Settlement patterns, size and growth of puerulus and juvenile rock lobster Jasus lalandii at an oyster farm in Saldanha Bay, South Africa

  • JC Groeneveld
  • CL Greengrass
  • DL van Zyl
  • GM Branch

Abstract

Trends in the abundance, size and growth of newly settled pueruli and early juveniles of the rock lobster Jasus lalandii were determined from samples obtained from mesh bags used for oyster mariculture in Saldanha Bay, South Africa. Totals of 3 842 lobster pueruli and 10 158 juveniles were captured between August 2005 and June 2006, and distinct puerulus settlement events were identified in November and January. Juveniles also peaked during these months as well as in March. The size of newly settled pueruli increased significantly between October and March. The carapace length (CL) of pueruli and juveniles overlapped between 8.5 mm (smallest juvenile) and 10.4 mm (largest puerulus), and 50% of pueruli moulted into juveniles by 9.5–9.6 mm CL. There was a size progression in juveniles, with larger individuals in February and March reflecting an accumulation of juveniles from the earlier settlement events. The estimated growth increment from puerulus to first juvenile instar was 0.5–1.5 mm (4.9–16.1%), increasing to 1.4–2.5 mm (14.4–23.3%) for the second instar. Recruitment of J. lalandii pueruli occurred during periods when strong southerly winds prevailed, which results in a general offshore movement of surface waters along the West Coast and upwelling of cold nutrientrich bottom waters. However, specific settlement events appeared to coincide with a change in wind direction, reduction in upwelling strength and increase in surface water temperatures, implying that larvae may take advantage of landward movements of surface waters during downwelling, or reversal of upwelling, to return them to shallow coastal waters.

Keywords: growth, Jasus lalandii, juvenile, puerulus, recruitment, rock lobster, settlement pattern, size, upwelling

African Journal of Marine Science 2010, 32(3): 501–510

Author Biographies

JC Groeneveld
Oceanographic Research Institute, PO Box 10712, Marine Parade, Durban 4056, South Africa
CL Greengrass
Marine Biology Research Institute, Department of Zoology, University of Cape Town, Rondebosch 7701, South Africa
DL van Zyl
Branch Fisheries, Department of Agriculture, Forestry and Fisheries, Private Bag X2, Rogge Bay 8012, South Africa
GM Branch
Marine Biology Research Institute, Department of Zoology, University of Cape Town, Rondebosch 7701, South Africa
Section
Articles

Journal Identifiers


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