Population irruption of the clam Meretrix morphina in Lake St Lucia, South Africa

Authors

  • Nelson A. F. Miranda SARChI Chair: Shallow Water Ecosystems, Nelson Mandela University, Port Elizabeth, South Africa http://orcid.org/0000-0002-9308-6688
  • Nasreen Peer SARChI Chair: Shallow Water Ecosystems, Nelson Mandela University, Port Elizabeth, South Africa http://orcid.org/0000-0003-4786-1257
  • Renzo Perissinotto 1. SARChI Chair: Shallow Water Ecosystems, Nelson Mandela University, Port Elizabeth, South Africa 2. School of Life Sciences, University of KwaZulu-Natal, Durban, South Africa
  • Nicola K. Carrasco School of Life Sciences, University of KwaZulu-Natal, Durban, South Africa
  • Salome Jones School of Life Sciences, University of KwaZulu-Natal, Durban, South Africa
  • Ricky H. Taylor Hydrological Research Unit, Department of Hydrology, University of Zululand, KwaDlangezwa, South Africa
  • Caroline Fox Ezemvelo KwaZulu-Natal Wildlife, St Lucia Estuary, St Lucia, South Africa

DOI:

https://doi.org/10.17159/sajs.2017/20160397

Keywords:

bivalve molluscs, poleward spread, estuaries, climate, salinity

Abstract

The thick-shelled clam Meretrix morphina, previously referred to as Meretrix meretrix, now occurs in the west Indian Ocean region, along the eastern seaboard of Africa, from the Red Sea to the Mlalazi Estuary, close to the Tugela River. Its presence in South Africa is only of recent recording. Meretrix morphina was detected for the first time in Lake St Lucia in 2000. The population declined and was not detected from 2005 until 2011, most likely as a result of a severe drought that resulted in widespread desiccation and hypersalinity in the lake. The system then experienced increased freshwater input resulting in lower salinities from 2011 until 2014, during which time M. morphina reappeared and their population gradually increased. In 2015, M. morphina became abundant in St Lucia, attaining unprecedented densities of 447 ind./m2. Biomass, expressed as a fresh weight, varied in the different basins of St Lucia, ranging from 195 g/m2 at Lister’s Point to 1909.8 g/m2 at Catalina Bay. However, in 2016, when drought conditions returned, M. morphina disappeared. This species appears to thrive under brackish salinities and high temperatures. It is able to establish large populations with high biomass and can become dominant. However, M. morphina is sensitive to desiccation and hypersaline conditions. This clam has substantial commercial value and is exploited along the African east coast, particularly in Mozambique. In future, it may feature more prominently in South African estuaries. However, the ecology of M. morphina is still largely unknown.

Significance: 
  • First record of population irruption of M. morphina in South Africa.
  • Report on the largely unknown ecology of a commercially valuable bivalve.
  • Update on the taxonomy and poleward spread of M. morphina.

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Published

2017-07-31

How to Cite

1.
Miranda NAF, Peer N, Perissinotto R, Carrasco NK, Jones S, Taylor RH, Fox C. Population irruption of the clam Meretrix morphina in Lake St Lucia, South Africa. S. Afr. J. Sci. [Internet]. 2017 Jul. 31 [cited 2021 Sep. 21];113(7/8):5. Available from: https://sajs.co.za/article/view/3998

Issue

Section

Research Letter

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