Sustainable shrimp farming in Sri Lanka; Utilization of BMPs and antibiotics use

Objective

In the context of the fast-expanding shrimp farming industry in Sri Lanka, this study aimed to evaluate the distribution and understanding of BMPs, examine the relationship between BMPs and disease outbreaks, and analyze the current antibiotic usage trends through a fact-finding survey.

Materials and Methods

A questionnaire survey was conducted in 131 shrimp farms located in Puttalam District in North Western Province, where shrimp farming is thriving in Sri Lanka. The survey was conducted from September to October 2021. In addition, in August 2022 and August 2023, interviews were conducted with shrimp farms in Puttalam district and Batticaloa district, shrimp hatcheries, and export companies. Data were analyzed using descriptive statistics, Probit, and Tobit regression analysis.

Results

The item-count technique revealed a significant (p < 0.05) difference in the use of antibiotics without consulting experts, signifying inappropriate use. No aquaculture farmer reported being unaware of BMPs, and among the 45 farmers who attended a BMPs seminar, 30 claimed to possess a good understanding of BMPs. Probit and Tobit regression results revealed that the rate of understanding of BMPs, education level, and obtaining information on the sanitation management of shrimp farming from extension and guidance organizations were inversely associated with both disease incidence in shrimp farming and shrimp discards.

Conclusion

Although the use of antibiotics is prohibited in BMPs, the analysis results suggest inappropriate use of antibiotics. The findings indicate that enhanced BMP understanding can reduce disease incidence and shrimp discards, emphasizing the need for incentives to promote BMP adoption and reduce the necessity for antibiotics.

Non-Invasive Methods for Assessing the Welfare of Farmed White-Leg Shrimp (Penaeus vannamei)

Gradually, concern for the welfare of aquatic invertebrates produced on a commercial/industrial scale is crossing the boundaries of science and becoming a demand of other societal actors. The objective of this paper is to propose protocols for assessing the Penaeus vannamei welfare during the stages of reproduction, larval rearing, transport, and growing-out in earthen ponds and to discuss, based on a literature review, the processes and perspectives associated with the development and application of on-farm shrimp welfare protocols. Protocols were developed based on four of the five domains of animal welfare: nutrition, environment, health, and behaviour. The indicators related to the psychology domain were not considered a separate category, and the other proposed indicators indirectly assessed this domain. For each indicator, the corresponding reference values were defined based on literature and field experience, apart from the three possible scores related to animal experience on a continuum from positive (score 1) to very negative (score 3). It is very likely that non-invasive methods for measuring the farmed shrimp welfare, such as those proposed here, will become a standard tool for farms and laboratories and that it will become increasingly challenging to produce shrimp without considering their welfare throughout the production cycle.

Antimicrobial Secondary Metabolites from the Mangrove Plants of Asia and the Pacific

Microbes such as the White Spot Syndrome Virus account for severe losses in the shrimp farming industry globally. This review examines the literature on the mangrove plants of Asia and the Pacific with antibacterial, antifungal, or antiviral activities. All of the available data published on this subject were collected from Google Scholar, PubMed, Science Direct, Web of Science, ChemSpider, PubChem, and a library search from 1968 to 2022. Out of about 286 plant species, 119 exhibited antimicrobial effects, and a total of 114 antimicrobial natural products have been identified including 12 with MIC values below 1 µg/mL. Most of these plants are medicinal. The mangrove plants of Asia and the Pacific yield secondary metabolites with the potential to mitigate infectious diseases in shrimp aquaculture.

Establishment of a visualized isothermal nucleic acid amplification method for on-site diagnosis of acute hepatopancreatic necrosis disease in shrimp farm

Acute hepatopancreatic necrosis disease (AHPND) is a significant deadly infectious disease in the shrimp farming industry, causing serious economic losses globally every year. Because of the rapid progress speed, lack of effective treatment and high mortality rate of AHPND, monitoring with frequent diagnostic tests is vital for a successful prevention. The conventional histopathological diagnosis fell far short of the requirement for efficient monitoring, and the polymerase chain reaction (PCR)-based molecular diagnostic methods that rely on sophisticated thermocycler and trained personnel are hardly applicable in the field. Combining the recombinase polymerase amplification (RPA) and the lateral flow strips (LFSs), a diagnostic method suitable for on-site everyday monitoring of AHPND has been established in this study. This RPA-LFS method targeted the binary toxic photorhabdus insect-related genes PirA and PirB on a virulence plasmid of the AHPND-causative Vibrio parahaemolyticus strains. The diagnostic test was completed within 30 min at 37°C and showed good specificity and good sensitivity of 20 fg DNA of the AHPND shrimp or one colony-forming unit of the causative bacterium per reaction, which was better than the administration-approved standard AP4 assay. Crude templates from sample boiling could be directly used. Tests of clinical samples showed 100% consistency of this method with the standard AP4 assay. This RPA-LFS method can be a good choice for on-site diagnosis of AHPND with quick response time, easy procedure and low demand for resources, and should have significant value for the control of spreading of this dangerous disease in farmed shrimp.

Semiquantitative dot-blot immunogold assay for specific detection of white spot syndrome virus

A dot-blot immunogold assay (DBIA) was developed to detect white spot syndrome virus (WSSV) using the polyclonal antibody VP26 (anti-VP26). The anti-VP26 was immobilized on gold nanoparticles (Ab-AuNPs), and a nitrocellulose membrane was used as a detection pad. When the target WSSV bound to the Ab-AuNPs a reddish dot appeared on the surface of the membrane used within 2-5 Min, which could be seen with the naked eye. The test was able to detect WSSV at concentrations as low as 10⁵ copies μL^-1 of WSSV. The DBIA developed had good specificity, and the colloidal gold probe can be applied within 2-3 days when stored at 4 °C. For real sample analysis, the DBIA was applied to samples of seawater used for shrimp cultivation without sample preparation. The results indicate that sample 1 showed a positive result, whereas samples 2 and 3 produced negative results. Then, samples 2 and 3 were spiked with WSSV for method validation. To confirm the performance of the DBIA developed, polymerase chain reaction (PCR) was conducted and the PCR results were the same as those found by the DBIA. Therefore, the DBIA developed could be applied for WSSV detection in real water samples.

Vulnerability of coastal livelihoods to shrimp farming: Insights from Mozambique

Millions of people around the world depend on shrimp aquaculture for their livelihoods. Yet, the phenomenal growth of shrimp farming has often given rise to considerable environmental and social damage. This article examines the impacts of commercial, export-oriented shrimp aquaculture on local livelihood vulnerability by comparing the exposure, sensitivity, and adaptive capacity of shrimp farm employees with non-farm employees in rural Mozambique. Exposure to stressors was similar between the two groups. Shrimp farm employees had higher assets and higher adaptive capacity than non-farm employees. However, because their income is heavily dependent on a single commodity, shrimp farm employees were highly susceptible to the boom crop nature of intensive shrimp farming. The implications for aquaculture policy and vulnerability research are discussed. The article argues that coastal vulnerability is dynamic, variable, and influenced by multiple processes operating at multiple scales.