Niwooti Whangchai

Climate risk management in river-based tilapia cage culture in northern Thailand

Purpose – The purpose of this paper is to analyse how fish farmers manage climate-related risks and explore possible ways to strengthen risk management under current and future climate. Design/methodology/approach – In total, 662 fish farmers in sites across Northern Thailand were interviewed about risks to the profitability of their fish farms and ways such risks were managed. Nonlinear canonical correlation analysis was used to relate risk factors to management practices at farm and river levels. In total, 68 in-depth interviews with farmers and other stakeholders provided additional information on climate risk management practices. Findings – Farmers use a combination of adjustments to rearing practices, cropping calendars and financial and social measures to manage those risks, which they perceive as being manageable. Many risks are season, river and place specific; implying that the risk profiles of individual farms can vary substantially. Individual risks are often addressed through multiple practic...

Tilapia diseases and management in river-based cage aquaculture in northern Thailand

ABSTRACT A total of 662 farmers who rear tilapia in river-based cages in Northern Thailand were interviewed on their knowledge and perception on disease constraints and their control measures. Most farms (84%) had disease problems in the last two years. Exophthalmia ranked higher than other clinical signs. Most farmers noticed that the risk of disease problems was similar every month. Most (95%) believed that fish diseases were caused by bacterial pathogens. To treat perceived disease outbreaks, most farmers (96%) removed infected and dead fish and applied, usually inappropriately, antibiotics. As disease prevention through good management is better than treatment, farmers and fish disease experts could use these research findings as a tool to work together to develop better control strategies.

Access to Fish Cage Aquaculture in the Ping River, Northern Thailand

Aquaculture in rivers and other public water bodies raises issues of access and property rights. Over the past few years an industry has developed around the rearing of hybrid red and Nile tilapia (Oreochromis niloticus L.) in cages in the Ping River in northern Thailand. In this article we report on a study of how households gain access to river cage sites to farm fish. The findings are based on a case-control study of 400 households, half of which had a history of fish farming and half which did not. Additional information was gathered from qualitative in-depth interviews with 93 stakeholders. Households with good access to farming sites, financial capital, and social networks are more likely to farm fish. Proximity to the river front was a very important factor and operated at a micro-level within villages with river borders. Land and vehicle assets were also associated with fish farming—more so than monthly income levels—probably because they reflect access to credit. Social capital measured as belonging to various kinds of groups was also associated with fish farming, but may have been in part an outcome rather than a pre-requisite. Many fish farmers start through encouragement and invitations by firms or the fisheries department. Sites for cage aquaculture in rivers have characteristics somewhere between a private and a club good: those who don’t live near the river are usually excluded, but rivalry for sites among those who live close becomes an issue with congestion of farms arising from expansion in number of cages or other factors that reduce availability of suitable rearing sites like variability in climate, water flows, water quality, and government regulations.

Effect of gaseous ozone fumigation on organophosphate pesticide degradation of dried chilies

ABSTRACT The objective of this work was to study the effects of ozone fumigation on pesticides’ residue degradation in dried chilies while maintaining its qualities. Gaseous ozone with a gas rate of 5.5 g/h was applied to four organophosphate pesticides for 5 to 30 min. The degradation kinetics of the pesticide residue was then analyzed. The results showed that gaseous ozone degraded malathion, chlorpyrifos, profenofos, and ethion with half-life periods (t1/2) of 17.4, 27.4, 34.1, and 18.0 min, equivalent to 99.9% shorter half-life period as compared to non-ozone degradation. Furthermore, ozone fumigation did not significantly affect (p0.05) the water activity, color, and capsaicin content of dried chilies.

EFFECT OF TiO2-COATED SUBSTRATE PHOTOCATALYSIS ON CHLOPYRIFOS INSECTICIDE DEGRADATION

The efficiencies of photocatalysis using TiO2-coated substrates to reduce chlorpyrifos insecticides was evaluated. Three different glass substrates (glass ball, glass slide and glass bead) were prepared and tested with KI solution for efficiency of oxidation test. It was found that TiO2-coated glass beads at 45 mg/ml for 60 min had the highest iodine liberation rate. A 1 mgL -1 standard chlorpyrifos was subjected to those TiO2-coated substrates photocatalysis for 15, 30, 45 and 60 minutes. The percentage reduction of chlorpyrifos was calculated. It was shown that TiO2-coated glass bead photocatalysis had high reduction rate of chlorpyrifos concentration within 15 minutes, which correlated with an increase in iodine liberation rate. The effectiveness of TiO2 in photocatalysis to reduce contaminated chlorpyrifos in Chinese kale was determined by treatments with different TiO2-coated substrate photocatalysis and sampled every 15 minutes for 60 minutes. It was found that TiO2-coated glass bead reduced chlorpyrifos concentration to 53% when compared with the control. In addition, in the quality of Chinese kale after treatment withTiO2 in photocatalysis and stored for 12 days at 5 ° C was also investigated. There was no significant difference in the quality of Chinese kale in weight loss, leaf color, total soluble solids and ascorbic acid content.

USE OF FLUE GAS DESULFURIZATION GYPSUM FOR THE REMOVAL OF OFF-FLAVOR COMPOUNDS IN FISH POND WATER

Accumulation of off-flavor in fish flesh caused by the presence of geosmin and 2- methylisoborneol (MIB) in pond waters is a worldwide quality problem in aquaculture. This study investigated the effectiveness of synthetic flue gas desulfurization gypsum, (FGDG) a cheap and readily soluble material from coal-fired electric utilities, for the removal of off flavor substances: geosmin and MIB, in fish pond water. Water samples from fish ponds were spiked with known concentrations of geosmin and MIB and varying amounts of FGDG (0, 200, 400 and 600 mg/L) were added to compare the removal rates of geosmin and MIB, chlorophyll a levels and orthophosphate. The experiment was conducted for 9 days. It was revealed that FGDG had significantly reduced both geosmin and MIB in spiked pond waters when compared with the control (0 mg/L) (P 0.05) different from 600 mg/L. The highest removal rate of MIB (75.63%) was found with the treatment with 400 mg/L CFG after 6 days. In addition, 200 mg/L FGDG was also highly effective in reducing chlorophyll a and orthophosphate concentration through calcium phosphate precipitation. It was suggested that 200 mg/L FGDG is the suitable dose to apply for the removal of off-flavor compounds in fish pond waters.