| || || Naqasima, Milika R.|
| || || An investigation of public health and fisheries issues concerning Anadara antiquata (Mollusca, Bivalvia : Arcidae) and Batissa violacea (Bivalvia : Corbiculacea)|
Author:Naqasima, Milika R.
Institution: University of the South Pacific.
Subject: Shellfish fisheries--Health aspects--Fiji, Bivalvia--Fiji
Call No.: pac QL 430 .6 .F3 N36
Copyright:Under 10% of this thesis may be copied without the authors written permission
Abstract: Bivalves have the ability to accumulate high levels of pollutants in their tissues due t o their mode of feeding. This bioaccumulation of contaminants can pose a threat to public health. Samples of two bivalve species: Anadara antiquata, a marine cockle, and Batissa viotacea, a freshwater mussel, were collected at 2-monthly intervals from eight popular shellfish-harvesting areas. The bivalves were analysed for levels of the faecal coliform Escherichia coli, using t h e Most Probable Number technique. Three of the eight sites showed high E. coli levels on s o m e sample dates, indicating intermittent sewage pollution at those sites. The two bivalves a r e processed in different ways by local people before consumption, Anadara antiquata is n o r m a l l y eaten raw after rnarination in lemon juice and B. violacea is usually left to depurate in c l e a n fresh water overnight before boiling. The effects of marination, depuration and boiling o n bacterial content of the shellfish were examined, and numbers of viable bacteria were seen t o decrease after processing. The ability of A. antiquata to accumulate and depurate mercury f r o m its tissues was examined, to assess its suitability as a bio-indicator of mercury pollution. R e s u l t s showed that mercury was accumulated, however this species' potential as an indicator o r g a n i s m will need to be further investigated with some refinement to the mercury concentrations and t h e sampling intervals used. The density, stock abundance, distribution and yield of B. violacea i n the Rewa River was assessed to determine the size of the fishery and its importance to t h e livelihood of the rural population. It is estimated that the density of B violacea is 7 9 individuals/m2. and the standing crop is 5.9 x 108 individuals in the 7.5 km2 section of the R e w a where it is actively harvested. Their distribution appears to be related to the substratum t y p e , i i i with the greatest abundance observed where the substrate was gritty or gravelly sand. The fishery yield is 130 tonnes/annum. The B. violacea fishery is the largest freshwater fishery in Fiji in terms of both tonnage and value, and any sewage pollution of stocks would cause significant public health and economic stresses. Some options to manage any public health risk in Fiji's bivalve fisheries are discussed.