Effects of climate change on rearing Tilapia in earthen ponds

Part of the larger project AQUADAPT: Inland Aquaculture and Adaptation to Climate Change in Northern Thailand, this policy and practice brief provides climate and technical information on fish pond risks and adaptation due to weather conditions such as drought or excess rain. Farmers rearing large fish often have to contend with dying fish during seasonal transition periods. Practice guidelines help farmers minimize risks associated with the seasonal transition period

Musty/earthy off-flavor in aquatic animals: impact, causes, and solutions

Musty/earthy off-flavor in aquatic animals has been reported in aquatic organism worldwide. Although there is no negative effect on human health, it causes an unacceptable for consumer consumption. The purpose of this article is to review some of the available literature relating to musty/earthy off-flavor in aquatic animals. Geosmin (GSM) and 2-methylisoborneol (MIB) are two major off-flavor compounds. These compounds are caused by metabolites produced by blue-green algae including Anabaena sp., Oscillatoria sp., Lyngbya sp., Symploca sp., Phormidium sp., and Aphanizomenon sp. and some bacteria such as Streptomyces. Fish with high fat content or raised in earthen ponds with enriched algae and bacteria mentioned earlier increase in risk of off-flavor problem. The influences of temperature, season, and climate change had been also discussed. Finally, the various practical methods for undesirable flavor were described. This information will be beneficial for fish farmers to control an off-flavor problem

Off-flavor characterization in high nutrient load tilapia ponds in northern Thailand

These findings are an important step towards the prediction, control and management of the off-flavor problem in tilapia culture in high-nutrient load ponds. The aim was to determine the levels of odorous compounds (geosmin or 2-methylisoborneol (MIB) that potentially cause off-flavor problems in fish reared in integrated, high-nutrient-load ponds in northern Thailand. Without proper management of fish and animal numbers, as well as good water exchange, water quality can deteriorate and result in eutrophication which promotes cyanobacterial blooms that can harmfully affect water quality and produce odorous compounds. The paper details observations of Chlorophylla and Cyanobacterial abundance

Effect of Water De-stratification on Dissolved Oxygen and Ammonia in Tilapia Ponds in Northern Thailand

For Nile tilapia cultured in earthen ponds in Thailand, mortality from disease outbreak frequently occurs when dissolved oxygen (DO) levels are low and ammonia concentrations are high. Repeated analysis of variance (ANOVA) showed that water depth and fish culture systems have significant effects on total ammonia nitrogen (TAN). TAN concentrations near the surface were lower than at the bottom, and increased after water de-stratification. TAN in the integrated culture system was significantly higher than in commercial and subsistence systems. Effects of de-stratification on pond water quality provided by this study are useful towards improved pond management practices and monitoring DO thresholds

Relation of Light Intensity with Dissolved Oxygen and Chlorophyll-a in Nile Tilapia Ponds

These research findings suggest that farmers who raise fish in intensive culture ponds should adopt appropriate strategies to maintain favorable levels of dissolved oxygen (DO) in order to reduce risk of production losses, for example from periods of prolonged cloud cover which block sunlight reducing photosynthesis by phytoplankton. When light intensity was high from the afternoon to late afternoon, DO in fish ponds increased as light on ponds increased. Chlorophyll-a varied significantly by season and culture system. Intensive culture ponds contained higher concentrations of chlorophyll-a and hence higher DO levels than extensive culture ponds

Study on toxigenic cyanobacteria of aquaculture ponds in Thailand

Proliferation of cyanobacteria is frequently encountered in natural eutrophicated lakes as well as in aquaculture ponds, since daily feeding contributes to the high nutrient loading for the intensive aquaculture. The extensive growth of cyanobacteria presents a considerable threat to human health because many species have the potential to produce cyanotoxin. Microcystis, in particular, is a typical bloom-forming cyanobacterial genus that produces a strong hepatotoxin microcystin. In this study, aquaculture ponds of catfish and tilapia in Thailand were surveyed to obtain the basic information on the occurrence of harmful cyanobacteria and cyanotoxins. This study provided two significant facets of information. One, from a viewpoint of the evaluation of the risk of cyanotoxins in aquaculture; the other, on the ecological study of toxigenic cyanobacteria at various environmental conditions. The relationship between the proliferation of toxigenic cyanobacteria and environmental conditions such as nutrients, temperature and kinds of cultured fish in aquaculture ponds were illuminated by mainly using conventional water quality analysis, quantitative real time PCR method (a molecular ecological method) and linear model analysis for the results. The results were summarized as follows. In September and December of 2009 and March of 2010, 22 ponds for commercial farming of Nile tilapia (Oreochromis niloticus) and 17 ponds for hybrid catfish (Clarias macrocephalus x C. gariepinus) were surveyed in the provinces of Chiang Mai, Chiang Rai and Phayao. Fish species (tilapia or catfish) did not significantly affect the occurrence of toxigenic cyanobacteria. Actually, mcyD gene was detected in 8 tilapia ponds and 11 catfish ponds. Then microcystin analyzed by HPLC was detected in only 4 tilapia ponds and 6 catfish ponds. However, these differences between catfish pond and tilapia pond were not statistical significant. On the other hands, chl-a, as a surrogate of total biomass of phytoplankton, depended on both T-N and T-P. Then the concentration of chl-a in high temperature season (March) was higher than that in low temperature season (December). On the other hand, total cyanobacteria mainly depended on T-P, then it was found much in December than in March. The detection probability of mcyD in aquaculture ponds was explained by a logistic model, mainly with T-P. The probability in March was lower than that in December

Impacts of floods and drought on fish cage culture in rivers

This article reviews evidence about the impacts from flooding and drought or low flows on fish cage culture in rivers in Thailand. Major floods damage cages, result in fish escapes and kill fish while low flow results in water depths too shallow for cages, increasing effective fish densities, which when combined with poor water circulation, leads to low dissolved low water quality. Floods and droughts are a significant source of financial losses. Farmers may be forced to oxygen concentrations and poor harvest carly sell fish at smaller-than-standard size and thus at a low price. Losses due to floods and droughts can be reduced by improving management of risks at farm and reach level

River-based cage aquaculture of tilapia in Northern Thailand : sustainability of rearing and business practices

Whereas most studies of cage culture have been carried out in ponds, lakes or reservoirs, cage-based aquaculture in rivers and other public water bodies raises issues of natural resource management that are closer to fisheries management than aquaculture in fish ponds on private land. This paper analyzes an emerging industry in the Upper Ping River in northern Thailand which helps serve the large and growing demand for farmed fish in Chiang Mai. Farmers appear to pay attention to environmental and market factors that pose risks to profitability of their operations, as good water quality means aquaculture can continue