ESTADOS ESPECÍFICOS DE INCONCIENCIA

Summary

This study was carried out at waters located immediately downstream of Bakun Hydroelectric and Batang Ai Hydrolectric Dam. These areas were previously natural river systems that changed into regulated ecosystem after impoundment and operation of the dams. Changes in habitat have been shown to affect the state of health of fishes living in the area. However, fishes are able to adapt towards changes that occur around them, as part of the evolutionary process to ensure survival. How well these fishes gradually adapt to this change over long period of time is still unknown. Batang Ai Dam was impounded about 31 years ago and the tail water environment is considered to have stabilized as compared to Bakun Dam which was impounded about 10 years ago. Therefore, the objective of this study was to compare the length-weight relationship (LWR) of Cyclocheilichthys apogon living in the tail water environment of the two dams. Linear regression analysis of LWR was conducted using SPPS to obtain the b values of this species for each area. The results showed that C. apogon living in tail water of Batang Ai Dam has higher b value (3.122, N=190) as compared to those living below Bakun Dam (2.927, N=80). Although this result shows that it is possible for fishes that live at tail water to tolerate and adapt to the impact of changes in habitat due to impoundment over time, it is still not an ideal habitat as indicated by the K factor obtained for the two areas.

Keywords: Tail water; Cyclocheilichthys apogon; Length-Weight Relationship; Condition factor; Tropical Hydroelectric Dam

Introduction

Sarawak is a rapidly developing state, as many power intensive industries have established their presence in the state. Hydroelectric dams were built by the State government to meet the high demand of energy. Tail water environment refers to the environment that is located below a dam. Before a river is impounded, the tail water is a natural river ecosystem with non-regulated flow regime. Once the dam is operational, the whole environment changed into a regulated river ecosystem. This has a huge impact towards fish assemblages in that area. However, fishes are known to adapt towards changes that occur around them as part of the evolutionary process to ensure their survival. However, adaption of fishes to changes due to tail waters in tropical Sarawak is still unknown. Throughout 31 years of its operation, the status of fish health below Batang Ai Hydroelectric Dam tail water is still unclear. Although few researches have been conducted in the area, most studies were focus in the reservoir area. Meanwhile, Bakun Dam started it operation 10 years ago and is therefore relatively new. This allows a comparison on the temporal effect towards the well-being of fish in the tail water area.Therefore, the objective of this study was to compare the length- weight relationship (LWR) of Cyclocheilichthys apogon living in the tail water environment of the two dams.

Materials and Methods

This study was carried out at two locations namely, Batang Ai Hydroelectric Dam and Bakun Hydroelectric Dam. Batang Air Hydroelectric Dam is located 175km away from Kuching. The study site is located at the section of Batang Ai that is below the power house or its tail water starting from Skarok (N01˚06'42.8" E111˚51'49.20") to Rasau (N 01˚05'50.17" E111˚44'00.26"). Samplings were carried out in October 2014 and January 2015.

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Bakun Hydroelectric Dam is located 780 km away from Kuching. The sampling area was also at the tail water of Bakun power house starting from Long Bangu (N2˚46’17.6” E114˚01’57.9”)to Long Segaham (N2˚46’39.6” E114˚56’ 05.1”). Samplings were carried out from February 2016 until February 2017.

Fish samples were collected using monofilament and 3 layered gill nets. The mesh sizes for monofilament nets used were 2.5 cm, 5.0 cm, 6.4 and 7.6 cm. For the three layered net, the outer mesh size was 17.8cm and the inner layer was 10.2 cm. Fish samples were labelled and placed into iced cooler box and were later identified to the species level following Kottelat et al. (1993) and Robert (1989).

The formula used for LWR analysis is as follows; log W= log a + b log L (Keys, 1928)

where, W is the body mass of the fish sample, L is the total length and a and b are constants. The Condition factor (K) was calculated using the equation;

K = 100W/L3 _{(Pauly, 1983)}

Samples with gonads present were omitted for this analysis. Eighty individuals were selected from Bakun and 190 individuals from Batang Ai. All samples were measured and weighted. Total length was measured from the snout till the end of the caudal finand body mass was measured using Shimadzu ELB 300 balance. All significant difference between study areas were determined using 2 tail independent t-test using SPSS window version 22.0.

Results

LWR results showed that fish in Bakun recorded lower b value compared to fish in Batang Ai (Table 1). The b value recorded in Bakun was 2.927 (Figure 1), which indicates that the individuals are experiencing negative allometric growth (Wotton, 1991). Meanwhile the b value recorded in Batang Ai was 3.122 (Figure 2), which indicates that they are experiencing positive allometric growth (Wotton, 1991). The a value recorded in Bakun was 1.9 with r2_{= 0.95, while in Batang Ai was 2.0 with r}2_{= 0.98.}

The mean of both total length and body mass was significantly different between the study areas (p<0.01). The mean length recorded for C. apogon in Bakun was 16.4 ± 3.4 cm, while in Batang Ai was 14.5 ± 2.9 cm. The mean mass was 52.73 ± 32.44 g in Bakun and 43.93 ± 23.05 g in Batang Ai (Table 1). Although the average total length of fish in Bakun was longer compared to those in Batang Ai, greater variation of fish length or higher SD was observed for fishes in Bakun. Similar value was also recorded for fish body mass in Bakun area.

K factor was also significantly different between study areas(p<0.01). The K factor recorded in Bakun was 1.1, meanwhile in Batang Ai was 1.3 (Table 1). According to Baxter & Barnham (1998) and Hamid et al. (2015), K = 1.00 indicate a poor condition fish, K = 1.2 indicate a moderate condition fish and K = 1.4 indicate a well-proportion fish. This indicates that the environmental conditions at both areas are not ideal for this species to grow.

Table 1: LWR parameters of C. apogon recorded from both study areas.

Area Mean Length _(cm) Mean Mass _(g) Mean _{K value} b _value a r2

Bakun 16.4 ± 3.4 52.73 ± 32.44 1.1 2.927 1.9 0.9₅

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y = 2.4543e0.1761x

R² = 0.9162

Discussion

Cyclocheilichthys apogon living in the tail water of Batang Ai Dam showed sign of adaptation towards the environment. Despite the unfavorable environmental condition in both areas as expressed by the K factor, C. apogon in Batang Ai experienced positive allometric growth. Individuals in Batang Ai were shorter in length to compensate for a relatively good body mass. However, this was not observed in C. apogon living in tail water of Bakun Dam. According to Pervin & Mortuza (2009) and Hamid et al. (2015), high b values indicate a good appetite and gonad content of the fish. However, since this study had excluded individuals with gonad, it showed better representation of appetite and food availability as important factors affecting LWR. Offem et al. (2007); Kamal et al. (2011) and Hamid et al. (2015) also

y = 1.1318e0.2386x R² = 0.961 y = 3.1222x - 2.0374 R² = 0.9812 y = 2.9275x - 1.8853 R² = 0.9506

Figure 1: The growth curve of C. apogon from Batang Ai (left) and Bakun (right)

Figure 2: The LWR regression plot of C. apogon from Batang Ai (left) and Bakun (right).

Total length (cm) Total length (cm)

Body mass (g) Body mass (g)

Logtotal length (g) Log total length (g)

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reported that body mass of fish increases through feeding for growth and energy. Moreover, Iskandar (2014) reported that C. apogon feeding habit in tail water of Batang Ai changed from carnivorous to omnivorous behavior. Therefore, it is postulated that fish in tail water of Batang Ai adapt towards the utilization of food availability within the area throughout time and develop new way of feeding strategies, which allow them to be more efficient for survival in that area.

In addition, it is possible that individuals living in tail water of Batang Ai reduced their somatic growth to preserved energy for reproduction. According to Lester et al. (2004), a fish is sexually matured will divert its energy expenditure from somatic growth into reproduction. This could be the reason for the decrease in total length of C. apogon in tail water of Batang Ai. In contrast, C. apogon in tail water of Bakun Dam were trying to attain their traditional body mass before becoming sexually matured. The growth curve of C. apogon living in tail water of Bakun Dam showed elongation trend to the right which indicated slower body mass gained as the fishes grow. Studies by Leunda et al. (2006), Hossain et al. (2006), Pervin &Mortuza (2009), Emanuel et al. (2013),Hamid et al. (2015) and Noor et al. (2017)also reported that sexual maturation affects LWR. It is possible that by trying to achieve earlier sexual maturation, C. apogon in Batang Ai showed greater b value according to the cube law. However, the overall environment still causes stunted growth for this species.

A significantly higher K factor was recorded in the tail water of Batang Ai Dam as compared to Bakun Dam. Nonetheless, both areas scored below ideal condition for fish survival. The primary factor that potentially affects fish health is water quality of the environment. The continuous input of the tail water comes from the released reservoir water. Studies conducted by Ling et al. (2016) and Ling et al. (2017) in Bakun Reservoir reported that tail water environment are susceptible to environmental impact due to changes in physicochemical parameters cause by the upstream reservoir. Important parameter that affects fish health such as pH and DO was reported to be low. Meanwhile, Iskandar (2014) reported that fluctuation of flow regime in tail water of Batang Ai Dam affects the water quality. Subsequently, this phenomenon affects fish survival. Therefore, it is believed that environmental condition especially less favorable water quality in tail water affects fish survival and growth.

Conclusion

Cyclocheilichthys apogon living in Batang Ai tail water showed better tolerance to the detrimental effect of impoundment through time as compared to fishes in tail water of more recently impounded Bakun Dam. However, the overall condition for both environments is still unfavorable for fish growth. Continuous studies, involving more species should be carried out to monitor this effect spatially and temporally.

Acknowledgements

The authors greatly appreciate the facilities and assistance provided by Universiti Malaysia Sarawak and Sarawak Energy Berhad for the financial support through research grants GL (F07)/SEB/5A/2013 (28) and GL(F07)/SEB/2A/2013 (16).

References

Barnham, C., & Baxter, A. (1998). Condition Factor, K, for Salmonid Fish (pp. 1-3, Rep.). Victoria, Australia: Department of Primary Industries.

Emmanuel, L., Oluwakemi, A., & Omobolaji, G. (2013). Aspects of the Biology of African Moony, Monodactylus sebae from Badagry Creek, Lagos, Nigeria. Advances in Life Science and Technology, 12, 5-12.

Hamid, M. A., Mansor, M., & Nor, S. A. (2015). Length-weight Relationship and Condition Factor of Fish Populations in Temengor Reservoir: Indication of Environmental Health. Sains Malaysiana, 44(1), 61-66.

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Hossain, M. Y., Ahmed, Z. F., Leunda, P. M., Jasmine, S., Oscoz, J., Miranda, R., & Ohtomi, J. (2006). Condition, length-weight and length-length relationships of the Asian striped catfish Mystus vittatus (Bloch, 1794) (Siluriformes: Bagridae) in the Mathabhanga River, southwestern Bangladesh. Journal of Applied Ichthyology, 22(4), 304-307.

Iskandar, N. (2014). Fish Assemblages and Water Quality at Downstream of Batang Ai Hydroelectric Dam, Lubok Antu, Sarawak. Unpublished bachelor degree thesis. Universiti Malaysia Sarawak, Kota Samarahan. Kamal, A. M., Kamaruddin, I., Christianu, A., Daud, S., Amin, S., & Abit, L. Y. (2011). Length-weight Relationship and Condition Factor of Three Dominant Species from the Lake Tasik Kenyir, Terengganu, Malaysia. Journal of Fisheries and Aquatic Science, 6(7), 852-856.

Keys, A. B. (1928). The Weight-Length Relation in Fishes. Proceedings of the National Academy of Sciences, 14(12), 922-925.

Lester, N. P., Shuter, B. J., & Abrams, P. A. (2004). Interpreting the von Bertalanffy model of somatic growth in fishes: the cost of reproduction. Proceedings of the Royal Society B: Biological Sciences, 271(1548), 1625- 1631.

Leunda, P. M., Oscoz, J., & Miranda, R. (2006). Length-weight relationships of fishes from tributaries of the Ebro River, Spain. Journal of Applied Ichthyology, 22(4), 299-300.

Ling, T., Gerunsin, N., Soo, C., Nyanti, L., Sim, S., & Grinang, J. (2017). Seasonal Changes and Spatial Variation in Water Quality of a Large Young Tropical Reservoir and Its Downstream River. Journal of Chemistry, 2017, 1-16.

Ling, T., Soo, C., Heng, T. L., Nyanti, L., Sim, S., & Grinang, J. (2016). Physicochemical Characteristics of River Water Downstream of a Large Tropical Hydroelectric Dam. Journal of Chemistry, 2016, 1-7.

Noor, I., Nyanti, L., Ling, T. K., & Jongkar, G. (2017). Comparison of Length-Weight Relationship and Condition Factor of Three Fish Species between Regulated and Natural Rivers.

Offem, B. O., Akegbejo-Samsons, Y. & Omoniyi, I. T. (2007). Biological assessment of Oreochromis niloticus (Pisces: Cichlidae; Linne, 1958) in a tropical floodplain river. African Journal of Biotechnology, 6(16), 1966- 1971.

Pauly, D. (1983). Some Simple Methods for the Assessment of Tropical Fish Stock (1st ed.). Rome: Food and Agriculture Organization.

Pervin, M. R., & Mortuza, M. G. (2009). Notes on Length-Weight Relationship and Condition Factor of Fresh Water Fish, Labeo boga(Hamilton) (Cypriniformes: Cyprinidae). University Journal of Zoology, Rajshahi University,27(2009), 97-98.

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