Life-history parameters of white stumpnose Rhabdosargus globiceps (Pisces: Sparidae) in Saldanha Bay, South Africa, with evidence of stock separation

  • CG Attwood
  • TF Næsje
  • L Fairhurst
  • SE Kerwath

Abstract

White stumpnose Rhabdosargus globiceps were sampled over 24 months in Saldanha Bay on the west coast of South Africa. The species is a rudimentary hermaphrodite, with < 1% of mature fish having simultaneously developed ovaries and testes. Spawning activity extended from September to March and peaked in October and February. Mature males developed spawning colouration in spring, which can be used as an indicator of spawning activity. The amount of abdominal fat correlated with the spawning cycle in both sexes, suggesting that abdominal fat reserves are used in the development of gonads. Seasonal variation in the condition index suggests a slightly greater investment in reproduction by males than females. Females grew slightly faster than males and attained a larger size. The Saldanha Bay fish grew more rapidly and matured earlier than fish from populations on the south coast of South Africa. Age-at-50% maturity was 2+ for females and 1+ for males, and size-at-50% maturity was 222 mm (fork length) for females and 194 mm for males. It is necessary to use area-specific growth and life-history parameters for the assessment of the stock status of white stumpnose in South Arica.

Keywords: growth; life history; reproduction; Rhabdosargus globiceps; Saldanha Bay; stock separation

African Journal of Marine Science 2010, 32(1): 23-36

Author Biographies

CG Attwood
Marine Research Institute, Department of Zoology, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
TF Næsje
Norwegian Institute for Nature Research, NO-7485 Trondheim, Norway; South African Institute for Aquatic Biodiversity, Private Bag 1015, Grahamstown 6140, South Africa
L Fairhurst
LaquaR Consultants CC, PO Box 474, Eppindust 7475, South Africa
SE Kerwath
Marine Research Institute, Department of Zoology, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa; Department of Agriculture, Forestry and Fisheries, Private Bag X2, Rogge Bay 8012, South Africa
Published
2010-05-20
Section
Articles

Journal Identifiers


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