| || || Penaeus monodon -- Virus diseases -- Fiji, Shrimps -- Diseases -- Fiji, Shrimp industry -- Fiji|
| || || The quality of black tiger shrimp Penaeus monodon broodstock among natural populations in the Fiji Islands : their viral-disease status |
Author: Waqairatu, Salote.
Institution: University of the South Pacific.
Subject: Penaeus monodon -- Virus diseases -- Fiji, Shrimps -- Diseases -- Fiji, Shrimp industry -- Fiji
Call No.: Pac QL 444 .M33 W37 2008
Copyright:Under 10% of this thesis may be copied without the authors written permission
Abstract: As a growing multi-billion dollar industry, the world-wide shrimp industry has encountered diseases especially due to viruses that have been a major stumbling block to its expansion. In the South Pacific, shrimp industries are currently operating in New Caledonia, French Polynesia, Solomon Islands, Vanuatu and Fiji (Litopenaeus stylirostris). In Fiji alone there is a large and growing demand for shrimp. The high potential of Penaeus monodon or black tiger shrimp as a major source of revenue, and its natural presence in Fiji waters, led to the initiation of this study. The objectives of the study were three-fold; (i) to assess the quality of Fiji P. monodon for aquaculture by determining their viral-disease status; (ii) to determine the possible origin (indigenous or introduced) of any viruses found in Fiji P. monodon, and (iii) to obtain information about Fiji P. monodon broodstock availability by documenting traditional knowledge of capture methods, seasonality, and geographical and temporal abundance. Wild P. monodon shrimp samples were collected from five study sites (Dreketi, Muanisolo, Vunibau, Buretu and Moala) located in the North, South, Central-Eastern and Western divisions of Fiji. These samples were analysed at the Commonwealth Scientific and Industrial Research Organisation (CSIRO) Aquaculture Health Laboratory (Livestock Industries division) Brisbane, Australia; as part of the 'Sustainable aquaculture development in the Pacific region and northern Australia' project. The project was funded by the Australian Centre for International Agricultural Research (ACIAR). A total of 247 shrimp (from the five different sites within Fiji) were screened for eight different shrimp viruses namely; Hepatopancreatic parvovirus (HPV), Monodon baculo virus (MBV), Infectious hypodermal and haematopoietic necrosis virus (IHHNV), White spot syndrome virus (WSSV), Mourilyan virus (MoV), Taura syndrome virus (TSV), Gill-associated virus (GAV) and Yellow head virus (YHV). All samples were collected and tested in 10 separate pools, each containing 5 shrimp. Polymerase chain reaction (PCR) and histology were the two diagnostic methods used. The PCR method was used in three different formats, namely conventional PCR, Realtime PCR and Real-time PCR primers used in a conventional format. In situ hybridisation and routine haemotoxylin and eosin (H&E) staining were used as histological tools to determine any abnormal histology of shrimp tissue, which may support the PCR data. Fiji shrimp viral DNA was sequenced to determine the presence of any unique viral DNA strains. The PCR results of the study revealed HPV, MBV, IHHNV, MoV and GAV to be present in all samples except for MBV absent in one of the five sites (Vunibau). H & E stains and in situ hybdridisation of selected samples that were positive for certain viruses, also supported the PCR results. Of the four viral DNA sequences studied (HPV, MBV, MoV and GAV) HPV from Fiji showed a significant 19.4% difference to the Thai (control) HPV strain, but was 99.6% similar to an Indian strain. Fiji GAV and MoV were 0.4% to 2.6% different to the Australian GAV and MoV strains respectively. Fiji MBV was also highly similar (99.1%) to an Indian strain. The sequences of Fiji HPV and MBV suggest an introduction of the viruses via an Indian origin. Fiji GAV and MoV sequences were very similar to the Australian strain and suggest a possible origin from this region. However, as shrimp virus diagnostic tests have not been performed on samples collected prior to the introduction of Australian P. monodon PL into Fiji there may be other sources of these viruses. Further research would need to be carried out to confirm the origins of these viruses. Study of traditional knowledge held by the five communities revealed that the significance of shrimp depends largely on its availability and monetary value. Of the five study sites, Moala is the best site for P. monodon broodstock collection; however Vunibau and Buretu can also be potential sites for the same purpose. Availability of broodstock sizes is seasonal (October-March). Muanisolo and Dreketi mainly yielded small juveniles of a size suitable for on-growing. If small juveniles were also present at Moala, Vunibau and Buretu, then they were not easily caught by the fishing methods in use there. Value can potentially be added to these fisheries through grow-out of larger juveniles via aquaculture techniques. The traditional methods of capture at some sites are efficient but can be modified depending on the purpose of capture. An increase in shrimp demand may be a motivating factor to catch more shrimp and therefore build up traditional knowledge further. This study has shown that viruses exist in Fiji P. monodon and were all detected in a sub-clinical state in the absence of overt disease signs. The implications of this study are positive for Fiji's potential shrimp aquaculture industry, capacity-building for The University of the South Pacific and the South Pacific region as a whole.