysters, whereas shell density was higher in Namibian oysters. In AB only, Chilean seed suffered substantially higher summer mortalities than Namibian seed, suggesting that the latter are more suited to temperatures in AB. AB should also be assessed for culture of the indigenous oyster species that occur there.

Keywords: bivalves, fatty acid composition, long-line culture, mortality, phenotypic plasticity, phytoplankton

African Journal of Marine Science 2014, 36(4): 481–491

Author Biographies

A Nel
Department of Botany and Zoology, Stellenbosch University, Stellenbosch, South Africa; current address: Department of Ichthyology and Fisheries Science, Rhodes University, South Africa
G Pitcher
Branch: Fisheries Management, Department of Agriculture, Forestry and Fisheries, Cape Town, South Africa; Department of Biological Sciences, University of Cape Town, Cape Town, South Africa
NB Richoux
Department of Zoology and Entomology, Rhodes University, Grahamstown, South Africa
S Jackson
Department of Botany and Zoology, Stellenbosch University, Stellenbosch, South Africa; current address: Department of Ichthyology and Fisheries Science, Rhodes University, South Africa
Published
2015-04-01
Section
Articles

Journal Identifiers


eISSN: 1814-2338
print ISSN: 1814-232X