12.                   FISHERIES

 

12.1               Introduction

 

12.1.1         This section of the EIA presents details of the assessment of the potential impacts to fisheries resources within the study area and describes the sensitive receivers present, potential impacts from the project and recommends suitable mitigation measures. In order to achieve the aforementioned measures, the major objectives of the assessment are as follows:

 

¨             description of the physical environmental background;

¨             description and quantification as far as possible of the existing fisheries activities;

¨             identification of parameters and area that are important to fisheries;

¨             identification and quantification as far as possible of any direct or indirect and on-site or off-site impacts to fisheries; and

¨             proposals for any practicable alternatives or mitigation measures to prevent  or minimise adverse impacts on fisheries.

 

12.2               Relevant Legislation and Assessment Criteria

 

12.2.1         Relevant legislation applicable to this Study includes:

 

¨             the Marine Fish Culture Ordinance (Cap. 353) 1983 which regulates and protects marine fish culture zones (FCZ) that are designated under the ordinance. It is a criminal offence to discharge polluting substances into an FCZ;

 

¨             the Fisheries Protection Ordinance (Cap. 171) 1987 which regulates fishing activities for the conservation of fisheries resources and other marine life; and 

 

¨             reference was also made to Annexes 9 and 17 of the Technical Memorandum EIAO (Cap. 499) 1997 in order to determine the potential impacts to fisheries resources in the Study Area. The criteria include the following:

 

-           to prevent any significant impacts to sensitive fisheries areas particularly the nursery and spawning grounds of commercially important species of fish, crustaceans, molluscs and other marine life;

-           to prevent significant loss or interference with the use of fishing grounds and FCZ’s; and

-           to prevent significant impacts to local fishery resources and fishing activities.

 

12.2.2         A review of relevant EIA’s and reports has also been conducted in order to assist the assessment criteria. These reports include the following:

 

¨             New Airport Master Plan (Greiner-Maunsell, 1991);

¨             Feasibility Study & Environmental Impact Assessment for Aviation Fuel Pipeline (Montgomery Watson, 1996);

¨             Feasibility Study for Additional Cross-border Links Stage 2 (Mouchel, 1998);

¨             EIA for the Proposed Sand Extraction from The Brothers’ Marine Borrow Area (Hyder Consulting, 1998);

¨             EIA Study for Disposal of Contaminated Mud in the East Sha Chau Marine Borrow Pit (ERM, 1997);

¨             EA Study for Backfilling of Marine Borrow Pits at North of the Brothers (Mouchel, ongoing);

¨             Route 10 North Lantau to Yuen Long Highway Investigation and Preliminary Design EIA (Mott Connell, 1999); and

¨             Port Survey 96/97, Fisheries Management Division, AFCD (AFCD, 1998).

 

12.2.3         Reports from the ongoing environmental monitoring and audit at the contaminated mud pits at East of Sha Chau (Mouchel, 2001a; ongoing) also provide a large amount of relevant fisheries data and have also been reviewed. The fisheries data provided in the aforementioned EM&A study provides the most up to date information on the fisheries resources of the study area.

 

12.3               Baseline Conditions

 

12.3.1         Description of Physical Habitat

 

12.3.1.1   A detailed description of the physical marine habitat is presented in Section 7.4.2 and the key aspects are summarised below.  The PAFF is located within the western waters of Hong Kong that are highly influenced by the variable estuarine conditions of the Pearl River Delta and a well-scoured tidal channel running east-west (the Urmston Road).  Thus, the seabed in the area is predominantly made up of soft muds, although the scouring of the tidal channel along the Urmston Road provides some coarser habitat containing muddy shelly sand. The benthic habitat in the study area is, therefore, highly sediment laden, both in suspension and on the seabed, and existing fauna are dominated by representatives that tolerate these high ambient loads (see Section 7.4). The soft-bottom sediments characteristic of the study area are predicted to be contaminated (see Section 6.2.5).  In terms of water quality, the Pearl River outputs significant nutrient loading resulting in generally eutrophic conditions (Section 6.2.4) and the predominantly estuarine fish inhabiting the study area are, therefore, already subjected to certain environmental stresses (notably high suspended solid concentrations).

 

12.3.2         Capture Fisheries

 

12.3.2.1   Recent information on the capture fisheries is summarised in the Port Survey of 1996/97 (AFCD, 1998) and in the Report on Fisheries Resources and Fishing Operations in Hong Kong Waters (ERM, 1998). The PAFF pipeline and berthing jetty passes interfaces with two fishing areas, namely, the Tap Shek Kok and Lung Kwu Sha Chau fishing areas, as identified in the Port Survey Report (AFCD, 1998). The proposed 4.8km twin subsea pipeline is located approximately equally in each fishing area.  The two fishing areas within the PAFF study area are significantly different in size and comprised the following:

¨              Area 33 - Lung Kwu Sha Chau comprising an area of 3,616.46 ha; and

¨              Area 43 – Tap Shek Kok comprising an area of 822.57 ha.

 

12.3.2.2   The total value and ranking of the fisheries resources in each of these fishing areas that lie within the study area are presented below in Table 12.1. The Lung Kwu Sha Chau fishing area is of reasonably high value and ranks quite highly in terms of adult fished biomass and overall value per hectare on a Hong Kong wide basis. The fishing area at Tap Shek Kok is ranked lower and in terms of adult fish production is ranked 105 out of 189 fishing areas in Hong Kong.

 

Table 12.1       Fisheries Production in Each Fishing Area (all fishing vessels)

 

Fishing Area (ha)

Total Production

Production (ha-1)

Rank Production (ha-1)

Adult Fish (kg)

Fry (tails)

Value (HK$)

Adult Fish (kg)

Fry (tails)

Value (HK$)

Adult Fish

Fry

Value

Lung Kwu Sha Chau

3,616.46

651,700.0

-

11,828,364.8

180.2

-

3,270.71

53

-

82

Tap Shek Kok

822.57

66,218.3

-

1,958,466.6

80.5

-

2,380.9

105

-

98

Note: Based on the 189 fishing areas in Hong Kong waters (AFCD, 1998).

 

12.3.2.3   The two fishing areas are subunits of a wider sector area that occupies the sea around North of Lantau.  It is conceivable that impacts from the dredging operations could reach these wider regional areas and so a summary of the fishery for the region is included here. Thus, in terms of production by hectare the region ranks quite highly (4th out of 12 sectors) and is relatively valuable, however, the fry fishery is not nearly so productive (ranked 9 out of 12).  The major difference at the regional level is that smaller boat (< 15m) operators are insignificant in this sector and are ranked in the lower third across Hong Kong for production and value per hectare.  Thus, impacts from the dredging operations to small boat operators are likely to be localised around the study area and are not likely to range wider.  Large trawling vessels (>15m) are, however, dominant in this region and the fleet operating here is the second largest in Hong Kong waters and not surprisingly their catch ranks highest in value per hectare (AFCD, 1998). 

 

12.3.2.4   Apart from a category labelled as mixed fish, the AFCD Port Survey identifies the top four species caught in the region as scad (Caranx kalla), gizzard shad (Clupanodon punctatus), sardine (Sardinella jussieu) and croaker (Argyrosomus spp.).  These fish catches reflect the operations in the area, which are dominated by larger fishing vessels and notably hang trawlers fishing pelagic species. On a smaller scale, mixed fish species were also the most abundant fisheries resource in each of the fishing areas, followed by shrimp scad, gizzard shad and sardine (Lung Kwu Sha Chau) and gizzard shad, lionhead and croaker (Tap Shek Kok). A summary of the top ten adult fisheries resources caught in each fishing area is presented below in Table 12.2.

 

Table 12.2    Most Abundant Adult Fisheries Resources from the Study Area (by Biomass)

 

Rank by Biomass

Fishing Area

Lung Kwu Sha Chau

Tap Shek Kok

1

Mixed Species

Mixed Species

2

Caranx kalla (shrimp scad)

ClupanodonPunctatus(gizzard shad)

3

Clupanodon Punctatus (gizzard shad)

Collichthys lucida (lionhead)

4

Sardinella jussieu (sardine)

Argyrosomus spp. (croaker)

5

Trichiurus haumela (hairtail)

Mugil affinis (mullet)

6

Mugil affinis (mullet)

Caranx kalla (shrimp scad)

7

Argyrosomus spp. (croaker)

Acetes spp. (silver shrimp)

8

Collichthys lucida (lionhead)

Platycephalus indicus (flathead)

9

Decapterus lajang (scad)

Ilisha elongata(white herring)

10

Stolephorus spp. (anchovy)

Eleutheronema tetradactylus (threadfin)

Note: Mixed species is mixed fish considered of lower commercial value.

 

12.3.2.5   The most recent (May 2001) demersal trawl surveys conducted in locations near the study area at sites around Lung Kwu Chau, off the airport and around the mud pits as part of the ongoing EM&A for the contaminated mud pits at East Sha Chau (Mouchel, 2001a) recorded a total of 186 different species. The trawling locations are presented in Figure 12.1. Of these species, crabs, fish, gastropods, mantis shrimp, prawns and shrimps were the most abundant.  The crabs are numerically dominant in the Northwestern waters and 7028 individuals were trawled in May 2001, although it should be noted that not all these crabs represent commercial species. 

 

12.3.2.6   Fish were also abundant (2225 individuals recorded representing 72 different species) and in terms of numerical dominance, the most common fish recorded were the pony fish (Leiognathus brevirostris), the croaker (Johnius belangerii), the gobies Oxyurichthys tentacularis and Trypauchen vagina and another croaker Johnius macrorhynus. The commercially important mantis shrimps (mostly Oratosquilla interrupta) and prawn (Penaeus japonicus) were also numerically abundant components of the trawls. The commercially important species (cephalopds, crabs, mantis shrimp, shrimp and fish) trawled from locations around Sha Chau are presented below in Table 12.3.

 

Table 12.3    Species Composition and Abundance of Individuals (Total Counts) from Trawling in May 2001 (Mouchel, 2001a)

 

Group

Species

FS1

FS2

FS3

FS4

FS5

FS6

Total

Cephalopod

Loligo duvaucelii

 

 

1

 

 

 

1

 

Loligo sp.

 

 

2

9

 

 

11

 

Octopus membranaceus

 

 

2

2

 

 

4

 

Sepiella japonica

1

 

3

 

 

2

6

Cephalopod Total

 

1

 

8

11

 

2

22

 

 

 

 

 

 

 

 

 

 

Crab

Arcania heptacantha

 

 

 

1

 

 

1

 

Calappa philargius

 

 

4

 

 

 

4

 

Charybdis acuta

6

17

3

1

108

15

150

 

Charybdis affinis

51

402

227

51

577

25

1333

 

Charybdis callianassa

 

 

 

 

 

1

1

 

Charybdis cruciata

18

2

36

42

29

24

151

 

Charybdis hellerii

1

 

 

1

1

 

3

 

Charybdis japonica

198

549

232

219

1406

236

2840

 

Charybdis truncate

 

 

 

 

1

6

7

 

Charybdis variegata

1

 

 

 

1

 

2

 

Clibanarius sp.

49

36

34

32

62

8

221

 

Diogenes deflectomanus

18

2

1

14

3

 

38

 

Diogenes sp.

 

 

 

15

39

 

54

 

Doclea gracilipes

9

19

1

4

5

2

40

 

Doclea ovis

1

3

 

 

 

 

4

 

Dorippe polita

11

43

20

47

13

19

153

 

Eriochier sp.

1

 

 

 

 

 

1

 

Ethusa indica

7

10

58

40

33

45

193

 

Eucrate costata

5

4

1

 

72

6

88

 

Eucrate crenata

 

19

1

 

100

10

130

 

Eucrate solaris

 

 

2

1

5

1

9

 

Eucrate sp.

 

6

 

 

 

 

6

 

Galene bispinosa

9

12

3

2

9

31

66

 

Goniohellenus vadorum

 

 

1

3

 

4

8

 

Halimede sp.

 

 

 

 

1

 

1

 

Leucosia vittata

2

5

4

 

2

3

16

 

Macrophthalmus japonicus

 

 

 

 

 

2

2

 

Parapanope euagora

 

2

 

 

14

 

16

 

Platylambrus validus

6

8

25

12

62

23

136

 

Portunus hastatoides

1

3

3

1

 

6

14

 

Portunus pelagicus

2

2

3

1

34

5

47

 

Portunus sanguinolentus

595

265

57

37

50

157

1161

 

Procelain crab

 

 

2

1

2

53

58

 

Thalamita sima

 

13

21

9

10

1

54

 

Typhlocarcinus nudus

6

2

4

 

1

7

20

Crab Total

 

997

1424

743

534

2640

690

7028

Fish

Acanthocepola limbata

1

 

 

 

 

 

1

 

Acanthopagrus latus

 

 

1

 

 

1

2

 

Acentrogobius caninus

1

1

11

2

19

15

49

 

Ambassis gymnocephalus

56

 

 

2

1

5

64

 

Amblychaeturichthys hexanema

4

28

 

1

4

 

37

 

Apogon kiensis

 

1

 

 

 

1

2

 

Apogon lineatus

 

4

 

 

 

 

4

 

Argyrosomus japonicus

24

26

6

4

16

3

79

 

Awaous ocellaris

 

 

 

 

3

 

3

 

Butis butis

 

1

 

 

 

1

2

 

Caranx para

 

 

1

3

 

 

4

 

Chiloscyllium plagiosum

 

 

 

 

1

 

1

 

Coilia mystus

1

3

 

 

2

 

6

 

Collichthys lucidus

2

8

 

 

 

 

10

 

Cryptocentrus filifer

 

 

 

1

1

 

2

 

Cynoglossus abbreviatus

 

3

 

 

 

 

3

 

Cynoglossus arel

4

10

1

 

16

30

61

 

Cynoglossus itinus

 

1

 

 

6

 

7

 

Cynoglossus joyneri

18

3

38

36

1

3

99

 

Cynoglossus kopsii

 

 

 

1

 

 

1

 

Cynoglossus puncticeps

1

8

 

 

5

1

15

 

Cynoglossus semilaevis

 

1

 

 

2

 

3

 

Dasyatis zugei

 

 

 

 

4

 

4

 

Dendrophysa russelii

22

1

15

22

2

17

79

 

Diagramma pictum

 

 

 

 

 

1

1

 

Evynnis cardinalis

 

1

 

 

2

1

4

 

Gerres filamentosus

 

 

1

 

 

 

1

 

Gerres lucidus

1

 

18

1

1

 

21

 

Grammoplites scaber

1

 

 

 

 

 

1

 

Gymnothorax favagineus

 

 

 

 

2

 

2

 

Gymnothorax reevesii

 

 

 

 

2

 

2

 

Hapalogenys nitens

 

1

 

 

 

 

1

 

Harpadon nehereus

15

9

 

 

 

 

24

 

Ilisha elongata

1

1

 

 

 

 

2

 

Inimicus japonicus

 

 

 

 

4

 

4

 

Johnius belangerii

2

5

 

3

252

4

266

 

Johnius macrorhynus

18

6

13

24

68

6

135

 

Lagocephalus sceleratus

 

 

1

 

 

 

1

 

Leiognathus brevirostris

9

 

144

26

10

119

308

 

Lepidotrigla alata

1

 

 

 

1

 

2

 

Monacanthus sulcatus

 

 

2

 

 

 

2

 

Mugil cephalus

 

 

2

 

 

 

2

 

Muraenesox bagio

1

 

 

 

 

1

2

 

Nematalosa come

 

 

7

 

 

1

8

 

Nemipterus virgatus

 

 

1

 

 

 

1

 

Odontamblyopus rubicundus

 

 

6

10

 

 

16

 

Oxyurichthys tentacularis

7

1

115

30

6

49

208

 

Pampus argenteus

14

1

1

1

2

 

19

 

Parachaeturichthys polynema

12

6

3

12

44

17

94

 

Pennahia pawak

 

 

 

1

 

 

1

 

Platycephalus indicus

12

3

3

1

28

12

59

 

Plotosus lineatus

1

 

1

 

 

 

2

 

Polycaulus uranoscopa

2

 

1

 

28

39

70

 

Psenopsis anomala

 

 

 

1

 

 

1

 

Repomucenus richardsonii

2

8

4

 

14

2

30

 

Saurida elongata

 

 

11

1

 

 

12

 

Sebastiscus albofasciatus

 

1

 

 

 

 

1

 

Sebastiscus marmoratus

 

 

 

 

11

3

14

 

Siganus fuscescens

 

1

1

1

 

2

5

 

Sillago sihama

 

 

1

4

1

2

8

 

Solea ovata

4

6

1

1

75

1

88

 

Symphurus orientalis

 

 

 

 

1

 

1

 

Syngnathus acus

8

3

29

14

1

 

55

 

Takifugu oblongus

 

 

1

 

 

1

2

 

Thryssa chefuensis

 

 

 

1

 

 

1

 

Thryssa hamiltonii

1

1

 

1

 

 

3

 

Trichiurus lepturus

1

 

 

 

 

 

1

 

Trypauchen vagina

25

24

16

20

37

34

156

 

Uroconger lepturus

 

 

 

 

5

1

6

 

Valamugil formosae

 

 

1

 

 

 

1

 

Vespicula trachinoides

6

 

 

 

 

 

6

 

Zebrias zebra

2

21

1

 

13

 

37

Fish Total

 

280

198

458

225

691

373

2225

Mantis shrimp

Clorida latreillei

2

 

 

 

 

1

3

 

Cloridopsis scorpio

1

 

 

 

 

 

1

 

Dictyosquilla foveolata

14

21

5

7

14

12

73

 

Harpiosquilla harpax

5

1

13

39

19

31

108

 

Oratosquilla interrupta

163

410

29

19

300

124

1045

 

Oratosquilla oratoria

8

48

3

2

24

 

85

Mantis shrimp Total

 

193

480

50

67

357

168

1315

Prawn or shrimp

Alpheus brevicristatus

 

 

 

 

41

 

41

 

Alpheus distinguendus

28

18

5

6

40

4

101

 

Alpheus hoplocheles

2

 

 

 

1

 

3

 

Atypopenaeus stenodactylus

 

19

7

12

4

2

44

 

Exopalaemon annandalei

1

 

 

 

 

 

1

 

Exopalaemon carinicauda

 

5

 

 

 

 

5

 

Hippolysmata ensirostris

 

2

 

 

 

 

2

 

Hippolysmata vittata

 

1

 

 

 

2

3

 

Metapenaeopsis barbata

 

1

1

 

3

1

6

 

Metapenaeopsis palmensis

 

 

1

 

 

 

1

 

Metapenaeus affinis

54

9

1

7

 

 

71

 

Metapenaeus burkenroadi

2

 

 

 

 

 

2

 

Metapenaeus ensis

46

13

7

9

22

18

115

 

Metapenaeus intermedius

 

 

 

 

1

 

1

 

Metapenaeus joyneri

6

3

4

3

1

5

22

 

Parapenaeopsis hardwickii

1

1

 

 

 

 

2

 

 

 

 

 

 

 

 

 

 

Parapenaeopsis hungerfordi

1

 

44

27

2

6

80

 

Penaeus japonicus

92

36

50

6

42

14

240

 

Penaeus orientalis

 

 

2

 

1

 

3

 

Scyllarus martensii

 

 

 

1

1

1

3

 

Solenocera crassicornis

 

9

 

 

 

 

9

 

Trachypenaeus curvirostris

 

7

1

 

43

 

51

 

Trachypenaeus fulvus

 

88

3

1

11

5

108

Prawn or shrimp Total

 

233

212

126

72

213

58

914

Note: Not all crab species are commercially important although they are important components of the marine system and are included for completeness. 

 

12.3.3         Fisheries Resources

 

12.3.3.1   The Report on Fisheries Resources and Fishing Operations in Hong Kong Waters (ERM, 1998) generally supports the information provided in the Port Survey data.  The area is not identified as a primary nursery ground, however it is noted as a spawning ground for Leiognathus brevirostris, Lateolabrax japonicus and Clupanodon punctatus, which probably explains the high catches recorded for the former species in the EM&A at East Sha Chau (Mouchel, 2001a) and the latter species in the Port Survey Report (AFCD, 1998). 

 

12.3.4         Culture Fisheries

 

12.3.4.1   The nearest culture fishery is the mariculture zone at Ma Wan located approximately 14km to the east of Tuen Mun Area 38 (this represents the nearest point between the PAFF and the FCZ).  This is the only FCZ in the area which may potentially be affected by construction and operation of the PAFF. The Ma Wan FCZ consists of 138 licensed floating rafts and the main species cultured are spotted grouper (Epinephelus chlorostigma), goldlined seabream (Rhabdosargus sarba), mangrove snapper (Lutjanus argentimaculatus) and pompano (Trachinotus blochii) (Mott Connell, 1999).  

 

12.4               Sensitive Receivers

 

12.4.1         The sensitive receivers are the mariculture zone at Ma Wan and potentially operators of capture fisheries and the spawning grounds.

 

12.5               Key Issues

 

12.5.1         Background

 

12.5.1.1   The key potential issues associated with the PAFF project with respect to fisheries are associated with temporary alteration to the seabed, loss of habitat and suspension of sediments during the construction phase and the risk of an aviation fuel spill during the operational phase.  A detailed account of the potential impacts attributed to alterations of the seabed and suspension of sediments to marine ecological receivers are presented in Section 7.6.2 and as such impacts are also applicable to fisheries resources, only a summary is provided below. Potential impacts associated with an aviation fuel spill to marine ecological receivers including fisheries species are presented in Section 11 and are not repeated fully in the foregoing sections.

 

12.5.2         Potential Impacts

 

Loss of Seabed Habitat

 

12.5.2.1   Temporary loss of the seabed due to the trenching of the 4.8km pipeline is estimated to require 274,000 m3 of dredging that may lead to direct impacts on fisheries resources both through direct physical impacts and long-term loss of prey items. The habitat temporarily lost to the pipeline is, however, insignificant when compared to the size of the fishing areas it passes through. Furthermore, as discussed previously in Section 7.6.4, the area of seabed temporarily disturbed during pipeline installation will following backfilling, likely return to a pre-dredged state rapidly as the relatively uncontaminated sediments of the study area are rapidly colonised by macroinvertebrates (Mouchel, 2001a).

 

12.5.2.2   In addition to the potentially negative impacts of seabed loss described above, there are also potential positive effects of dredging to fisheries resources within the immediate vicinity of the works. In the short-term, the disturbance to the seabed during dredging is likely to provide opportunities for feeding by fish as resident invertebrate prey populations are displaced from the sediments. Dredging has, for example, been known to attract dolphins (Hyder, 1998; Jefferson pers. comm.) that are presumably attracted to the vicinity of dredged areas to feed on fish similarly attracted by dislodged invertebrates.

 

Suspension of Sediments

 

12.5.2.3   Dredging operations may lead to localised high ambient concentrations of suspended sediments. The potential impacts of suspended solids on ecological receivers were described previously in Section 7.6.2 and are also applicable to fisheries resources. The potential direct and indirect impacts from suspended solids to fisheries resources are summarised below.

 

Direct Impacts

 

12.5.2.4   Direct impacts are associated with the following:

 

¨             physical abrasion and clogging of gills;

¨             interference with feeding apparatus;

¨             alteration of behaviour (especially in species that rely heavily on visual cues);

¨             higher susceptibility to diseases; and

¨             smothering of early-life stages particularly eggs.

 

 

 

Indirect Impacts

 

12.5.2.5   Indirect impacts comprise:

 

¨      suspended matter may reduce light penetration and alter primary productivity;

¨      large volumes of deposited suspended solids may alter the nature of the seabed; and

¨      suspended matter may contain organics that have an oxygen demand leading to reduced dissolved oxygen.

 

12.5.2.6   High suspended solid concentrations can have a lethal effect on adult fish through suffocation as gills clog and dysfunction.  At lower concentrations, sublethal effects may be manifest as disruption to feeding, mating behaviour (loss of visual cues) and may also increase the susceptibility of the fish population to a range of chronic diseases including fungal, parasitic, bacterial and viral infections. The impacts from suspended solids are most notable to the younger stages such as larvae and eggs. The eggs of fisheries species are particularly vulnerable to sediment deposition as smothering prevents/impedes gaseous exchange inducing mortality to the developing embryo. Most adult fish are, however, adapted to the naturally-occurring sediment fluxes of the Northwestern waters and will respond to localised elevated concentrations of suspended solids by avoiding the area. Avoidance behaviour will not, however, be possible under mariculture conditions although it should be noted that elevated suspended solids are not predicted to reach the Ma Wan FCZ (see Section 6).

 

12.5.2.7   The indirect impacts from elevated suspended solid concentrations in the marine environment are difficult to quantify owing to numerous other confounding factors present. There is, however, evidence that elevated suspended solid concentrations can reduce photosynthesis (thereby interfering with primary productivity that may initially have implications for herbivorous fish); alter the seabed leading to losses of prey items; and, when suspended matter has a high organic content there is potential for an increased oxygen demand leading to localised hypoxia.

 

Suspension of Contaminated Sediments

 

12.5.2.8   Resuspension of highly contaminated sediments may lead to the desorption of contaminants into the water column that may eventually be taken-up into food chains that are linked to fisheries resources. The sediments in the study area are, however, relatively uncontaminated (Section 6.2.5); suspension during dredging should be minimal (Section 6.7); and sediment re-suspension is not considered likely to cause significant elevation of potentially polluting naturally-bound constituents such as metals in ambient waters through desorption. There is, therefore, no predicted toxic impacts from suspension of sediments to fisheries resources and this potential impact is not considered further.

 

 

 

 

12.6               Impact Evaluation

 

12.6.1         Construction and Operational Phases

 

12.6.1.1   Annex 9 of the TMEIAO provides general criteria that can be applied in the assessment of impacts to fisheries due to developments. Construction phase impacts to fisheries associated with the PAFF project are mostly related to the potential for impacts from suspended solids, loss of habitat and impacts from percussive piling. The only potential operational phase impact to fisheries resources is due to an aviation fuel spill. The risks of such a spill have, however, been calculated to be within acceptable levels (Section 10) and the assessment of fuel spills on fisheries are also considered insignificant, as assessed in detail in Section 11.

 

12.6.2         Impact from Suspended Solids on Fisheries Resources

 

12.6.2.1   The PAFF study area is known to be an important spawning and nursery ground for many commercially important penaeid shrimp and fish species (AFCD, 1998; Figures 6.2 on sensitive receivers).

 

12.6.2.2   Fish are typically highly mobile and will generally avoid disturbed areas. On cessation of the construction phase activity, it is likely that fish will rapidly recolonise the area. Species inhabiting the areas adjacent to the dredging will be exposed to some localised elevated suspended solid levels although impacts from suspended material is likely to be minimal as it is likely that fish will either avoid the area or are adapted to local conditions (i.e., the high suspended sediment loads carried in the water column and/ or the re-suspension of soft-bottom sediments characteristic of the Northwestern waters). Furthermore, lethal impacts from suspended solids are not usually induced in fish until ambient concentrations reach 1,000 mg l-1 and it is notable that a recent study with a local fish species, the mangrove snapper (Lutjanus argentimaculatus) showed that extremely high suspended solid concentrations failed to induce toxicity. The mangrove snapper tolerated high total suspended solid loadings and the 48-h NOEC (no observable effect concentration) was 5,000 mg l-1 (AFCD, 2001).

 

12.6.2.3   The loss of some soft-bottom benthic habitat to dredging of the trench is only a localised temporary impact and the decrease of potential invertebrate food sources and impacts on fish and fisheries resources are considered insignificant. It is possible that detritus feeding species may be attracted through disturbance to sediments and construction may be beneficial to these species.

 

12.6.2.4   Dredging operations may result in some short lived plumes of sediment within the bottom layer.  This bottom layer is naturally subject to large variability in suspended sediment conditions as a result of natural processes of sediment deposition and erosion.  Demersal species inhabiting these waters are consequently tolerant to such variability in suspended sediment conditions.  Suspended sediment concentrations within the middle and upper layers would generally not increase by more than about 5 mg/l across the study area.  There would be a few transient plumes with slightly higher levels up to a maximum of about 10-15 mg/l above ambient which is within the natural variability experienced in the North Western waters.  Thus pelagic species are also unlikely to be significantly impacted and are unlikely to move far from the dredging operation. Spawning activities are also unlikely to be disrupted.  Fishing activities may be locally disrupted due to vessel movements and traffic restrictions, however, this will be short-term and given the high volume of marine traffic currently operating in the area, considered insignificant. The home-range of the fish involved will also generally be wider than the works area and opportunities will still exist to catch the fish elsewhere in the two fishing areas. The mariculture zone at Ma Wan is sufficiently distant from the works (>14km) that there will be no increase in suspended sediment concentrations as a result of the project. Construction-phase dredging for the trench required to accommodate the pipeline is not, therefore, likely to be a factor influencing operations at the FCZ.

 

12.6.2.5   As the dredging work is highly localised and will be conducted to minimise sediment resuspension (Section 6.7), impacts due to suspended solids on fisheries resources are considered insignificant and acceptable. The mitigation measures described in Section 6.7 to protect water quality sensitive receivers from elevated suspended solid concentrations should prove adequate to prevent significant impacts of suspension of the seabed sediments to fisheries resources in the study area.

 

12.6.2.6   In summary, the PAFF construction will result in minimal loss of the seabed as the pipeline is located in a trench, covered in rock armour and installed 3m below the seabed surface. The structure will have minimal impact to the benthic fish prey items inhabiting sediments and will also not interfere with fishing activities.

 

12.6.2.7   An evaluation of the PAFF project using criteria detailed in Annex 9 of the TMEIAO is provided below in Table 12.4. 

 

Table 12.4       Impact Evaluation

 

Criteria

Predicted Impacts

Impact Evaluation/ Mitigation

Nature of impact

Dredging of a submarine trench for the PAFF Pipeline,

 

Temporary Seabed Loss and Potential Food Resources,

 

Permanent Loss of Seabed to Piled Jetty 

 

Percussive Piling of the PAFF Jetty- Percussive piling is know to produce high powered sounds in the marine environment (see Section 7.6) that can impact certain species, notably cetaceans.

 

Impacts are temporary (recolonisation of seabed is rapid as discussed in Section 7) and temporary loss of seabed insignificant as the seabed present is homogeneous throughout the study area. The permanent loss of seabed to the piled jetty represents an insignificant area and the fishing area affected (Tap Shek Kok) does not support a high value fishery.  Provided that the good dredging practices recommended in Section 6.7 are adhered to, water quality impacts and hence impacts to fisheries are insignificant.  No other mitigation measures are required.

 

 

 

 

The percussive piling is to be mitigated (see Section 7.8.2) due to concerns over noise impacts on dolphins that use acoustic echolocation (following mitigation it is predicted that noise will have an insignificant impact to these highly sensitive organisms). Fish (and fisheries species) are not considered to rely heavily on acoustic information and impacts both to capture and culture fisheries at the Ma Wan FCZ are considered to be insignificant.

 

 

 

Size of affected area

Pipeline is 4.8km and represents a relatively small proportion of the total fisheries habitat and fishing grounds in Hong Kong. The suspension of sediments during the construction phase (dredging required for laying of the pipeline in the trench) is predicted to be highly localised and elevated suspended solids are not predicted outside of a highly localised works area.

N/A

Loss of fisheries resources/ production

The pipeline and associated works is located in two fishing areas. Lung Kwu Sha Chau is of reasonably high value and ranks quite highly in terms of adult fished biomass and overall value per hectare on a Hong Kong wide basis. The fishing area at Tap Shek Kok is ranked lower and in terms of adult fish production is ranked 105 out of 189 fishing areas in Hong Kong.

 

Provided that the good dredging practices recommended in Section 6.7 are adhered to, water quality impacts and hence impacts to fisheries are insignificant.  No other mitigation measures are required.

Destruction and disturbance of nursery and spawning grounds

The study area is known to be a spawning ground for several important commercial fisheries.

Provided that the good dredging practices recommended in Section 6.7 are adhered to, water quality impacts and hence impacts (direct impacts attributable to elevated suspended solids and indirect impacts such as reduced dissolved oxygen) to fisheries are insignificant.  No other mitigation measures are required.

Impact on fishing activity

A dredging vessel (s) will be required to dredge a trench for the pipeline and this vessel may interfere with fishing activity in the study area.

The study area has an extremely high volume of marine traffic (e.g., Urmston road major shipping channel; ~ 30 hydrofoil ferries pass through the area daily; river-going vessels to the RTT; and numerous trawl vessels) and (Jefferson pers. comm.) estimated that up to 200 vessels are present in the study area. The dredging is also likely to be completed in about 30 days and predicted impact on fishing activity due to dredging vessels is, therefore, considered insignificant.

Impact on aquaculture activity

Dredging of the trench for the pipeline may lead to elevated suspended solids.

Insignificant elevated suspended solid concentrations are predicted and higher levels will be highly localised (i.e., within the works area/ dredging location). Elevated suspended solid concentrations are not predicted at the Ma Wan FCZ (see Section 6) which is located >14km from the PAFF and dredging operations on the FCZ are considered to represent an insignificant impact.

 

12.7               Conclusions

 

12.7.1         There are two fishing areas (Tap Shek Kok and Lung Kwu Sha Chau) directly within the study area, both of which support capture fisheries. The fishing area at Tap Shek Kok is ranked low in terms of adult fish production (ranked 105 out of 189 fishing areas in Hong Kong) although the Lung Kwu Sha Chau fishing area is of reasonably high value and ranks quite highly (ranked 53) in terms of adult fished biomass and overall value per hectare on a Hong Kong wide basis. Further afield, there are no predicted impacts attributable to the PAFF project at the Ma Wan FCZ.

 

12.7.2         The major impacts to fisheries resources are predicted to be due to the temporary loss of seabed and suspension of sediments during dredging. The temporary loss of seabed was, however, considered to be insignificant in relation to the amount of adjacent homogeneous benthic habitat available and it is notable that on cessation of pipeline laying operations, the overlying sediment is likely to be recolonised rapidly thereby restoring both habitat and prey items (note that construction phase activity will dislodge invertebrates that may prove beneficial to fisheries resources). Both direct and indirect impacts from suspended solids are known to have lethal and sublethal effects on fish. The suspended solid concentrations required to induce mortality in marine fish are however of the magnitude of 1,000 to > 5,000 mg l-1 and although more subtle sublethal impacts cannot be entirely discounted, it is likely that fish species resident in the study area are (naturally) adapted to elevated suspended solid levels and have various physiological (such as mechanisms for clearing clogged gills) and behavioural (such as avoidance of highly impacted areas) adaptations to high sediment loadings. The suspension of solids due to dredging activity is also predicted to be highly localised and only of a transient nature as dredging is expected to be completed within about 30 days.

 

12.7.3         In summary, the overall predicted impacts due to the PAFF on fisheries resources are insignificant and no specific monitoring and audit programme is required as the EM&A designed to detect unacceptable impacts to water quality will provide adequate for the protection of fisheries resources.

 

12.8               Mitigation Measures         

 

12.8.1         The construction phase impacts due primarily to dredging activity were predicted to be highly localised, confined to the vicinity of the works area and represent an insignificant impact to fisheries resources in the study area. The mitigation measures recommended to protect water quality sensitive receivers presented in Section 6.7 are adequate to prevent adverse impacts to fisheries resources.  Mitigation measures associated with the control, containment and cleanup of an oil spill are detailed in Section 11. These measures are also summarised in the Environmental Mitigation Implementation Schedule in Appendix B.

 

12.9               Residual Impacts

 

12.9.1         Significant impacts on fisheries are not predicted and thus, no adverse residual impacts are predicted.

 

12.10           Environmental Monitoring and Audit

 

12.10.1     The monitoring and audit programme designed to detect any unacceptable impacts to water quality (see Section 6.9) will provide adequate protection of fisheries resources in the study area.  Predicted impacts to fisheries are insignificant and, therefore, no, EM&A programme designed specifically to assess impacts on commercial fisheries resources is required.

 

12.11           References

 

AFCD (1998). Port Survey 96/97. Agriculture, Fisheries and Conservation Department, Hong Kong Government of the SAR.

 

AFCD (2001). Consultancy Study on Fisheries and Marine Ecological Criteria for Impact Assessment. Agriculture, Fisheries and Conservation Department, Hong Kong Government of the SAR.

 

ERM (1998). Fisheries Resources and Fishing Operations in Hong Kong Waters. Prepared for AFCD.

 

Hyder (1998).  Supplement EIA for the Proposed Sand Extraction from the Brothers Marine Borrow Area. Prepared for CED.

 

Jefferson TA (2000). Population biology of the Indo-Pacific Hump-backed dolphin in Hong Kong waters. Wildlife Monographs 144, 1-65.

 

Mouchel (2001a). Environmental Monitoring and Audit for Contaminated Mud Pit IV at East Sha Chau. First Quarterly Report, May to July 2001. Prepared for CED.