|
Consultancy Ref.: AFCD/FIS/02/19 Consultancy Service
for Environmental Impact Assessment Study for Designation of New Fish Culture
Zones Environmental
Impact Assessment (EIA) Report for Establishment of Fish Culture Zone at Mirs
Bay November
2022 |
This Section presents the findings of the marine ecological impact assessment
associated with the construction and operation of the Project. It also summarises the key findings on the
baseline ecological conditions, the details of which are presented in Appendices 4A to 4C.
The criteria and scope
for evaluating marine ecological impacts are laid out in the
Annexes 8 and 16 of the EIAO-TM and
the Study Brief. Legislative
requirements and evaluation criteria relevant to this assessment are listed
below. The details on each are presented
in Appendix 4A.
n
Marine Parks Ordinance (Cap.
476);
n
Wild Animals Protection
Ordinance (Cap. 170);
n
Protection of Endangered
Species of Animals and Plants Ordinance (Cap. 586);
n
Country Parks Ordinance (Cap.
208);
n
Town Planning Ordinance (Cap.
131);
n
Environmental Impact
Assessment Ordinance (Cap. 499) and the Technical Memorandum on Environmental
Impact Assessment Process under the Environmental Impact Assessment Ordinance
(EIAO-TM);
n
Environmental Impact
Assessment Ordinance (EIAO) Guidance Notes No. 6/2010, 7/2010 and 11/2010;
n
Hong Kong Planning Standards
and Guidelines Chapter 10 (HKPSG);
n
United Nations Convention on
Biodiversity (1992); and
n
Peoples’ Republic of China
(PRC) Regulations and Guidelines.
In accordance with Clause 3.4.4.2
of the Study Brief, the Assessment Area for marine ecological impact assessment
(Figure
B1.1 of Appendix 4B) shall be the
same as the assessment area for Water Quality Impact Assessment covering the
Mirs Bay Water Control Zone (WCZ) and the Tolo Harbour and Channel WCZ. Detailed description of the physical
characteristics of the marine environment of the Assessment Area and compliance
of WQOs is provided in Section 3.
Marine ecological
important habitats and species within and in the vicinity of the Project site
as well as within the Assessment Area are evaluated, including existing marine
parks, horseshoe crab breeding and nursery grounds, mangroves, seagrass beds,
coral communities, marine benthos of conservation interest, and marine
ecological important species including Finless Porpoises (FPs), amphioxus and
horseshoe crabs. The marine ecological
profiles and characteristics of these habitats and species are described in
further details below. A habitat map on
the marine ecology of the Assessment Area is provided in Figure 4A.2.1 of
Appendix 4A.
A literature review was conducted to review the baseline marine
ecological conditions within the Assessment Area and to identify information
gaps to determine whether field surveys are required to provide sufficient
information for the marine ecological impact assessment. Findings of this literature review are
presented in detail in Appendix 4A.
Some of the baseline information was collected recently and is
considered to be up-to-date and representative of the existing conditions of
the Assessment Area. In accordance with
the requirements in Appendix C of the Study Brief, field surveys at selected
habitats within the Assessment Area where potential impact could occur and
up-to-date baseline information is not present were conducted to fill the
identified data gaps, verify and update the latest marine ecological conditions
of these habitats. The methodology for
the field surveys is presented in Appendix
4B. Field survey findings
are presented in detail in the following sections.
Marine
ecological surveys were conducted in Mirs Bay in accordance to the methodology
as stated in Appendix 4B. Surveys
were conducted from September 2020 to February 2021 and the details are
summarised in Table 4.1.
Table 4.1 Marine
Ecological Baseline Surveys
|
Survey |
Season & Date |
|
Subtidal Benthos Survey |
Wet Season: 25 Sep 2020, 19 Oct 2020 Dry Season: 21 Jan 2021, 1 Feb
2021 |
|
Coral Survey |
19 Nov 2020, 23 Nov 2020 |
|
Drop Camera Survey |
18 Dec 2020 |
A total of 1,625 individual organisms were
collected from the fourteen grab samples from Mirs Bay during the wet season
survey. Locations of sampling stations
MB11, MB12 and MB14 have been revised during the survey as the originally
proposed sampling locations consisted of mostly rocky substrate and sampling
was unable to be conducted at those sites.
The revised locations are provided in the updated Figure B2.3 of Appendix 4B. The specimens belong to 8 Phyla with a total of 12 classes, 77 families and 115 species identified.
Table 4.2 provides a summary
on the abundance, biomass, taxonomic richness, Pielou’s Evenness and Shannon
Diversity of infauna collected at each location. A complete set of raw data is presented in Table
4C.1 of
Appendix 4C.
Results of the wet season
survey showed that infaunal abundance, biomass and taxonomic richness (here
represented by number of families and species of infaunal organisms) were low
in general compared to dry season (Table 4.2
and Table 4.3). In terms of infaunal abundance, the majority
(~73%) of
organisms recorded were from the Phylum Annelida. The polychaete worm, Cirriformia sp. was the
most abundant species (total abundance = 173 individuals).
The Amphioxus, Branchiostoma
belcheri, was recorded in the survey at Stations MB9, MB12 and MB14 (total
abundance = 64, 3 and 8 individuals respectively), with MB9 recorded with the
highest abundance. In terms of infaunal
biomass, organisms from the Phylum Mollusca contributed ~54% of the total biomass recorded,
while organisms from Annelida
also contributed significant biomass (~25%).
The high biomass of Mollusca
was contributed by a number of species,
primarily by a bivalve species, Paratapes
undulatus.
A total of 2,387 individual organisms were
collected from the fourteen grab samples during the dry season survey. The specimens belong to 9 Phyla with a total of 16 classes, 88 families and 125 species identified. Table 4.3
provides a summary on the abundance, biomass and taxonomic richness of infauna
collected at each location. A complete
set of raw data is presented in Table
4C.2 of Appendix 4C.
Results of the dry season
survey showed that infaunal abundance, biomass and taxonomic richness (here represented
by number of families and species of infaunal organisms) were relatively high
comparing to wet season (Table 4.2
and Table 4.3). In terms of infaunal abundance, the majority
of organisms recorded were from the Phyla Annelida and Arthropoda (~59% and
~25% respectively). The polychaete worm,
Micronephtys sphaerocirrata was the
most abundant species (total abundance = 287 individuals).
Three species of Amphioxus were recorded, with Branchiostoma belcheri recorded at Stations MB9 and MB14 (total
abundance = 34 and 3 individuals respectively); Branchiostoma japonicum recorded at Station MB9 (total abundance =
3 individuals); and Branchiostoma
malayanum recorded at Station MB9 (total abundance = 5 individuals). In terms of infaunal biomass, organisms from
the Phylum Mollusca contributed ~32% of the total biomass recorded, while
organisms from Phyla Annelida and Echinodermata also contributed significant
biomasses (~26% & ~25% respectively).
The high biomass of Mollusca was contributed by a number of species,
primarily by a bivalve species, Modiolus
nipponicus.
Table
4.2 Density and Indices of Richness, Evenness and
Diversity of Infaunal Assemblages at the Sampling Locations for the Soft Bottom
Habitat Surveys at the Assessment Area during the Wet Season
|
Station |
Number
of Infaunal Individuals |
Number
of Individuals per m2 |
Taxonomic
Richness (No. Families) |
Taxonomic
Richness (No. Species) |
Pielou’s
Evenness (J)(Note1) |
Shannon
Diversity (H’) |
Total
Biomass (g wet weight) |
Mean
Biomass per Individual (g wet weight) |
|
MB1 |
75 |
781.25 |
18 |
22 |
0.84 |
2.59 |
0.509 |
0.007 |
|
MB2 |
31 |
322.92 |
12 |
14 |
0.85 |
2.25 |
1.126 |
0.036 |
|
MB3 |
57 |
593.75 |
22 |
26 |
0.88 |
2.88 |
0.623 |
0.011 |
|
MB4 |
53 |
552.08 |
14 |
17 |
0.78 |
2.22 |
1.176 |
0.022 |
|
MB5 |
40 |
416.67 |
10 |
14 |
0.86 |
2.26 |
0.572 |
0.014 |
|
MB6 |
71 |
739.58 |
19 |
22 |
0.83 |
2.57 |
0.668 |
0.009 |
|
MB7 |
77 |
802.08 |
15 |
18 |
0.80 |
2.30 |
0.964 |
0.013 |
|
MB8 |
60 |
625.00 |
15 |
18 |
0.78 |
2.27 |
0.648 |
0.011 |
|
MB9 |
178 |
1854.17 |
26 |
33 |
0.68 |
2.38 |
2.023 |
0.011 |
|
MB10 |
122 |
1270.83 |
17 |
24 |
0.81 |
2.57 |
0.703 |
0.006 |
|
MB11 |
62 |
645.83 |
17 |
21 |
0.91 |
2.76 |
9.655 |
0.156 |
|
MB12 |
406 |
4229.17 |
45 |
55 |
0.83 |
3.31 |
1.380 |
0.003 |
|
MB13 |
229 |
2385.42 |
29 |
36 |
0.84 |
3.02 |
0.463 |
0.002 |
|
MB14 |
164 |
1708.33 |
35 |
40 |
0.90 |
3.33 |
1.917 |
0.012 |
Table
4.3 Density and Indices of Richness, Evenness and
Diversity of Infaunal Assemblages at the Sampling Locations for the Soft Bottom
Habitat Surveys at the Assessment Area during the Dry Season
|
Station |
Number
of Infaunal Individuals |
Number
of Individuals per m2 |
Taxonomic
Richness (No. Families) |
Taxonomic
Richness (No. Species) |
Pielou’s
Evenness (J) |
Shannon
Diversity (H’) |
Total
Biomass (g wet weight) |
Mean
Biomass per Individual (g wet weight) |
|
MB1 |
163 |
1697.92 |
31 |
38 |
0.88 |
3.22 |
3.2290 |
0.0198 |
|
MB2 |
141 |
1468.75 |
36 |
40 |
0.82 |
3.03 |
3.0586 |
0.0217 |
|
MB3 |
96 |
1000.00 |
30 |
38 |
0.91 |
3.30 |
2.8809 |
0.0300 |
|
MB4 |
76 |
791.67 |
25 |
33 |
0.89 |
3.12 |
0.6077 |
0.0080 |
|
MB5 |
57 |
593.75 |
19 |
24 |
0.92 |
2.92 |
0.3649 |
0.0064 |
|
MB6 |
57 |
593.75 |
20 |
24 |
0.87 |
2.76 |
2.9004 |
0.0509 |
|
MB7 |
71 |
739.58 |
23 |
27 |
0.83 |
2.75 |
0.4876 |
0.0069 |
|
MB8 |
67 |
697.92 |
19 |
24 |
0.81 |
2.57 |
2.5117 |
0.0375 |
|
MB9 |
73 |
760.42 |
14 |
18 |
0.71 |
2.05 |
1.7663 |
0.0242 |
|
MB10 |
126 |
1312.50 |
17 |
25 |
0.83 |
2.66 |
1.2002 |
0.0095 |
|
MB11 |
144 |
1500.00 |
31 |
41 |
0.88 |
3.29 |
1.3807 |
0.0096 |
|
MB12 |
244 |
2541.67 |
25 |
35 |
0.72 |
2.57 |
2.2077 |
0.0090 |
|
MB13 |
448 |
4666.67 |
32 |
40 |
0.74 |
2.72 |
1.2582 |
0.0028 |
|
MB14 |
624 |
6500.00 |
57 |
70 |
0.83 |
3.54 |
10.9179 |
0.0175 |
During
the surveys, the weather was fine and the sea was calm. The visibility was however poor and generally
ranged between 0.5 m and 2 m. The
general substrata and biological conditions noted along each transect during
the qualitative spot dive reconnaissance check are presented in Table 4.4.
Table 4.4 Description
of the Seabed Recorded along Each Transect during the Qualitative Surveys (Spot
Dive Reconnaissance Check Surveys)
|
Transect |
Depth |
Description |
|
T1 |
-3 to - 7 mCD |
The seabed was mainly composed of boulders and bedrock in shallow
water (-3 to - 4 mCD) and deep water (-5 to -7 mCD). Sparse colonies of hard corals, such as Acropora solitaryensis, Montipora
peltiformis and Plesiastrea versipora were recorded in shallow and deep waters. Sparse octocorals, such as Dendronephthya sp., and black corals, Antipathes curvata and Cirripathes sp. were identified in deep water. |
|
T2 |
-3 to -7 mCD |
The seabed was mainly composed of boulders and bedrock in shallow
water (-3 to - 4 mCD) and deep water (-5 to -7 mCD). Sparse colonies of hard corals, such as Porites sp. and Plesiastrea versipora were recorded at shallow and deep waters. |
|
T3 |
-3 to -6 mCD |
The seabed mainly was composed of boulders in shallow water (-3 to -4
mCD), and was mainly composed of bedrock in deep water (-5 to -6 mCD). Sparse colonies of hard corals, such as Porites sp. was observed to be more
commonly observed in deep water than at shallow water. |
|
T4 |
-3 to -6 mCD |
The seabed mainly composed of boulders and sand in shallow water (-3
to -4 mCD), and was dominated by sand in deep water (-5 to -6 mCD). Sparse colonies of hard corals, such as, Porites sp. was commonly observed at
shallow water. Other hard corals, such
as Cyphastrea chalcidicum, Favites chinensis and Plesiastrea versipora were observed at shallow and deep waters. |
|
T5 |
-3 to -6 mCD |
The seabed mainly composed of boulders in shallow water (-3 to -4
mCD), with a mixture of sand and rocks in deep water (-5 to -6 mCD). Sparse colonies of hard corals, such as, Porites sp. was commonly observed at
shallow and deep waters. |
Transects
are located at the natural shores of East of Tap Mun and Sai Kung East Country
Park at Mirs Bay (T1, T2, T3, T4 & T5) (Figure B2.1 of Appendix 4B). The site
mainly comprised of large boulders, bedrock and sand. On the hard substrata, sessile benthos
primarily comprised of encrusting sponges and isolated barnacles. At most transects, relative low coverage of
hard coral colonies (<5% - 10%) and low to moderate coverage of other
benthos (<5% - 30%), such as sea anemones, zoanthids and sponges were
identified (Table 4C.3 of Appendix 4C).
A total of thirty-three hard coral species, one species of octocoral, two black coral
species, five species of sea anemones, three algae species and species of
zoanthid, sponges, bryozoan and ascidian species were identified (Table 4C.4 of Appendix 4C). The majority of coral recorded were common
and widespread species in Hong Kong, such as hard corals Montipora peltiformis, Plesiastrea
versipora and Porites sp.. Small amount of soft coral Dendronephthya sp., black corals Antipathes curvata and Cirripathes sp. were recorded at deep
water of transect T1. Other corals and
benthos were present in isolated colonies.
Representative photos of the seabed and coral conditions during the
surveys are presented in Figure 4.1.
Overall, results of the dive surveys indicated that the subtidal hard substrate of the Assessment Area showed moderate amount of sessile taxa. Common and widespread hard corals were recorded in low percentage coverage (<5% - 10 %). Scarce octocorals and black corals were recorded at the deeper water of one of the sites (transect T1).
Drop camera surveys were
carried out at Mirs Bay at the survey locations presented in Figure B2.1 of Appendix 4B. A total of
sixteen stations were surveyed within the Project site with the use of a drop
camera system to record the benthic attributes by positioning the system ~1 m
above the seabed. The results showed
that the seabed at the survey locations (~-16 mCD) dominated by silty mud with
no hard substrate or benthic organism recorded, except for sites MB1, MB12 and
MB16. The seabed at MB1 was dominant with
silty mud and rocks with sparse coverage of hard corals and gorgonians; at
location MB12, a fish was observed on silty mud; and at MB16, the seabed
consisted of a mixture of sand and rocks with low coverage of hard corals. Representative photographs are presented in Figures
4.2a to 4.2d.
The key findings of the
literature review and field surveys are summarised below.
Recognised sites of conservation
importance within the Assessment Area include Country Parks, Marine Park and Sites of Special Scientific Interest (SSSI). No Special Area is located within the
Assessment Area. Some of these that are
relevant to marine ecology and are located in the Assessment Area are discussed
below.
The existing country parks in
the Assessment Area include the Sai
Kung East Country Park, Sai Kung West Country Park and Sai Kung West Country
Park (Wan Tsai Extension). However, as
all three country parks are of terrestrial conservation interest, it
is considered that the impact of the Project on these country parks are not
anticipated. Locations of the country
parks are provided in Figure 4A.2.1 of Appendix
4A ([1]).
Hoi Ha Wan Marine Park (HHWMP) is
the marine park within the Assessment Area.
No proposed or potential marine parks are identified within the
Assessment Area. Details of the HHWMP
are provided in Table 4A.2.1 of Appendix 4A. The location of the HHWMP is provided in Figure
4A.2.1 of Appendix 4A ([2]).
The SSSI which is considered
relevant to the marine works of the Project is the Hoi
Ha Wan SSSI. Details of
Hoi Ha Wan SSSI are provided in Table 4A.2.1 of Appendix 4A.
The location of the Hoi Ha Wan SSSI is provided in Figure
4A.2.1 of Appendix 4A ([3]).
According to
the latest AFCD Marine Mammal Monitoring Report 2021/22, no records of Hong
Kong’s resident marine mammal species, the Finless Porpoise, Neophocaena phocaenoides and the Chinese
White Dolphin (CWD) Sousa chinensis
were reported in the Assessment Area. Considering the Project site located at the northeastern waters
in Mirs Bay while CWDs in Hong Kong are mainly distributed at western and
southwestern Lantau waters and FPs are mostly distributed in the southern and
eastern waters of Hong Kong, the impact to marine mammals from the Project is
therefore not anticipated. The distribution of FPs in Hong Kong waters is provided in
Figure 4A.2.4 of Appendix 4A ([4]).
Two species of horseshoe
crab, Tachypleus tridentatus and Carcinoscorpius rotundicauda, have previously
been recorded around Hong Kong waters.
Based on the abundance of juveniles, Luk Keng and Sha Tau Kok are
identified as the key nursery grounds for C.
rotundicauda and T. tridentatus. Adult horseshoe crabs are not recorded in the
northeastern waters of Hong Kong. The
nearest records of occurrence were from the beaches in Lai Chi Wo in YCTMP
which is out of the Assessment Area, therefore, the impact of the Project on horseshoe crabs is not
anticipated.
Four mangrove stands are found in
the Mirs Bay FCZ and one mangrove stand is found in the Tolo Harbour and
Channel WCZ within the Assessment Area.
No mangrove stands were found at the Project site. The nearest mangrove stand from the Project
site is located at Chek Keng and Ham Tin Wan which are 3.1 km away
(Figure 4A.2.1 of Appendix 4A). These sites are considered to be far away
from the Project site and the impact of the Project on mangroves is therefore
not anticipated. Locations
of the mangroves are provided in Figure 4A.2.1 of Appendix 4A
([5]).
Coral
communities in the eastern waters of Hong Kong generally have a higher
diversity and abundance as the surrounding marine environment is less
influenced by the Pearl River outflow compared to the western waters of Hong
Kong with lower salinity and higher turbidity ([6]). Literatures have reported that hard coral,
octocoral and black coral were recorded within the Assessment Area, with a wide
range of hard coral coverage recorded in HHWMP (10- 50% to >50%) and in Port
Island (Chek Chau) (30-75%) in some early studies. Recent surveys including those conducted
during Reef Check 2021 have also recorded an average coral coverage of 50% at
Hoi Ha Wan and 19.3% in Port Island. Locations of the coral communities are provided in Figure 4A.2.1 of Appendix 4A
([7]) ([8]) ([9]).
Results of the
Feasibility Study of this Project has revealed that coral communities were
mostly sparse with low coverage (<5%), except from one deep water transect
with 11 – 30% coral coverage. A total of
35 hard coral species, six octocoral species and
three black coral species were identified in Mirs Bay
during these surveys. The species
identified during the survey were generally regarded as common and widespread
species in Hong Kong waters, such as hard corals Hydnophora exesa, Pavona decussata, and Plesiastrea versipora. Some
uncommon corals were also identified, including Acropora
digitifera, Acropora pruinosa, Acropora solitaryensis, Cyphastrea chalcidicum,
Favites flexuosa, Psammocora haimiana, Montipora mollis and Astrea curta. A survey site within Nam
She Wan has been previously identified to have high
ecological concern due to the presence of relatively high hard coral diversity
and / or relatively high
octocoral and black coral abundance and diversity.
Field surveys were
conducted to fill in the information gap of the Feasibility Study, with
findings showing that the majority of corals recorded were common and
widespread species in Hong Kong, including hard corals Montipora
peltiformis, Plesiastrea versipora and Porites sp.. Small amount of soft coral Dendronephthya
sp., black corals Antipathes curvata and Cirripathes sp. were
recorded at deep water of transect T1.
Overall, the surveyed areas showed low coral coverage (<5% - 10%) and moderate amount of sessile
taxa on the subtidal hard substrate. Results of drop camera survey showed that the
seabed of this site (~-16 mCD) was dominated by silty mud with sparse coral
coverage at two surveyed locations.
Amphioxus
are mostly present within Hong Kong’s eastern waters, with densities ranging
from 10 to 400 ind/ m2 predominantly at sites in Tai Long Wan, Nam
She Wan, Long Ke Wan and Pak Lap Wan off the Sai Kung Peninsula ([10]).
However, no studies have been conducted at the Project site previously. Field surveys were conducted to fill in this
information gap. The baseline subtidal
benthos survey reported that three species of amphioxus were found at the Project
site, including Branchiostoma belcheri found in both wet and dry seasons, and two other species
Branchiostoma japonicum and Branchiostoma malayanum were found
during dry season only. The
sampling Station MB9 in particular was found to have high density of amphioxus
during both seasons (results refer to Section 4.3.2.2).
Other intertidal and subtidal benthos species reported
in the Assessment Area from the field surveys and literature review are common
and widespread in Hong Kong with no species of conservation importance. As the
Project site is located away from the shorelines, the assessment on intertidal
hard bottom assemblages is considered not necessary. Potential marine ecological impact would
occur mostly on the subtidal environment and the impact on intertidal habitats
is not anticipated.
There are studies
which showed that benthic communities at northeastern waters, Tolo Channel and
western Mirs Bay which overlaps with the Assessment Area are impoverished. None of these species is unique to a particular
location of the Assessment Area, and many of these species were also reported
elsewhere in Hong Kong waters. Seagrass (Halophila
minor), with high
ecological value was reported to be present
at To Kwa Peng, however, as it is located at 3.9 km away from the Project site,
the impact of the Project on the seagrass is therefore not anticipated. Location of the seagrass bed
is provided in Figure 4A.2.1 of Appendix 4A ([11]).
Findings of white-bellied
sea eagle (WBSE) was spotted on Port Island and Tsim Chau within the Assessment
Area, located at 2.7 km and >4 km and away from the Project site
respectively. It was reviewed from
literature and previous field surveys that the species is uncommon but
widespread in Hong Kong. As the nesting
grounds of WBSE is far away from the Project site and that the foraging
distance generally reaches 2 km from their nesting location, the impact of the Project on the WBSE is therefore not anticipated. Locations
of the WBSE nesting grounds are provided in Figure 4A.2.1 of Appendix 4A
([12]).
The existing conditions of the
marine ecological habitats and resources within the Assessment Area have been
assessed. These baseline conditions have
been based on available literature and, where considered necessary, focused
field surveys and data review to update and supplement the data. Based on this information presented in Section 4.3.2, Section 4.3.3, Appendices 4A and 4C the ecological importance of each habitat has been determined
according to the EIAO-TM Annex 8
criteria.
Within the Assessment Areas
(mainly marine ecology) of this EIA, which covers quite a large areal extent,
variations in the ecological characteristics of habitats across different
locations (which are kilometres apart) are likely to be present. To provide information of key relevance to
the marine ecological assessment, the ecological importance of habitats
presented in this baseline is therefore primarily focused on the vicinity of
the works areas of the Project site.
The ecological importance of
the habitats was determined through reference to the following:
n
Literature review;
n
Findings of the field surveys;
n
Comparison with other areas in
Hong Kong; and
n
Annexes 8 and 16 of the EIAO-TM.
Outcomes of the evaluation of
ecological importance of the marine habitats and species within the Assessment
Areas are presented in Tables 4.5 to 4.9.
Table 4.5 Marine Ecological Importance of Existing Marine
Parks and SSSI within the Assessment Area
|
Criteria |
Hoi
Ha Wan Marine Park (HHWMP) |
Hoi
Ha Wan SSSI |
|
Naturalness |
Natural intertidal and subtidal hard and
soft bottom habitat and marine waters |
Natural intertidal and subtidal hard and
soft bottom habitat and marine waters |
|
Size |
~260 ha |
~278 ha |
|
Diversity |
Moderate |
Moderate |
|
Rarity |
Habitat and species are uncommon in the
northeastern water of Hong Kong. Species
of conservation importance including numerous species of hermatypic hard
coral, ahermatypic cup coral, black coral, and octocoral |
Habitat and species are uncommon in the
northeastern water of Hong Kong.
Species of conservation importance including numerous species of
hermatypic hard coral, ahermatypic cup coral, black coral, and octocoral |
|
Re-creatability |
Not re-creatable |
Not re-creatable |
|
Fragmentation |
Unfragmented |
Unfragmented |
|
Ecological Linkage |
Linked to the intertidal and subtidal
habitats |
Linked to the intertidal and subtidal
habitats. |
|
Potential Value |
Already designated as marine park |
Already designated as a SSSI |
|
Nursery / Breeding Area |
Nursery grounds for juvenile of fishes and
other marine invertebrates |
Nursery grounds for juvenile of fishes and
other marine invertebrates |
|
Age |
Designated as marine park in July 1996 |
Designated as SSSI in January 1989 |
|
Abundance |
Historically high abundance of hard
coral. Old coral colonies and regarded
as location of considerable carbonate accumulation |
Historically high abundance of hard
coral. Old coral colonies and regarded
as location of considerable carbonate accumulation |
|
Ecological
Importance |
High |
High |
Table
4.6 Ecological
Importance of Intertidal Habitats within
and in the vicinity of the Project site
|
Criteria |
Soft
Bottom Intertidal Habitat |
Hard
Bottom Intertidal Habitat |
Artificial
Intertidal Habitat |
|
Naturalness |
Natural habitat |
Natural habitat |
Artificial |
|
Size |
Small, only small patches of sandy shore
recorded |
Large, majority of the shoreline within
and in the vicinity of the Project
site |
Small, comprise of small piers and seawall |
|
Diversity |
Low |
High |
Low |
|
Rarity |
Ghost crab (Ocypode cordimana, previously known as Ocypode cordimanus), oligochaete worms (Heronidrilus bihamis) and fiddler crabs (Uca lactea) were
recorded. No rare species found |
Common rocky shore flora and fauna were
recorded e.g. bivalve Perna viridis,
and short-spined sea urchin Heliocidaris
crassispina |
Not surveyed in the literature reviewed, it
is assumed that the assemblages comprise common
and widespread intertidal species in Hong Kong
like Barnacle Balanus
amphitrite, Bivalve Grafrarium
pectinatum, and snails Nassarius
festivus, Monodonta labio, Batillaria multiformis, B. zonalis |
|
Re-creatability |
Re-creatable; substrata may be re-colonised
by intertidal and subtidal organisms |
Not re-creatable |
Re-creatable; substrata may be re-colonised
by intertidal and subtidal organisms |
|
Fragmentation |
Fragmented |
Unfragmented |
Fragmented |
|
Ecological Linkage |
Not functionally linked to any high value
habitat in a significant way |
Not functionally linked to any high value
habitat in a significant way |
Not functionally linked to any high value
habitat in a significant way |
|
Potential Value |
Unlikely to become an area of conservation
value |
Unlikely to become an area of conservation
value |
Unlikely to become an area of conservation
value |
|
Nursery / Breeding Area |
No significant records identified |
No significant records identified |
No significant records identified |
|
Age |
N/A |
N/A |
N/A |
|
Abundance |
Lower abundance compared to natural rocky
shore habitat |
Low abundance |
Lower abundance compared to natural rocky shore
habitat |
|
Ecological
Importance |
Low |
Low |
Low |
Table 4.7 Ecological
Importance of Subtidal Hard-Bottom Habitats within and in the vicinity of the
Project site
|
Criteria |
Mirs
Bay |
West of Tap Mun |
West of
Port Island |
Hoi Ha Wan Marine Park and SSSI |
|
Naturalness |
Natural |
Natural |
Natural |
Natural |
|
Size |
Large. About 4.8 km across waters between Kung Chau and Nam She Wan. |
Large. The natural rocky shore at Outer tap Tap Mun
is about 1.5 km in length. |
Large. The natural rocky shore at the West of Port
island is about 1 km in length. |
~260 ha for marine park and 278 ha for SSSI |
|
Diversity |
Moderate |
Low
|
Low
to Moderate |
High |
|
Rarity |
Assemblages comprise typical common and widespread species in Hong
Kong, except for some uncommon coral species
identified. Coral communities of high
ecological concern identified at Nam She Wan. |
Assemblages mainly comprise typical
common and widespread species in Hong Kong, except for some uncommon coral species identified.
Coral communities of high ecological concern were identified at the
mid of west shore of Tap Mun in the vicinity of this site |
Assemblages is
considered to mainly comprise typical common and widespread species in Hong
Kong, except Montipora mollis |
Habitat and species are uncommon in the
northeastern water of Hong Kong.
Species of conservation importance including numerous species of
hermatypic hard coral, ahermatypic cup coral, black coral, and
octocoral. |
|
Re-creatability |
Not re-creatable |
Not re-creatable |
Not
re-creatable |
Not re-creatable |
|
Fragmentation |
Unfragmented |
Unfragmented |
Unfragmented |
Unfragmented |
|
Ecological Linkage |
Functionally linked to amphioxus habitat at Nam She Wan |
Not functionally linked to any high value habitat in a significant
way. |
Not functionally linked to any high value
habitat in a significant way |
Not functionally linked to any high value habitat
in a significant way |
|
Potential Value |
Habitat is relatively undisturbed which might exhibit some potential
value. |
One particular site at the mid of
west shore of Tap Mun has higher hard coral coverage which exhibit higher
ecological value. |
Habitat has some potential value for a few
uncommon coral species |
Already designated as marine park and SSSI |
|
Nursery / Breeding Area |
No significant records identified |
No significant records identified |
No significant records identified |
Nursery grounds for juvenile of fishes and other
marine invertebrates |
|
Age |
N/A |
N/A |
N/A |
Designated as marine park in July 1996 and as
SSSI in January 1989 |
|
Abundance |
Low coverage of coral is present in general with higher coral coverage
identified near shores at Nam She Wan |
Low coverage of coral is present in
general, except at the mid of west shore of Tap Mun where higher coral
coverage was recorded |
Moderate to high hard coral cover was recorded in literatures, however, low coverage of coral is recorded in recent
studies |
Historically high abundance of hard coral. Old
coral colonies and regarded as location of considerable carbonate
accumulation |
|
Ecological
Importance |
Low to Moderate |
Low to Moderate |
Low to Moderate |
High |
Table 4.8 Ecological Importance of Subtidal Soft
Benthos Assemblages within the Project site
|
Criteria |
Mirs Bay (between Kung Chau and
Nam She Wan) |
|
Naturalness |
Natural |
|
Size |
<410 ha |
|
Diversity |
Moderate |
|
Rarity |
The assemblages are typical of similar habitats in the Hong Kong
waters, which are dominated by polychaetes.
Some locations are recorded with amphioxus. |
|
Re-creatability |
Re-creatable; substrata may be recolonised by
benthic organisms |
|
Fragmentation |
Unfragmented |
|
Ecological Linkage |
Functionally linked to amphioxus habitat at Nam
She Wan |
|
Potential Value |
Amphioxus habitat is present within the Project
site. One sampling location exhibit
potential value due to the high density of amphioxus recorded. |
|
Nursery / Breeding Area |
No significant records identified |
|
Age |
N/A |
|
Abundance |
The assemblages are of moderate to high
abundance and biomass. High density of amphioxus was recorded at
one of the benthic sampling stations and low density of amphioxus was
recorded at two of the benthic sampling stations. |
|
Ecological
Importance |
In
general low; moderate at specific locations with amphioxus habitat. |
Table 4.9 Ecological
Importance of Marine Waters
|
Criteria |
Waters in Mirs Bay and in the vicinity |
|
Naturalness |
Natural |
|
Size |
~410 ha |
|
Diversity |
Potential sighting of FP but rarely present |
|
Rarity |
FP is a resident species in Hong Kong. Commonly observed in eastern
waters but not in northeastern waters of Hong Kong |
|
Re-creatability |
Not re-creatable |
|
Fragmentation |
Unfragmented. |
|
Ecological Linkage |
Linked to FP and marine habitat nearby |
|
Potential Value |
It is unlikely that the habitat could develop conservation importance |
|
Nursery / Breeding Area |
No significant records identified |
|
Age |
N/A |
|
Abundance |
Very low density of FP in comparison to other waters of Hong Kong |
|
Ecological
Importance |
Low |
In accordance with EIAO-TM
Annex 8 criteria, an evaluation of species of conservation importance
recorded from the Assessment Area is presented in Table 4.10.
Table
4.10 Species
of Conservation Importance within the Assessment Area
|
Common Name |
Scientific Name |
Protection Status |
Distribution, Rarity and Other Notes |
Literature |
Surveys |
Recorded Location |
|
Hard
Coral (>40
spp.) |
Duncanopsammia peltata Oulastrea crispata Porites sp., Acropora spp, Cyphastrea chalcidicum, Favites
flexuosa, Psammocora haimiana, Montipora mollis and Astrea curta, etc. |
Protection of Endangered
Species of Animals and Plants Ordinance (Cap.586) |
Majority
being common and widely distributed in the eastern waters of Hong Kong, with
some uncommon species |
ü |
ü |
In the vicinity of the Project site and throughout northeastern waters
of Hong Kong, such as Port Island located at 2.7 km from the Project site |
|
Black
corals |
Antipathes
curvata, Cirripathes sinensis, Antipathes sp., Cirripathes sp. |
Protection of
Endangered Species of Animals and Plants Ordinance (Cap.586) |
Common
but sparsely distributed in the north-eastern waters of Hong Kong |
ü |
ü |
In
the vicinity of the Project site and throughout northeastern waters of Hong
Kong, e.g. Port Island, Shek Ngau Chau,
Breaker
Reef and Gruff Head
|
|
Cup
Coral |
Balanophyllia sp., Tubastrea / Dendrophyllia sp. |
Protection of
Endangered Species of Animals and Plants Ordinance (Cap.586) |
Common
and widely distributed in Hong Kong, especially in western waters |
ü |
|
Present at West of Tap Mun, Shek Ngau Chau and Breakers Reef located at ~1.8 km, ~4 km and ~4 km from the Project site
respectively |
|
Amphioxus
|
Branchiostoma belcheri, Branchiostoma japonicum and Branchiostoma malayanum |
Listed
as “Grade II National Key Protected Species” in China Listed as
“Endangered” in the China Species Red List |
Recorded
from across Hong Kong waters, but major records were found in eastern waters |
ü |
ü |
Mostly
present within Hong Kong’s eastern waters, present at the Project site within
Nam She Wan and >3 km away at Tai
Long Wan |
|
Seagrass |
Halophila minor |
Considered as
important habitats in Environmental Impact Assessment Ordinance |
Uncommon / rare in Hong Kong. |
ü |
|
Mainly in To Kwa Peng, 3.9 km from Project
site |
|
White-bellied
Sea Eagle |
Haliaeetus
leucogaster |
Listed
in Wild Animals Protection Ordinance (Cap. 170) Listed
in Protection of Endangered Species of Animals and Plants Ordinance (Cap.
586) Class II
Protected Animal of PRC Listed
as Regional Concern in Fellowes et al. (2002) |
Uncommon
resident. Widely distributed in coastal areas throughout Hong Kong |
ü |
|
Nesting ground located at
Port Island and Tsim Chau, at 2.7 km and >4 km away from the Project site
respectively |
Based on the review of available
information within the Assessment Area, marine ecological sensitive receivers
have been identified in accordance with the EIAO-TM
criteria. These sensitive receivers and
their distance from the Project site are listed in Table 4.11. Locations
of sensitive receivers can be referred to Figure
4A.2.1 of Appendix 4A.
Table 4.11 Approximate
Shortest Distance to Marine Ecological Sensitive Receivers (SRs) around the
Project site
|
|
Name |
Shortest Separation
(Geodesic) Distance (km) |
|
Coral |
Port Island (CR3) |
3.1 |
|
Shek Ngau Chau (CR4) |
4.0 |
|
|
Hoi Ha Wan Moon Island (CR13) |
4.1 |
|
|
Hoi Ha Wan Coral Beach (CR14) |
4.0 |
|
|
Heung Lo Kok (CR16) |
4.9 |
|
|
Mangrove Stand / Intertidal Habitat |
Hoi Ha Wan (M6) |
4.5 |
|
Tai Tan (M7) |
3.7 |
|
|
To Kwa Peng (M8) |
3.9 |
|
|
Chek Keng (M9) |
3.1 |
|
|
Ham Tin Wan (M10) |
3.1 |
|
|
Designated Marine Park |
Hoi Ha Wan Marine Park and Artificial Reef
within the Marine Park (MP2) |
3.2 |
|
Artificial Reef |
Long Harbour (AR1-AR6) |
1.8 |
|
Designated SSSI |
Hoi Ha Wan SSSI (SSSI1) |
3.3 |
The Method Statement on Marine Ecological Impact Assessment for Mirs Bay
Fish Culture Zone under this assignment was approved on 12 October 2020 and is presented
in Appendix 4B. A desktop
literature review and supporting field surveys were conducted in order to
establish the ecological profile of the area within and surrounding the
Project. The importance of
potentially-impacted marine ecological resources identified within the
Assessment Areas was evaluated using the methodology defined in the EIAO-TM.
Potential impacts to these resources due to the construction
and operation of the Project were assessed (following the EIAO-TM Annex 16 guidelines)
and the impacts evaluated (based on the criteria in EIAO-TM Annex 8). Findings of water quality modelling are used,
where appropriate, to assess potential impacts on the identified marine
ecological resources.
The construction of the proposed
Project will mainly involve the setup of fish farm structures, including fish
rafts / cages, auxiliary facilities and mooring system. No dredging work is required during the
construction phase.
The scale
of construction work on-site is relatively small. Main components of the rafts / cages are
manufactured off-site and will be towed to the Project site using tug
boat. On-site assembly and anchoring of
the fish rafts / cages will be assisted by a small number of marine vessels
such as sampans and small speed boats for up to a few trips per day. Anchoring of these vessels might be
required. No heavy construction plant
would be used. Fish rafts / cages and
auxiliary facilities, such as storage space and shelters, would be positioned
by anchor lines attaching to the anchorage points on the seabed. Use of winch might be required during the
assembly and anchorage of fish rafts / cages.
All construction activities shall be conducted during daylight hours.
Potential
impacts to marine ecological resources arising from these works may be divided
into those related to:
n
Disturbance of marine habitats; and
n
Underwater sound from marine
construction activities and marine vessels.
Direct impacts to
marine ecology include disturbance caused by assembly and installation
activities on-site. The installation of fish farm structures are expected
to be completed within a few weeks for each fish raft, and would
cause temporary disturbance to marine habitats, such as marine waters with an
area of approximately 410 ha and small area of benthic habitats. Fish farm structures, such as fish cages will
occupy a section of the water column and the disturbance of seabed due to the
anchorage of fish farm structures will be
confined to a thin surface layer (<0.5 m) within a small area. It should be noted that only a small number
of vessels will be used and the frequency / trip of these vessels would also be
relatively low. No disturbance to other marine
ecological sensitive receivers, including HHWMP which
is located far away (~3.2 km from Project site), is expected.
Within the Project
site, the seabed composition was found to mainly consist of silty mud with
rocky and sandy substrates recorded at a few sites. The benthic assemblages were dominated by polychaete
worms and characterised by similar species diversity and biomass as elsewhere
in Hong Kong. Three species of
amphioxus which are of conservation importance were found at three sampling
stations within the Project site, including Branchiostoma belcheri found in both wet and dry seasons, and
B. japonicum and B. malayanum found during dry
season only. The
sampling station MB9 was found to have high density of amphioxus during both
seasons. As the typical
habitat of amphioxus is generally found in shallow,
subtidal sand flats([13])
([14])
and the majority of the Project site is of muddy and silty nature, the Project
site is not considered as an important recruitment area and spawning ground for
amphioxus. The overall
coral coverage within and in the vicinity of the Project site is considered to
be low and other species recorded are considered to occur frequently in Hong
Kong. A seagrass species and its
associated habitats are only found at a distance (~3.9 km) at To Kwa Peng which
is considered far away. Overall
the subtidal habitats within the Project site were considered as of low
ecological importance, with a few species of conservation importance present.
While high density of
amphioxus was recorded in both wet and dry seasons at the sampling station MB9
within the Project site during the baseline survey, such high density of
amphioxus was also recorded in other locations in eastern Hong Kong
waters, including Tai Long Wan, Nam She Wan, Long Ke Wan and Pak Lap Wan off
the Sai Kung Peninsula based on literature review ([15]). The high density of amphioxus found in a
particular area of the Project site represents a very small portion of habitats
when comparing to other available habitats in eastern Hong Kong waters. Considering the
availability of similar habitats for amphioxus in eastern Hong Kong waters, the
typical habitat of amphioxus is generally shallow, subtidal sand flats compared
to the muddy and silty nature of the seabed within the Project site, and the
disturbance of seabed due to the anchorage of fish farm structures will be confined to a thin surface layer (<0.5 m) within a small area, unacceptable impacts to amphioxus habitat
are not expected. In order to minimise
the impacts to amphioxus habitat, mitigation measure is recommended to avoid
any construction works, such as anchoring of fish farms at areas identified as
coarse sediments at and in the vicinity of Station MB9, where high density of
amphioxus was recorded.
Considering
the temporary nature of the disturbance (a few weeks for each fish raft /
cage), the small extent of area affected and low ecological importance of the
affected area, impacts are considered to be of minor significance and
unacceptable impacts on marine ecological resources are not expected. Marine
ecological resources are expected to return to the area following the cessation
of fish farm construction activities.
Construction
activities, such as during the assembly of fish raft, would generate noise,
glare and dust which may affect marine ecology.
Potential impacts to marine life, mostly fish species, would include
temporary avoidance of areas in the vicinity of works area or close to the
source of disturbance. Considering the temporary nature of the construction
works, impacts from the generation of noise, glare and dust on marine habitats
are considered negligible, and unacceptable impacts on the marine ecological
resources are not anticipated. Major
lighting sources will be pointed inward and downwards to avoid disturbance to
wildlife, unacceptable impacts on the marine ecological resources are not anticipated.
Intermittent sounds, which occur during assembly
and installation activities on-site and marine vessel movement, may have an impact on marine
ecological resources. Potential effects
of increased underwater sound include physiological stress, avoidance and
injury (at high pressure levels). The
level of impact is however dependent upon background sound, number and type of
species affected, proximity of organism to the sound source, attenuation
properties of seabed sediments and hearing capabilities of the species
affected, etc..
Most marine invertebrates do not possess air-filled space
and thus it is generally considered that sound would have limited physiological
or behavioural effects on marine invertebrates, except if they are located
within a few metres of the sound source.
Therefore, underwater sound generated from marine works is expected to
have negligible impact on marine invertebrates in the Assessment Area.
The impact of underwater sound generation from
construction activities on fish is highly depended upon the hearing
capabilities of the different species present in the area, with the hearing
specialists being of greatest concern.
The significance of these effects is dependent upon the proximity of
fish to the sound source. Considering
that a small number of marine vessels would be present temporarily at the
Project site during fish farm construction, fish species that are sensitive to
the generation of sound are likely to instinctively avoid the area once works
commence and would be temporarily displaced to other areas where similar
habitat conditions are present.
Fishes are
expected to return to the area following the cessation of fish farm
construction activities.
Waters within the Assessment Area
and its vicinity is subject to moderate to high levels of marine traffic by
similar types of vessels. It is
reasonable to assume that marine organisms are habituated to background level of underwater sound, and a small increase in vessel activity
associated with the construction of this Project is not anticipated to result
in unacceptable impacts on marine organisms at and in the vicinity of the
Project site. Overall, unacceptable
impacts on marine ecological resources are not expected.
Mariculture
activities, such as management of fish raft / cages and fish stocks within the
Project site will be undertaken during operational phase. Limited numbers of small power generators
will be used on fish rafts to support daily mariculture activities. The transportation of fish stocks, fish feed,
fish raft equipment and workforce as well as occasional visitors will make use
of mainly small marine vessels such as sampans and speed boats for a few trips
a day. No maintenance dredging or
sediment removal is anticipated during FCZ operation. All operation activities shall be conducted
during daylight hours. The potential
impacts on marine ecology of the Assessment Area include:
n
Changes in marine habitats (marine
waters and benthic habitat);
n
Temporary relocation of rafts under
typhoons or algal blooms;
n
Underwater sound from daily
operations and marine vessels;
n
Perturbations to key water quality
parameters during fish farm
operation, including fish feed wastage, fish excretion and dead fish; and
n
Introduction of invasive species.
As
discussed in Section 4.5.1.1, the fish farm structures will not fully occupy
all of the Project site area but mainly a section of the water column and a
small area of seabed confined to a thin surface layer
(<0.5 m), the area of marine ecological habitat affected is
<410 ha. The area affected which is of low ecological importance, impacts are
considered to be of minor significance and unacceptable impacts on marine
ecological resources are not expected.
While high density of
amphioxus was recorded in both wet and dry seasons at the sampling station MB9
within the Project site during the baseline survey, such high density of
amphioxus was also recorded in other locations in eastern Hong Kong
waters, including Tai Long Wan, Nam She Wan, Long Ke Wan and Pak Lap Wan off
the Sai Kung Peninsula based on literature review ([16]). The high density of amphioxus found in a
particular area of the Project site represents a very small portion of habitats
when comparing to other available habitats in eastern Hong Kong waters. Considering the
availability of similar habitats for amphioxus in eastern Hong Kong waters, the
typical habitat of amphioxus is generally shallow, subtidal sand flats compared
to the muddy and silty nature of the seabed within the Project site, and that
the fish farm structures will mainly occupy a section of the
water column and a small area of seabed confined to
a thin surface layer (<0.5 m), unacceptable
impacts to amphioxus habitat are not expected.
In order to minimise the impacts to amphioxus habitat, mitigation
measure is recommended to avoid FCZ operation at areas
identified as coarse sediments at and in the vicinity of Station MB9, where
high density of amphioxus was recorded.
Fish rafts
/ cages and anchoring equipment would provide hard substrate for the settlement
of epifaunal organisms that would not otherwise be successful in colonising the
area. Where permitted, colonisation of the
structures over time is expected to lead to the development of a marine fouling
community. Effects associated with
creation of artificial habitat may include increased biological productivity
and increased diversity of habitats.
Overall, the structures of the fish farm are expected to result in
potential positive effect on marine ecological resources of the waters within
and in the vicinity of the Project site.
All the
fish rafts / cages will be floating with permeable nets to allow water
exchanges with the marine environment.
Consequently, it is predicted that no unacceptable changes in
hydrodynamics will occur.
Operational activities, such as cleaning of fish cages and the use of lighting, would generate noise, glare and dust
which may affect marine ecology.
Potential impacts to marine life, mostly fish species, would include
temporary avoidance of areas in the vicinity of works area or close to the
source of disturbance. Considering the
temporary nature of the cleaning activities, impacts from the generation of
noise, glare and dust on marine habitats are considered negligible,
and unacceptable impacts on the marine ecological resources are not
anticipated. Major lighting sources will be pointed inward and
downwards to avoid disturbance to wildlife, unacceptable
impacts on the marine ecological resources are not anticipated.
In
general, relocation of fish rafts adopting advanced mariculture technologies
are not necessary under adverse weather (e.g. typhoon) given the framework of
fish cages would use weather-resistant and durable materials (e.g. HDPE cages,
steel truss cages). For other potential
circumstances (e.g. red tide event, outbreak of fish disease), the licensees will
review the need of fish raft relocation and propose the fish raft relocation
plan as necessary for agreement with AFCD on a case-by-case basis, depending on
the type of algal bloom (any toxicity to fish), expected duration of such
circumstances, feasibility for early harvesting of fish stock, feasibility of
implementing onsite control measures etc.
In case fish raft relocation is considered necessary, the fish rafts
will be relocated away from the areas of circumstances, avoid marine fairways
and utilities and at some distance away from ecological and fisheries sensitive
receivers (e.g. about 200 m away from established coral communities) to
minimise potential impacts to these sensitive receivers. Such relocation will be temporary (e.g. a few
weeks) and the fish rafts will return to the Project site upon the cease of the
circumstances. The
mobilisation of the fish rafts will cause temporary disturbance to marine
habitat. Increased operation of marine
vessels will occur due to the towing of fish rafts to the new location, and the
re-anchoring of fish rafts will cause temporary disturbance to the water column
and seabed. The corresponding impacts
would be similar to those occurred in the construction phase (Section
4.5.1). Overall, impacts are
considered to be of minor significance and unacceptable impacts on marine
ecological resources are not expected.
Operation of the fish farm would produce underwater sound from the
management of fish rafts / cages and fish stocks, and operation of marine
vessels. The daily operations of mainly
small marine vessels, such as sampans or speed boats would be temporary which
the underwater sound characteristics of these vessels are similar to the
operations at Tap Mun FCZ, Kau Lau Wan FCZ and marine traffic at ferry routes
nearby. Marine organisms in these waters
are habituated to the background level of underwater sound, and a small
increase in mariculture and vessel activities associated with the operation of
this Project are not anticipated to result in unacceptable impacts on marine ecological
resources and also marine habitats within HHWMP which is located far away (~3.2 km from
Project site).
Mariculture activities would
result in an increase in water quality pollutants primarily
from fish feed, feed wastage, fish excretion and dead fish. The increase in pollution load would affect the water quality in the receiving waters and the potential impacts on marine ecological resources are as follows:
n
Suspended solids (SS)
dispersion;
n
Dissolved oxygen (DO)
depletion; and
n
Elevated nutrient levels.
To estimate the impacts on marine ecological
sensitive receivers of the Assessment Area, computer modelling of changes in water quality were conducted under two scenarios:
n
Baseline scenario, which
covered the “without-project” condition in 2023; and
n
Project scenario, which took
into account the additional pollution load from the mariculture activities at
the Project site, as well as the other nearby proposed new fish culture zones
at Outer Tap Mun and Wong Chuk Kok Hoi (each at their carrying capacity).
Relevant assessment criteria, i.e. Water Quality
Objectives (WQOs) in the Mirs Bay and Tolo Harbour and Channel WCZs, were then
used to assess potential impacts on marine ecological resources .
Fish farm operation are expected to generate SS within
the water column as a result of fish feed, fish feed wastage and fish
excretion, contributing to an increase in sediment deposition in close
proximity of the Project site.
The water quality modelling results have indicated
that at all marine ecological sensitive receivers, SS elevations as a result of
fish farm operation are predicted to be compliant with the relevant WQOs for
both wet and dry seasons. Impacts to
subtidal assemblages, such as fish, corals and benthic assemblages within and
in the vicinity of the Project site are expected to occur temporarily as the
modeling results indicate that the mariculture activities would only result in
short-term, localised elevations of SS.
The habitats affected are expected to be generally confined to the
Project site and subtidal assemblages in proximity to the Project site are
considered to be of low to moderate ecological value. As the areas affected are predicted to have limited
or no change of SS levels between baseline and project scenarios, organisms are
expected to be exposed under similar environmental conditions as the fish farm
operates. Based on the assumption that
eventually the affected areas will be recolonised by fauna typical of the area,
the temporary impact on these low ecological assemblages is not considered to
be unacceptable. Unacceptable impacts to
ecological assemblages, including species of conservation importance such as
amphioxus, marine mammals and horseshoe crabs, if present in the vicinity of
the Project site arising from elevated SS levels are not anticipated. Other marine ecological sensitive receivers
are predicted to be unaffected (as defined by the WQO and tolerance criterion).
With the fish farm standing stock kept within the Project
site’s maximum carrying capacity and the use of pellet feed within fish farms,
potential impacts to marine ecological resources will be well managed. Although the Project site occupies a moderate
proportion of the habitats, the Project site generally supported ecological
assemblages of low ecological value with only a very small area identified with
high presence of amphioxus. Other areas
which supported marine ecological resources of moderate to high values are
recorded at HHWMP which is located at far way (~3.2 km from the Project
site). Consequently, unacceptable
impacts on marine ecological resources are not expected to occur.
The relationships between SS and DO are complex, with
elevated SS in the water column together with a number of other factors to
reduce DO concentrations. Elevated SS
(and turbidity) reduces light penetration, lowers the rate of photosynthesis by
phytoplankton (i.e. primary productivity) and thus lowers the rate of oxygen
production in the water column.
Furthermore, the decomposition of organic matter in fish feed, fish
excretion and dead fish in the water column may consume DO in the receiving
waters. The resulting overall DO
depletion has the potential to cause an adverse effect on marine organisms,
especially to sessile organisms, such as corals, which cannot escape from the
hypoxia zone and could potentially cause mortality.
The water quality modelling results have indicated that DO
depletion associated with fish farm operation are predicted to be low and
remain compliant with the relevant WQO DO criteria at water sensitive receiver
AM1 (Amphioxus Habitat within and near Proposed Site) within the Project
site. Beyond the immediate vicinity of
the Project Site, no unacceptable change in DO level is predicted at other
marine ecological sensitive receivers in both baseline and project
scenarios. Overall, there is limited
change in the predicted DO levels at baseline and project scenarios and
unacceptable impacts to marine ecological resources are not expected to occur.
High levels of nutrients released from fish feeds,
fish excretion and dead fish to the water column may potentially cause rapid
increases in phytoplankton population, on occasions to the point that an algal
bloom occurs. An intense bloom of algae can lead to sharp decreases
in the levels of DO. This decrease will initially occur in the
surface water, and then spread to deeper waters as dead algae fall through the
water column and decompose on the seabed. Anoxic conditions may
result if DO concentrations are already low or are not
replenished. This may result in mortality of marine organisms due to
oxygen deprivation.
The water quality modelling results have indicated
that the levels of nutrients as a result of fish farm operation are expected to
be low in general within the Assessment Area.
Predicted levels of unionized ammonia and Total Inorganic Nitrogen (TIN)
at the Project site and water sensitive receiver AM1 (Amphioxus Habitat within
and near Proposed Site) within the Project site are below the corresponding
assessment criterion. Overall, the
increased levels of nutrients in the water column as a result of fish farm
operation are considered to be of minor significance and unacceptable impacts
to marine ecological resources are not expected to occur.
Chlorophyll-a
is a photosynthetic pigment of phytoplankton and is commonly used as a direct
indicator of algal biomass. As mentioned
above, increased levels of phytoplankton due to nutrients released from fish
farms could potentially trigger algal blooms, in which could reduce DO levels
in the water column and result in mortality of marine organisms.
The water
quality modelling results have indicated that the levels of chlorophyll-a vary
spatially across the Assessment Area and are generally higher at the surface
level and areas with shallower water depth.
The predicted change of chlorophyll-a levels
between baseline and project scenarios at the Project site and all other marine ecological sensitive receivers within
the Assessment Area is limited and below the corresponding assessment
criterion. Therefore, fish farm
operation is not expected to result in significant increase of chlorophyll-a
and unacceptable impacts to marine ecological resources are not expected to
occur.
The new fish stocks to the Project site will have
potential risks in introducing invasive species to the marine environment if
invasive species are cultivated and escaped from the fish farms. Invasive species may result in increased
biological interactions (e.g. competition and predation) with native marine
species, and therefore may pose threats to the local marine biodiversity.
Regular
maintenance of fish farm equipment, typically the condition of fish cages and
fish nets would be performed by the fish farm owner, to minimise the potential
risk of fish escape to the nearby marine environment. Details of these
operation measures and practices are presented in Appendix
2A. Upon implementation of these
measures, unacceptable impacts on the
marine ecological resources are not anticipated.
Based upon the information
presented in Section 4.5, the significance of marine ecological impacts
associated with the construction and operation of the Project has been
evaluated in accordance with the EIAO-TM (Annex 8, Table 1). The outcomes of this evaluation are
summarised in Table 4.12.
Table
4.12 Significance of Marine Ecological Impacts
Associated with the Construction and Operation of the Project Evaluated in accordance
with EIAO-TM
|
Potential
Impact |
Source |
Receiver |
Nature
of Impact |
Overall
Impact Significance |
Mitigation
/ Precautionary Measures Required |
|||||
|
Habitat
Quality |
Species
Affected |
Size
|
Duration |
Reversibility |
Magnitude |
|||||
|
Construction phase |
||||||||||
|
Habitat
disturbance |
Construction of fish farms
structures (including production of noise, glare and dust). |
Marine waters and benthic habitats within and in
the vicinity of the Project site. |
Low to moderate |
Common fish species, benthic fauna dominated by polychaetes. Amphioxus species recorded at specific locations within the Project
site. |
All of the Project site (~410 ha). |
Temporary and short term (a few weeks) in the
active works area. |
Reversible |
Moderate |
Minor to moderate |
Yes; mitigation measures would further reduce impacts on amphioxus
habitat. |
|
Underwater sound |
Construction of fish farm structures and marine vessels. |
Marine
waters within and in the vicinity of the Project site. |
Low to moderate |
Common fish species, benthic fauna dominated by polychaetes. Amphioxus species recorded at specific locations within the Project
site. |
Localised to sound-generating activities, e.g. assembly of fish rafts,
installation of mooring system, marine vessels. |
Temporary and short term (a few weeks) in the
active works area. |
Reversible |
Small |
Minor |
No |
|
Operation phase |
||||||||||
|
Changes in
marine habitat |
Fish farm operational activities (including
the production
of noise, glare and dust). |
Marine waters
and benthic habitat within and in the vicinity of the Project site. |
Low to moderate |
Common fish species, benthic fauna dominated by polychaetes. Amphioxus species recorded at specific locations within the Project
site. |
Localised to the fish farm structures (<410 ha) |
Long-term over Project duration. |
Reversible |
Moderate |
Minor to moderate |
Yes; mitigation measures would further reduce impacts on amphioxus
habitat. |
|
Temporary
relocation of fish rafts / cages |
Fish farm |
Marine waters and benthic habitats within and in
the vicinity of the Project site. |
Low to moderate |
Common fish species and benthic fauna dominated by polychaetes. Amphioxus species recorded at specific locations within the Project
site. |
Localised to the immediate vicinity of the area
of fish rafts / cages relocation. |
Temporary |
Reversible |
Small |
Minor |
The licensees will review the need of fish raft
relocation and propose the fish raft relocation plan as necessary for
agreement with AFCD. |
|
Underwater sound |
Operational activities of fish farm and marine vessels |
Marine waters within and in the vicinity of the
Project site. |
Low to moderate |
Common fish species, benthic fauna dominated by polychaetes. Amphioxus species recorded at specific locations within the Project
site. |
Localised to the immediate vicinity of the
sound-generating activities e.g. maintenance of the fish cages and marine
vessel movement. |
Long-term over Project duration but reversible. |
Reversible |
Small |
Minor |
No |
|
Changes in water quality due to fish farm operational activities |
Fish farm operational activities (e.g. fish feed,
fish drugs, waste water, etc.) |
Marine
waters, intertidal natural shores and benthic habitat within and in vicinity
of the Project site. |
Low to moderate |
Common fish species and benthic fauna dominated by polychaetes Amphioxus species recorded at specific location within the Project
site. |
Localised to the vicinity of the fish farm. |
Long-term over Project duration. |
Reversible |
Moderate |
Minor |
Water quality mitigation measures would further reduce impacts. |
|
Introduction of invasive species |
Fish stock in fish farm |
Marine waters within and in vicinity of the
Project site. |
Low to moderate |
Common fish species. |
Within and in the vicinity of Project site (~410 ha). |
Long-term over Project duration. |
Reversible but with difficulty |
Small |
Minor |
Operation measures and Practices in Appendix 2A would
further reduce impacts. |
As there are no other existing or committed
non-FCZ projects identified in the vicinity of the Project site, the Water Quality Impact Assessment
conducted is based on the worst-case scenarios of concurrent operation of all
existing and planned FCZs as sources of pollution. It is expected that all FCZs will be operated
within the maximum carrying capacity and therefore, unacceptable impacts to
water quality are not anticipated.
Consequently, unacceptable cumulative impacts to marine ecological
resources are not predicted to occur.
Amphioxus
which is a species of conservation importance is found within the Project
site. Specific mitigation measures as
mentioned in Section 4.8.1 will be implemented to avoid habitat disturbance
and potential cumulative impacts. As for
other marine organisms, including marine mammals and horseshoe crabs are not
found within and in the vicinity of the Project site, potential cumulative
impacts on these animals are not anticipated and these impacts are expected to
mainly affect fishes and benthic assemblages if identified. Potential operational impacts
presented in Section 4.5.2 were examined to evaluate potential cumulative
impacts with other operations / developments in the northeastern Hong Kong
waters. Outcomes of this evaluation, excluding
the impact on water quality are summarised as follows:
n
Changes in Marine Habitat: In the northeastern waters, the
changes in habitat would be approximately be 500 ha in
total, including the Project site (410 ha), the proposed Wong Chuk Kok Hoi FCZ
(35 ha) and the proposed Outer Tap Mun FCZ (55 ha). Although the area affected covers a certain
extent of Hong Kong waters, the
provision of the proposed FCZs would support more mariculture operations in
Hong Kong and thus providing more fisheries resources to the local and global
fisheries market. Considering that the marine
ecological resources in the northeastern waters where the Project site is
located are generally regarded as of low ecological value, the overall impacts
are minor, it
is unlikely that the construction of the Project would exert an unacceptable
cumulative effect on the marine environment.
n
Underwater Sound: This Project is located at ~1.1 km from Kau Lau Wan
FCZ, ~1.2 km away from Tap Mun FCZ, 1.5 km away from Sham Wan FCZ, and >1.5
km away from other existing and planned FCZs.
For this Project, mainly small marine vessels e.g. sampans and speed
boats operated by fishermen would be used during FCZ operation. The underwater acoustic profiles generated by
works vessels of this Project would therefore be similar to the daily
operations of the nearby Tap Mun, Kau Lau Wan FCZ, Sham Wan FCZ and nearby
ferry routes. Cumulative effects of
works vessels operational sound, if any, are anticipated to be negligible. It is not expected to result in significant
cumulative impact to the marine ecological resources within the Assessment
Area.
n
Marine Traffic: This Project is located at sufficient distance from
other FCZs in the vicinity. It is
expected to involve a relatively small number of mainly small marine vessels,
such as sampans and speed boats that travel to and from the Project site during
daily operations. Given that existing
marine traffic is present within Outer Tap Mun near Tap Mun FCZ and Tap Mun
pier, and that the waters off northeastern Hong Kong have moderate levels of
existing marine traffic, such as the ferry route between Ma Liu Shui to Lai Chi
Wo / Kat O and Ma Liu Shui to Tap Mun, the cumulative effects of marine traffic
disturbance to the nearby marine ecological resources are anticipated to be
negligible.
Overall, the cumulative impacts on
marine ecological resources within the Assessment Area are predicted to be
minor and acceptable.
In accordance with the guidelines in
the EIAO-TM on marine ecology impact assessment, the general policy for
mitigating impacts to marine ecological resources, in order of priority, are:
n
Avoidance:
Potential impacts should be avoided to the maximum extent practicable by
adopting suitable alternatives;
n
Minimisation:
Unavoidable impacts should be minimised by taking appropriate and practicable
measures such as confining works in specific area or season; and
n
Compensation:
The loss of important species and habitats may be provided for elsewhere as
compensation. Enhancement and other
conservation measures should always be considered whenever possible.
Impacts
to marine ecological resources and habitats have largely been avoided and minimised
through proper planning and design of the works. The Project site is selected to be far from
key marine ecological habitats, such as coral habitats in HHWMP and ARs in Long
Harbour, such that impact to these habitats are avoided. The construction work of the FCZ is properly
designed such that no dredging work is required. To minimise the impacts to the vicinity of
the Project site, it is designed to have minimal construction work on site. The scale of construction work on-site is
relatively small, and the number of vessels operating concurrently are limited
to a small number. The installation time
of fish farm structures is minimised and is expected to be completed within a
few weeks for each fish raft which would only cause temporary disturbance to
marine ecological habitat. Main
components of the rafts / cages are manufactured off-site and will be towed to
the Project site using tug boat. On-site
assembly and anchoring of the fish rafts / cages will be mainly assisted by a
small number of marine vessels such as sampans and small speed boats for up to
a few trips per day. No heavy
construction plant would be used. To
minimise change of marine habitat, the fish farm is designed to occupy minimal
space which will only occupy a thin surface layer (<0.5 m) within a small
area. These measures are expected to
control and reduce potential impacts to marine ecological resources.
The
mitigation measures proposed to mitigate water quality impact would also
mitigate the potential impact to marine ecological resources during
construction and operation phase. Detail
of the relevant mitigation measures proposed are presented in Section 3.9.
Although
amphioxus were recorded within and in the vicinity of the Project site, only
one sampling station was found to have high density of amphioxus within a very
small area. Considering the
availability of similar habitats for amphioxus in eastern Hong Kong waters,
unacceptable impacts to amphioxus habitat due to the habitat disturbance as
well as change in habitat and water quality are not expected. Specific
mitigation measures for amphioxus are recommended to minimise disturbance of
their habitat and detailed in Section 4.8.1.1.
It is
recommended that the construction and operation of the Project should avoid any
construction and operational works, such as anchoring of fish farms and FCZ
operation at areas identified as coarse sediments at and in the vicinity of
Station MB9. The area of avoidance is
presented in Figure 4.3.
Considering
that amphioxus are usually found in shallow, subtidal sand flats compared to
the muddy and silty nature of the seabed within Project site, it is therefore
considered that the impact of the Project on amphioxus is minor and acceptable
with the implementation of mitigation measures.
Taking into consideration
the impact assessments in the previous sections and with effective
implementation of the proposed mitigation measures, the significance of residual
impacts on marine ecological sensitive receivers such as marine park (Table 4.12) have been
evaluated in accordance with Annex
8 of the EIAO-TM. Residual impacts occurring as a result of the
proposed Project have been determined and are discussed as follows:
n
<410 ha of marine ecological
habitat will be affected during operation of the FCZ. While the design of fish
farm will only occupy a section of the water column and a small area of seabed,
with the overall low marine ecological value in the context of surrounding
similar habitat, the impact due to the change in marine habitat is considered
to be acceptable. Furthermore, with the implementation of the proposed
mitigation measures, the potential impact on marine ecological resources will
be further minimised. No unacceptable residual marine ecological impacts during
the construction and operation of the Project are therefore anticipated.
n
In addition, the fish farm
structures, which would provide artificial substrates for forming habitat and
shelter for juveniles or adult fisheries, would provide positive effects on
marine ecological resources within and adjacent to the Project Site.
As no
unacceptable impacts have been predicted to occur during the construction and
operation of this Project, monitoring of marine ecological resources during
these project phases is not considered necessary.
A review of
baseline information on marine ecological resources surrounding the waters of
the proposed Project from available literatures and field surveys has been
undertaken, covering the intertidal, subtidal soft bottom and hard bottom
habitats, and marine waters. Results of
the review and field surveys indicated that marine ecological resources in the
vicinity to the Project site are generally regarded as of low ecological value,
whereas further afield habitats and sensitive receivers of ecological value, including
the corals and artificial reefs within existing marine park (i.e. HHWMP) are
located at some distance from the Project site.
Amphioxus which are of species of conservation importance
are recorded at specific locations within and in the vicinity of the Project
site. Seagrass Haliophila minor is located within the
Assessment Area, which is at To Kwa Peng with ~3.9 km from the Project
site. Marine mammals and horseshoe crabs
are not reported within the Assessment Area.
During the
construction of the Project, direct impacts arising from the proposed marine
works include disturbance to the marine habitat (i.e. ~410 ha, including the
water column and a small area of seabed confined to
a thin surface layer (<0.5 m)). Considering the temporary nature of the
disturbance and the overall low ecological value of marine ecological resources
at and in the vicinity of the Project site, unacceptable impacts on marine
ecological resources are not expected.
Impact of elevated levels of underwater sound as a result of
construction activities are considered acceptable with the presence of existing
underwater sound from the nearby Tap Mun FCZ, Kau Lau Wan FCZ, Sham Wan FCZ, as
well as nearby ferry routes. Specific
mitigation measures, including area of avoidance during FCZ construction will
be implemented to avoid disturbance to amphioxus habitat.
During FCZ
operation, there will be changes in marine habitat at the location of fish farm
structures (<410 ha). The structures
mainly occupy a section of the water column and a small area of seabed confined to a thin surface layer (<0.5 m). The presence of fish farm structures will
also provide hard substrates that could be colonised by a variety of marine
organisms and bringing potential positive effect on marine ecological
resources. Although the area affected is
relatively moderate in the context of surrounding similar habitat, the overall
marine ecological assemblages is of low importance at and in the vicinity of
the Project site, unacceptable impacts on marine ecological resources are not
expected. Potential impacts of elevated
levels of underwater sound generated from the marine vessels in the vicinity of
the Project site are considered acceptable with the presence of existing
underwater sound from the Tap Mun FCZ, Kau Lau Wan FCZ, Sham Wan FCZ, as well
as nearby ferry routes. Temporary
relocation of fish rafts due to potential circumstances may occur over a short
time, therefore, unacceptable impacts are not anticipated. Impacts of changes in water quality arising
from FCZ operation are predicted to be largely confined in the vicinity of the
Project site within the maximum carrying capacity. No unacceptable change in water quality is
predicted at all marine ecological sensitive receivers in both baseline and
project scenarios. Impact on the
introduction of invasive species would be considered minor with regular
monitoring of mariculture facilities.
Specific mitigation measures, including area of avoidance during FCZ
operation will be implemented to avoid disturbance to amphioxus habitat.
Overall, no unacceptable impacts to marine ecological resources and species of
conservation importance are expected to occur.
All of the potential construction and operational marine ecological impacts
identified are deemed acceptable.
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