Observations on the Bloom-Forming Jellyfish Crambionella stuhlmanni (Chun, 1896) in the St Lucia Estuary, South Africa

Renzo Perissinotto ,Nicola K Carrasco ,R H Taylor ,Caroline H Fox

doi:10.5733/afin.054.0110

Renzo Perissinotto , Nicola K Carrasco + Show 2 more

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https://doi.org/10.5733/afin.054.0110

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Journal: African Invertebrates	Publication Date: Jan 1, 2013
Citations: 8	License type: cc-by

Affiliation: University of KwaZulu-Natal

Abstract

ABSTRACT Opportunistic observations made in the St Lucia estuarine lake, mainly during the period 1991 to 2000, show that the rhizostomatid scyphozoan Crambionella stuhlmanni often forms aggregations with densities in excess of 1 ind.m-3. Its salinity tolerance varies in the range of 12–65 ‰, with the highest jellyfish concentrations often observed at hypersaline levels of 40–65 ‰. Considering that the species has persisted in the system under the present closed mouth conditions, it is suggested that it is capable of completing its life cycle within the estuarine lake. Its role in the ecosystem needs to be investigated, with emphasis on its potential ability to remove suspended sediment particles from the water-column.

Highlights

Scyphozoan jellyfish are conspicuous because of their relatively large size and ability to form dense blooms at seasonal intervals (Brusca & Brusca 2003)
Jellyfish blooms have been reported with increased frequency from several parts of the world and it has been suggested that this phenomenon might be related to over-fishing and other human activities that are driving marine ecosystems off balance (Pauly et al 1998)
We report on findings for C. stuhlmanni, mostly obtained during a decade of opportunistic observations made in the St Lucia estuarine lake, between 1991 and 2000

Summary

Introduction

Scyphozoan jellyfish are conspicuous because of their relatively large size and ability to form dense blooms at seasonal intervals (Brusca & Brusca 2003). Jellyfish blooms have been reported with increased frequency from several parts of the world and it has been suggested that this phenomenon might be related to over-fishing and other human activities that are driving marine ecosystems off balance (Pauly et al 1998) This view has been contested by some researchers (Condon et al 2012, 2013), it has contributed to the formulation of the “fishing down the food chain” hypothesis (Pauly et al 1998), which is based on the assumption that the reduction in fish populations and of other large marine predator populations is promoting the growth of organisms from lower levels of the food chain (Graham 2001). The considerable phenotypic plasticity and crypsis that many species exhibit complicates their identification as well as attempts to carry out research on them (Dawson 2005; Neethling et al 2011)

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