Shrimp health assessment in the west coast of Peninsular Malaysia with emphasis on the impact of aquaculture activity
Rapid growth of shrimp farming has caused destruction of mangroves, pollution of coastal waters due to nutrient loading, reduced biodiversity of wild shrimp and increased disease occurrence. The present study was undertaken to assess biodiversity of wild shrimp and prevalence of shrimp virus in dis...
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| Format: | Thesis |
| Language: | English |
| Published: |
2009
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/85593/1/FPV%202009%206%20ir.pdf |
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| Summary: | Rapid growth of shrimp farming has caused destruction of mangroves, pollution
of coastal waters due to nutrient loading, reduced biodiversity of wild shrimp and increased disease occurrence. The present study was undertaken to assess biodiversity of wild shrimp and prevalence of shrimp virus in disturbed
mangrove and pristine areas. The study also quantified stress in Penaeus
monodon exposed to ammonia, and their subsequent susceptibility to white
spot syndrome virus (WSSV).
Coastal waters off Matang and Kuala Selangor were selected as pristine and
disturbed mangrove areas respectively for monthly sampling of shrimp and
water from March 2006 to February 2007. Shrimp were sampled for the first 6
months during high tide by trawling and for the following 6 months during low tide by cast net. Penaeus monodon were challenged by WSSV following the
exposure of different levels (B.1, 3.B and 1.1 mg/L) of total ammonia nitrogen
(TAN), Haemo-chemicals [alanine transaminase (ALT), aspartate transaminase, (AST), total protein (TP), glucose and electrolytes (Na+, cI, and K+)] were
measured to quantify the stress caused by ammonia and WSSV. TaqManbased
real-time PCR was used to relatively quantify WSSV load in the shrimp
exposed to different levels of TAN with positive control shrimp which were not
exposed to TAN, but challenged with WSSV.
A total of 11,099 shrimp belonging to 12 penaeids and two palaemonids
species were collected over 12 months from both sites. Mean number of
species (7.44 ± 0.35), density (0.7B±O.1 shrimp/m2) and Shannon-Wiener
diversity index (1.4±0.1) of shrimp caught in the coastal waters off Matang were
significantly higher (p-c 0.01) than that off Kuala Selangor (6.29±O.35, 0.49±O.07
shrimp/m2 and 1.1±0.1 respectively). Nutrients (TAN, total nitrogen, and total
phosphorous) and chlorophyll a were significantly higher in the coastal waters
off Kuala Selangor than that off Matang. Prevalence of WSSV in Kuala
Selangor which was significantly correlated with TAN (~ = 0.B26, p<0.01) and
nitrite (~ = 0.962, p<0.01) was 5.1% in seven shrimp species, including
Macrobrachium equidense, Macrobrachium rosenbergii, Parapenaeopsis
hardwickii, and Metapenaeus affinis caught in the wild. In the coastal
ecosystem of Kuala Selangor, the destruction of mangroves and elevated
nutrient loadings due to shrimp farming activity might have diminished the biodiversity of shrimp. Furthermore, escapees of shrimp and other aquatic
organisms from adjacent shrimp ponds might have been the source of infection
to the wild shrimp population, where the infection would probably be
predisposed by the elevated nutrients (TAN).
The shrimp exposed to 8.1 mg/L TAN for 10 days revealed significantly high
haemolymph ALT, AST and TP, while shrimp exposed to 3.8 mg/L TAN showed
significantly low TP. These changes in haemolymph parameters showed that
exposure to 3.8 mg/L TAN for 48 hrs was sufficient to stress the shrimp. Stress
in shrimp exposed to ammonia for 10 days further increased significantly when
shrimp were challenged to WSSV. In addition, TP in shrimp exposed to 1.1
mg/L, 3.8 mg/L and 8.1 mg/L TAN decreased with increase in TAN treatments.
There was significantly higher virus load in shrimp exposed to three different
concentrations of TAN in the same ascending order as for the haemo-chemical
parameters. Even at low concentration (1.1 mg/L TAN) ammonia stress can
increase shrimp susceptibility to infection as shown by fold difference of WSSV
load. Therefore, exposure of shrimp to ammonia increases their susceptibility to
WSSV by decreasing the immuno competence as illustrated by haemochemical
parameters. |
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