Social, Economic, and Production Characteristics of Freshwater Prawn Macrobrachium rosenbergii Culture in Thailand

Abstract

The objective of this survey was to assess the current state of production for the giant river prawn Macrobrachium rosenbergii in Thailand and assess the feasibility for adoption of a nutrient recycling system. A socioeconomic and technical survey of 100 prawn farmers was conducted during 1 May-31 July 2005 in Thailand. The majority of respondents were male (70%) and average age was 46 ± 1. Most farmers (77%) had completed an elementary level of schooling (4 years) and experience on the farm as owner, manager, or both averaged approximately 10 ± 1 years. Most respondents (92.9%) obtained information about prawn culture from their neighbors and only 19% received formal training. Monoculture was the dominant system (96%) while remaining farmers utilized polyculture with prawns and white shrimp Litopenaeus vannemei. The most common management strategy included nursing postlarvae for 30 to 60 days and harvesting with the combined method, culling only the largest market-sized individuals beginning at 5 months followed by every 30 to 45 days (66% of farmers used this system). Culture practices at the time of this survey were intensive. Most farmers stocked at densities below 20 pieces m-2 and average production was 2,338 kg ha-1 yr-1. However, some farmers utilized stocking densities and obtained production values above those described as semi-intensive. Also, commercially produced, nutritionally complete feed was most common, water exchange and aeration was utilized to maintain suitable water quality, and water quality management throughout the cycle was practiced if respondents had the resources. After the culture period, water was generally discharged directly into canals without treatment. Average net profits were 3,918 US$ ha-1 yr-1. Variables that significantly affected yearly gross prawn production (kg ha-1 year-1) included feed inputs (kg ha-1 year-1), frequent water exchange, and stocking prawns directly (R2 = 0.299). Yearly net profits (US$ ha-1 year-1) were most influenced by gross prawn production (kg ha-1 year-1), feed inputs (kg ha-1 year-1), and years of experience of the respondent (R2 = 0.795). A recycling system that isolates production from the environment and integrates organisms which retain nutrients was simulated for 50 of the surveyed farms. Net profits were lower than average survey results. However, recycling systems do have promise; many farmers seemed to be aware of the environmental effects of current production and attributed multiple problems to water pollution. External pollution was severe for 16% of respondents, moderate for 46%, not an issue for 38%, and was perceived to be caused by multi-user effects. Major problems identified were diseased or poor quality seed supply (67%), disease outbreak within the crop (64%), and external pollution (37%). In 2005 the freshwater prawn industry in Thailand was valued at US$79,096,000 and ranked 3rd behind China and India (FAO 2005). To maintain this level of production, alternative systems are necessary and must balance adequate environmental benefits and economic returns similar to or better than monoculture.