How climate risks are understood and perceived by farmers is important because it can influence their management practices. Farmers in Northern Thailand who rear fish in floating cages in rivers can cope with modest fluctuations in water levels, but appear vulnerable to more extreme changes in flow. This study used in-depth interviews and a quantitative survey across many sites to explore how fish farmers perceive climaterelated risks and understand climate change. Important climate-related risks -such as floods and droughts -vary by season, year and location, and are modified by water infrastructure. Recent experience of negative impacts increases levels of concern about risks. Risks from droughts were perceived to have significantly worsened. The overall level of awareness of climate change among fish farmers is high, suggesting that future work should focus on building on from how farmers manage risks under the current climate, to then take into account climate change. This study shows that a good understanding of risk perception is likely to be important in improving climate risk management, and thus adaptation to climate change.
Cage-based aquaculture in rivers raises issues of natural resource management more familiar to fisheries management than does aquaculture in fish ponds on private land. Hybrid red and black Nile tilapias (Oreochromis niloticus L) are reared for 4-5 months in cages in the upper Ping River in northern Thailand. Observed mean stocking density was 49 ± 16 fish•m −3 , feed conversion ratio 1.47 ± 0.43 kg feed per kg fish and yield density 26.6 ± 8.1 kg•m −3. Input costs were dominated by feed (70%) and stock (16%). Most farms borrowed money and participated in contracts. Fish farming was usually a component of a portfolio of household activities but for some a core business. To succeed fish farmers must manage a combination of market, climate and environmental-related risks. Cage-based aquaculture in rivers faces many challenges; further research on farm practices and vulnerabilities, river and water management, and the commoditychain are needed.
This study investigated the relationships among the parameters of dissolved oxygen, chlorophyll-a and phytoplankton composition in tilapia ponds. Each pond (a total of 18 ponds) was sampled once in the dry, winter season between January and March and again early in the rainy season between May and June. The data were analyzed by examining correlations among parameters as affected by season, altitude and culture system. Observations were made at sites located in 5 selected provinces of northern Thailand: Chiangrai, Chiangmai, Phayao, Lampang and Nakornsawan. Mean elevation of these areas range from 25 to 582 meters above sea level (masl) and were categorized into low (<400 masl) and high (>400 masl) elevation sites. Ponds were 0.8-2.0 m deep, 0.16-0.64 ha in area and could be further categorized into high and low input systems.Mean air temperature in winter ranged between 16.5˚C-35.8˚C while mean water temperature ranged between 25.5˚C-27.1˚C. In rainy season, air temperature ranged between 22.0˚C-37.3˚C and water temperature ranged between 29.4˚C-31.8˚C. The amount of chlorophyll-a in both seasons were comparable (p > 0.05), but chlorophyll-a in high input system was significantly higher (p < 0.05) than in low input ponds. Only weak correlation was found between chlorophyll-a, DO max and DO min. Multifactor-ANOVA was used to analyze the difference of total bacteria and filamentous cyanobacteria in ponds based upon elevation, culture systems and season. Result shows that there is a significant interaction observed between elevation, culture system and season (p < 0.05). Species diversity and composition of phytoplankton in fish ponds in 2 seasons revealed the presence of 90 genera of phytoplankton under all 7 divisions. Divisions Chlorophyta and Cyanophyta had the most number of genera identified in both seasons with Pediastrum spp., and Scendesmus spp., and Anabaena spp. as dominant genera/genus, respectively.
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