Inland capture fisheries are an important sector of many local economies in Thailand and are considered to be important in sustaining the livelihoods of many rural communities. They are also important sources of domestic fish consumption. The importance of the inland fisheries sector has been highlighted in many reports and its significance in providing food security and generating local income is frequently highlighted.2 The present official statistics report a contribution of inland fisheries production to domestic fish supply of around 200 000 tonnes per year, which is less than 10 percent of total fisheries production (from 1994 to 2005). The most recent national census in the agricultural sector throughout the country (2003) showed a high participation rate of Thai people in inland fisheries activities, with the main purpose of these fishing activities being for household consumption.
Inland capture fisheries production in Thailand is carried out nationwide and in a traditional way. As in many other countries in the region, it is difficult to collect data for statistical records when large numbers of people participate in traditional fishing activities. Hence, the inland capture fisheries production reported has not been reliable and does not reflect the true status of this sector. It is believed that the figures for inland fisheries, especially production figures, are underestimated and thus undervalued.
Even though the figures for production and value in this sector are not high, it is still an important sector for local economies. The proportion of the population participating in this sector, and the various habitats they can access for freshwater fisheries resources in each region of the country are presented in Table 2. The results show that an average of 14 percent of the households in Thailand conducts inland fisheries activities. The major system of inland fisheries habitats is shown in Table 3. There are four major types of inland fisheries habitats. This detailed habitat information is also linked to the detailed fishing habitat information of an agricultural census.
Information on the inland capture fisheries sector in Thailand is usually presented in normal statistical formats and has been since the foundation of DoF. Even though there are many research surveys and studies, both published and ongoing, on inland fisheries in Thailand, most of them deal with specific locations and hence can be of only limited use in supporting a national fisheries statistics system and in obtaining a clear picture of the inland sector as a whole. The collection and compilation of inland capture fisheries statistics in Thailand started about 40 years ago and these activities may now be considered routine activities of DoF.
Table 2 Population, economic contribution of inland captures fisheries and habitats important for inland capture fisheries production
Region |
Population |
Households and percentage of fishing households |
GPP inland capture fisheries (US$/year) |
Major freshwater resources |
Central |
20 689 566 |
7 413 300 |
32 350 842 |
The Central region occupies most of the area of the Chao Phraya Basin. Almost all of the mountainous part of northern Thailand is drained to the Chao Phraya river through the Ping, Wang, Yom and Nan rivers. The low-lying floodplain and delta of the Chao Phraya river in the Central Plain generate a huge amount of freshwater fish. Apart from the Chao Phraya river and its large lowland floodplain and delta area, large dams and reservoirs, including natural swamps in the Central Plain, are other important freshwater fisheries utilized by the rural people in this region. |
North | 11 883 517 |
3 768 261 |
86 064 311 |
The four river basins of Ping, Wang, Yom and Nan in the north, the Salaween river basin in the northwest and the Mekong river in the northeast are all important river systems with abundant fish. Large dams, reservoirs and human-made waterbodies in all provinces generate fish production. |
Northeast | 19 953 411 |
5 036 322 |
154 356 259 |
The Mekong main stream along the border between Thailand and Lao PDR and large tributaries of the Mekong are other important resources. Many of the Mekong tributaries are dammed and many weirs are found along the river and streams for fishing purposes. |
South | 8 516 860 |
2 484 891 |
52 120 955 |
Fisheries resources are more limited on peninsular Thailand. Important inland fisheries habitats are small river basins and large freshwater lakes and a few large dams. |
Total |
61 043 354 |
18 702 774 |
Table 3 The major systems of inland fisheries habitats in Thailand included in the analysis
Environment |
Detailed information related to habitat and fisheries |
Area (ha) |
Source |
Rivers and streams |
|
More than 56 137 km. |
GIS database ESRI, Thailand |
Inundated plains |
|
No details. |
|
Swamps, marshes, lakes, reservoirs |
|
28 956 |
|
|
3 198 |
| |
342 826.5 |
| ||
Wet rice inundated paddy fields |
|
Estimated at |
Virapat et al. (2000) |
Figure 1 Map of 25 major river basins in Thailand
There are two major categories of inland fisheries statistics: capture fisheries statistics and aquaculture production statistics. For each of these categories, yield and value are collected on a yearly basis and are used to indicate the status and trend in the fisheries sector at the national level.
Figure 2 Fisheries production by sector, 1985 to 20043
The reported total inland fisheries production (capture and aquaculture) is between 700 000 and 800 000 tonnes, of which 200 000 tonnes4 are capture fisheries production. However, over the years it has been stated many times that the official figures for the inland freshwater sector probably underestimate the true figure. One reason for this could be the way in which the data are produced, i.e. data are collected mainly from major landing sites in large reservoirs. Furthermore, these data do not cover all the reservoirs in Thailand. The inland fisheries production data in Thailand has always been of doubtful reliability, but progress in resolving this issue has been slow.
The process of collecting fisheries statistics has been improved gradually over the years and there has been considerable support allocated to all the provincial fisheries offices to help in the collection of data for national statistics purposes, but it is still not clear if this process has improved reporting.
In Thailand, the rate of utilization of freshwater fish is high, as almost all kinds of fish are eaten. The freshwater fish base ensures food security for the steadily expanding population, especially the low-income rural communities and urban poor (Menasveta, 2000). Inland capture fisheries in Thailand are considered mostly to be SSF and, as stated above, contribute approximately 200 000 tonnes per year (Figure 2), which was valued at about 7 436 million baht in 2004 (Table 4, Figure 2). Although the share from inland fisheries is not high (comparing official inland capture fisheries production to official marine capture fisheries production), it is considered the most accessible and inexpensive source of protein for the majority of Thais (Pawaputanon, 2003).
Table 4 Total inland capture fisheries (1 000 tonnes) in Thailand from 1981 to 20055
Year |
Total production |
Capture (1 000 tonnes) |
% Inland production |
Value (million baht) |
Average value/kg of inland fishes | ||
Marine |
Inland |
Marine |
Inland | ||||
1981 |
1 989.0 |
1 756.9 |
116.5 |
8.3 |
no data |
no data |
no data |
1982 |
2 120.1 |
1 949.7 |
87.7 |
6.3 |
no data |
no data |
no data |
1983 |
2 255.4 |
2 055.2 |
108.4 |
6.9 |
no data |
no data |
no data |
1984 |
2 134.8 |
1 911.5 |
114.4 |
7.7 |
no data |
no data |
no data |
1985 |
2 225.2 |
1 997.2 |
92.2 |
7.5 |
no data |
no data |
no data |
1986 |
2 536.3 |
2 309.5 |
98.4 |
7.4 |
16 976.3 |
2 069.9 |
21.0 |
1987 |
2 779.1 |
2 540.0 |
87.4 |
6.4 |
19 357.1 |
2 113.1 |
24.2 |
1988 |
2 629.7 |
2 337.2 |
81.5 |
7.0 |
19 823.0 |
1 784.7 |
21.9 |
1989 |
2 740.0 |
2 370.5 |
109.1 |
7.3 |
19 935.3 |
2 228.2 |
20.4 |
1990 |
2 786.4 |
2 362.2 |
127.2 |
8.3 |
20 738.4 |
3 301.7 |
26.0 |
1991 |
2 967.7 |
2 478.6 |
136 |
8.7 |
26 403.7 |
3 290.8 |
24.2 |
1992 |
3 239.8 |
2 736.4 |
132 |
8.5 |
32 833.0 |
2 998.8 |
22.7 |
1993 |
3 385.1 |
2 752.5 |
175.4 |
10.0 |
36 224.1 |
4 489.5 |
25.6 |
1994 |
3 523.2 |
2 804.4 |
202.6 |
10.6 |
36 337.2 |
4 805.6 |
23.7 |
1995 |
3 572.6 |
2 827.4 |
191.7 |
10.9 |
45 183.2 |
4 601.1 |
24.0 |
1996 |
3 549.2 |
2 786.1 |
208.4 |
12.3 |
46 815.3 |
4 995.4 |
24.0 |
1997 |
3 384.4 |
2 679.5 |
205 |
12.0 |
47 134.2 |
5 154.2 |
25.1 |
1998 |
3 505.9 |
2 709.0 |
202.3 |
12.2 |
48 380.8 |
7 687.5 |
38.0 |
1999 |
3 625.9 |
2 725.2 |
206.9 |
12.7 |
48 444.8 |
7 221.3 |
34.9 |
2000 |
3 713.2 |
2 773.7 |
201.5 |
12.7 |
49 401.8 |
7 024.8 |
34.9 |
2001 |
3 648.4 |
2 631.7 |
202.5 |
13.2 |
53 718.5 |
7 049.4 |
34.8 |
2002 |
3 797.0 |
2 643.7 |
198.7 |
13.0 |
58 374.5 |
6 290.3 |
31.7 |
2003 |
3 914.0 |
2 651.2 |
198.4 |
14.3 |
64 169.5 |
7 069.9 |
35.6 |
2004 |
4 099.6 |
2 635.9 |
203.7 |
17.7 |
61 800.5 |
7 436.2 |
36.5 |
2005 |
4 118.5 |
2 615.6 |
198.8 |
17.9 |
63 222.7 |
7 852.8 |
39.5 |
Inland capture fishing activities in Thailand are carried out in natural and human-made freshwater bodies of various types, from rivers and their tributaries to reservoirs and fishponds. Fish caught from inland habitats are multispecies and vary in abundance depending on the productive status of the water bodies (Pawaputanon, 2003). The main fishing gears are fish trap, gill net, long line, hand line, cast net, harpoon and landing net. Silver barb, Nile tilapia, striped snake-head fish, Jullien's mud carp, walking catfish and common climbing perch generally are the dominant species in various freshwater bodies (Appendix 1 and Figure 3). The production and value of inland capture fisheries, particularly obtained from natural reservoirs, which are the main freshwater bodies, have been increasing (Appendix 2). Freshwater fish contributed more than 99 percent of total production, whereas most of the remainder, only 0.29 percent, consisted of shrimps (Figure 4).
Figure 3 Production and value of 12 important species of inland capture fisheries obtained from natural reservoirs, freshwater landing places and pond traps, 20036
In 2003 approximately 3.13 million fishers participated in fishing in inland capture fisheries. Most of them (60.49 percent) are located in the northeast of Thailand. The rest are in the northern (25.34 percent), central (9.15 percent) and southern (5.02 percent) parts of Thailand (Fishery Information Technology Center (FITC), 2007, personal communication). The fishers generally go fishing for periods of four to seven days per week. Approximately 2.72 million fisher households participated in fishing in inland capture fisheries. Of these households, 96.22 percent fished for food consumption, whereas the remainder (3.78 percent) fished for trade. There are no systematic records of the total number of fishing boats employed in inland capture fisheries. This is mainly because most of the fishing boats are small-scale and are not obliged to register. There are only occasional surveys of the number of fishing boats operating in some natural reservoirs. For instance, it was found that 300 fishing boats operated in Beung Boraped area (Nakhon Sawan Inland Fisheries Research and Development Center, 2007). There are also constraints in producing information on other key aspects of inland fisheries. The main constraints are lack of up-to-date basic data, lack of accuracy of the data collection, lack of knowledge of scientific data collection methodologies, as well as the data being scattered over a wide area (Pawaputanon, 2003).
Figure 4 Composition of inland capture fisheries by species 2004
Gross domestic product (GDP) and gross provincial product (GPP) are used as national indicators of socio-economic status. According to the Office of the National Economic and Social Development Board (ONESDB), the objectives of using GDP and GPP are to determine the overall socio-economic status of Thailand and to indicate the trend and direction of economic growth.7 Relevant government agencies are requested to provide detailed information on value added of various products at province level to help determine the province's socio-economic status.
Fish production contributed about 1.4 percent of the total GDP in 2003 (note that this figure is based on production estimates that are possibly underestimated). As fish production is one of many sectors to be combined for determining the status and trend of the national economy, the Fisheries Information Technology Center (FITC) of the DoF, Thailand has produced survey guidelines for carrying out the GPP survey since 2003. These guidelines have been distributed to all provinces that are to conduct surveys to gather data for GPP estimation. These guidelines provided details of survey techniques including forms for data collection, which have been categorized into marine and inland production. Furthermore, types of fisheries activities in each category are also divided into capture fisheries and aquaculture.
Fish production data are collected from sampled households by using statistical sampling techniques and interview forms to gather information on household production, fishing activities, fishing frequency, income and expenditure. There are five habitat types categorized under the agricultural census survey. These five habitat types are considered to be the most important habitats for freshwater fisheries production and fishing grounds for the rural people. Local communities normally have free access to these habitats for fisheries purposes. Hence, these habitats generate significant amounts of production.
For the GPP survey, data on the value of inland capture fisheries are estimated for five different habitat types: river, pond trap, reservoir, natural swamp and community pond. Thereafter, the total production from all types of habitat is combined to present the total quantity of production with the value derived from the capture fisheries sector.
The overall framework used for the estimation of inland capture fisheries production considered the production yield of fishing households rather than the production of professional fishers (Box 1). Fishing household could be commercial-scale, large-scale or medium-scale fishing households as well as a vast number of small-scale fishing households. The large and medium-scale fishing households are a group that uses large gear and conducts fishing to extract the resources for trade whereas the small-scale fishing households utilize the inland fisheries resources mainly for their own consumption.
Box 1 The overall framework for estimating inland capture fisheries production
In order to get detailed data on fishing households and participation in fisheries for the assessment of production, agricultural census data that provided information on fishing households at the village level were linked with the household production data from the GPP survey. Then the data from the different sources were combined and analyzed to quantify the total freshwater production yield of the fishing households.
A database was developed which effectively merged the data sets required for assessing inland capture fisheries. The data sets included in the database are: the agricultural census, the sample of fishing households under the GPP survey, census and GIS data on water bodies. These data sets were stored together and shared the same spatial references and were further linked to provincial political boundaries. In addition, data on household production and the household participation in the fisheries sector were matched with the GIS database for further spatial analysis. Using GIS gives considerable power in analyzing large data sets and the database also enabled overlay and mapping analysis. Hence, detailed information on production status and trends of inland capture fisheries in Thailand could be more accurately presented and estimated and should therefore be more useful for fisheries resources management and policy.
DATA SETS USED IN THE ESTIMATION
In order to estimate the inland fisheries production, two major parts of official statistics and data sets were used to extrapolate inland capture fisheries production.
INLAND CAPTURE FISHERIES PRODUCTION ESTIMATION
Before carrying out the "trial" estimate of inland capture fisheries production two main aspects were considered. First, data and information should be routinely collected to determine the status and trend of the fisheries sector. Second, the data should cover small-scale fishing households, which are always overlooked. Small-scale fishing households represent a large group of people in the rural area that utilize fisheries production for their own consumption and there is no useful statistical report of production from this sector. Therefore, the study aimed to cover all major groups of people who participate in the fisheries sector and to present more reliable information on inland fisheries production.
Besides strengthening inland capture fisheries information, the study also aimed to provide comments that could help to improve the process of fisheries data collection In addition, the information obtained can help clarify the status and trend in the inland capture fisheries sector and ultimately help to determine two main indicators, namely, a) the participation in the fisheries sector (number of people); and b) the socio-economic value of this sector.
Data derived from the agricultural census in 2003 showed that about 13.9 percent of the total households, or 2.5 million households throughout Thailand, conducted fishing activities in various inland fisheries habitats (Figure 5). The highest participation in inland fishing activities is in the North and Northeast regions where people depend more on freshwater fisheries resources to meet their dietary needs. Figure 6 presents the number of fishing households at district level in Thailand.
Figure 5 Total households and fishing households in Thailand and by region
SAMPLING OF FISHING HOUSEHOLDS
The trial study sampled fishing households that had been interviewed under the GPP survey of the inland capture fisheries sector. The sampled households had been asked to report the amount of household production, expenditure and income from fishing activities by habitat type. This survey was carried out throughout the country to estimate inland fisheries production and the value of this sector. Data from the GPP household survey of 2005 was used. After being checked, cleaned and stored in the database, a total of 2 215 households were available for analysis and used for production estimation and mapping.
DISTRIBUTION OF HOUSEHOLD PRODUCTION
The distribution of household production is shown in Figures 6 and 7. Household production by region varied widely among the small-scale and middle-scale to commercial-scale fishing households. Of the total 2 215 households, 77.1 percent reported production less than 300 kilograms (Figure 7). It could be assumed that one-third of the sampled fishing households' production is less than 25 kg/month.
Inland capture fisheries are very important to the livelihoods of the Thai people. Most of the households in the low-production group utilized their production mainly for household consumption, whereas the production from middle-scale to commercial-scale fishing was mainly for sale (Figure 8).
As in other studies/surveys in the fisheries sector, household production distribution from the GPP survey is skewed to the right. Mean production of the total 2 215 households is 401.6 ± 1 090.5 kg/year where half of the total sampled households (median of production distribution) reported their production less than 120 kg/year and 75 percent of the total sampled households reported their production less than 281 kg/year (Figure 9).
Figure 6 Distribution of fishing household in Thailand
Figure 7 Distribution of household production of total 2 215 sample fishing households
Figure 8 Distribution of production of sampled households
Figure 9 Distribution of household production by region
Quantiles | |||||||
Level |
Minimum |
10% |
25% |
Median |
75% |
90% |
Maximum |
Central | 4.8 |
33.44 |
60 |
120 |
758.55 |
2 480 |
9 672 |
North | 2 |
22.24 |
42 |
100 |
240 |
497 |
26 500 |
Northeast | 2 |
25 |
45.4 |
120 |
240 |
700 |
18 900 |
South | 24 |
56.12 |
103.575 |
218 |
542.5 |
1 309.9 |
5 850 |
Means and Std Deviations | ||||||
Level |
Number |
Mean |
Std Dev. |
Std Err Mean |
Lower 95% |
Upper 95% |
Central | 301 |
817.091 |
1 625.05 |
93.666 |
632.76 |
1 001.4 |
North | 745 |
252.353 |
1 032.86 |
37.841 |
178.07 |
326.6 |
Northeast | 911 |
355.601 |
935.80 |
31.004 |
294.75 |
416.4 |
South | 258 |
511.056 |
828.60 |
51.586 |
409.47 |
612.6 |
Figure 10 Distribution of production of sampled households divided into four regions
The average household production is different in the four regions (Figure 10). Interestingly, the mean production is highest in the central and southern regions where there were a smaller number of sampled households.
A comparison of the small-scale fishing households and the group of fishing households using larger gear or conducting fishing activities for commercial purpose reveals that the total production of the small-scale fishing households is lower (Figure 11).
Means and Std Deviations | ||||||
Level |
Number |
Mean |
Std Dev. |
Std Err Mean |
Lower 95% |
Upper 95% |
Consumed |
1 291 |
145.470 |
265.29 |
7.383 |
130.99 |
159.96 |
Sell |
924 |
759.686 |
1 591.86 |
52.368 |
656.91 |
862.46 |
Figure 11 Distribution of production of sampled households based on the utilization of production
Means and Std Deviations | ||||||
Level |
Number |
Mean |
Std Dev. |
Std Err Mean |
Lower 95% |
Upper 95% |
-1 (M/CFHHs) | 552 |
1 305.62 |
1 916.14 |
81.556 |
1 202.5 |
1 420.9 |
0 (SSFHHs) | 1 663 |
101.65 |
73.88 |
1.812 |
96.9 |
106.7 |
Figure 12 Distribution of production of sampled households divided into two groups based on amount of fish caught
Following the distribution analysis on household production, 75 percent of the sampled households' production was less than 281 kg/year. Therefore, the fishing households are separated into two groups based on production reported, i.e. households reporting a production over 281 kg/year (large catch households (LCH)) and households reporting a production less than 281 kg/year (small catch households (SCH)). All production amounts from each sampled household are summed even if they came from different fishing habitats. The mean production of the SCH is 101.6 kg/year and for the LCH the mean production is 1 305.6 kg/year (Figure 12). These mean productions are then used to calculate the total production by multiplying with the total number of households in small-scale fishing households (SSFHH) and medium-scale to commercial-scale fishing households (M/CSFHH) (Table 5).
Table 5 Average, median household production of all sampled households and average household production of small-scale and middle-scale to large-scale fishing households and inland fisheries production estimation (tonnes)
Item |
Population |
Estimated production from “median” production |
Estimated production from “mean” production |
Estimated production from “mean” of 75% SSFHHs |
Estimated production from “mean” of 25% M/CSFHHs |
Agricultural census | |||||
Total fishing HHs |
2 639 582 |
1 979 687 |
659 896 | ||
Central | 7 413 300 |
234 171 |
234 171 |
||
North | 3 768 261 |
672 742 |
672 742 |
||
Northeast | 5 350 322 |
1 600 873 |
1 600 873 |
||
South | 2 484 891 |
131 796 |
131 796 |
||
Purpose: for consumption |
18 702 774 |
2 540 771 |
2 540 771 |
||
GPP survey | |||||
Total sampled HHs |
2 215 |
2 215 |
1 663 |
552 | |
Purpose: for consumption |
1 297 (58%) |
1 291 (58%) |
1 133 (68%) |
164 (30%) | |
Purpose: for sale |
924 (42%) |
924 (42%) |
533 (32%) |
391 (70%) | |
Average production (kg/year) |
418.2 |
401.6 |
101.6 |
1 305.6 | |
Std Dev. | 1 088.9 |
1 088.9 |
73.9 |
1 916.1 | |
Median | 120 |
||||
Upper 95% mean | 418.4 |
106.7 |
1 420.9 | ||
Lower 95% mean | 385.0 |
96.9 |
1 202.5 | ||
% production | 100.0 |
24.99 |
75.01 | ||
Estimated production | |||||
Two groups of SSFHH |
201 136 |
861.560 | |||
and M/CSFHH (tonnes) |
|||||
Total production from capture (tonnes) |
316 749 |
1 060 056 |
1 062 696 |
AN ESTIMATION OF INLAND CAPTURE FISHERIES PRODUCTION
As stated, the estimation of the total production yield for Thailand is based on two data sets from two different surveys: the agricultural census and the GPP survey of inland capture fisheries. Table 5 summarizes the number of fishing households from the agricultural census and the results of the descriptive analysis of production of 2 215 sampled fishing households including the trial analysis of production. Two methods are used to estimate the total production: (1) estimation of production yield based on all sampled fishing households; and (2) estimation of production yield by separating fishing households into two groups of small-scale (SSFHHs) and medium-scale to commercial-scale fishing household (M/CSFHH).
Mean production derived from a descriptive analysis of the two methods is then multiplied by the number of fishing households from the agricultural census. Results from the two methods are summarized below.
Estimated production based on all sampled fishing households:
Estimated production based on two separate groups of small-scale and medium-scale to commercial-scale sampling fishing households:
The use of production data estimated from fishing households multiplied by the total number of fishing households could be a proper approach for estimating capture fisheries production. Range of fisheries production yield from various habitats including river and stream, reservoir, canal, natural swamp and man-made fish pond, etc. could be estimated to produce about 901 974 to 1 158 592 tonnes per year. This is a little higher than the production estimated in the previous study by Coates (2002) which was from five major habitats types and stated to be 472 314 to 1 118 909 tonnes per year and other estimates (Table 6).
Table 6 Reported and estimated production from inland capture fisheries
Sources of reported production |
Officially reported annual production (tonnes) |
Factor increase from reported to estimated production |
Basis of the indicative figures |
(a) National total (1999) Primarily reservoirs |
226 510 |
0.54-1.4 |
The Thai figures apply mainly to reservoirs, which are confirmed by reference to estimates made by Virapat et al. (2000) of 122 314 to 318 909 (reservoirs only) |
(b) National total (2005) All inland areas |
198 800 |
– |
Available but localized survey data for Thailand and comparisons with similar areas. These figures include the full range of estimated production for reservoirs and between 350 000 and 800 000 tonnes (Coates, 2002) or fisheries outside reservoirs including capture production from rice-fields and brackishwater inland fisheries (currently reported as coastal production). |
POTENTIAL SOURCES OF ERROR IN THE GPP PROCESS
In the GPP survey, information on household production, expenditures and income earned from capture fisheries is collected by means of interviewing a sample of households selected using a statistical sampling technique. The whole process of sampling fishing households and conducting the survey is carried out by the Provincial Fisheries Office. Since some of the provincial fisheries officers do not have basic knowledge of statistical processes, this might cause sampling errors. Preferably, random samples of households should be selected throughout the country by FITC and thereafter the provincial offices should conduct the field surveys.
Besides sampling errors, the ability of households to recall the actual production figure could be another possible source of error. The usual method of collecting fishing statistics is to conduct an interview with the household head and to ask him/her to recall monthly production and the fishing effort spent. It has been demonstrated in scientific surveys that the ability to accurately recall information decays within 48 hours (Coates, 2002). This problem is more prominent in the small-scale production fishing households since the respondents probably get only a small production per day and do not conduct fishing activities throughout the year.
2 Coates (2002); Pawaputanon Na Mahasarakarm (2007); Blake and Pitakthepsombat (2006); Hortle and Suntornratana (2008).
3 DoF (2006a).
4 DoF (2007).
5 Fishery Information Technology Centre, DoF, Thailand 2007.
6 DoF (2005a), (2005b), (2005c).
7 ONESDB (2005).
8 "The idea of the closed segment is to account in a rigorous manner for all of the land, livestock, etc., within the boundaries of the segment at the time of the interview regardless of what farm, or part of a farm, may be involved. Thus, the basic unit for enumeration becomes a "tract" which is a farm or part of a farm within a sample segment." (Houseman and Becker, 1967, p. 19).