Blackwell Science, LtdOxford, UKFISFisheries Science0919-92682005 Blackwell Science Asia Pty Ltd 2005714791798Original ArticleIncentive for shift in water managementC Kasai et al. FISHERIES SCIENCE 2005; 71: 791–798 Incentive for shifts in water management systems by shrimp culturists in southern Thailand Chifumi KASAI,1 Thongchai NITIRATSUWAN,2 Osamu BABA3 AND Hisashi KUROKURA1* 1Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan, 2Faculty of Science and Fisheries Technology, Rajamangala Institute of Technology, Trang 92150, Thailand and 3Faculty of Fisheries, Tokyo University of Marine Science and Technology, Tokyo 108-8477, Japan ABSTRACT: Water management systems and other business situations of shrimp culturists were surveyed in two districts in southern Thailand. There were three types of water management systems in southern Thailand, namely closed, semiclosed and open systems, categorized by the frequency of exchange of pond water. Shrimp culturists in those districts tended to shift their system from the open system to the closed system of their own accord, and the average net income ratio decreased due to the change of water management system in a district from more than 2 to less than 1. The reason for this shift, in spite of the decrease in the profit rate, was prevention of infectious disease caused by water exchange. In conclusion, it was proven that independent shrimp culturists, such as medium and small scale shrimp pond owners in southern Thailand, would accept short-term decreases in profit rate in order to stabilize production. KEY WORDS: closed system, incentive, shrimp culture, Thailand, water management. INTRODUCTION propagation of infectious disease and degradation of environment, such as cutting down the stocking Cultured shrimps are the main product for export density and feeding levels, are unpopular with in several developing countries. At the same time, aquaculturists as those countermeasures decrease because of recent worldwide interest in environ- production. mental conservation, shrimp culture has received The authors’ objective is to obtain useful and recognition as a major pollutant source in coastal important information for improvement and prop- environments.1 Therefore, there needs to be a new agation of sustainable shrimp culture methods in enlightened approach from shrimp culturists in developing countries by studying the experience of developing countries to reduce pollutant from the aquaculturists and the present status of shrimp culture ponds. culture in Thailand. The factors which prompted From the 1970s, giant tiger prawn Penaeus mon- the shift in culture methods were considered to be odon culture has developed in south-east Asia, and of particular importance. In this study, the authors the culture areas have now expanded beyond those selected two districts in Thailand as research sites, borders. In countries such as Taiwan, the shrimp and conducted personal interviews with shrimp culture industry decreased their activities after culturists to assess the process of changes in rapid development because of environmental aquaculture methods and the incentives which degradation.2 In contrast to those countries, the affect the selection of culture methods. shrimp culture industry in Thailand is continu- ously expanding to keep up its leading position in the world in terms of production, overcoming the MATERIALS AND METHODS damage of infectious disease, coastal environment pollution, and economic crisis. Generally, effective The present study was mainly composed of three and sustainable countermeasures to reduce the interview surveys. The locations of the survey areas are shown in Fig. 1. The first preliminary survey was performed in Trang Province in 2001 to obtain *Corresponding author: Tel: 81-3-5841-7500. basic information about the typical modern Fax: 81-3-5841-5187. Email: [email protected] shrimp culture industry in southern Thailand. Received 30 September 2004. Accepted 8 February 2005. Trang Province faces the Andaman Sea, the coastal 792 FISHERIES SCIENCE C Kasai et al. ease. Shrimp culture in Trang is more intensive compared to other provinces. Trang Province was known as the place where high productivity (pro- duction from unit area) could be achieved from the initiation of the modern shrimp culture industry.3 Because of a lack of follow-up research in this area, it is not clear whether the high productivity in this area is still maintained or not. For a detailed survey, the authors selected Sikao district as a typical area of shrimp culture in Trang Province. Sikao is located in the western part of Trang Province and the main industry is rubber plantation. The authors randomly selected 18 cul- ture shrimp farms located within 3 km of the coast in Sikao and conducted an interview survey in July and August 2002, asking about the water manage- ment system and their business situation. Simultaneously, 26 shrimp farms in Ranot dis- trict in Songkhla Province were surveyed for com- parison. Songkhla is located on the other side of Trang in the Malay Peninsula and faces the Gulf of Thailand. The area of Songkhla province is 7393 km2, and the land is flat with a large brackish lake (Songkhla Lake) in the central part of the prov- Fig. 1 Locations of survey area. ince. The maximum tidal range on the coast is 1.8 m. Generally, the coast of the Gulf of Thailand is stagnant when compared with the coast of the Andaman Sea. However, the coastal water of area which has been recently developed for shrimp Songkhla is not stagnant and water quality is better culture in Thailand.3 The authors performed the than the inner part of the Gulf of Thailand, because survey in the coastal districts of Trang (Kangtan, there is a water current along the coast of Songkhla Sikao, Palian, Yan Ta Khao, Hat Samran) from Sep- Province. Annual rainfall in Songkhla is 1400– tember to November 2001. In these districts, 13 2000 mm with 140–160 rainy days. The modern shrimp farms were surveyed in Kangtan district, 11 shrimp culture industry in Songkhla started during in Sikao district, eight in Palian district, two in Yan the same period as that in Trang, although the Ta Khao district, and one in Hat Samran (a total of development in terms of the increase in number of 35 farms). Shrimp culturists in these areas can eas- shrimp culture farms was more rapid in Songkhla. ily obtain information on modern shrimp culture The number of shrimp culture businesses in techniques from shrimp culturists in Nakhon Si Songkhla reached 1424 in 1991, and the maximum Thammarat, a major culture shrimp production number of 1995 farms was recorded in 1994. Pro- area in Thailand. Trang Province is mountainous, ductivity was also high in Songkhla as in Trang, and shrimp culture was performed using small flat with an extremely high productivity (0.744 kg/m2) areas along the mangrove canal. The coast is recorded in 1989, though the value decreased rap- mainly covered with mangrove forest. The maxi- idly to half of the maximum record in 1991 due to mum tidal range is 3.7 m and the current along the the damage caused by infectious disease. Ponds in coast is strong throughout the year. Stagnation of the Songkhla province were mainly constructed in coastal water scarcely occurs. Annual rainfall is paddy fields or palm plantations. Ranot District is 1700–2400 mm with a total of 140–180 rainy days. flat and located towards the northern border of the The rainy season starts in May and continues to province, bordering on Nakon Si Thammrat, the October. The dry season is from November to April. major culture shrimp production area in Thailand. The major industry in the province is rubber plan- The authors prepared a questionnaire asking tation. The modern shrimp culture began in 1989, mainly about pond water management systems. and the number of shrimp culture farms increased From the results of the preliminary survey, the rapidly from 1991 to 1994. The number reached water management systems were categorized into more than 1000 in 1995, though the number the following three types: open system, pond water decreased to around 700 in 1996 because of a is exchanged from the first month of culture to decrease in production caused by infectious dis- maintain water quality; semiclosed system, water Incentive for shift in water management FISHERIES SCIENCE 793 was exchanged only from the third month; and Table 1 Outline of shrimp farms in Trang province in closed system, water was not exchanged during the 2001 culture period. Other items in the questionnaire Average of 35 shrimp farms were: place (distance from mangrove canal, dis- Number of ponds 3.9 tance from coast), number and size of the ponds; Average pond size 5148 m2 year and reason for the shift (in cases where the Duration of one crop 108 days water management system was shifted); frequency Stocking density at the beginning of water change per month and total number in dry season 55.7 inds./m2 each water management system; water exchange wet season 60.7 inds./m2 Survival rate 0.48 ratio in each change; side business, source of main 2 income (if the pond owner had a side business); Productivity from unit area 0.43 kg/m Farm gate price 206.7 Bahts/kg production costs; yield (kg and Bahts); use of Average success in production† 0.618 chemicals, probiotics and antibiotics; and sources Total production costs‡ 168.1 Bahts/kg of information. For feed 89.1 Bahts/kg For the evaluation of the impact on profit mar- Seed 20.0 Bahts/kg gins by water management shifts, net income Chemicals 18.4 Bahts/kg ratios (NIR) were calculated before and after a Fuel 32.8 Bahts/kg water saving shift using the following equation: Workers§ 4.6 Bahts/kg Electricity 3.1 Bahts/kg NIR = (total income - total production cost)/total Net income ratio¶ 0.679 production cost (1) †Ratio of farms which could achieve their production goals.