PROCEEDINGS OF THE BURAPHA
UNIVERSITY INTERNATIONAL
CONFERENCE 2013
GLOBAL CHANGE
OPPORTUNITY&RISK
4-5 JULY 2013
JOMTIEN PALM BEACH
HOTEL & RESORT, PATTAYA,
THAILAND
Burapha University International Conference 2013
Burapha University, Thailand
July 4-5, 2013
HUO10-21
Do sediments impact fish catch in a shallow lagoon? Fishermen
points of view: case study in Songkhla Lake, Thailand
Siriporn Pradit 1,2,*, Gullaya Wattayakorn 3, Saowapa Angsupanich4,
Martine Leermakers2 and Willy Baeyens2
1
Marine and Coastal Resources Institute, Prince of Songkla University,
Hat Yai, Songkhla, 90110, Thailand
2
Analytical and Environmental Chemistry, Vrije Universiteit Brussel,
1050, Brussels, Belgium
3
Department of Marine Science, Faculty of Science, Chulalongkorn University,
Bangkok, 10330,Thailand
4
Department of Aquatic Science, Faculty of National Resources, Prince of Songkla
University, Songkhla, 90112, Thailand
* Corresponding author: Siriporn Pradit
E-mail : siriporn.pra@psu.ac.th, spradit22@gmail.com
ABSTRACT
A socio-economic study linked to environmental data and considerations was carried out. The
targeted population consisted of local fishermen living in 13 districts located around Songkhla Lake, a
shallow lagoon in southern Thailand. Statistically it was sufficient to select 365 fishing households from a
total population of 4,227 fishing households. The results of the research showed that the majority of fishers’
household agreed that the quantity of catches decreased and consequently, their incomes were reduced.
There was a need expressed by local communities concerning preservation of natural resources for future
generations, as well as the realization that all community members should participate in natural resources
management. Impressively, most fishermen knew that the sediments were also a key factor in relation to
their fisheries. This finding will be helpful in formulating realistic a management and control of the
sediment quality based on the present assessments.
Keywords: socio-economic, Songkhla Lake, shallow lagoon, fishermen, Thailand.
INTRODUCTION
In general trace metal levels in surficial sediments in Songkhla Lake were within international
standards, with the exception of As at the mouth of Phawong canal in the Outer Section (Sirinawin and
Sompongchaiyakul, 2005; Sompongchaiyakul and Sirinawin, 2007; Pradit et al., 2010) but a rather high
sulfide content was observed in the eastern part of the Middle and the Outer Sections (particular at these
canals; Samrong, U-Taphao and Phawong) (Pradit et al., 2010). The sediment toxicity which was tested
on tanaid species indicated that sediments from Somrong canal, Outer Section of the Lake, were very toxic
showing a high mortality of the species (Pradit et al., 2012, unpublished), If tanaid, which is the main food
source of demersal fish (Angsupanich et al., 2005), could not survive what can we expect for the demersal
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July 4-5, 2013
fish species? During 1997-2001 fish mortality was observed, with in the year 2000 a huge mortality in the
Inner Section, and in the year 2002 in the Middle and Outer Sections. Most of the dead fish belonged to
the demersal species, especially catfish, Arius maculates. Hypothesis of the water column is a real threat
to all living organisms. In addition in the Inner and Middle Sections a problem of algae bloom occured (i.e.
Najas sp., Cladophora sp. and Enteromorpha sp.) as a result of Eutrophication (Sompongchaiyakul, 2005).
Important sedimentation occurred in the Lake. From the hydrographic maps of the area drawn by the Royal
Harbor Department (at present the Marine Department) in 1975 and 2002 (Sojisuporn, 2005) found that
the average accumulation rate of sediment in the lake is 2.5-3.5 mm/yr with at some places even >15
mm/yr. If this rate was sustained, the Lake would only remain a lake for another 300 - 400 years.
The Songkhla Lake is a shallow coastal lagoon located in the southern part of Thailand and has a
surface of approximately 1,042 km2 (Ratanachai et al., 2005). The lake itself is a very important natural
and economic resource for the people who live in Songkhla Province, Phatthalung Province and some parts
of Nakhon Si Thammarat Province, as a nursery ground and as a major fish stock for local fishermen. The
lake is divided into 4 sections; Thale Noi, Inner Section, Middle Section and Outer Section. The salinity
ranges from fresh in Thale Noi to saline in the Outer Section, which is open to the sea. It is deeper in the
Inner Section (more than 2 m), quite shallow in the Middle Section and the Outer Section. The lake itself
is facing problems of environmental degradation, shallowness, urban expansion (Maneepong and
Angsupanich 1999; Sukapan et al., 2006), decreasing of catch and low incomes for the fishermen (Masae
et al., 2005).
The fishermen around the lake are local indigenous people. Typical fishing households have some
parts of the Lake near their home or the communities where they are living in have been allowed for fishing
in the Lake since their ancestors’ time. They generally install stationary fishing gears, such as sitting cage,
set bag net, stationary lift net and bamboo stake trap. In the Outer Section of the lake, fishing activities are
mostly active all year round.
Fishery research has been conducted since 1965 by the National Institute of Coastal Aquaculture
(NICA), Phattalung Fresh Water Fishery Station and Prince of Songkla University. A study conducted in
2002 listed 450 species. Economic valuable and abundant species in Songkhla Lake include: Brown
Spotted Grouper, Giant Perch, Grey Mullet, Marine Catfish, Cyprininds, Sand Goby, etc. (Ratanachai et
al., 2005). Some extinct fish species from Songkhla Lake are for example Pra Prom (Thynnichthys
thynnoides), Pla Mein (Osphronemus goramy), Pla Toom (Puntius bulu) and Pla Lampam (Puntius
schwanenfeldii). Catfishes and more particularly Osteogeneious militaris (Linnaeus, 1758) and Arius
maculates (Thunberg, 1792) (Angsupanich et al., 2005) are a group of demersal fish that is dominant in
Songkhla Lake and found the year round. Two studies about the amount of fish caught in Songkhla Lake
were performed: the first during 1984-1986 (12,290 tons/year) and the second during 1994-1995 (9,634
tons/year) (Ratanachai et al., 2005). In 2003 the Marine and Coastal Resources Department reported that
the catch from sitting cage decreased significantly from 3.6 kg/day in 1996 to 0.9 kg/day in 2002. This is
a one of the indications and proof that catch declined in the past decade (Masae et al., 2005).
Why catch was decreasing and why some fish disappeared from the Lake? Several answers can be
put forward here such as for example the introduction of innovative and more efficient fishing methods,
the use of a destructive gear such as the push net, over exploitation, deterioration of the ecosystem, waste
water from surrounding industries and household waste into the lake etc. Since Songkhla is a shallow
lagoon with an average depth of around 1-2 meter, the sediment will play an important role as sink and for
source of pollutants that can be transferred to the lake’s aquatic organisms. Do these sediments affect or
have an impact on the catch in Songkhla Lake? Pradit et al. (2010) reported that the sediments in the Outer
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July 4-5, 2013
Section of Songkhla lake, in particular the sediments at the mouths of the canals Phawong, Samrong and
U-Taphao, significantly were enriched in trace elements due to municipal, agricultural and industrial
discharges entering the Lake through the canals. The Samrong canal is an important source of Ni, Cu, Zn,
Cd and Pb, whereas contamination of As is principally originating from the Phawong and U-Taphao canals.
From sediment toxicity tests with tanaid species we could deduce that Somrong’s sediment was the main
“hot spot” among those three sources, with an average of 89% mortality (Pradit et al., 2012: unpublished).
Local ecological studies within the framework of coastal zone management for a sustainable use of fish
resources have been reported by a number of researchers (Gerhardinger et al., 2009; Drew et al., 2005;
Mackinson and Nøttestad, 1998).
This study was thus a follow-up of the study on sediment characteristics of Songkhla Lake. It is an
attempt to investigate the socio-economic situation of fishermen and their local knowledge about lake
sediments as well as their points of view about the ecological situation of the lake.
MATERIALS AND METHODS
Population
The targeted population in this study was a group of local fishing households located within 13
districts surrounding the Songkhla Lake namely; Ranot, Krasae Sin, Sathingphra, Singhanakhon, Muang
Songkhla, Hat Yai, Bang Klam, Khuan Niang, Pak Phayun, Bang Kaeo, Khao Chaison, Muang Phatthalung
and Kuan Khanun (Figure 1). The local fishing household population 2007-2008 of all 13 districts
amounts to 4,227 (data were provided by Thai Ministry of Fishery Department: personal communication).
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Thailand
Inner
N
Y Ra n o t
#
K ua n K h a n u n
W
E
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Y
#
S
10
P ha tth a l un g
10
K ra sa e S i n
Y
#
Y
#
Kilometers
Middle
S ath i n g P hr a
K ha o C h a iso n
Y
#
0
Y
#
B an g K a e o
Y
#
Gulf of Thailand
P ak P h a yu n
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Y
#
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S in g h a na k h on
Y
#
Y
#
K hu a n N ia n g
Y
#
Mu a n g S o n g kh la
B an g K l a m
Y
#
Outer
Y
#
Ha t Y a i
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hao
U-Tap
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Y Sa mp ling dis trict
#
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Fig. 1 Districts surrounding Songkhla Lake that was sampled in 2008.
Sample size
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July 4-5, 2013
To determine the sample size of fishing households in relation to a predefined confidence interval
we used Yamane’s formula (1973):
n
N
1  N ( e) 2
(1)
Where n is the sampling size, N is the total population, e = 0.05% corresponding to a confidence
interval at 95%
n
Then
4227
1  4227(0.05) 2
= 365.42
To satisfy the criteria we have set, it is thus statistically sufficient to select 365 respondents as a
sample size of a total population of 4,227 fisher’s households. The researcher endeavored to get a
proportional sample size in each district according to:
ni 
N i  365
4227
(2)
Where ni is the fishing household sample size in district i, Ni is the total fishing household
population in district i. The sample size for each district is shown in Table 1
Research instruments
The research instrument for this study is a self-prepared questionnaire. The questionnaire contained
closed ended questions except for the “other (please specify)” questions. The questionnaire was written in
Thai in order to make sure that the intended meaning of the questions was correctly expressed. The draft
questionnaire had been tried out with 10 fishermen from the Muang Songkhla district. The fishermen were
asked to respond to all questions in the questionnaire and to specify any ambiguous or incomplete items,
to evaluate the content and to give suggestions and comments to improve the questionnaire. The
investigator took care of all these suggestions and revised the drafts into a final version.
The fishermen questionnaire consisted of 3 main parts. Part 1 contained 6 questions asking for
information related to the general background of fishing households and incomes (items 1-6). Part 2
included 3 questions related to fishing activities (items 7-9). Part 3 related to the Lake’s environment and
management aspects with a total of 3 questions further divided into 8 sub-questions (items 10-12).
Table 1. The fisherman sample size in each district.
No
Fisherman household
Fisherman sample
population
size
District
Province
1
Ranot
Songkhla
160
14
2
Krasae Sin
Songkhla
74
6
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July 4-5, 2013
3
Sathing Phra
Songkhla
521
45
4
Singhanakhon
Songkhla
733
63
5
Muang Songkhla
Songkhla
191
17
6
Hat Yai
Songkhla
184
16
7
Bang Klam
Songkhla
30
3
8
Khuan Niang
Songkhla
455
39
9
Pak Phayun
Phatthalung
1094
95
10
Bang Kaeo
Phatthalung
133
11
11
Khao Chaison
Phatthalung
266
23
12
Muang
Phatthalung
Phatthalung
257
22
13
Khuan Khanun
Phatthalung
129
11
4227
365
Total
Note: the data of Khuan Khanun District was only from the sub-district of Phanangtung
Data collecting procedures
The data collection via face to face interviews was carried out during the whole month of March,
2008. The investigators (2-4 persons) contacted list of pre-selected fishermen and asked them if they
accepted to participate in the interviews. In each selected household, the family’s head or his/her
representative was interviewed. Before interviewing, the investigator asked for permission to take notes
during the interview session. Each interview was conducted in Thai, and it took approximately 20 minutes
from start to finish. Each fisherman was requested to answer the same questions in the same order based
on a structured interviewing procedure.
RESULTS
Demographic characteristics of respondents
A total of 365 questionnaires were obtained from the fishermen. The demographic characteristics
of respondents were analyzed and the results were expressed in frequency and percentage. This part
included gender, age, educational level, occupation and monthly income of household as indicated in Table
2. From this analysis, the demographic characteristics of respondents were the following:
1. Gender. 88.22% (322 persons) of the respondents were males whereas females accounted for
only 11.78% (43 persons).
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2. Age. Respondents between 20-30 years old accounted for 7.40% (27 persons); 31-40 years old
for 14.52%(53 persons); 41-50 years old for 36.99% (135 persons); 51-60 years old for 25.21 % (92
persons) and over 60 years old for 15.89% (58 persons), respectively.
3. Educational background. The respondents with an education background corresponding to the
primary school level were 85.75% (313 persons); secondary school level were 10.68% (39 persons); higher
than secondary school level were 10.68% (39 persons) and having no-degree were 0.27 % (1 person).
4. Main occupation. Almost all of the respondents were Lake fisherman which accounted for
84.11% (307 persons). It was followed by rubber farmers (6.30% or 23 persons), rice farmers (3.84% or
14 persons), business people (1.64% or 6 persons), aquaculture farmers (1.10% or 4 persons) and others
(3.01% or 11 persons).
5. Co-occupation. The respondents from Lake Fisheries accounted for 15.89% (58 persons),
aquaculture farmers for 4.93% (18 persons), rice farmers for 6.85% (25 persons), business people for 3.84%
(14 persons), rubber farmers for 5.48% (20 persons), others for 33.97% (124 persons) and no jobs for
29.04% (106 persons).
6. Monthly income 60.82% (222 persons) of the respondents earned less than 5,000 Baht per month
and 39.18% (143 persons) more than 5,000 Baht.
Table 2. Demographic characteristics of respondents.
No.
1
Demographic
characteristics
Frequency
Percentage
No.
4
Gender
Male
Female
Total
Demographic
characteristics
Percentage
a) Main occupation
322
88.2
Lake fishing
307
84.1
43
11.8
Aquaculture
4
1.1
365
100.0
Rice Farming
14
3.8
6
1.6
Rubber farming
23
6.3
Others
11
3.0
365
100.0
Business
2
Frequency
Age
20-30 years old
27
7.4
31-40 years old
53
14.5
41-50 years old
135
37.0
51-60 years old
92
25.2
b) Cooccupation
Over 60 years old
58
15.9
Lake fishing
58
15.9
365
100.0
Aquaculture
18
4.9
Total
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3
Educational level
None
Rice Farming
25
6.8
Business
14
3.8
Rubber farming
20
5.5
1
0.3
313
85.8
Others
124
34.0
Secondary
39
10.7
None
106
29.0
Higher than
Secondary
12
3.3
365
100.0
365
100.0
Less than 5,000
Baht
222
60.8
Over 5,000 Baht
143
39.2
365
100.0
Primary
Total
Total
5
Monthly income
Total
Fishing activities
The reason to become a professional fisherman was, for all of them, to have an income by selling
part of the catch and keeping the remaining part for household consumption. Species of fish caught were
mostly demersal dwellers such as cat fishes. All of the fishermen declared that the amount of fish catch
declined over the past ten years. There is almost no more fish to catch in the Inner and Middle Sections, so
some fisherman who lived in the Middle Section moved fishing in the Outer Section where fish still remain.
Others are looking for a new job and sold their boats and all related equipment.
Fishermen in the Outer Section told us that at once mortality of fish (outside and inside cages) was
observed after a rain event. They thought that this occured because industrial waste (mainly related to
rubber and food products) was released during raining.
Fishermen in the Middle and Inner sections encountered problems of algae blooms followed by
huge fish mortality. During the algae bloom season (i.e. Enteromorpha sp: their shape is like long cotton
thread) tanaid species (i.e. Ctenapseudes sapesis) were wrapped by algae when they swam above the
bottom sediment and got killed (observed by authors). The problems raised by fishermen are shown in
Figure 2.
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Thailand
Inner
Eutrophication
Decline of aquatic species
N
Y
#
W
E
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

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Y
#
S
10
Y
#
Y
#
10
Kilometers
Middle
Y
#
Y
#
Y
#
Gulf of Thailand
Y
#
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Eutrophication
Sedimentation
Decline of aquatic species
0
Y
#
Y
#
Y
#
Sedimentation
Fishery and aquaculture overdone
Y
#
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
hao
U-Tap

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

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Outer
Y
#
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Fig. 2 Summary of the fishermen problems (March, 2008)
Fishermen opinions on Lake environmental conditions
The answers of fishermen on the Lake Environment (Table 3) were as follows:
1. Sediment color at fishing ground. 74.25% of the fishermen noticed that the sediment had a black
color, 16.16% said it was brown, 7.40% responded that it was gray.
2. Sediment texture at fishing ground. 95.62% of respondents said the sediment was muddy, 1.92%
said clay, 1.10 % said sand and 1.37% noted that it was mixed.
3. The effect of sediment texture on fishing activities. 73.42% of respondents said yes and only
26.58% of them said no.
4. Water quality. 53.99% of the fishermen noticed that the water was saline, 23.14% said it was
freshwater and only 22.87% responded that it was brackish water.
5. Have seen benthic organisms inside Lake Sediment. 80.82% of respondents pointed out that
they had seen benthic organisms inside the sediment; while only 19.18% of them said no.
6. Benthic organisms are beneficial to demersal fish. 80.82% of the people remarked that benthic
organisms are beneficial to demersal fish, while 19.18% said no.
7. Sediment problem. 11.51% of the fishermen noticed that there was no problem. 30.68% said it
was low, 42.19% responded that it was medium, while only 15.62 % of them said it was high.
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8. Water quality problem. 0.82% of respondents said there existed no problem. 3.29% said low,
42.19% said medium and 53.70% noted that it was high.
DISCUSSION
The results of this study show that the majority of fishers’ households agree that the quantity of
fish catch is decreasing and that their future is very uncertain. Moreover, most fishermen have a low
education and a low income. Impressively, most fishermen know that the sediment is also a key factor in
relation to their fishing activities (quality and quantity of their fish stock) and they know that benthic fauna
which live in the sediments are an important food source for fish. These findings will be helpful in
formulating realistic management tools for sediment quality based on up to date assessments. Some
fisherman told us that ten years ago the water in the lake was very clear and that we could see the lake’s
bottom as well as the benthic fauna. Nowadays the water is very turbid and light penetration is strongly
reduced.
The fishermen also highlighted that since the waste from shrimp farming was re-injected into the
lake and covered the lake sediments, especially at the Eastern part of Middle Section, caught decreased. A
part of the lake seems to become shallower especially in the Middle and Outer Sections. For example our
boat was grounded in a small canal where fishermen normally dock their boats and could not go out for
fishing.
There was a need expressed by local communities concerning preservation of natural resources for
future generations, and a wish that all community members should participate in natural resources
management. Only when all stakeholders are involved, the lake will have a future but the local community
should be the initiator and driving force of the whole process.
Table 3 Fishermen’s opinions on Lake Environment.
Environmental
No.
1
opinion
Frequency
Percentage
Black
271
74.2
Brown
59
16.2
Gray
27
7.4
8
2.2
365
100.0
Mud
349
95.6
Sand
4
1.1
Clay
7
1.9
Sediment color at fishing ground
Others
Total
2
Sediment texture at fishing ground
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Mixed
5
1.4
365
100.0
Yes
268
73.4
No
97
26.6
365
100.0
Fresh
87
23.1
Brackish
86
22.9
Saline
203
54.0
Total (remark: some people prefer more
than one)
376
100.0
Yes
295
80.8
No
70
19.2
365
100.0
Yes
295
80.8
No
70
19.2
365
100.0
None
42
11.5
Low
112
30.7
Medium
154
42.2
57
15.6
365
100.0
3
0.8
Total
3
Sediment texture having an effect on
fishing operations
Total
4
5
Water salinity preference
Observed benthic organisms in lake
sediments
Total
6
Benthic organisms are benefic to
demersal fish
Total
7
Lake sediments are a problem
High
Total
8
Lake water is a problem
None
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Low
12
3.3
Medium
154
42.2
High
196
53.7
365
100.0
Total
CONCLUSIONS
It is clear from the answers of the fishermen that they are aware that the sediments have a serious
effect on the catch. On the one hand the quality of sediments in the lake increased; with as a consequence
a reduced depth and increased turbidity, on the other hand the quality of the sediments decreased which
was clearly demonstrated by tested the sediment’s toxicity on tanaid species. For the fishermen this has
dramatic consequences because reduced fish stock and fish qualities imply that many families have no
more income. So the local knowledge acquired from this study should be combined with that of other
scientists and fishery managers to make a plan for achieving a sustainable catch in the Lake, before it is
too late and all fish disappeared and the lake became dry.
ACKNOWLEDGEMENTS
The work described in this paper is supported by a Ph.D. Scholarship from the Flemish
Interuniversity Council (VLIR) in Belgium. Fishermen who live around Songkhla Lake are really
appreciated for their excellent cooperation and provision of valuable information. Thanks are extended to
Sakya Pradit for his assistance in the questionnaire survey.
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