Songkhla lake, environment related to fisheries and aquaculture

Transcription

1 Songkhla lake, environment related to fisheries and aquaculture NIKHOM LA-ONGSIRIWONG Narathiwat Coastal Aquaculture Research and Development Center Department of Fisheries, Thailand

2 Overview topics I. General information of Songkhla lake Characteristics of Songkhla lake Climate characteristics Fisheries resources and Fisheries activities Problems in Songkhla lake II. Important environmental aspects in Songkhla lake DO Salinity Chlorophyll a

3 Overview topics (con.) III. Effects of environment on fisheries and aquaculture in Songkhla lake Oxygen depletion Salinity Eutrophication condition

4 I. General information of Songkhla lake

5 Characteristics of Songkhla lake Unique lagoon in Thailand and one of 117 lagoonal lakes in the world Located at southern region of Thailand in the provinces of Songkhla and Pattalung Largest lagoonal water in Thailand and Southeast Asia with a total area of km 2 (98, 680 ha) Devided into 4 parts : Thale Noi, Upper lake, Middle lake and Outer lake

6 Figure 1. Map showing Songkhla lake in Southern Thailand

7 Table 1.Some morphometric data on the Songkhla lakes (at 0 m MSL) Division Thale Noi Inner lake Middle lake Outer lake Surface area(km 2 ) Mean depth(m) Retention time(days) Salinty range

8 Depth (m) Entrance Ko Yo Pak Ro Pak Payoon Nakorn Srithammarat U-tapao river Thale Noi Characteristics of Songkhla Lake Basin P h a t t h a l u n g Upper lake 1.8 m 491 km 2 GULF OF THAILAND 1.0 m 376 km 2 Middle lake Outerlake Basin area 9,807 km 2 Lake Properties: 1.3 m 190 km 2 Area 1,182 km 2 Length ~80 km Width ~22 km S a t u n Hat Yai S on g k h l a Thale Sap Songkhla Klong Luang Thale Sap M A L A Y S I A Thale Luang

9 Characteristics of Songkhla lake (con.) Thale Noi The upper most part of the lake The smallest of four parts with a total area of 28 km 2 A freshwater lagoon located in Pattalung province Densely populated by various aquatic macrophytes Very shallow lake; 1 meter in depth

10 Figure 2. Scenery of Thale Noi

11 Characteristics of Songkhla lake (con.) Upper lake Located adjacent to the southern part of Thale Noi The largest part of the lake with a total area of 459 km 2 Normally oligohaline brackish water nearly over the year but maximum salinity may be reached to > 11 psu in the end slightly rainy season of the drought year Deepest with an average 2 meters Highly eutrophic condition

12 Figure 3. Dark green color of water in Upper lake showing eutrophication problem

13 Characteristics of Songkhla lake (con.) Middle lake Covers a total area of 377 km 2 Average depth only 1 m. Mixing zone between fresh and seawater Connected to Outer lake with deep narrow canal Eastern coast is populated by various aquatic macrophytes Irregulary blooming of macrophytes (Najas sp.) and macroalgae (Cladophora sp. and Enteromorpha sp.) in 2003 and 2004

14 Figure 4. Sceneries of the Middle lake

15 Figure 5. Blooming of macrophytes (Najas sp.) and macroalgae (Cladophora sp. and Enteromorpha sp.) in the Middle lake occurred in 2003 and 2004

16 Characteristics of Songkhla lake (con.) Thale Sap Ton Nok Covers a total area of 176 km 2 Average depth about 1.5 m. Connected to the Gulf of Thailand Dense with fishing gears and fish-cage culture Surrounded with human activities Port (deep sea port and fishing port) Fisheries Industries Cities (Songkhla, Hat Yai)

17 ST 7 ST ST 8 ST 6 ST 5 ST 3 ST 9 ST 4 ST 2 ST 10 ST Figure 6. Map showng the Outer lake

18 Figure 6. Activities in the Outer lake

19 Figure 6. (con)

20 Climate characteristics of Songkhla lake Equatorial monsoon climate High temperature exist all year round The average, range of weather temperature is 27.5 o C, o C The coolest month is in December with a mean average temperature of 26 o C and hottest month in April (31 o C) the average total annual fall is 1,965 mm. About 60% of the total annual rainfall normally occurs from October to December

21 Rainfall (mm) Monthly Rain at Hat Yai City, Songkhla 300 mm 100 mm Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

22 Climate characteristics of Songkhla lake (con.) 2 season : Dry season and Wet season Dry season : the middle of February to the middle of May Wet season is divided into 2 periods A light rainy period : effected by the southwest monsoon (from the middle of May to the middle of October) A heavy rainy period : effected by the northeast monson (from the middle of October to the middle of February)

23 Fisheries resources and fishing activities in Songkhla lake In the past, one of the most abundance of aquatic animals 700 species of fish, crab, shellfish and prawn Dominant species 43 estuarine species : Lates calcarifer, Plotosus canius, Mugil sp., Arius sp. 19 freshwater species : Macrobrachium rosenbergii, Clarias spp.

24 M. ensis P. merguiensis Plotosus canius Figure 7. Some commonly economical fishes in Songkhla Lake

25 Scatophagus augus Lates calcarifer Arius sp. Arius sp. Figure 7. (con)

26 Chana striata Clarias spp. Macrobrachium rosenbergii Figure 7. (con.)

27 Fishery activities in Songkhla lake 2 types of fishery activities : aquaculture and capture fishery Capture fishery At least 7,000 tons of fish per year caught from the Songkhla lake Thale Noi : 528 tons, all fresh water Upper lake : tons, mainly fresh water fish but occasionally brackish water fish Middle lake : tons, mostly marine shrimp (Penaeus merguiensis and Metapenaeus spp.) Outer lake : tons, mostly marine shrimps and brackish water fish

28 Fishery activities in Songkhla lake (con.) Capture fishery (con.) Quantity of capture fishery in the lake now lower than in the past probably due to illegal fishing and environmental degradation Fishing gears : stationary gears and moving gears Stationary gears :standing trap, set bag Moving gears : gill net, hook, scoop net

29 Figure 8. Some commonly stationary gears in Outer Lake

30 Figure 9. Standing trap in Songkhla Lake

31 Fishery activities in Songkhla lake (con.) Capture fishery (con.) Common size of captured fishes was small Metapenaeus ensis : cm (TL) Swimming crab: cm (carapace length) Abundance of captured fishes by standing trap depend on salinity juveniles

32 trap gill net scoop net Figure 10. Some commonly moving gears in Outer Lake

33 Fishery activities in Songkhla lake (con.) Aquaculture : shrimp farming and fishcage culture Shrimp farming First established in Intensive culture About 1,372 hectares, 1412 tons all white shrimp

34 Figure 11. Cultured-species of shrimp in Songkhla lake area and earthen ponds for shrimp culture

35 Fishery activities in Songkhla lake (con.) fish-cage culture First practiced in 1980 at Ban Bor Keng near the lake mouth Rapidly expanded and now > 7,000 cages, 1,100 farmers was established in Outer lake Mostly seabass (Lates calcarifer) culture The fisheries farmers always face problem of fish mortality since 1986

36 Figure 12. Netcages

37 Figure 13. Seabass culture

38 Mari-culture activities Khao Khieo Mari-culture (No. of cages): Hua Khao Ko Yo ~ 1,854 Hua Kao Dang ~479 Kao Keaw ~593 Seabass Mariculture Ko Yo 1997 Vel. Meas Vel. Meas.

39 Problems in Songkhla lake Shallowness

40 Water level in Songkhla lake system Thale Noi Bangkok Upper lake Gulf of Thailand Andaman Sea Songkhla Lake Malaysia Middle lake Gulf of Thailand Outer lake Ko Nu Ko Yo

41 2.5 ความล กของน า (เมตร) น ำตำย... น ำเก ด 0.0 ม.ย ส.ค. ต.ค. ธ.ค. ก.พ. เม.ย. ระยะเวลาในรอบป (เด อน) average depth is m. with a minimum in August and maximum in December

42 Problems in Songkhla lake Pollutions Community Industry aquaculture

43 Problems in Songkhla lake Construction of stationary fishing gear Standing trap 1984 : traps 1993 : 8,750 traps 2005 : >20,000 traps set bag : 1979 : 1,029 units 2005 : >2,300 units

44 Problems in Songkhla lake eutrophication

45 Problems in Songkhla lake Declination of fishery resources Extinction : Dugong, turtle Endangered species : Clarias sp.irrawaddy dolphin (Orcaella brevirostris),puntius schwanenfeldi Decreasing of catch effort and captured size Standing trap: kg/day kg/day

46 II. Important environmental aspects in Songkhla lake

47 Dissolved Oxygen (DO) Very important and sensitive indicator of the health of aquatic systems Provides key information about the system state -Algal blooms -Oxygen depletion Low DO can cause the loss of aquatic animals

48 Surface Exchange -Algae -Macrophyte -Fish -Zooplankton Photosynthesis Respiration Respiration Dissolved Oxygen Decomposition Oxidation -Fe 2+ -Mn 2+ -S 2- -NH 4+ -Organic Matter -SOD Figure 14. Process effecting dissolved oxygen content Sources : GÖnenç and Wolflin (2005)

49 Dissolved Oxygen (DO)(con.) spatial and seasonal fluctuation in Songkhla lake Varies wide limits in Upper lake Lower than criteria value for normal fish growth (4.8 mg/l) in the vinicity of fish-cage In the restricted water exchange areas, oxygen depletion can be occurred at dawn, especially when the wind calm and neap tide oxygen depletion in Songkhla lake sometimes caused by eutrophication

50 latitude (N) longitude (E) Figure 15. Spatial distribution of DO content (% saturation) in Songkhla lake

51 latitude latitude latitude longitude longitude longitude Figure 16. Spatial-seasonal distribution of DO content (% saturation) in Songkhla lake

52 mg/l mg/l time 16:00 At the vinicity of fish-cage in Outer lake In Upper lake 19:00 22:00 1:00 4:00 7:00 10:00 13:00 16:00 time Figure 17. Diurnal change of DO content in Songkhla lake 19:00 22:00 1:00 4:00 7:00 10:00 13:00

53 Important environmental aspects in Songkhla lake (con.) Salinity the total quantity of dissloved salts in seawater Vary widely in Songkhla lake which are affected by tidal flow, freshwater runoff Spatial and seasonal variation with precipitation and the distance away from the sea Before 2006, salinity in the Outer lake usually sharply rised in the beginning of hot season (February) Unnormal change of salinity in Songkhla lake was occured since 2006

54 latitude longitude Figure 18. Spatial distribution of salinity in Songkhla lake

55 latitude (N) latitude (N) latitude (N) longitude (E) longitude (E) longitude (E) Figure 19. Spatial-seasonal distribution of salinity in Songkhla lake

56 PSU Jan-03 Apr-03 Jul-03 Oct-03 Jan-04 Apr-04 Jul-04 Oct-04 Jan-05 Apr-05 Jul-05 salinity Oct-05 Jan-06 Apr-06 Jul-06 Oct-06 Jan-07 Apr-07 Jul-07 Oct-07 Figure 20. Variation of salinity and rainfall in Outer Songkhla lake during rain mm.

57 Salinity Intrusion in Songkhla Lake System, ppt 5 ppt

58 Important environmental aspects in Songkhla lake (con.) Chlorophyll a The photosynthetic pigments of plants Various chlorophyll, identified by symbols a, b, c, d occur in water plants Chlorophyll a is the most important; it indicated biomass of phytoplankton Indicator of eutrophication; > 10 μg/l Spatial-temporal typically change of chlorophyll a level in Songkhla lake was found

59 Important environmental aspects in Songkhla lake (con.) Chlorophyll a (con.) In Upper lake, typically higher than μg/l over the year and maximum as 180 μg/l was recorded At the fish-cage culture area, normally lower than 10 μg/l but sometime may be reached to 160 μg/l In Outer lake, chlorophyll a level in heavy rainy period often found higher than others

60 latitude longitude Figure 21. Spatial distribution of chlorophyll a level in Songkhla lake

61 latitude (N) latitude (N) latitude (N) longitude (E) longitude (E) longituude (E) Figure 22. Spatial seasonal distribution of chlorophyll a level in Songkhla lake

62 III. Impact of environment on fisheries and aquaculture

63 Salinity Effected to fish distribution and sea bass culture Migration of fish Food, breeding and spawning, environmental adaptation Fish distribution in Songkhla lake Freshwater group, salinity <0.5 ppt Estuarine group or brackish group, salinity ppt Marine group, salinity >33 ppt 3 groups of aquatic fauna Resident Migrant displacement

64 Salinity of environment Distribution (function of salinity preference and tolerance) Reproduction success (function of tolerance and osmoregulatory ability) Eggs Larvae Migration orientation (response To salinity gradients) Survival Juveniles Adults Distribution Eggs Larvae Juveniles Abundance to fishery Recruitment Abundance to spawning stock Figure 23. Influence of environmental salinity on the distribution and abundance of fish

65 DEMERSAL PELAGIC FRESHWATER ESTUARINE INSHORE postlarvae Mysis Protozoea nauplii juveniles eggs Spawning adults Figure 25. Life cycle of Metapenaeus brevicornis in Songkhla lake

66 DEMERSAL PELAGIC FRESHWATER ESTUARINE INSHORE juveniles postlarvae Mysis Protozoea nauplii Spawning adults Spawning adults eggs Figure 26. Life cycle of Metapenaeus tenuipes in Songkhla lake

67 Oxygen depletion Normally occured at fish-cage-vinicity in Outer lake but seldomly found in other areas e.g. Upper lake Normally caused by several factors as co-factors Fish respiration Tidal flow (blocked by the dense of fish cage) Water level Wind (reaeration) Algal bloom Usually found lowest DO content at dawn

68 Oct water level(cm) estimated (in the sea) measured (Yo Island) 5 north v(cm/s) 0-5 south temperature(ž ) inside outside 34 salinity(psu) inside outside 10 DO(mg/l) 5 0 inside (A) outside (B) (C) Oct 12 Oct 13 Oct 14 Oct 15 Oct 16 Fig. 5 : Time-Variation of Water Level, Velocity, Water Temperature, Salinity and DO

69 เมตร/ว นาท เวลา กระช ง สะพาน Figure 27. speed fluctuation in mari-culture area at Ko Yo Island, Outer lake Thailand

70 air DO available Current dispersion Oxygen consumption Water level air Oxygen consumption DO available stagnant Benthic DO Flux Water level Flux DO sediment sediment Figure 29. Effects of DO depletion to seabass culture

71 Figure 30. Mass mortallity of fishes caused by oxygen depletion (top : cultured fish; bottom : natural fish)

72 Figure 31. Aeration with long-tail boat motor

73 Eutrophication First reported in the data book of the world lake by Kira (1984) Overfertilization of nitrogen and phosphorus that come from paddy field, municipality, industry and aquaculture One major caused of fish resources declining in Songkhla lake Serious problem now in Songkhla lake

74 Figure 32. Dark green of water color showing phytoplankton bloom result in high DO and ph in daily light

75 Figure 33. Macro algae bloom in Middle lake ( ) and Outer lake (2008) (bottom right)

76 Figure 33. Rapid growth of macrophyte in Middle lake during

77 Figure 34. Color of oxic sediment (upper left ) and anoxic sediment (upper light) bottom : anoxic sediment caused by degradation of macro algae

78 Thank you for your attention