Wednesday, 26 October 2011

THESIS 3 - DIVERSITY AND FEEDING GUILDS OF FISH POPULATIONS IN PENGKALAN GAWI – PULAU DULA SECTION OF TASIK KENYIR TERENGGANU, MALAYSIA

Kamaruddin, I.S. (2011). Diversity and feeding guilds of fish populations in Pengkalan Gawi - Pulau Dula section of Tasik Kenyir Terengganu, Malaysia. Master of science thesis. Universiti Putra Malaysia. 94p. 



CHAPTER 3

MATERIALS AND METHODS

3.1          Site Description
Tasik Kenyir is the biggest man-made lake in Malaysia with a surface area about 36,900 hectares. It lies at latitude 4° 41’ north and longitude 102° 40’ east (Figure 3.1). This man-made lake was initially inundated in 1986 to generate hydroelectric power, receiving water inputs from two main rivers that are the Terengganu River and the Terengan River (Furtado et al., 1977). Tasik Kenyir is located 55 km from the city of Kuala Terengganu and the nearest town Kuala Berang is about 38 km from the lake. The main entry to the lake is through jetty Pengkalan Gawi which is near the Saddle Dam.
               
Tasik Kenyir was inundated in 1982 with the construction of Saddle Dam at Gawi in the north, the Jenagor Dam in the south-east and several smaller dams that blocked the water flow from 13, 320 rivers and tributaries. The lake was built without pre-clearing and lies within a thickly forested region (Ambak and Jalal, 1998). It holds 23.6 million m³ of waters used to generate electricity through the Sultan Mahmood Hydro Electric Power plant at the Jenagor Dam (main dam). The name of the lake is taken after the name of Kenyir River nearby.

               
Tasik Kenyir is standing about 138 m above the sea level and the temperature is around 31 C between May and June and decrease during monsoon season between December and February every year. The lake has an average depth of 37 meters with a maximum depth of 145 meters. The average water level drawdown of the lake was 7 to 10 meters annually and it is recorded almost at the same level every year. It was recorded that the highest water level of the lake was in November 1986 at 146.4 m and the lowest level was recorded on 23 November 1990 at 133.62 m depth. During the drought season the lake is dotted with more than 340 islands but only 100 islands can be seen during rainy season when it reaches the maximum depth. There are more than 14 waterfalls and numerous rapids and rivers. Its beautiful landscape and the surrounding natural environment provide a pleasant recreational retreat for urban residences.
               
The State Government of Terengganu since its inundation has developed Tasik Kenyir to be one of the world tourist destinations. Many infrastructures have been constructed such as construction of roads to the Pengkalan Gawi, car parks, a floating jetties, water and electricity supply, tourism centre, handicraft centre and rest house for the Government servants. Other facilities and services that provided by the private operators such as hotels, chalets, fishing equipments, boats for lake touring, houseboats for recreational fisherman and tourist guide services. Lake Kenyir also known as a commercial fish culture in net cage located in Sungai Como.



3.2          Study Location and Study Duration
This study was conducted at the Pengkalan Gawi- Pulau Dula section of Tasik Kenyir which extended from Pengkalan Gawi (Gawi Jetty) in the north to Pulau Dula (Dula Island) in the south (Figure 3.1). The section is only a small part of the lake with an area at about 30 km². The section is located at the main entrance for visitors to access to the Tasik Kenyir where a boat jetty is available. This section was chosen because it is the most accessible section of the lake. This section is important too because it is located near to human activities and the lake water received inputs from the catchment area that surrounded by human settlements. Human activities and settlements are believed to influence the fish population in this section. Furthermore, with limited sources in terms of man power and time, it is appropriate to conduct a comprehensive study that focus only on the section of the lake.

The study was done every month for one year from February, 2008 to January, 2009.  The one year duration was selected in order to get a monthly pattern for the temporal data of fish species diversity and their feeding habits.





Figure 3.1: Tasik Kenyir in Terengganu is the biggest man-made lake in Malaysia. The square box shows the location of Pengkalan Gawi – Pulau Dula section.


3.3          Data Collection and Sampling
The main data for this study consist of the number of fish species, composition of fish species percentage, length of fish, weight of fish and stomach content data to determine fish feeding habits. Water quality parameters were measured in situ as a secondary data.

3.3.1       Sampling Stations
Fish and water qualities were sampled monthly at three sampling stations set up in the study section of the lake. Each station is characterising by general descriptions of Tasik Kenyir where the littoral zone is steep and narrow with many dead trees emerged from the lake water, while the limnetic zone is clear and rather deep.

These stations designated as station A, station B and station C. Station A was located near Pulau Dula (Dula Island) to the south of Pengkalan Gawi. This is the furthest station from Pangkalan Gawi. Station B was located near Sungai Ikan (River Ikan) to the southwest of Pengkalan Gawi where this station located near the river mouth of Sungai Ikan. Meanwhile station C is the nearest station to Pengkalan Gawi and located near Pulau Pupi (Pupi Island) to the southeast of Pengkalan Gawi.

The selection of these sampling stations is based on the reason that the areas are the main fishing grounds for the local people and anglers. Furthermore, the sampling locations that scattered from the north to south are considered representative for the fish community in the Pengkalan Gawi – Pulau Dula section of Tasik Kenyir.

3.3.2       Fish Sampling Technique
Fish sampling was conducted using gill nets of same specification at all the three stations. Each gill net measure 100 meter long, and having a stretch mesh size of 6.35 cm (2.5 inches). The gill nets were set at the water surface at 1800 hours and maintained in position for a night and hauled in the next morning at 0800 hours. The time was chosen is due to the best time to catch fish in Tasik Kenyir is in the late evening or during sunset (DOF, 1994). The used of gill net is the most efficient method in fish sampling technique in Tasik Kenyir and the specification of gill net used in this study is the same to that used by the local fisherman. In order to avoid bias, only one sampling gear (gill net) was adopted and only one mesh size of net (6.35 inches) was used. The mesh size of the net is following to the minimum size that was allowed by the Department of Fisheries Malaysia in Tasik Kenyir.

3.3.3       Field Analyses of Samples
All fish caught were identified for species using standard taxonomic keys following to Mohsin and Ambak (1983) and Hua (2002) and the numbers of individual per species were counted. Standard length (cm) of each fish was measured using measuring board and the wet weight (g) of each fish was taken using digital balance model METTLER BD 1201 to the nearest centimetre and gram respectively.

For gut analyses, the stomach was removed from all fish that were caught beginning from the upper end of the esophagus near the gill to the anal opening. The degree of stomach fullness (SF) of fish was estimated by subjective method of each individual fish following Hyslop (1980). The fullness degree were categorised into five categories which are: 0 (empty), 1 (¼ full), 2 (½ full), 3 (¾ full) and 4 (full stomachs). The stomachs were then transferred into sampling bottles containing with 5% formalin solution for laboratory analyses later on.

3.3.4       Water Quality Analyses
Water samples were collected in situ from every month at each station and were analyzed both for chemical and physical parameters. The mean results are shown in Table 3.1 in order to characterizing the sampling sites and months.

For water quality parameters such as ammonia-nitrogen (NH3-N), nitrate-nitrogen (NO3-−N) and phosphorus-orthophosphate (PO43−) the water samples were measured using the HACH DR/2400 Portable Spectrophotometer with the reagent powder pillows.

3.3.4.1    Phosphorus-Orthophosphate (PO43−)
Phosphorus-orthophosphate was measured follows the PhosVer 3 (ascorbic acid) method where 10 ml of water sample was added with PhosVer 3 phosphate reagent powder pillow.

3.3.4.2    Nitrate-Nitrogen (NO3-−N)
Nitrate-nitrogen was analyzed following to the cadmium reduction method. 10 ml of water sample was added with NitraVer 5 nitrate reagent powder pillow.
3.3.4.3    Ammonia-Nitrogen (NH3-N)
Ammonia-nitrogen was measured using the salicylate method. 10 ml of water sample was used and added with ammonia salicylate and ammonia cyanurate reagent powder pillow.

3.3.4.4    Temperature, Dissolved Oxygen and pH
Water quality parameters such as temperature (C), dissolved oxygen (DO) (in mg/l) and pH were also collected in situ. Temperature and dissolved oxygen reading was recorded using portable dissolved oxygen meter model YSI 55 D.O. Meter. Meanwhile portable pH meter model HACH EC 10 was used to determine the hydrogen ion concentration in the water. The lake water visibility was read by lowering the secchi disk (20 cm in diameter) and the reading was determined by the average between initial and final reading. 


Table 3.1: Mean water quality parameters (mean±SD) that were collected in situ at each station and month in Pengkalan Gawi – Pulau Dula section of Tasik Kenyir.

Months
and Stations
Temp
(⁰C)
D.O
(mg/l)
pH
Secchi Disk
(cm)
NO3-−N
(mg/l)
NH3-N
(mg/l)
PO43− (mg/l)








Stations







Pulau Dula (A)
29.66 ± 1.17
6.18 ± 0.56
6.97 ± 0.43
447.41 ± 55.06
0.55 ± 0.32
0.08 ± 0.06
0.01 ± 0.01
Sungai Ikan
(B)
30.15 ± 1.38
6.27 ± 0.43
6.73 ± 0.37
370.77 ± 62.50
0.55 ± 0.28
0.06 ± 0.02
0.02 ± 0.01
Pulau Pupi (C)
29.47 ± 1.40
6.10 ± 0.49
7.03 ± 0.53
434.66 ± 48.61
0.56 ± 0.30
0.07 ± 0.05
0.02 ± 0.01








Months







March

29.02 ± 0.27
7.26 ± 0.39
7.45 ± 0.69
389.33 ± 58.76
0.53 ± 0.25
0.04 ± 0.01
0.02 ± 0.01
April

30.80 ± 0.61
6.55 ± 0.23
7.12 ± 0.68
469.25 ± 47.48
0.70 ± 0.26
0.04 ± 0.02
0.01 ± 0.02
May

30.90 ± 0.63
6.26 ± 0.09
6.78 ± 0.15
488.25 ± 30.01
0.23 ± 0.23
0.05 ± 0.02
0.02 ± 0.01
June

30.52 ± 0.10
6.25 ± 0.23
6.72 ± 0.19
341.75 ± 13.58
0.77 ± 0.25
0.11 ± 0.02
0.01 ± 0.00
July

30.30 ± 0.23
5.98 ± 0.03
6.54 ± 0.11
435.92 ± 25.10
0.80 ± 0.30
0.04 ± 0.02
0.01 ± 0.00
August

30.03 ± 0.62
6.03 ± 0.16
6.51 ± 0.08
466.42 ± 41.26
0.20 ± 0.17
0.11 ± 0.05
0.03 ± 0.01
September

30.70 ± 0.38
6.41 ± 0.08
6.81 ± 0.22
439.75 ± 69.05
0.47 ± 0.21
0.06 ± 0.02
0.00 ± 0.00
October

30.88 ± 0.47
5.67 ± 0.36
6.54 ± 0.08
395.25 ± 68.99
0.63 ± 0.31
0.07 ± 0.03
0.01 ± 0.01
November

29.43 ± 0.08
5.79 ± 0.49
6.90 ± 0.18
388.83 ± 79.31
0.67 ± 0.15
0.03 ± 0.03
0.01 ± 0.01
December

27.68 ± 0.39
5.86 ± 0.20
7.13 ± 0.33
429.83 ± 3.30
0.80 ± 0.17
0.06 ± 0.03
0.01 ± 0.01
January 2009
27.08 ± 0.44
5.98 ± 0.23
7.55 ± 0.09
349.17 ± 25.55
0.27 ± 0.06
0.15 ± 0.05
0.02 ± 0.02










3.3.5       Laboratory Analyses of Samples
In the laboratory, the larger part of the gut was analyzed. After removal from the stomach, food item were transferred into a petri dish with a grid size of 0.5 cm2 to which was added 10 ml of 70% of ethanol solution. Organisms present in stomach were taxonomically identified and counted. To examine the food organisms eaten by the fish, two types of microscopes were used. For large organisms Leica EZ4 dissecting microscope with magnification between 20X to 30X were used.

Meanwhile Carl Zeis Primo Star compound microscope with magnification 40X and 100X were used to identify smaller organisms like zooplankton and phytoplankton. Each food item was identified according to their taxonomic level and were categorised as fish, insects, mollusks (snails), crustaceans (shrimp), plant materials, detritus, copepods, cladocerans, rotifer, Bacillariophyta, Chlorophyta, Euglenophyta and Cyanophyta. Food item that could not be identified were identified as unidentified materials.

3.4          Data Analyses

3.4.1       Species Diversity of Fish
To determine the species composition of fish population in this area, the number fish species in the samples and the number of individual in each species were counted. Three indices associated with species composition were calculated manually; species diversity, species evenness and species richness. These fish diversity indices were analyzed based on their spatial and temporal patterns.

3.4.1.1    Fish Species Diversity
Fish species diversity was calculated using Shannon-Weaver Index (1963) as follows:                                                      
                                                                                H’ = - ∑ Pi ln Pi
Where:
H’ = diversity index
Pi = ni/N = number of individuals within species (ni) divided by the total number of individuals (N).  
ln = normal log

3.4.1.2    Fish Species Evenness
Fish species evenness was calculated using Pielou Evenness Index (1969) as follows:

                                                                                E’ =     H’    .           
                                                                                       H’ max
Where:
H’ = number derived from Shannon-Weaver index formula
H’ max = lnS = is the maximum value of H’ 


3.4.1.3    Fish Species Richness
Fish species richness was calculated using Margalef Index (1958) as follows:

                                                                                D = (S – 1)
                                                                                       Log N
Where:
S = Number of species
N = Total number of individuals


3.4.2       Feeding Habits of Fish
Selected species of fish in the study area were determined their feeding habits by using two indices. These indices are frequency of occurrence of food items (FOFI) in percentage (%) and composition of food items (CFI) in percentage. Both methods were followed according to Hynes (1950), Pillay (1952) and Hyslop (1980) where it is simple and considered satisfactory for studying food habits of fishes. These two indices were calculated using SPSS software version 17.0 in order to determine the percentage and the total number of food item occurred in the stomach. Fish species were determined their feeding habits as herbivore, omnivore, carnivore, insectivore, piscivore or detritivore according to the highest proportion of food item consumed and occurred in their stomach.


3.4.2.1    Percentage Composition of Food Item (CFI)
The CFI method was used to count the food composition that present in every stomach and the total was expressed as a percentage of the total number of food item occurred.

                                CFI (%) =     Number of food A item occurring       x 100
                                                       Total number of food items sampled

3.4.2.2    Frequency of Occurrence of Food Item (FOFI)
The FOFI method was used by recording the number of stomachs containing one type of food item and the total was expressed as a percentage of the total number of stomachs examined.

         FOFI (%) = Total number of stomachs containing food item A   x 100
                                   Total number stomachs examined


3.4.2.3    Trophic Level (Troph) 
The Trophic level of individual fish was performed using Troph-Lab computer program introduced and developed by ICLARM-FAO (Pauly et al., 2000). The equation is as per below:
TROPH = 1  +  ∑ DCij  x  TROPHj
 
3.4.3       Condition Factor of Fish (K)
To compare the length and weight, and in order to know the growth condition for selected species of fish, a condition factor (K) formula was used. This index to quantify the state of condition of a fish was followed Tesch (1971) and Weatherley (1972). The value of the growth exponent of 3 was used for the calculation. The K of fish species was calculated as follows:
                                                                       K =     W
                                                                                       L3
Where:  
W = weight (g)
L = standard length (cm)                                                   

3.4.4       Length-Weight Relationship
In this study, selected species of fish were identified their length-weight relationship (LWR). This LWR was calculated by the equation applied by Ricker (1975).
W = aLb
Where:
W            = The total weight (g)
L             = The total standard length (cm)
a              = constant
b              = growth exponent
A least square linear regression was estimated to make the relationship become linear:
Log10W = Log10 a + b Log10 L



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