4    Baseline Conditions & Sensitive Receivers

 

4.1    Introduction

 

This Section of the report describes the environmental baseline conditions in the Study Area focussing on the key elements of the Project.  The information is taken from a variety of sources including published literature, consultancy reports, recent field survey information and grey literature.  References are presented in each of the following sections for data sources.  Where previously approved EIA Reports have been referred to, the guidelines in the EIAO-TM have been followed.

 

4.2    Water Quality

 

4.2.1    Introduction

 

This Section describes baseline hydrodynamics, water and sediment quality within the Study Area for the proposed CMPs at South Brothers/East of Sha Chau.

 

4.2.2    Hydrodynamics

 

The hydrodynamic regime in the vicinity of the proposed CMPs at South Brothers and East of Sha Chau is complex and varies with a number of factors including the lunar cycle (spring and neap cycle), the season and the rate of flow of the Pearl River.  In general, the main ebb tide currents flow south along the Urmston Road, with a subsidiary flow bifurcating northwest of Chek Lap Kok to flow south down the west coast of Lantau, and southeast around the east of Chek Lap Kok Island.  Flood tides show the reverse pattern.

 

During the dry season the influence of the Pearl River is at its least because of reduced flows, resulting in typically well-mixed coastal waters.  In contrast during the summer (wet) season, the flow of the Pearl River increases and the coastal waters become highly stratified as the large influx of brackish water overlies the denser, more saline oceanic waters near the sea bed. 

 

Currents in the area are generally strongest on dry season spring tides.  The strength of the currents has been measured in two studies.  The first found moderate to low velocities (generally less than 0.4 m s-1) predominated by velocities rising to 1.0 - 1.5 m s -1 during spring tides ([1]).  The second study, which looked only at spring tides, recorded a maximum of 0.6 m s-1 ([2]). Acoustic Doppler Current Profiler surveys were undertaken in the vicinity of the CMP IV pits as part of the EIA Study on the spring tide of 19-20 January 1996 (dry season) and the spring and neap tides of July-August 1996 (wet season).  These data were used in calibration and validation of the TELEMAC model which was used in the previous CMP IV EIA.  The study found current velocities of up to 1.1 m s-1 on spring tides and up to 0.7 m s-1 on neap tides. 

 

Within the Study Area lies the Airport Sea Channel.  The airport platform was designed such that the channel between it and the northern coast of Lantau Island would be retained.  The main purpose of this channel was to achieve adequate flows in the East Tung Chung Bay, which would not have been possible had the airport been connected to the Lantau coastline.  The design of the sea channel was such that it should be at a minimum self-flushing (complete exchange of water in the channel at least once per day).  A series of water quality monitoring surveys have been conducted around the airport platform, in the Airport Sea Channel and East Tung Chung Bay.  Early field investigations (ADCP measurements) and computer modelling studies revealed that flows within the Airport Sea Channel were exceeding specifications and so the design purpose of the channel was confirmed.  The predicted flows within the sea channel have also since been confirmed.

Further to the east of the Airport is Tai Ho Bay, which is located and enclosed by the North Lantau Expressway.  The bay is connected to the sea via one main box culvert through which small vessels can pass and this is the main area for tidal exchange.  There are two other smaller culverts along the reclamation seawall.  The current velocities within Tai Ho Bay have been demonstrated in recent field investigations to be extremely low (0.08 ms-1 median velocity at the landward side of the box culvert at the mouth of the bay decreasing to 0.02 ms-1 within 300m of the box culvert ([3])). 

 

South Brothers

 

The current velocities are generally very low in the area around the proposed pits (Part 2, Section 2.2).  Current velocities are highest in the surface layer and range from < 0.25 m s-1 during slack tides to < 0.75 m s-1 during peak flood and peak ebb.  Velocities in the bed layer do not exceed 0.25 m s-1.  An examination of the plots for each of the three pits (see Part 2, Section 2) indicates that in general Pit A can be considered as the most dispersive as the current velocities are highest of the differing states of the tide and seasons.  Pit C is the least dispersive as current velocities rarely exceed 0.25 m s-1. 

 

East of Sha Chau

 

The pits are located closer to the main flow path of the Urmston Road and consequently, in comparison to the current velocities at South Brothers those at East of Sha Chau are generally much higher (see Part 3, Section 3).  Current velocities can reach 2.0 m s-1.  Ebb tide currents are towards the southeast where the flood tide currents move to the northwest.  In a similar fashion to the South Brothers site the bed layer currents are of low velocity rarely exceeding 0.25 m s-1.

 

4.2.3    Water Quality

 

Changes in the hydrodynamic regime that result from changes in the flow of the Pearl River have a major influence on the water quality in the vicinity of the CMPs at South Brothers and East of Sha Chau.  During the summer (wet) season (mid-April to mid-October) there is a large influx of freshwater from the Pearl River which results in steep salinity gradients.  The river water typically carries high silt and organic pollutant loads which impact the ambient water quality.  In contrast, during the winter (dry) season (mid-October to mid-April), freshwater input is much lower, and conditions are more typically oceanic, as saline water moves northwards into the Pearl River Delta and the water bodies become well-mixed.  Data from the Environmental Protection Department (EPD) collected under the Routine Water Quality Monitoring Programme have been utilised to define the background water quality parameters in the Study Area (Table 4.1Table 4.1Table 4.1).  In addition to the annual average, both wet and dry season means have been calculated.

 

The data from EPD, which were collected between 1998 and 2002, appear to indicate that there have been elevations in Suspended Solids (SS), Total Inorganic Nitrogen (TIN) and Ammonia Nitrogen over time.  There has also been a sharp increase in E. coli, which has been attributed to an increase in sewage discharges through the Northwest New Territories Outfall ([4]).  In terms of compliance with WQOs, no exceedances have been recorded with the exception of TIN, which regularly exceeds the WQO.  The average annual 90th percentile suspended solids concentration (ambient) for the period 1998 – 2002 was 17.4 mg L-1.  In the dry season the ambient was 19 mg L-1 and in the wet season the ambient was 15.5 mg L-1.  These values would give an allowable increase in suspended sediment concentrations according to the WQO of 5.2 mg L-1 annually (or 5.7 mg L-1and 4.7 mg L-1for dry and wet season respectively). 

 

Information on metal concentrations in the water column in the vicinity of the CMPs at South Brothers and East of Sha Chau is presented in Table 4.2Table 4.2Table 4.2.  These data were collected between November 1997 and December 2000 during the CMP IVa and IVb EM&A programme.  It should be noted that the objective of the monitoring was to identify whether there were differences between concentrations of contaminants in waters samples collected in areas down-current from the CMP during backfilling operations in comparison to those up-stream.  As such, the data collected at the up-stream stations can be considered to be reflective of ambient conditions.

 


Table 4.1    EPD Routine Water Quality Monitoring Data Collected between 1998 and 2002

Parameter

EPD Water Quality Monitoring Station

 

 

NM2

 

 

NM3

 

 

NM5

 

 

NM6

 

 

Annual

Wet Season

Dry Season

Annual

Wet Season

Dry Season

Annual

Wet Season

Dry Season

Annual

Wet Season

Dry Season

Temperature

(°C)

23.7

(16.8- 29.7)

26.3

(21.8- 29.7)

21.1

(16.8- 28.1)

23.5

(16.8- 28.9)

26.0

(21.8- 28.9)

21.0

(16.8- 28.2)

23.7

(16.8- 30.1)

26.3

(21.9- 30.1)

21.6

(16.8- 28.4)

23.8

(16.3- 29.6)

26.9

(21.8- 29.6)

20.8

(16.3- 27.9)

Salinity

(ppm)

28.2

(9.4 - 33.3)

26.6

(9.4- 32.6)

31.3

(25.7- 33.3)

28.8

(11.1- 33.2)

26.5

(11.1- 32.2)

31.1

(19.6- 33.2)

27.4

(4.9- 33.2)

24.6

(4.9- 32.1)

29.6

(7.9- 33.2)

26.1

(7.6- 33.7)

21.4

(7.6- 31.2)

30.7

(26.2- 33.7)

Dissolved Oxygen (mg L-1)

(Depth Average)

6.0

(3.2- 9.2)

5.6

(3.2- 8.9)

6.5

(3.4- 9.2)

5.9

(2.2- 8.8)

5.2

(2.2- 8.6)

6.6

(3.7- 8.8)

5.9

(2.3- 9.2)

5.1

(2.3- 9.2)

6.4

(3.2- 9.0)

6.5

(3.9- 11.8)

6.1

(3.9- 11.8)

6.8

(4.1- 9.5)

Dissolved Oxygen (mg L-1)

(Bottom)

5.9

(3.2- 8.4)

5.1

(3.2- 7.6)

6.6

(4.3– 8.4)

5.6

(2.2- 8.6)

4.6

(2.2- 7.0)

6.7

(4.4- 8.6)

5.5

(2.3- 8.8)

4.4

(2.3- 6.3)

6.4

(3.2- 8.8)

6.4

(3.9- 11.8)

6.0

(3.9- 11.8)

6.9

(4..5- 9.2)

Dissolved Oxygen

(% Saturation)

(Depth Average)

83.4

(46.0- 132.0)

74.3

(52.0- 93.0)

87.0

(52.0- 120.0)

81.2

(32.0- 128.0)

74.1

(32.0- 128.0)

88.2

(55.0- 109.0)

80.6

(33.0- 130.0)

73.3

(33.0- 130.0)

86.4

(45.0- 114.0)

89.0

(56.0- 170.0)

86.9

(56.0- 170.0)

91.0

(59.0- 120.0)

Dissolved Oxygen

(% Saturation) (Bottom)

81.1

(46.0- 114.0)

73.6

(46.0- 114.0)

88.3

(66.0- 109.0)

77.9

(32.0- 108.0)

66.7

(32.0- 98.0)

89.1

(66.0-108.0)

75.9

(33.0- 110.0)

63.5

(33.0- 94.0)

85.9

(45.0- 110.0)

88.8

(56.0- 167.0)

85.0

(56.0- 167.0)

92.6

(61.0- 116.0)

Suspended Solids

(mg L-1)

8.2

(1.1- 47.0)

6.4

(1.7- 32.0)

10.0

(1.1- 47.0)

10.5

(1.2- 71.0)

9.6

(1.8- 46.0)

11.5

(1.2- 71.0)

12.7

(1.6- 210.0)

15.0

(2.0- 210.0)

10.8

(1.6- 73.0)

9.6

(1.2- 60.0)

7.4

(1.2- 25.0)

11.8

(2.1- 60.0)

5-day Biochemical Oxygen Demand (mg L-1)

0.7

(0.1- 3.5)

0.8

(0.1- 3.5)

0.5

(0.1- 1.5)

0.7

(0.1- 2.2)

0.8

(0.1- 1)

0.6

(0.1- 1.7)

0.8

(0.1- 4.1)

0.8

(0.1- 2.9)

0.8

(0.1- 4.1)

0.9

(0.1- 4.9)

1.0

(0.1- 3.5)

0.8

(0.1- 4.9)

Unionised Ammonia

(mg L-1)

0.005

(0.001- 0.02)

0.01

(0.001- 0.02)

0.04

(0.002- 0.01)

0.005

(0.001- 0.03)

0.005

(0.001- 0.03)

0.004

(0.001- 0.01)

0.006

(0.001- 0.03)

0.006

(0.001- 0.02)

0.006

(0.002- 0.03)

0.005

(0.001- 0.02)

0.006

(0.001- 0.02)

0.003

(0.001- 0.01)

Total Inorganic Nitrogen

(mg L-1)

0.4

(0.1- 1.4)

0.5

(0.2- 1.4)

0.3

(0.1- 1.0)

0.4

(0.2- 1.3)

0.5

(0.2- 1.3)

0.3

(0.2- 0.6)

0.5

(0.1- 1.6)

0.7

(0.2- 1.6)

0.4

(0.1- 1.4)

0.5

(0.05- 1.6)

0.7

(0.1- 1.6)

0.3

(0.05- 0.6)

Chlorophyll-a

(mg/L)

3.0

(0.0- 23.0)

3.3

(0.5- 18)

2.7

(0.0- 23.0)

2.7

(0.2- 25.0)

2.4

(0.3- 1.2)

2.9

(0.2- 25.0)

3.0

(0.2- 28.0)

3.0

(0.2- 23.0)

2.9

(0.3- 28.0)

3.8

(0.4- 44.0)

4.5

(0.4- 44.0)

3.0

(0.4- 27.0)

E. coli

(cfu 100 ml-1)

681

(5- 6,000)

739

(5- 6,000)

625

(24- 3,300)

2893

(46-180,000)

4,557

(46-180,000)

1,250

(56- 34,000)

1189

(13- 28,000)

1356

(13- 28,000)

1,055

(48- 6,400)

66

(1- 720)

77

(1- 720)

56

(0.4- 350)

Notes:

1.                           Data presented are depth averaged, except as specified.

2.                           Data presented are annual arithmetic mean except for E. coli, which are geometric means and dissolved oxygen, which are 10th percentile.

3.                           Data enclosed in brackets indicate the ranges.

4.                           Shaded cells indicate non-compliance with the WQOs


Table 4.2    Dissolved Metal Data Recorded between 1997 and 2000 at East of Sha Chau

Parameter

DLa

All Stations

Upstream (Control) Stations

 

 

Ave

Min

Max

Ave

Min

Max

Cadmium (mg L-1)

0.2

0.1

0.1

0.4

0.1

0.1

0.2

Chromium (mg L-1)

1.0

0.5

0.5

11.0

0.8

0.5

11.0

Copper (mg L-1)

1.0

0.9

0.5

11.0

0.9

0.5

3.0

Lead (mg L-1)

1.0

0.5

0.5

4.0

0.5

0.5

0.5

Mercury (mg L-1)

0.1

0.1

0.1

0.3

0.1

0.1

0.3

Nickel (mg L-1)

1.0

1.4

0.5

5.0

1.7

0.5

4.0

Silver (mg L-1)

1.0

0.5

0.5

0.5

0.5

0.5

0.5

Zinc (mg L-1)

10.0

6.2

5.0

90.0

6.3

5.0

20.0

Arsenic (mg L-1)

2.0

1.8

1.0

10.0

1.4

1.0

8.0

Note:   

a.          DL = Detection Limit

 

4.2.4    Sediment Quality

 

EPD collects sediment quality data as part of the marine sediment quality monitoring programme.  There are three monitoring stations in the vicinity of the CMPs at South Brothers and East of Sha Chau.  Data for these stations have been published in the latest marine water quality monitoring report and are presented in Table 4.3.  The published data represent the range of values obtained in the period 1996 to 2002. 

 

Recent data on sediment quality in the vicinity of the proposed CMPs at South Brothers and East of Sha Chau have also been collected under the CMP IVa and IVb EM&A programme ([5]).  Under this monitoring programme a number of sediment stations were monitored, however, for the purposes of providing background information on the sediment quality in the vicinity of the proposed CMPs, one set of regional sampling stations is considered to be most representative of background conditions.  These stations are located within the RMB site and are presented on Figure 4.2a.  Data from these stations collected between November 1997 and December 2000 presented in Table 4.4Table 4.4Table 4.4. According to the data collected at these stations no exceedances of either the Lower Chemical Exceedance Level (LCEL) or Upper Chemical Exceedance Level (UCEL), as set by the ETWBTCW 34/2002, were recorded. 

 

 

 

 

 

  

 


TTable 4.3    EPD Routine Sediment Quality Monitoring Data collected between 1996 and 2002

Parameter

LCEL1

UCEL2

EPD Sediment Quality Monitoring Station

 

 

 

 

NS2

 

 

NS3

 

 

NS6

 

 

 

 

Average

Min

Max

Average

Min

Max

Average

Min

Max

Particle Size Fraction (<63mm) (% w/w)

-

-

74

46

94

57.5

5

87

57.2

26

92

Total Solids (% w/w)

-

-

51.7

46

58

55.3

47

69

60.6

47

71

Total Volatile Solids (%TS)

-

-

6.28

5

7.2

6.17

3.1

7.5

5.07

3

8.3

Dry Wet Ratio -

-

-

0.496

0.46

0.54

0.552

0.44

0.69

0.592

0.47

0.72

Chemical Oxygen Demand (mg kg-1)

-

-

13,600

10,000

16,000

15,140

8,400

18,000

12,370

7,400

17,000

Total Carbon

-

-

0.55

0.5

0.7

0.58

0.4

0.7

0.48

0.4

0.7

Ammonia Nitrogen (mg kg-1)

-

-

3.65

1

7.2

5.52

0.5

12

3.755

0.51

16

TKN (mg kg-1)

-

-

306

270

360

305

250

360

240

160

370

Total Phosphorus (mg kg-1)

-

-

183

170

200

186

150

240

139.3

73

230

Total Sulphide (mg kg-1)

-

-

17.33

1

47

25.8

4.7

94

4.7625

0.6

15

Total Cyanide (mg kg-1)

-

-

0.1

0.1

0.1

0.2

0.1

0.5

0.1

0.1

0.1

Aluminium (mg kg-1)

-

-

27,500

21,000

35,000

25,400

13,000

36,000

22,460

9,600

48, 000

Arsenic (mg kg-1) *

12

42

11.3

9.2

14

11. 8

6.3

14

11.6

8

22

Barium (mg kg-1)

-

-

33.7

25

41

31.3

17

44

27.5

16

48

Boron (mg kg-1)

-

-

23

20

29

20.6

11

28

18.1

11

31

Cadmium (mg kg-1)

1.5

4

0.1

0.1

0.1

0.14

0.1

0.3

0.15

0.1

0.2

Chromium (mg kg-1)

80

160

33.5

30

43

32.1

16

41

25.8

15

45

Copper (mg kg-1)

65

110

35

27

50

34.3

17

47

16.3

7

34

Iron (mg kg-1)

-

-

29300

26000

36000

28300

15000

35000

26200

14000

45000

Lead (mg kg-1)

75

110

39.4

32

55

38.9

20

54

29.8

17

49

Manganese (mg kg-1)

-

-

448

400

510

447

230

620

374

200

700

Mercury (mg kg-1)

0.5

1

0.09

0.06

0.16

0.12

0.06

0.19

0.1

0.05

0.15

Nickel (mg kg-1)

40

40

18.7

16

24

18.7

10

25

16

9

27

Silver (mg kg-1)

1

2

1

1

1

1

1

1

1

1

1

Vanadium (mg kg-1)

-

-

34.3

28

41

37.9

17

54

33

19

65

Zinc (mg kg-1)

200

270

96.9

73

120

90

48

120

68.6

34

120

Total PCBs (mg kg-1)

23

180

8.67

5

15

12.3

8

15

9

9

9

Notes:

1.        LCEL = Lower Chemical Exceedance Level                                                               

2.        UCEL = Upper Chemical Exceedance Level

3.        Grey shaded cells indicate exceedance of LCEL

4.        * Arsenic data are only available for 1996-2000


Table 4.4    Sediment Quality Data Collected between 1997 and 2000 at East of Sha Chau

Parameter

DL1

LCEL2

UCEL3

Average

StDev

Min

Max

Metals (mg kg-1)

 

 

 

 

 

 

 

Cadmium

0.02

1.5

4

0.07

0.02

0.05

0.10

Chromium

0.05

80

160

20

6

12

30

Copper

0.05

65

110

15

4

11

23

Mercury

0.05

0.5

1

0.07

0.02

0.05

0.10

Nickel

0.05

40

40

12

4

7

19

Lead

0.05

75

110

27

7

22

38

Silver

0.05

1

2

0.12

0.04

0.09

0.20

Zinc

5

200

270

51

15

33

76

Metalloid (mg kg-1)

 

 

 

 

 

 

 

Arsenic

0.5

12

42

8

2

6

12

Organic - PAHs (mg kg-1)

 

 

 

 

 

 

 

Low M Wt PAHs

50

550

3160

75

0

75

75

High M Wt PAHs

150

1700

9600

26

2

25

32

Organics - non - PAHs (mg kg-1)

 

 

 

 

 

 

 

Total PCBs

2

23

180

1.2

0.2

1.0

1.6

Notes:

1.        DL = Detection Limit

2.        LCEL = Lower Chemical Exceedance Level

3.        UCEL = Upper Chemical Exceedance Level

 

Ground Investigation Works

 

In addition to the background data presented above, a ground investigation and marine sediment sampling survey was conducted within both the South Brothers and East of Sha Chau areas as part of the Site and Disposal Option Selection phase of the study.  Although the primary objective of this survey was to investigate the thickness of mud, sediment samples were also analysed to determine the potential for contamination. 

Locations of the vibrocores are presented in Figure 4.2a.  The results from vibrocore V12 are considered to be applicable to the South Brothers area, this sample exhibited no exceedances of the LCEL.  Vibrocore V1 provided information on the sediment quality in the East of Sha Chau area, which also exhibited no exceedances of the LCEL.  It can be concluded from the ground investigation works that the sediments in the two locations appear to be predominantly uncontaminated.

 

4.2.5    Water Quality Sensitive Receivers

 

The sensitive receivers that may be affected by changes in water quality during the construction or operation of the facility are listed in the Study Brief, discussed below and presented on Figure 4.2b.  For each of the sensitive receivers, established threshold criteria or guidelines have been identified and the method of reviewing these sensitive receivers (either through discrete points or contour plots) during the water quality modelling has been described.  The shortest distances from the water quality sensitive receivers to the CMPs at South Brothers and East of Sha Chau is presented in Table 4.5.

 

Table 4.5    Water Quality Sensitive Receivers (SR)

SR

Name

Shortest Distance to CMPs (m)

 

 

 

South Brothers

East of Sha Chau

 

Marine Parks

Sha Chau and Lung Kwu Chau SE (MP1)

7,289

2,005

Sha Chau and Lung Kwu Chau E (MP2)

9,291

3,594

Sha Chau and Lung Kwu Chau NE (MP3)

11,595

6,090

 

Sha Chau and Lung Kwu Chau SW (MP4)

9,570

4,926

Fish Culture Zone

Ma Wan N (FCZ1)

8,114

10,885

Ma Wan S (FCZ2)

7,932

10,949

Artificial Reefs

Airport AR (AR1)

2,397

1,041

Sha Chau and Lung Kwu Chau AR (AR2)

9,778

4,232

Beaches

Lung Kwu Tan Lower (B1)

9,162

4,795

Lung Kwu Tan Upper (B2)

10,951

6,662

Butterfly Beach (B3)

5,596

2,730

Tuen Mun Beaches (B4)

5,681

4,653

Intakes

Airport (I1)

3,047

1,700

Airport (I2)

2,113

2,186

Airport (I3)

4,109

4,967

Airport (I4)

5,185

4,583

 

Tuen Mun (I5)

5,246

3,435

 

Castle Peak Power Station (I6)

8,737

3,950

 

Area 38 Industries (I7)

6,746

2,150

Seagrass & Horseshoe Crabs

San Tau (SG1)

4,645

5,491

Tai Ho Bay (SG2)

1,016

5,079

Yam O Bay (SG3)

4,129

7,942

Horseshoe Crab Tung Chung Bay (HC1)

4,449

5,890

EPD WQM Stations

 

NM1 – close to Yam O

5,418

8,100

NM2 – close to Castle Peak Bay

4,858

3,822

NM3 – close to River Trade Terminal

5,031

566

NM5 - Urmston Road

9,854

4,477

NM6 – between Marine Park and Airport

7,107

2,666

 

Fish Culture Zone

 

There is only one fish culture zone (FCZ) located within the northwestern waters of Hong Kong, which is at Ma Wan.  This FCZ is actually outside of the water quality assessment area but is included for completeness.  The only Water Quality Objective (WQO) that is specific to FCZs is for dissolved oxygen, which is set at no less than 5 mg L-1.  In addition to dissolved oxygen there is a general water quality protection guideline for suspended solids (SS), which has been proposed by AFCD ([6]).  The guideline requires that SS levels remain below 50 mg L-1.  With regard to the water quality modelling, the FCZs were included as discrete points for evaluation in the assessment against the above criteria and guideline.

 

Marine Ecological Resources

 

The following Marine Ecological Resources have been identified as water quality sensitive receivers.

 

Marine Parks

 

There is one designated Marine Park located within the Study Area which is the Sha Chau and Lung Kwu Chau Marine Park (see Section 4.3).  The park was designated specifically for the protection of the Indo-Pacific Humpback Dolphin (Sousa chinensis).  There are no specific legislative water quality criteria for Marine Parks rather; the water quality at this sensitive receiver is typically compared with the WQO.  The Marine Park will be plotted as a discrete point at the marine water boundary facing the proposed mud pits for evaluation in the water quality assessment.

 

Artificial Reef Deployment Sites

 

There are two gazetted Artificial Reef Deployment Sites (ARD) within the Study Area:

 

·         Sha Chau and Lung Kwu Chau ARD site (situated within the Sha Chau and Lung Kwu Chau Marine Park);

·         Airport ARD site (Figure 4.2b).

 

The ARD sites are proposed as a fisheries resource enhancement tool to encourage growth and development of a variety of marine organisms and provide feeding opportunities for the Indo-Pacific Humpback Dolphin.  There is no specific water quality criterion for the ARD sites; rather water quality impacts are measured presently against compliance with the WQO.  The ARD sites will be treated as discrete points in the model.

 

Seagrass Beds, Mangroves & Horseshoe Crabs

 

There are seagrass beds, mangroves and areas where horseshoe crabs are known to breed within the Study Area, such as within Tung Chung Bay, Tai Ho and Yam O Bays (see Section 4.3).  There are no specific legislative water quality criteria for these seagrass beds/breeding areas, rather, the water quality at these sensitive receivers is typically compared with the WQO.  The sensitive habitats will be plotted as discrete points for evaluation in the water quality assessment.

 

Non-Gazetted & Gazetted Bathing Beaches

 

There are several non-gazetted and gazetted bathing beaches within the Study Area, which have been identified in the Study Brief as sensitive receivers.  These include the beaches at Lung Kwu Tan and around Tuen Mun.  Water quality impacts are determined based on the compliance with the WQO.  Bathing beaches have been plotted as discrete points for evaluation in the water quality assessment. 

 

Seawater Intakes

 

There are several water intakes in the Study Area which are mainly for cooling purpose.  In absence of specific criteria for each intake we have assumed the WQO as a default. The exception to the above is for the Castle Peak Power Station intake for which there is a specific requirement that suspended sediment concentrations be maintained below a level of 150 mg L-1 within a 5 km radius of the intake.  The intakes will be plotted as discrete points for evaluation in the water quality assessment. 

 

Summary

 

A summary of the assessment criteria to be applied for each sensitive receiver for this Project is presented in Table 4.6

 

Table 4.6    Summary of Assessment Criteria for Water Quality Sensitive Receivers

Sensitive Receiver

Specific Assessment Criteria

Value

Fish Culture Zone (FCZ)

Dissolved oxygen

Suspended Solids

No less than 5 mg L-1

No more than 50 mg L-1

Marine Park, Artificial Reefs, Seagrass, Horseshoe Crabs, Non-gazetted & Gazetted Bathing Beaches

Water Quality Objectives

 

Seawater Intakes

Water Quality Objectives

Water Quality Objectives

 

4.3    Marine Ecology

 

4.3.1    Introduction

 

This section of the report presents baseline information on the marine ecological resources within the Study Area, summarises their ecological value and identifies sensitive receivers, examples of which can be see in Figure 4.2c.

The marine ecology of north Lantau is well documented.  The distribution of the marine ecological important habitats, including seagrass, mangrove, mudflat, dolphin and benthic soft bottom habitats, have been comprehensively studied, sources are listed below:

 

·               Barros NB, Jefferson TA and ECM Parsons (2004) Feeding habits of Indo-Pacific humpback dolphins (Sousa chinensis) stranded in Hong Kong. Aquatic Mammals. 30:179-188

·               Binnie Consultants Limited (1996)  Fill Management Study - Phase IV Investigations and Development of Marine Borrow Areas: Coral Growth at High Island Dam.  For the Civil Engineering Department, Hong Kong SAR Government.

·               Binnie Consultants Limited (1997)  Chek Lap Kok Qualitative Survey. Final Report.  For the Civil Engineering Department, Hong Kong SAR Government.

·               Chiu HMC and Morton B (1999) The distribution of horseshoe crabs (Tachypleus tridentatus and Carcinoscorpius rotundicauda) in Hong Kong. Asian Marine Biology. 16, 185-196.

·               CityU Professional Services Limited (2002) Agreement No. CE 69/2000 - Consultancy Study on Marine Benthic Communities in Hong Kong. Final Report.  Submitted to the Agriculture, Fisheries and Conservation Department.  Hong Kong SAR Government.

·               ERM – Hong Kong, Ltd (1995)  Proposed Aviation Fuel Receiving Facility at Sha Chau.  Environmental Impact Assessment.  Prepared for the Provisional Airport Authority. 

·               ERM - Hong Kong, Ltd (2000)  Northshore Lantau Development Feasibility Study.  Environmental Impact Assessment.  Final Report.  For the Civil Engineering Department, Hong Kong SAR Government.

·               ERM - Hong Kong, Ltd (2002)  Agreement No CE 44/97 - Environmental Monitoring and Audit for Contaminated Mud Pit IV at East of Sha Chau.  Final Report.  For the Civil Engineering Department, Hong Kong SAR Government.

·               ERM-Hong Kong, Ltd (2000)  Construction of an International Theme Park in Penny’s Bay of North Lantau together with its Essential Associated Infrastructures – EIA Report.  For the Civil Engineering Department, Hong Kong SAR Government

·               Fong TCW (1998) Distribution of Hong Kong seagrasses.  Porcupine! 18, December 1998.

·               Fong TCW (1999) Tai Ho Bay: breeding and nursery ground of horseshoe crabs. Porcupine! No. 20, November 1999.

·               Jefferson TA (2000) Population biology of the Indo-Pacific Humpback dolphin in Hong Kong waters. Wildlife Monographs 144:1-65.

·               Jefferson TA (2002) Monitoring of Indo-Pacific Humpback Dolphins (Sousa chinensis) in Hong Kong waters.  Final Report.  For the Agriculture, Fisheries and Conservation Department, Hong Kong SAR Government.

·               Jefferson TA and SK Hung (2004) A review of the status of the Indo-Pacific humpback dolphin (Sousa chinensis) in Chinese waters. Aquatic Mammals. 30:149-158

·               Jefferson TA, Hung SK, Law I, Torey M and Tregenza N (2002) Distribution and abundance of finless porpoises in Hong Kong and adjacent waters of China. Raffles Bulletin of Zoology Supplement 10:43-55.

·               Lee SY (1997)  Annual cycle of biomass of a threatened population of the intertidal seagrass Zostera japonica.  Marine Biology 129: 183 - 193.

·               Lun JCY (2003)  Hong Kong. Reef Building Corals.  Cosmos Books Limited.

·               Mott Connell Ltd (2003) Environmental Impact Assessment for Tung Chung - Ngong Ping Cable Car Project.  Final Report.  For the MTR Corporation.

·               Mouchel Asia Limited (2002) Agreement No CEO 01/2001 - Environmental Assessment Study for Backfilling of Marine Borrow Pits at North of the Brothers.  Environmental Assessment Report.  For the Civil Engineering Department, Hong Kong SAR Government.

·               Mouchel Asia Ltd (2002)  Permanent Aviation Fuel Receiving Facility for Hong Kong International Airport.  Environmental Impact Assessment Report.  For the Airport Authority Hong Kong.

·               Scott PJB (1984)  The Corals of Hong Kong.  Hong Kong University Press.

·               Tam NFY and Wong YS (1997) Ecological Study on Mangrove Stands in Hong Kong: Volume 1. University Press, Hong Kong.

·               ERM – Hong Kong Ltd (2000)  Environmental Impact Assessment, Construction of an International Theme Park in Penny’s Bay of North Lantau and its Essential Associated Infrastructures.  Final EIA Report Annex (Volume 1)

·               ERM (1998) Seabed Ecology Studies: Composite Report for CED

·               ERM (2003) Study in Terrestrial Habitat Mapping and Ranking Based on Conservation Value.  Report for SDU.

·               ERM (2000) SUSDEV 21 Environmental Baseline Survey on Terrestrial Habitat Mapping and Ranking based on Conservation Value, Report for PlanD.

 

Taking into consideration the available literature, marine ecological baseline surveys were not considered necessary.  The existing conditions of each of the ecological sensitive areas at north Lantau are presented in the following sections. 

 

4.3.2    Existing Conditions and Ecological Value

 

The Study Area has been defined in the EIA Study Brief and is the same as that for the Water Quality Impact Assessment presented in Figure 4.2b.  The waters lie wholly in the North Western Water Control Zone (WCZ), the baseline conditions of which have been described in Section 4.2.  As unacceptable perturbations to water quality are unlikely to extend outside of the Study Area, the characterisation of existing conditions will focus on the marine ecological resources inside this area.


Based on current understanding of the Study Area, the following habitats and/or organisms of ecological interest have been identified within the Study Area:

·         Soft Bottom Habitats;

          -        Subtidal Soft Bottom Habitats

·                                            Infauna

·                                            Epibenthic Fauna

          -        Intertidal Soft Bottom Habitats

·                                            Mangroves

·                                            Mudflats (including Horseshoe Crabs)

·                                            Seagrass

·         Hard Bottom Habitats;

-        Subtidal Hard Bottom Habitats

          -        Intertidal Hard Bottom Habitats

·         Marine Mammals;

·         Sites of Special Scientific Interest (SSSI)

·         Marine Parks

 

Key locations of each of the above habitats are presented in Figure 4.3a.

The existing conditions of each of the above habitats/organisms based on currently available literature, are presented in the following sections.  Based on these conditions, the ecological value for each habitat has been determined according to the EIAO-TM Annex 8 criteria, as follows:

 

·         Naturalness

·         Size

·         Diversity

·         Rarity

·         Re-creatability

·         Fragmentation

·         Ecological Linkage

·         Potential Value

·         Nursery Ground

·         Age

·         Abundance


Soft Bottom Habitats

 

Subtidal Soft Bottom Habitats

 

Infauna

 

Soft sediments consisting of mud, clay and sand dominate the seabed of Hong Kong.  These soft bottom habitats support both infauna and epibenthic faunal marine communities, which in turn play a vital role as a food source for the majority of Hong Kong’s inshore fisheries resources.  A number of studies provide information on infaunal assemblages with the Study Area.  The most recent of these studies examined infaunal benthic assemblages throughout Hong Kong and, using multivariate statistics, identified 5 major groupings of infauna ([7]).  The data from the studies allow a comparison to be made of the diversity and abundance of infaunal benthic assemblages within the Study Area (represented by Stations 11 – 21, with those throughout Hong Kong waters ([8]) (see Figure 4.3a).

 

From the summer survey results, it appears that all the stations within the Study Area, with the exception of Stations 11 and 12 in the vicinity of Lung Kwu Chau, lie within the same group as those in Western Harbour, South Lantau waters, Southern and Eastern Waters, thus the majority of stations in Hong Kong (48.5% of stations surveyed).  Dominant fauna within this group were polychaetes.  No species considered to be of high ecological value were identified.  The two stations within the vicinity of Lung Kwu Chau were considered to be more similar to stations in Deep Bay due to the presence of more freshwater associated species present at these sites during the summer months.  In contrast, during the winter months, all stations within the Study Area were found to be similar to other stations in Hong Kong (49.5% of stations surveyed).  Dominant fauna within this group were again found to be polychaetes.  No species considered to be of high ecological value were identified in the winter survey. 

 

Based on the findings of the Hong Kong wide survey, the benthic infaunal assemblages within the Study Area can be expected to be typical of Hong Kong soft bottom habitats.  Two stations, located within close proximity to Lung Kwu Chau, were identified as demonstrating seasonal changes, which are likely to be as a result of the more estuarine conditions experienced at these sites  ([9]) .  The assemblages were all dominated by polychaetes and all species recorded occur frequently in Hong Kong with no rare species observed.  Following the EIAO-TM criteria, the ecological importance of the benthic infaunal assemblages both within and within close proximity to, the proposed CMPs at South Brothers and East of Sha Chau has been assessed in Table 4.7.

 

Table 4.7    Ecological Value of Benthic Infaunal Assemblages at the proposed CMPs at South Brothers and East of Sha Chau

EIAO-TM Criteria

South Brothers

East of Sha Chau

Naturalness

The assemblages are expected to be moderately disturbed due to fishing operations and high marine traffic within these waters

The assemblages are expected to be moderately disturbed due to fishing operations and high marine traffic within these waters

Size

Total area of the temporarily affected subtidal habitats will involve approximately 164 hectares

Total area of the temporarily affected subtidal habitats will involve approximately 115 hectares

Diversity

The assemblages are of similar diversity to the majority of other areas in Hong Kong

The assemblages are of similar diversity to the majority of other areas in Hong Kong

Rarity

No organisms were found that are considered as rare

No organisms were found that are considered as rare

Re-creatibility

The habitat can be expected to recreate naturally within a relatively short timeframe through sediment deposition

The habitat can be expected to recreate naturally within a relatively short timeframe through sediment deposition

Fragmentation

The surrounding environment contains many other areas of soft substrate

The surrounding environment contains many other areas of soft substrate

Ecological Linkage

The benthic infauna act as a food source for epibenthic organisms

The benthic infauna act as a food source for epibenthic organisms

Potential Value

Unlikely that the site can develop conservation interest

Unlikely that the site can develop conservation interest

Nursery Ground

None identified

None identified

Age

The sediments in the habitat are constantly accreting and eroding and the fauna present there are typically short lived

The sediments in the habitat are constantly accreting and eroding and the fauna present there are typically short lived

Abundance

Abundance of infauna are comparable to the majority of other areas in Hong Kong

Abundance of infauna are comparable to the majority of other areas in Hong Kong

Summary

The subtidal soft bottom habitat within the proposed CMP at South Brothers is likely to support species that are typical of Hong Kong with no rare species present.

The subtidal soft bottom habitat within the proposed CMP at East of Sha Chau is likely to support species that are typical of Hong Kong with no rare species present.

Ecological Value

Low

Low

 


Epibenthic Fauna

Subtidal soft bottom habitats, as well as supporting infaunal species, commonly support epibenthic macrofauna.  These organisms are generally greater than 1mm in size and live either on or within the surface sediments.  As part of the ongoing monitoring studies of the existing CMPs, data on the epibenthic fauna in vicinity of the proposed CMPs have been extensively collected.  Recent studies recorded species diversity as low in comparison to other areas in Hong Kong.  Such characteristics have been attributed to periodic fluctuations in the physio-chemical environment associated with Pearl River run-off and high anthropogenic impact through intensive demersal trawling ([10]).  Additional studies have also found the epibenthic faunal species within proximity to the proposed CMPs at South Brothers and East of Sha Chau to be composed of low commercial value bivalve, crab and shrimp species, commonly characterised by low abundance and diversity ([11]).

 

Following the EIAO-TM criteria, the ecological importance of the epifaunal assemblages both within, and within close proximity to the proposed CMPs at South Brothers and East of Sha Chau have been assessed in Table 4.8.

 

Table 4.8    Ecological Value of Epifaunal Assemblages at the proposed CMPs at South Brothers and East of Sha Chau

EIAO-TM Criteria

South Brothers

East of Sha Chau

Naturalness

The assemblages are expected to be disturbed due to fishing operations within these waters

The assemblages are expected to be disturbed due to fishing operations within these waters

Size

Total area of the temporarily affected subtidal habitats will involve approximately 164 hectares

Total area of the temporarily affected subtidal habitats will involve approximately 115 hectares

Diversity

The assemblages are of low diversity compared to the majority of other areas in Hong Kong

The assemblages are of low diversity compared to the majority of other areas in Hong Kong

Rarity

No organisms were found that are considered as rare

No organisms were found that are considered as rare

Re-creatibility

The habitat can be expected to recreate naturally within a relatively short timeframe

The habitat can be expected to recreate naturally within a relatively short timeframe

Fragmentation

The surrounding environment contains many other areas of similar substrate

The surrounding environment contains many other areas of similar substrate

Ecological Linkage

Epibenthic fauna act as a food source for demersal fisheries

Epibenthic fauna act as a food source for demersal fisheries

Potential Value

Unlikely that the site can develop conservation interest

Unlikely that the site can develop conservation interest

Nursery Ground

None identified

None identified

Age

The fauna appear to be typical of those present in Hong Kong's Epibenthic fauna assemblages

The fauna appear to be typical of those present in Hong Kong's Epibenthic fauna assemblages

Abundance

Abundance of epifauna is generally low in comparison to the majority of other areas in Hong Kong

Abundance of epifauna is generally low in comparison to the majority of other areas in Hong Kong

Summary

The subtidal epibenthic fauna assemblages within the proposed CMP at South Brothers are likely to be typical of common subtidal epibenthic fauna in Hong Kong with no rare species present.

The subtidal epibenthic fauna assemblages within the proposed CMP at East of Sha Chau are likely to be typical of common epibenthic fauna assemblages in Hong Kong with no rare species present.

Ecological Value

Low

Low

 

Intertidal Soft Bottom Habitats

 

Mangroves

 

Mangroves provide food, shelter and breeding grounds for a range of organisms including various pelagic and coastal fisheries, and birds ([12]).  Three main mangrove stands are present within the Study Area located at Tung Chung Bay, Tai Ho Bay and Yam O.  Within Tung Chung Bay, there are two separate stands, namely Tung Chung Bay itself and San Tau Beach (see Figure 4.3a).  On the basis of the presence of locally rare mangroves and seagrass beds at San Tau Beach, this area covering approximately 2.7 ha has been designated as an SSSI and is discussed later in this section under the corresponding heading.  One locally rare mangrove species has been recorded as present in Tung Chung Bay (San Tau Beach) during a Hong Kong wide study on mangrove habitats ([13]).  However, due to the relatively large mangrove stand at this site (2.14 ha) and high floristic diversity (18 mangrove species and associated flora), this habitat ranked highly in comparison to other mangrove habitats in Hong Kong.

 

The mangrove habitat at Tai Ho Bay was found to be smaller in size (~1.9 ha) in comparison to that at Tung Chung Bay, with less floristic diversity (12 species of mangrove and associated flora) ([14]).  The habitat is dominated by the relatively common mangrove Kandelia candel. 

 

Mangrove habitats have also been recorded at Yam O, in the northeast of the Study Area which also support 2 small stands (~0.5 ha) ([15]).  Of the two mangrove stands at Yam O, one at the Luk Keng entrance and one at Yam O Tuk (inner Yam O Bay), both were found to support moderate floristic diversity in comparison to other mangrove habitats in Hong Kong, particularly considering the small habitat size.  However, both habitats appeared to be disturbed, possibly due to the log storage area works in close proximity to the site and the nearby Yam O reclamation works.

 

Following the EIAO-TM criteria, the ecological importance of mangrove habitats within the Study Area for the proposed CMPs at South Brothers and East of Sha Chau has been assessed in Table 4.9.

 

Table 4.9    Ecological Value of Mangrove Habitats within the Study Area for the proposed CMPs at South Brothers and East of Sha Chau

EIAO-TM Criteria

Mangrove Habitat

Tung Chung Bay

Tai Ho Bay

Yam O Bay

Naturalness

The habitat is natural, although potentially affected by the Tung Chung Development

The habitat is natural

The habitat is natural, although potentially affected by the Yam O reclamation

Size

The 2 stands are both large (2.7 and 2.14ha)

Mangrove stand is medium in size (1.9ha)

Mangrove stand is small ~0.5ha

Diversity

Diversity is high in comparison to other mangroves in Hong Kong

Diversity is similar to other mangroves in Hong Kong

Diversity is moderate in comparison to other sites in Hong Kong

Rarity

One locally rare mangrove species has been recorded at San Tau Beach within Tung Chung Bay

No rare mangrove species recorded

No rare mangrove species recorded

Re-creatibility

Although re-creatable, the habitat may not return to it original status

Although re-creatable, the habitat may not return to it original status

Habitat is considered poor thus re-creatable

Fragmentation

The mangrove stand at this site is not fragmented

The mangrove stand at this site is not fragmented

The mangroves at this site are fragmented

Ecological Linkage

Site also includes mudflat, seagrass and horseshoe crab habitat

Site also includes mudflat, seagrass and horseshoe crab habitat

Site also includes mudflat and seagrass habitat

Potential Value

Mangroves provide high value habitat

Mangroves provide high value habitat

Mangroves provide high value habitat

Nursery Ground

Mangroves act as a nursery ground for many species

Mangroves act as a nursery ground for many species

Mangroves act as a nursery ground for many species

Age

Mangrove habitat are relatively slow growing

Mangrove habitat are relatively slow growing

Mangrove habitat are relatively slow growing

Abundance

Abundance of mangroves is high in comparison to other sites in Hong Kong

Abundance is similar to other mangroves in Hong Kong

Abundance is low in comparison to other sites in Hong Kong

Summary

The mangrove habitat has high species diversity and is large in comparison to other sites in Hong Kong.  The site has associated mudflat and seagrass habitat and has been recorded as a nursery ground for horseshoe crabs in Hong Kong.

The mangrove habitat has medium species diversity in comparison to other sites in Hong Kong.  The site has associated mudflat and seagrass habitat and has been recorded as a nursery ground for horseshoe crabs in Hong Kong.

The mangrove habitat is small in comparison to other sites in Hong Kong with moderate  species diversity.  The site has associated mudflat and seagrass habitat, however, is potentially under continued stress from nearby works.

Ecological Value

High

Medium

Low

 

Mudflats & Horseshoe Crab Habitats

 

Mudflats are classified as areas of fine-grained sediment (ie silt or fines) which lie between the high and low tide marks which are not covered by seagrass, mangroves or typical wetland vegetation and are generally fed with freshwater streams.  Generally considered to be habitats of ecological importance, mudflats provide key breeding grounds for a variety of species, and species present there act as food source for both fish and, resident and wintering birds in Hong Kong. 

Mudflats occur throughout Hong Kong, with the largest present in the Deep Bay area.  Within the Study Area, each of the above locations described above for mangrove habitats also have mudflat habitats present (see Figure 4.3a).  In addition of these mudflat habitats, those at Tung Chung Bay and Tai Ho Bay have been identified as having juvenile horseshoe crabs, namely the species Tachypleus tridentatus and Carcinoscorpius rotundicauda, recorded at each site ([16]) ([17]).  In addition, recent surveys at Tai Ho Bay identified breeding pairs Carcinoscorpius rotundicauda present ([18]).

 

Following the EIAO-TM criteria, the ecological importance of mudflat habitats within the Study Area for the proposed CMPs at South Brothers and East of Sha Chau has been assessed in Table 4.10.


Table 4.10  Ecological Value of Mudflat and Horseshoe Crab Habitats within the Study Area for the proposed CMPs at South Brothers and East of Sha Chau

EIAO-TM Criteria

Mudflat and Horseshoe Crab Habitat

Tung Chung Bay

Tai Ho Bay

Yam O Bay

Naturalness

The mudflats are natural but under stress from surrounding works and shellfish collection

The mudflats are natural

The mudflats are natural but under stress from surrounding works

Size

In comparison to other mudflats in Hong Kong the habitat is of medium size

In comparison to other mudflats in Hong Kong the habitat is of medium size

In comparison to other mudflats in Hong Kong the habitat is of small size

Diversity

In general species diversity on mudflats is high

In general species diversity on mudflats is high

In general species diversity on mudflats is high

Rarity

Two species of horseshoe crab have been identified as using these mudflats

Two species of horseshoe crab have been identified as using these mudflats

No rare species have been identified

Re-creatibility

The habitat can be expected to recreate naturally within a relatively short timeframe

The habitat can be expected to recreate naturally within a relatively short timeframe

The habitat can be expected to recreate naturally within a relatively short timeframe

Fragmentation

The mudflats at this site are relatively unfragmented

The mudflats at this site are relatively unfragmented

The mudflats at this site are relatively fragmented

Ecological Linkage

Site also contains mangroves and seagrass species

Site also contains mangroves and seagrass species

Site also contains mangroves and seagrass species

Potential Value

The site is of conservation interest

The site is of conservation interest

The site is of limited conservation interest due to small size and potential impact of nearby works

Nursery Ground

Mudflats act as a nursery ground for numerous species.  Also identified as nursery ground for two species of horseshoe crab

Mudflats act as a nursery ground for numerous species.  Also identified as nursery ground for two species of horseshoe crab

Mudflats act as a nursery ground for numerous species.

Age

Mudflats constantly accreting and eroding and the fauna present there are typically short lived

Mudflats constantly accreting and eroding and the fauna present there are typically short lived

Mudflats constantly accreting and eroding and the fauna present there are typically short lived

Abundance

Mudflats generally support organisms in high abundances in comparison to other marine habitats

Mudflats generally support organisms in high abundances in comparison to other marine habitats

Mudflats generally support organisms in high abundances in comparison to other marine habitats

Summary

The mudflats at Tung Chung Bay provide a nursery ground for horseshoe crabs in Hong Kong and have associated mangrove and seagrass habitat.

The mudflats at Tai Ho Bay provide a nursery ground for horseshoe crabs in Hong Kong and have associated mangrove and seagrass habitat. 

The mudflats at Yam O Bay have associated mangrove and seagrass habitat, however, are under stress from nearby works

Ecological Value

Medium

High

Low

 

Seagrass

 

Seagrass beds occur in shallow, sheltered or subtidal areas and are recognised as areas of high biological productivity.  They provide high value habitat as feeding and nursery ground for a range of marine species ([19]).  Within Hong Kong, seagrass beds have been recorded with a very low distribution, occupying less than 0.1% of the total land area.  Nevertheless, within the Study Area, three sites have been identified where seagrass beds have been recorded, namely San Tau, Tai Ho Bay and Yam O Bay ([20]) (see Figure 4.3a).

 

The mudflats at Yam O Bay and San Tau support seagrass beds of Halophila ovalis, with Zostera japonica also present at San Tau.  Although the latter of these species has been recorded elsewhere in Hong Kong, San Tau represents this species only habitat, albeit of a relatively small size (15m2), on Lantau.  In contrast, the seagrass beds (500m2) at Tai Ho Bay are seasonal and consist solely of the species Halophila beccarii.  Studies on this species appear to indicate that the habitat is an important feeding ground for juvenile horseshoe crabs ([21]). 

 

Following the EIAO-TM criteria, the ecological importance of seagrass beds within the Study Area for the proposed CMPs at South Brothers and East of Sha Chau has been assessed in Table 4.11.


Table 4.11  Ecological Value of Seagrass Beds within the Study Area for the proposed CMPs at South Brothers and East of Sha Chau

EIAO-TM Criteria

Seagrass Beds

San Tau

Tai Ho Bay

Yam O Bay

Naturalness

The seagrass beds are natural but under stress from surrounding works and shellfish collection

The seagrass beds are natural

The seagrass beds are natural but under stress from surrounding works

Size

Size of the Zostera japonica bed is relatively small (15m2) but the Halophila ovalis bed is large (2 ha)

Size of the seagrass bed is medium (500m2)

Size of the seagrass bed is relatively large (~ 1 ha)

Diversity

In general, species diversity associated with seagrass beds is high

In general, species diversity associated with seagrass beds is high

In general, species diversity associated with seagrass beds is high

Rarity

Seagrass beds are relatively rare in Hong Kong.  In addition, this site represents the only Zostera japonica habitat on Lantau.  Two species of horseshoe crab have also been identified as using these seagrass beds

Seagrass beds are relatively rare in Hong Kong.  In addition, two species of horseshoe crab have been identified as using these seagrass beds

Seagrass beds are relatively rare in Hong Kong. 

Re-creatibility

Seagrass beds have been found to be difficult to re-create in Hong Kong

Seagrass beds have been found to be difficult to re-create in Hong Kong

Seagrass beds have been found to be difficult to re-create in Hong Kong

Fragmentation

The seagrass beds at this site are relatively unfragmented

The seagrass beds at this site are relatively unfragmented

The seagrass beds at this site are relatively unfragmented

Ecological Linkage

Site also contains mangroves and mudflat habitat

Site also contains mangroves and mudflat habitat

Site also contains mangroves and mudflat habitat

Potential Value

The site is of conservation interest

The site is of conservation interest

The site is of conservation interest

Nursery Ground

Seagrass beds act as a nursery ground for numerous species.  Also identified as nursery ground for two species of horseshoe crab

Seagrass beds act as a nursery ground for numerous species.  Also identified as nursery ground for two species of horseshoe crab

Seagrass beds act as a nursery ground for numerous species.

Age

The seagrass beds at this site are somewhat seasonal, therefore, relatively short-lived

The seagrass beds at this site are somewhat seasonal, therefore, relatively short-lived

The seagrass beds at this site are somewhat seasonal, therefore, relatively short-lived

Abundance

Seagrass at this site is of relatively low abundance

Seagrass at this site is of medium abundance

Seagrass at this site is of medium abundance

Summary

The seagrass beds atSan Tau within Tung Chung Bay provide a nursery ground for horseshoe crabs in Hong Kong and have associated mangrove and mudflat habitat. Although small in size, these seagrass beds are the only site on Lantau for Zostera japonica

The seagrass beds at Tai Ho Bay provide a nursery ground for horseshoe crabs in Hong Kong and have associated mangrove and mudflat habitat.

The seagrass beds at Yam O Bay have associated mangrove and mudflat habitat, however, are under stress from nearby works

Ecological Value

High

Medium

High

 

Hard Bottom Habitats

 

Subtidal Hard Bottom Habitats

 

As described above, the majority of the subtidal habitat within Hong Kong waters, including those within the Study Area, consists of soft bottom habitat.  However, closer to the shoreline, the seabed will be commonly composed of hard bottom habitat, so much so that approximately 80% of Hong Kong's complex shorelines and many islands are composed of rocky outcrops.  Of the numerous marine organisms that inhabit this substratum, corals, due to the protected status and ecological value, are of particular concern.

 

Over 80 species of coral occur in Hong Kong, with the highest diversities recorded in eastern waters.  It appears that coral distribution in Hong Kong is primarily controlled by hydrodynamic conditions as Hong Kong’s western waters are influenced by the Pearl River, which lowers salinities and generally records higher concentrations of suspended solids.  As such, the western waters of Hong Kong, in which the Study Area is located has previously been identified as being relatively devoid of coral species ([22]) ([23]).

 

Surveys of subtidal hard bottom habitats within the Study Area, excluding Artificial Seawalls (see below) have, however, indicated the presence of both hard and soft corals, albeit in both limited density and of limited diversity.  Scattered hermatypic hard corals (family Faviidae), ahermatypic gorgonian seawhips and seapens have been identified within the Sha Chau and Lung Kwu Chau Marine Park, whereas, ahermatypic cup corals, soft corals such as Dendronephthya spp and seapens have also been recorded on the northern shore of the Study Area in the vicinity of Sham Tseng ([24]) ([25]).

 

Hermatypic hard corals possess vast numbers of symbiotic unicellular algae (zooxanthellae) within their endodermal lining.  These photosynthesising algae require light for growth.  The low salinity conditions coupled with high levels of suspended solids, which reduce light penetration, of the Study Area, reduce the potential for colonies of corals of high ecological value to be present.

 

Following the EIAO-TM criteria, the ecological importance of subtidal hard bottom habitats within the Study Area for the proposed CMPs at South Brothers and East of Sha Chau has been assessed in Table 4.12.

 

Table 4.12  Ecological Value of Subtidal Hard Bottom Habitats within the Study Area for the proposed CMPs at South Brothers and East of Sha Chau

EIAO-TM Criteria

Study Area

Naturalness

There is limited natural subtidal hard bottom habitat within the study area

Size

No subtidal hard bottom habitat will be permanently affected by the proposed works

Diversity

Due to the estuarine conditions, diverse assemblages are not expected to be present

Rarity

No rare species are expected to be present

Re-creatibility

Subtidal hard bottom habitats can be re-created

Fragmentation

The subtidal hard bottom habitat within the Study Area is fragmented

Ecological Linkage

The subtidal hard bottom habitats within the Study Area have low ecological linkage with habitats of conservation interest

Potential Value

Unlikely that these habitats can develop conservation interest within the Study Area

Nursery Ground

Unlikely that these habitats act as nursery grounds within the Study Area

Age

Subtidal hard bottom habitats within the study area are not expected to be mature

Abundance

Abundance of subtidal hard bottom associated species is expected to be low

Summary

Due to extensive development in the area, natural subtidal hard bottom habitat within the Study Area is limited.  Artificial subtidal hard bottom habitat (eg seawalls) generally support less abundance and diversity than natural substratum.  However, the estuarine conditions of the Study Area generally do not support subtidal hard bottom species of conservation interest. 

Ecological Value

Low

 

Intertidal Hard Bottom Habitats

 

The majority of the coastal areas in the Study Area, although particularly in vicinity of the proposed CMPs at South Brothers and East of Sha Chau, have been reclaimed, thus in general artificial seawalls have replaced naturally occurring intertidal hard bottom habitats.  The largest of these seawalls is at the Chek Lap Kok International Airport (see Figure 4.3a).  Surveys have been conducted on the colonisation of organisms on artificial seawalls in Hong Kong and fouling organisms have been recorded as common on such artificial seawalls, wharf piles and other marine structures ([26]). 

 

A relatively recent survey on the artificial seawall at the Chek Lap Kok International Airport found that colonisation had occurred by organisms such as polychaetes and bivalves, however, the habitat was considered to be in poor condition ([27]).  Whilst colonisation of organisms considered to be of high ecological value, such as corals, has been recorded on artificial seawalls or structures in the waters in the east of Hong Kong, it is unlikely for the reasons stated above (see Subtidal Hard Bottom Habitats) that the artificial seawalls in the Study Area will be able to support high ecological value assemblages ([28]). 

 

Following the EIAO-TM criteria, the ecological importance of intertidal hard bottom habitats within the Study Area for the proposed CMPs at South Brothers and East of Sha Chau has been assessed in Table 4.13.

 

Table 4.13  Ecological Value of Intertidal Hard Bottom Habitats within the Study Area for the proposed CMPs at South Brothers and East of Sha Chau

EIAO-TM Criteria

Study Area

Naturalness

There is limited natural intertidal hard bottom habitat within the study area

Size

No intertidal hard bottom habitat will be permanently affected by the proposed works

Diversity

Due to the estuarine conditions, diverse assemblages are not expected to be present

Rarity

No rare species are expected to be present

Re-creatibility

Intertidal hard bottom habitats can be re-created

 

The intertidal hard bottom habitat within the Study Area is fragmented

Ecological Linkage

The intertidal hard bottom habitats within the Study Area have low ecological linkage with habitats of conservation interest

Potential Value

Unlikely that these habitats can develop conservation interest within the Study Area

Nursery Ground

Unlikely that these habitats act as nursery grounds within the Study Area

Age

Intertidal hard bottom habitats within the study area are not expected to be mature

Abundance

Abundance of intertidal hard bottom associated species is expected to be low

Summary

Due to extensive development in the area, natural intertidal hard bottom habitat within the Study Area is limited.  Artificial intertidal hard bottom habitats (eg seawalls) generally support less abundance and diversity than natural substratum.  However, the estuarine conditions of the Study Area generally do not support intertidal hard bottom species of conservation interest. 

Ecological Value

Low

 

Marine Mammals

 

There are two resident species of cetacean in Hong Kong’s waters, the Finless Porpoise (Neophocaena phocaenoides) and the Indo-Pacific Humpback Dolphin, (Sousa chinensis).  Recent studies appear to indicate that the Finless Porpoise only occurs in the southern and eastern waters of Hong Kong, with no sightings being recorded in the Study Area ([29]) (2) (3).

The distribution, abundance, habitat use, and life history of Indo-Pacific Humpback Dolphins in Hong Kong has been extensively studied since 1995 ([30])(4).  The distribution and abundance of dolphins has been studied using line transect methods allowing any patterns to be determined.  As sightings are obtained relative to known levels of search effort, corresponding densities have been obtained. 

 

The line transect analysis of vessel surveys undertaken from 1995 to 2003 for the Indo-Pacific Humpback Dolphin Monitoring Programme showed that the abundance of dolphins is highest in the North Lantau area in all four seasons Figure 4.Figure 4.Figure4.3b. 

 

Figure 4.3b          Estimates of abundance of Indo-Pacific Humpback Dolphins in Hong Kong waters, based on line transect analysis of vessel surveys from 1995 to 2003 ([31])

 

In spring, almost all sightings of the Indo-Pacific Humpback Dolphins in Hong Kong have been made in North Lantau with a seasonal influx of individuals into South Lantau (and to a lesser extent, Deep Bay and East Lantau/Lamma areas) during summer, autumn and winter.  The seasonal influx of Indo-Pacific Humpback Dolphins is thought to be due to the spread of freshwater from the Pearl River, directly to the west of Hong Kong ([32]).  Indo-Pacific Humpback Dolphins are present in Hong Kong waters in their highest densities in summer and lowest in spring ([33]) ([34]).  The proportion of the local population that utilize the North Lantau waters as opposed to other areas of Hong Kong varies from 72% in spring to 92% in winter when the abundance of Indo-Pacific Humpback Dolphins occurring in Hong Kong waters is at its lowest ([35]).  

 

According to data from the Agriculture, Fisheries and Conservation Department, which has been collected between 1995 and 2004, it appears that the use of waters by Indo-Pacific Humpback Dolphins within the Study Area is not uniform (Figure 4Figure 4Figure 4.3c to Figure 4.Figure 4.Figure 4.3g).  In all four seasons, Indo-Pacific Humpback Dolphins are most abundant in the western waters between Castle Peak and Black Point in the east and the islands of Sha Chau and Lung Kwu Chau in the west.  High densities have also been recorded in areas to the north of the airport especially near the northeast corner and around the Brothers Islands ([36]).  

Figure 4.3c Indo-Pacific Humpback Dolphin distribution in the Study Area in Spring (Data collected between 1995 and 2004) ([37]).

Figure 4.3d          Indo-Pacific Humpback Dolphin distribution in the Study Area in Summer (Data collected between 1995 and 2004) ([38]).

Figure 4.3e          Indo-Pacific Humpback Dolphin distribution in the Study Area in Autumn (Data collected between 1995 and 2004) ([39]).

Figure 4.3f           Indo-Pacific Humpback Dolphin distribution in the Study Area in Winter (Data collected between 1995 and 2004) ([40]).

 

The exact status of the Hong Kong population of the Indo-Pacific Humpback Dolphin is not known with certainty.  An analysis of recent dolphin data by Dr Thomas Jefferson for the present study comprises data collected between 1995 and mid 2002 appears to indicate that the population may be relatively stable, or at least that it is probably not decreasing at a rapid rate (Figure 4.3g([41]).

Studies have also revealed several areas of very low Indo-Pacific Humpback Dolphin density in the North Lantau area.  One of these is the region along shore from Pillar Point to Brothers Point in the vicinity of the proposed CMPs at East of Sha Chau.  Another such region is in the approximate location of the CMP at South Brothers, ie directly to the east of the airport platform and extending east along the Lantau coastline to Sham Shui Kok.  Within this area very low numbers of dolphins have been sighted in comparison to other areas in North Lantau waters and in Hong Kong.  It should also be noted that the coastline of West Lantau has densities of Indo-Pacific Humpback Dolphin among the highest known in Hong Kong Figure 4.3h.

 

Based on the review of baseline information on Indo-Pacific Humpback Dolphins in Hong Kong, it appears that the areas proposed for CMPs at South Brothers and East of Sha Chau have both recorded low sightings of dolphins in comparison to other areas in North Lantau and Hong Kong. 

Following the EIAO-TM criteria, the ecological importance of the waters within the proposed CMPs at South Brothers and East of Sha Chau for marine mammals has been assessed in Table 4.14.

Figure 4.3g          Trends in abundance of Indo-Pacific Humpback Dolphins in North Lantau (data collected between 1995 and 2002)


Figure 4.3h          Distribution of Indo-Pacific Humpback Dolphin in Hong Kong

 


Table 4.14  Ecological Value of the Waters within the proposed CMPs at South Brothers and East of Sha Chau for Marine Mammals

EIAO-TM Criteria

South Brothers

East of Sha Chau

Naturalness

n/a

n/a

Size

Total area of the temporarily affected habitats is approximately 164 hectares

Total area of the temporarily affected habitats is approximately 115 hectares

Diversity

Only one species of marine mammal, Sousa chinensis, has been recorded within these waters

Only one species of marine mammal, Sousa chinensis, has been recorded within these waters

Rarity

Marine mammals are relatively common in western Hong Waters but are rarely sighted at the facility location

Marine mammals are relatively common in western Hong Waters but are less frequently sighted at the facility location

Re-creatibility

n/a

n/a

Fragmentation

This habitat is unfragmented

This habitat is unfragmented

Ecological Linkage

Areas of more frequent sightings are located to the west and northwest of the site

Areas of more frequent sightings are located to the west southwest and northwest of the site

Potential Value

Limited value due to relative small size in comparison to the more important marine mammal range areas to the west and northwest

Limited value due to relative small size in comparison to the more important marine mammal range areas to the west

Nursery Ground

The waters have not been identified as nursery grounds for marine mammals

The waters have not been identified as nursery grounds for marine mammals

Age

n/a

n/a

Abundance

Abundance of marine mammals within these waters are low to medium in comparison to other areas where marine mammals have been recorded in Hong Kong

Abundance of marine mammals within these waters are low to medium in comparison to other areas where marine mammals have been recorded in Hong Kong

Summary

The waters within the proposed CMP at South Brothers have relatively low sightings of marine mammals recorded in comparison to other sites in Hong Kong

The waters within the proposed CMP at East of Sha Chau have relatively low sightings of marine mammals recorded in comparison to other sites in Hong Kong

Ecological Value

Medium

Medium

 


Sites of Special Scientific Interest (SSSI)

 

Sites of Special Scientific Interest (SSSIs) may be land based or marine sites that are of special interest because of their flora, fauna, geographical, geological or physiographical features as identified by the AFCD.  Hong Kong has a total of 51 SSSIs distributed throughout the region, of which two are found within the Study Area (see Figure 4.3a). 

 

As described above, the intertidal marine habitat at San Tau supports mangrove stands, mudflats and seagrass beds.  As such, this diverse habitat, which covers an area of approximately 2.7 ha, has been designated as an SSSI.  The second of the SSSIs within the Study Area is the Lung Kwu Chau, Tree Island and Sha Chau SSSI and in within the Sha Chau and Lung Kwu Chau Marine Park, which is discussed below.  .

 

Following the EIAO-TM criteria, the ecological importance of SSSIs within the Study Area for the proposed CMPs at South Brothers and East of Sha Chau has been assessed in Table 4.15.

 

Table 4.15  Ecological Value of SSSIs within the Study Area for the proposed CMPs at South Brothers and East of Sha Chau

EIAO-TM Criteria

San Tau Beach SSSI

Lung Kwu Chau, Tree Island & Sha Chau SSSI

Naturalness

The SSSI at San Tau is natural under stress from surrounding works

The SSSI is natural and within the Marine Park

Size

No habitat will be lost through CMP works.  SSSI is 2.7ha

No habitat will be lost through CMP works.  The total land area of the SSSI is 78.7ha

Diversity

Species diversity within the SSSI is high

Species diversity within the SSSI would be expected to be relatively high

Rarity

Two species of horseshoe crab have been identified as using these mudflats as well as two species of seagrass

The SSSI is utilised during the winter by cormorants Phalacrocorax carbo

Re-creatibility

The SSSI would be expected to be difficult to recreate within a short timeframe

The SSSI would be expected to be difficult to recreate within a short timeframe

Fragmentation

The SSSI is relatively unfragmented

The SSSI is relatively unfragmented

Ecological Linkage

Site contains mangroves, mudflat habitat and seagrass species

The SSSI consists of numerous varying substratum but is land based

Potential Value

The site is of conservation interest

The site is of conservation interest and is designated within a Marine Park

Nursery Ground

The SSSI acts as a nursery ground for numerous species, including two species of horseshoe crab

The SSSI has been identified as night-time roosting site for cormorants

Age

Due to the nature of the habitat the substratum is accreting and eroding and the fauna present there are typically short lived

Not applicable

Abundance

The SSSI would be expected to support organisms in high abundances in comparison to other habitats

There are thought to be around 400 cormorants that roost during the winter.

Summary

The SSSI provides a nursery ground for horseshoe crabs in Hong Kong and has associated mangroves, mudflat habitat and seagrass beds

The SSSI provides night roosting opportunities for a large population of wintering cormorants.

Ecological Value

High

High

 

Marine Parks

 

There are currently four designated Marine Parks in Hong Kong waters and one Marine Reserve.  The Sha Chau and Lung Kwu Chau Marine Park, is located within the Study Area (see Figure 4.3a).  Covering an area of approximately 1,200 ha, the Marine Park encloses the Lung Kwu Chau, Tree Island and Sha Chau SSSI, which was designated for ornithological interest.

 

The marine environment of the Marine Park is greatly affected by the Pearl River freshwater run-off, with high organic loading and suspended sediments.  As such, marine organisms that are present within these waters are highly adapted to salinity fluctuations with periods of continuous low salinity, and highly turbid environments.  Nevertheless, the Marine Park acts as a protected habitat for fish species within the western waters and, according to recent surveys is an important feeding ground and nursery habitat for the Indo-Pacific Humpback Dolphin.

 

Following the EIAO-TM criteria, the ecological importance of the Sha Chau and Lung Kwu Chau Marine Park has been assessed in Table 4.16.


Table 4.16  Ecological Value of the Sha Chau and Lung Kwu Chau Marine Park

EIAO-TM Criteria

Sha Chau and Lung Kwu Chau Marine Park

Naturalness

The Marine Park is natural but under stress from surrounding works

Size

No habitat will be lost through CMP works.  The MP covers 1,200ha

Diversity

Species diversity within the Marine Park would be expected to be relatively high

Rarity

The Marine Park is extensively utilised by Sousa chinensis and birds

Re-creatibility

The Marine Park would be expected to be difficult to recreate within a short timeframe

Fragmentation

The Marine Park is relatively unfragmented

Ecological Linkage

The Marine Park consists of numerous varying substratum

Potential Value

The Marine Park is of conservation interest

Nursery Ground

The Marine Park has been identified as acting as a nursery ground for Sousa chinensis

Age

Due to the estuarine conditions, the habitats within the Marine Park are not expected to be mature

Abundance

Due to it’s protected status the Marine Park would be expected to support organisms in high abundances in comparison to other habitats

Summary

Due to its designation and the use of the waters by Sousa chinensis the Marine Park is of conservation importance

Ecological Value

High

 

4.3.3    Marine Ecological Sensitive Receivers

 

The ecological value of each of the marine ecological habitats/organisms within the Study Area has been presented above based on the criteria presented in the EIAO-TM.  A summary of the ecological values is presented below in Table 4.17.  Based on these values, these habitats/organisms are determined whether or not they are considered to be a marine ecological sensitive receiver to the construction and operation of the proposed CMPs at South Brothers and East of Sha Chau.


Table 4.17  Marine Ecological Sensitive Receivers to the proposed CMPs at South Brothers and East of Sha Chau

Habitat/Organism

Ecological Value

Marine Sensitive Receiver

 

 

South Brothers

East of Sha Chau

Study Area

 

Soft Bottom Habitats

 

 

 

 

Subtidal Soft Bottom Habitats

 

 

 

 

 

Infaunal

Low

Low

n/a

û

 

Epifaunal

Low

Low

n/a

û

Intertidal Soft Bottom Habitats

 

 

 

 

 

Mangroves

n/a

n/a

Low to High

û1

 

Mudflats

n/a

n/a

Low to Medium

û1,2

 

Seagrass

n/a

n/a

Low to High

û1

 

 

 

 

 

 

Hard Bottom Habitats

 

 

 

 

Subtidal Hard Bottom Habitats

n/a

n/a

Low

û

Intertidal Hard Bottom Habitats

n/a

n/a

Low

û

 

 

 

 

 

 

Marine Mammals

Medium

Medium

n/a

ü

 

 

 

 

 

 

Sites of Special Scientific Interest (SSSI)

n/a

n/a

High

ü

 

 

 

 

 

 

Marine Parks

n/a

n/a

High

ü

 

 

 

 

 

 

Notes:

1.        High ecological habitat considered a marine sensitive receiver under the San Tau Beach SSSI and Yam O seagrass bed.

2.        Due to it’s high ecological value Tai Ho Bay has been regarded as a marine sensitive receiver under SSSI.

 

4.4    Fisheries

 

This Section describes the baseline conditions of capture and culture fisheries resources within the Study Area.  This area was defined in the Study Brief as the area for the Water Quality Impact Assessment.  Consequently, this assessment of impacts has focussed on the fisheries resources and fishing operations of this area.  Baseline conditions are evaluated based on information from the literature.

 

4.4.1    Literature Review

 

The availability of literature on the fisheries resources of the Study Area comes mainly from the AFCD 1996-1997 ([42]) and 2001-2002 Port Survey ([43]).  Other relevant reports from the Study Area have been reviewed.

 

In Hong Kong, the commercial marine fishing industry is divided into capture and culture fisheries.  To assess the capture fishery within the Study Area, the most up-to-date information on the Hong Kong fishery was consulted (1).  Information from other relevant studies within the Study Area were also reviewed in order to determine if the areas are important nursery and spawning grounds for commercial fisheries (2).

 

The findings of fisheries surveys, fishermen’s interviews and accompanying literature reviews (3) conducted for AFCD’s Fisheries Resources and Fishing Operations in Hong Kong Waters Study have determined that commercial fish species reproduce throughout the year, though spawning for the majority of species appears to be concentrated during the period from June to September.  The marine waters within the Study Area were not identified as a primary nursery ground for commercial fisheries but were noted as a spawning ground for Leiognathus brevirostris (shortnose ponyfish), Lateolabrax japonicus (sea bass) and Clupanodon punctatus (gizzard shad).

 

Capture Fisheries

 

In 2002, the estimated fisheries production in Hong Kong waters from both capture and culture fisheries amounted to 173,198 tonnes, valued at HK$ 1,700 million (4).  Capture fisheries accounted for 98 % by weight (94.1 % by value) of the total production while the remaining 2 % (5.9% by value) corresponded to the culture sectors of the industry.  Within Hong Kong waters, the highest yields for local fisheries within Hong Kong waters were mainly derived from the eastern and north-eastern coasts (5).  The five most abundant fish species landed by weight from the capture sector were golden thread (Nemipterus virgatus 14%), lizardfish (Saurida sp 9%), big-eyes (Priacanthus sp 5%), scads (Decapterus sp 5%) and yellow belly (Nemipterus bathybius 4%).

 

Based on the latest AFCD Port Survey data (6), the highest range of fisheries production (ie 600 – 1000 kg ha-1) was recorded near Cheung Chau, Penny’s Bay, Kau Yi Chau, Po Toi, Ninepin Group and Tap Mun.  The top 10 families captured in Hong Kong were rabbitfish (Siganidae), sardine (Clupeidae), croaker (Sciaenidae), scad (Carangidae), squid, shrimp, anchovy (Engraulidae), crab, seabream (Sparidae) and threadfin bream (Nemipteridae).

 

For areas within the Study Area, the fisheries production ranged widely from <= 50 kg ha-1 (for areas west of the Chek Lap Kok Airport) to 200 – 400 kg ha-1 for areas near Sha Chau, Lung Kwu Chau and the Brothers (Siu Mo To) (7).  These values are not in the high range for production in Hong Kong.

 

Up-to-date information from AFCD is available for use in this EIA and can be collated to allow an assessment be made of the importance of Fishing Zones in the Study Area to the Hong Kong fishery.  The designated Fishing Zones within the Study Area have been identified and the importance of these zones is assessed and discussed below.

 

The Study Area interfaces with 14 Fishing Zones as identified in the AFCD Port Survey Report ([44]).  These Fishing Zones are identified as follows:

 

·         Sha Lo Wan

·         Tung Chung (South Brothers Study Area)

·         Chek Lap Kok (South Brothers Study Area)

·         Pak Mong (South Brothers Study Area)

·         Sham Shui Kok

·         Yam O

·         The Brothers (East of Sha Chau Study Area and South Brothers Study Area)

·         Lung Kwu Sha Chau

·         Tai Lam Chung

·         Pearl Island

·         Castle Peak Bay

·         Mong Hau Shek (East of Sha Chau Study Area)

·         Tap Shek Kok (East of Sha Chau Study Area)

·         Lung Kwu Tan

 

The area and number of vessels operating during 1996-1997 in each of the Fishing Zones is presented in Table 4.18.  The total number of vessels varies widely from 20.8 in Lung Kwu Tan Fishing Zone to 256.9 in Lung Kwu Sha Chau Fishing Zone.  Over 200 fishing vessels were reported to operate in The Brothers and Lung Kwu Sha Chau Fishing Zones and over 100 vessels were recorded for Sha Lo Wan, Sham Shui Kok and Yam O Fishing Zones. Except for Sha Lo Wan and Lung Kwu Sha Chau Fishing Zones where comparable numbers of < 15 m and > 15 m vessels were reported to operate in the fishing area, the other 12 fishing zones were found to be dominated by vessels < 15 m (Table 4.18).

 

According to the latest AFCD 2001-2002 Port Survey data, the most common type of vessel operating within the Study Area is sampan (P4/7) with particularly high numbers (100 - 400) recorded near Lung Kwu Chau, Sha Chau, The Brothers and along the northern coast of Lantau Island.  Hang trawlers were reported to operate within the Study Area with relatively higher numbers (10 – 50) being reported near Sha Chau.  Gill netters also operate in the area with numbers ranging from 0 to 50.  Shrimp trawlers were found to operate throughout the Study Area with relatively higher numbers (100 - 200) reported near The Brothers.  Relatively low numbers of other fishing vessels (<=10) such as stern trawler, pair trawler, long liner, hand liners and purse seiner and miscellaneous craft were also reported to operate within the Study Area.  The information presented in indicates that the fisheries production levels vary markedly within the Study Area. 

 

Of the 14 fishing zones identified, two of the fishing zones were ranked as recording high production (The Brothers 24th and Lung Kwu Sha Chau 53rd out of the 179 zones that reported a catch), seven recorded medium ranked catches (Sha Lo Wan 75th, Pak Mong 78th, Yam O 82nd, Sham Shui Kok 89th, Pearl Island 97th, Tap Shek Kok 105th and Tung Chung 106th), and the remaining four zones recorded low catches including Castle Peak Bay 123rd, Mong Hau Shek 135th, Lung Kwu Tan 142nd and Tai Lam Chung 148th.  Only one of the fishing zones reported fry catch (The Brothers) and ranked 76th out of the 89 fishing zones that did report fry catches.

According to the AFCD Port Survey data ([45]), the top five adult fish species caught in this sector North of Lantau (SE02) included the mixed species, Caranx kalla (scad), Clupanodon punctatus (gizzard shad), Sardinella jussieu (sardine) and Argyrosomus spp (croaker).  The main fish species reported in catches from the Study Area are of low commercial value including mixed species (juveniles of trash fish species such as pony fish, scad, rabbitfish and sardine) (Table 4.20).  Only the silver shrimp is regarded as of high commercial value.  Shrimp scad, hair tail, rock fish, sea bream, conger pike eel, mantis shrimp and prawn are regarded as of medium commercial value. 

 

A recent demersal trawl survey, conducted in May 2001 at locations within the Study Area at sites around Lung Kwu Chau and around the mud pits as part of the ongoing EM&A for the contaminated mud pits at East Sha Chau ([46]) , recorded a total of 186 different species .  Of these species, crabs, fish, gastropods, mantis shrimp, prawns and shrimps were the most abundant.  Crabs were numerically dominant in these waters (a total of 7,028 individuals were recorded) with Charybdis japonica and Charybdis affinis being the most abundant species at locations near the mud pits.

 

A total of 2,225 individuals representing 72 fish species were recorded in the trawl survey.  The most common fish recorded within the Study Area near the mud pits were the pony fish (Leiognathus brevirostris), the croaker (Johnius belangerii) and another croaker Johnius macrorhynus.  The commercially important mantis shrimps (mostly Oratosquilla interrupta) and prawn (Penaeus japonicus) were also abundant. 

 


Table 4.18  Area (Ha) and Number of Vessels Operating During 1996 - 1997 in Each AFCD Fishing Zone within the Study Area

Code

Fishery Area

Area (Ha)

Vessels < 15 m

Vessels > 15 m

All Vessels

18

Sha Lo Wan

961.00

72.7

77.7

150.4

19

Tung Chung

363.42

44.3

13.6

57.9

20

Chek Lap Kok

 

 

 

 

21

Pak Mong

533.22

47.1

21.9

69.1

22

Sham Shui Kok

531.60

135.8

15.3

151.1

23

Yam O

529.94

115.8

8.3

124.1

32

The Brothers

1,804.78

154.5

92.1

246.6

33

Lung Kwu Sha Chau

3,616.46

126.5

130.4

256.9

39

Tai Lam Chung

370.36

20.3

2.3

22.5

40

Pearl Island

286.83

13.1

5.7

18.8

41

Castle Peak Bay

579.77

28.7

10.2

38.9

42

Mong Hau Shek

1,329.63

41.0

22.5

63.6

43

Tap Shek Kok

822.57

73.5

19.2

92.7

44

Lung Kwu Tan

457.72

16.4

4.4

20.8

Total

 

12,187.3

*

*

*

Total of all Fishing Zones in Hong Kong

181,791

2,267

260

2,527

Percentage of Hong Kong Total

6.7%

*

*

*

*           No values can be calculated for these parameters from the information provided as it cannot be determined whether the vessels reported as operating within one zone are the same vessels that are reported for another zone.


Table 4.19  Total Value ($), Adult Catch (kg) and Fry Catch (tails) Displayed on a Total Production, Production (Ha-1) and Rank (Ha-1) Basis for the AFCD Fishing Zones in the Study Area (1996 - 1997 Port Survey)

 

Code

Fishing Area

Total Production

Production (Ha-1)

Rank Production (Ha-1)

 

 

Adult Fish (kg)

Fry (tails)

 

Adult Fish (kg)

Fry (tails)

 

Adult Fish

(out of 179)

Fry

(out of 89)

 

18

Sha Lo Wan

133,449.64

-

 

137.82

-