¨ 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.
¨ 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.
¨ 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).
12.3.2.1 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.
12.3.3.1 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).
12.3.4.1 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).
Loss of
Seabed Habitat
Suspension
of Sediments
Direct Impacts
¨ 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
¨ 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.
Suspension
of Contaminated Sediments
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.
12.6.2.1 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.
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. |
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.