In accordance with the EIA Study Brief No.
ESB-198/2008 Condition 3.4.8, fisheries impacts arising from
the dredging works and operation of the
This Chapter of the EIA
Report presents the results of the assessment of the potential impacts of the
dredging works on existing fisheries resources, fishing operations and marine culture activities based on the findings of the Water
Quality Impact Assessment. The structure is summarised as follows:
Section 6.2: Identifies existing environmental
legislation, standards, guidelines and criteria relevant to the fisheries impact assessment;
Section 6.3: Describes the assessment
methodology adopted for the fisheries impact assessment;
Section 6.4: Describes the existing baseline
conditions of the physical environment of the Study Area, overview of the
capture and culture fisheries;
Section 6.5: Identifies the potential
fisheries impacts due to the Project;
Section 6.6: Provides evaluation of
potential fisheries impacts;
Section 6.7: Proposes potential mitigation measures to address the identified impacts;
Section 6.8: Provides evaluation of
cumulative impacts due to concurrent projects;
Section 6.9: Evaluates the residual
impacts;
Section 6.10: Proposes appropriate
environmental monitoring and auditing programme; and
Section 6.11: Summarises the key findings of
this section.
Assessments have been conducted in
accordance with the requirements of the Study Brief and Annexes 9 and 17 of the Technical
Memorandum on the Environmental Impact Assessment Process. The dredging
area is situated within the Principal Fairways and the
Mitigation measures as recommended in the
Water Quality Chapter for minimizing water quality impacts will also minimize any
adverse environmental impact to fisheries. No fisheries-specific
mitigation measures are required during the
proposed dredging works. Apart from the routine Environmental
Monitoring and Auditing Programme recommended for water quality impact
monitoring, 24 hours monitoring at the monitoring stations of the four FCZs to
undertake continuous measurements of DO, temperature and turbidity to
supplement the routine monitoring activities in case where an action/limit
exceedance is evidence is also recommended.
6.2 Environmental Legislation, Standards, Guidelines and Criteria
The
following legislation and guidelines are applicable to the fisheries impact
assessment in
¡ Environmental Impact Assessment Ordinance – Technical Memorandum (EIAO-TM), Annexes 9 and 17. Annex 9 recommends the criteria that are to be used for evaluating fisheries impacts. Annex 17 prescribes the general approach and methodology for the assessment of fisheries impacts arising from a project or proposal, to allow a complete and objective identification, prediction and evaluation of the potential impacts.
¡ Fisheries Protection Ordinance (Cap 171). This Ordinance provides regulations for the conservation of fish and other aquatic life and regulates fishing practices.
¡ Marine Fish Culture Ordinance (Cap 353). This Ordinance regulates and protects marine fish culture and other related activities.
¡ Water Pollution Control Ordinance (WPCO) (Cap 358). This Ordinance sets limits to water quality parameters in various water control zones.
6.3 Fisheries Impact Assessment Methodology
According
to the EIA Study Brief Condition 3.4.8.2, the Study Area for Fisheries Impact
Assessment is the same as the Study Area for Water
Quality Impact Assessment and Marine Ecological Impact Assessment as
shown in Figure 5.1. Special attention was given to the fishing
activities and fishing, spawning and nursery grounds within the Study Area and
the following Fish Culture Zones (FCZs) (locations refer to Figure 3.1):
¡
Ma Wan
FCZ
¡
Lo Tik
Wan FCZ
¡
Sok Kwu
Wan FCZ
¡
Cheung
Sha Wan FCZ
The importance of fisheries resources and fishing
operations identified within the Study Area and the potential impacts due to
the dredging works in
¡ level of fisheries resources and composition of commercially important species in the Study Area;
¡ the level and pattern of fishing activity and fisheries production in the Study Area;
¡ sites of fisheries importance such as nursery and spawning grounds; and
¡ aquaculture activity in the Study Area.
A desk study of relevant published and unpublished literature and reports, including fisheries production, resources and activities, was carried out to obtain the baseline information regarding fisheries information within the Study Area and previous studies on dredging works. The review of findings of relevant studies was carried out to identify any information gaps within the Study Area for the assessment of potential fisheries impacts. Assessment for indirect impacts on fisheries arising from changes of water quality was made reference to the modelling results of water quality in Chapter 3 of this Report and the potential impacts from the sediment plume due to the proposed dredging works.
6.1.1 Description of the Physical Environment
The
Project is situated in the open
waters of
The latest baseline of marine water quality of the Study Area, based on the routine marine water quality monitoring by EPD in 2008 (EPD 2009), is presented in Tables 3.3 and 3.4 of Section 3.3. The levels of dissolved oxygen (DO) and unionised ammonia at the selected EPD Water Monitoring Stations comply with the statutory Water Quality Objectives (WQO). However the depth-averaged level of total inorganic nitrogen (TIN) at several monitoring stations in the Southern Water Control Zone and Victoria Harbour Water Control Zone are not compliant with the WQO.
Findings of the Consultancy Study on Marine
Benthic Communities in Hong Kong conducted by the CityU Professional Services
Limited (CPSL) revealed that the sediment characteristics of the existing
seabed near the proposed dredging areas at the
6.1.2.1
Overview
The
local fishery industry provides a major source of fish supply to local
consumption. In 2009, the total
fisheries production is estimated to be in 159,000 tonnes with a value
$2,000 million (AFCD 2010a).
The highest
yields of local fisheries production were mainly derived from the eastern and
north-eastern waters. The statistics of
Table 6.1: Figures of Hong Kong Capture Fisheries Industry in the past 6 years
|
Parameters |
2004 |
2005 |
2006 |
2007 |
2008 |
2009 |
|
No.
of vessels |
4,330 |
4,150 |
3,950 |
4,000 |
3,800 |
3,700 |
|
Local fishermen engaged in capture fisheries |
9,770 |
9,170 |
8,500 |
8,500 |
7,900 |
7,600 |
|
Production
(tonnes) |
167,540 |
162,000 |
154,500 |
154,000 |
158,000 |
159,000 |
Source: AFCD 2009a & 2010a
6.1.2.2
Findings
of Port Survey 2006 within the Study Area
Fishing Operation
As indicated in the results of the
Port Survey conducted by AFCD in 2006,
fishing activities are very rare at the proposed dredging areas. The
proposed dredging areas at
Fishing operations in the Project area are mainly small scale with vessels less than 15 metres in length, as indicated in Figure
6.2. The types of
fishing vessels operating in the Project area are presented in Table 6.2.
Table 6.2: Fishing operations within the Project area
|
Type of Fishing Vessel |
Location* (KTCB / NF / WF) |
No. of vessels / ha |
|
Shrimp Trawler |
WF |
£ 10 |
|
Hang Trawler |
WF |
10 – 50 |
|
NF |
£ 10 |
|
|
Gill Netter |
WF |
10 – 50 |
|
NF, KTCB |
£ 10 |
|
|
Long Liner |
WF |
£ 10 |
|
Hand Liner |
WF |
£ 10 |
|
Sampan |
WF |
10 – 50 |
|
NF, KTCB |
£ 10 |
Source: Port Survey 2006 (AFCD, 2009).
*KTCB =
Fisheries
Resources
In the proposed dredging area at Western Fairway, the adult fish production is in the lower class (50–100kg/ha), whilst the lowest class of fisheries production is recorded in the proposed
dredging areas at Kwai Tsing Container Basin and Northern Fairway, with less than 50kg/ha as indicated in Figure 6.4.
In terms of value, fisheries production within the Project area was rated
moderate-low with $1,000–2,000/ha in the portion of Western Fairway and below
$1,000/ha in Kwai Tsing Container Basin and the portion of Northern Fairway.
Distribution of value of fisheries production within the Study Area is shown in
Figure 6.5.
Mainly Rabbit Fish Siganus canaliculatus (family Siganidae)
were caught in the proposed dredging
areas with a production
of 10–20kg/ha.
This is a relatively low
production rate compared to other areas in
As recorded in the Port Survey 2006 there was no
fish fry production recorded in the proposed dredging areas. The
nearest area with relatively higher density of fish fry was
In summary, fisheries resources within the proposed dredging areas are of relatively low level with a relatively low abundance of
fish catch. Fishery spawning ground is
absent within and in the vicinity of the Project area, while nursery ground is
identified in
The estimated production of culture fisheries in 2009 was about 1,437 tonnes valued at $92 million, which catered for about 9% of local demand for live marine fish (AFCD 2010b). Ma Wan, Lo Tik Wan, Sok Kwu Wan and Cheung Sha Wan Fish Culture Zones (FCZs) are approximately 5km, 6km, 7km and 11km from the nearest dredging boundaries respectively.
In Sok Kwu Wan FCZ, 147 licensed rafts are reportedly operating as of January 2010. Species cultured included Spotted Grouper Epinephelus chlorostigma, Longtooth Grouper E. bruneus, Mangrove Snapper Lutjanus argentimaculatus, Russell’s Snapper L. russelli, John’s Snapper L. johnii, Black-striped Snapper L. vitta, Star Snapper L. stellatus, White-spotted Spinefoot Siganus canaliculatus, Black Fish Girella melanichthys and Pompano Trachinotus blochii (Maunsell 2003).
The
Ma Wan FCZ consists of 107 licensed rafts with a total licensed area of 14,554m2 as of January 2010, with the main culture
species being Spotted Grouper E.
chlorostigma, Goldlined Seabream Rhabdosargus
sarba, Mangrove Snapper L.
argentimaculatus and Pompano T.
blochii (AECOM 2009).
As reef fish cultured in sea cages are particularly vulnerable to any adverse changes in water quality, the Ma Wan, Lo Tik Wan, Sok Kwu Wan and Cheung Sha Wan FCZs are considered as fisheries sensitive receivers as stated in Condition 3.4.8.2 of EIA Study Brief No. ESB-198/2008. They are also considered as water sensitive receivers in the Water Quality Impact Assessment (refer to Section 3.4 of Chapter 3). The significance of the impacts on the culture fisheries due to the changes in water quality as a result of the Project was assessed with reference to the water quality modelling results.
Available information has been reviewed and presented to provide
an update on capture and culture fisheries within the Study Area. Assessment of potential fisheries
impacts was conducted based on
the review of literature and previous survey findings. No information gap was identified and therefore
no further fisheries field surveys
were considered to be
necessary.
6.2
Identification of Fisheries Impacts
This Section identifies and evaluates the
potential short and long-term impacts on both capture and culture fisheries,
during the decommissioning, construction and operation phase of this Project,
in accordance with Condition 3.4.8.3 of the EIA Study Brief No. ESB-198/2008.
Impacts to fisheries resources and fishing operations are expected to occur during the dredging works. These impacts are predicted to be confined within the dredging area and may occur through the following events:
6.2.1.1 Loss of Fishing Ground
Potential impacts on fisheries include the temporary loss of fishing ground and fisheries resources along
the dredged area at the existing seabed level reaching
approximately -17.5mC.D. after dredging. The approximate area of seabed to be dredged is about 446ha of which
about 220ha are within the Principal Fairways and about 226ha are outside the
Principal Fairways but within the
6.2.1.2
Disruption
of Fishing Operation
The proposed dredging works may potentially cause an impact on fishing activities. However, the major dredging areas are located in existing principal fairways which exclude fishing operations. Moreover, the areas to be dredged will be confined and during construction vessel speeds will be restricted, thus further reducing the chance of head-on collision between fishing vessels and construction craft. Those fishing vessels operating along the non-restricted areas may be temporarily affected by restriction on their entry to the proposed dredging area and its vicinity. This may potentially reduce the fisheries production in the region during the construction phase.
6.2.1.3 Changes in Water Quality
Suspended
Solids Elevation
Fluxes of suspended solids (SS) occur naturally in the marine environment. Consequently, fish have evolved behavioural adaptations (e.g. clearing their gills by flushing water over them) to tolerate the increased SS load in the natural environment. Where SS levels become excessive, fish will move to clearer waters. This level is defined as the tolerance threshold, which varies from species to species and at different stages of the fish life cycle. If SS levels exceed the tolerance thresholds, fish are likely to become stressed, injured and may ultimately die. Susceptibility generally decreases with age, with eggs being the most vulnerable and adults being the least sensitive to effects of SS. The rate, season and duration of SS elevations will influence the type and extent of impacts upon fish.
According to the Water Quality Impact Assessment,
the predicted suspended solids elevations at Ma Wan, Lo Tik Wan, Sok Kwu Wan
and Cheung Sha Wan FCZs caused by the proposed dredging works for Scenarios 1
to 6 as described in Section 3.5.2.3 are presented
in Table 6.3 (abstracted
from Tables 3.12, 3.14, 3.16, 3.18, 3.20
and 3.22 of Section 3.7.1.1) and summarised in Section 3.7.1.1.
The results as presented in Table
6.3 show that the predicted maximum concentration of suspended solids
at the fish culture zones for
Scenarios 1 to 6 in both dry and wet seasons were all compliant with the WQO criterion of not exceeding 30% of the ambient
level of suspended solids. Other than the WQO criterion, the
predicted concentration of SS at the fish culture zones would also not exceed 50 mg/L, which is the criterion for maximum SS concentration (i.e. half of the no
observable effect concentrations)
(CityU CCPC 2001).
Table
6.3: Predicted Suspended Solids Elevations
at Fish Culture Zones for Scenarios 1 to 6
|
Fish
Culture Zone |
Assessment Point |
Dry Season |
Wet season |
||
|
|
Maximum Depth-averaged SS elevation
(mgL-1) |
SS Criterion (mgL-1) |
Maximum Depth-averaged SS elevation
(mgL-1) |
SS Criterion (mgL-1) |
|
|
Scenario 1 |
|
|
|
|
|
|
Ma Wan |
F1 |
0.6 |
3.2 |
0.4 |
2.5 |
|
Lo Tik Wan |
F2 |
0.1 |
1.8 |
0.1 |
1.6 |
|
Sok Kwu Wan |
F3 |
<0.1 |
1.8 |
<0.1 |
1.6 |
|
Cheung Sha Wan |
F4 |
<0.1 |
2.6 |
<0.1 |
4.4 |
|
Scenario 2 |
|
|
|
|
|
|
Ma Wan |
F1 |
0.6 |
3.2 |
0.4 |
2.5 |
|
Lo Tik Wan |
F2 |
0.1 |
1.8 |
0.1 |
1.6 |
|
Sok Kwu Wan |
F3 |
<0.1 |
1.8 |
<0.1 |
1.6 |
|
Cheung Sha Wan |
F4 |
<0.1 |
2.6 |
<0.1 |
4.4 |
|
Scenario 3 |
|
|
|
|
|
|
Ma Wan |
F1 |
0.8 |
3.2 |
0.5 |
2.5 |
|
Lo Tik Wan |
F2 |
0.2 |
1.8 |
0.1 |
1.6 |
|
Sok Kwu Wan |
F3 |
<0.1 |
1.8 |
<0.1 |
1.6 |
|
Cheung Sha Wan |
F4 |
<0.1 |
2.6 |
<0.1 |
4.4 |
|
Scenario 4 |
|
|
|
|
|
|
Ma Wan |
F1 |
0.4 |
3.2 |
0.3 |
2.5 |
|
Lo Tik Wan |
F2 |
0.1 |
1.8 |
0.1 |
1.6 |
|
Sok Kwu Wan |
F3 |
<0.1 |
1.8 |
<0.1 |
1.6 |
|
Cheung Sha Wan |
F4 |
<0.1 |
2.6 |
<0.1 |
4.4 |
|
Scenario 5 |
|
|
|
|
|
|
Ma Wan |
F1 |
0.3 |
3.2 |
0.3 |
2.5 |
|
Lo Tik Wan |
F2 |
<0.1 |
1.8 |
<0.1 |
1.6 |
|
Sok Kwu Wan |
F3 |
<0.1 |
1.8 |
<0.1 |
1.6 |
|
Cheung Sha Wan |
F4 |
<0.1 |
2.6 |
<0.1 |
4.4 |
|
Scenario 6 |
|
|
|
|
|
|
Ma Wan |
F1 |
0.6 |
3.2 |
0.4 |
2.5 |
|
Lo Tik Wan |
F2 |
0.1 |
1.8 |
0.1 |
1.6 |
|
Sok Kwu Wan |
F3 |
<0.1 |
1.8 |
<0.1 |
1.6 |
|
Cheung Sha Wan |
F4 |
<0.1 |
2.6 |
<0.1 |
4.4 |
- Values in Bold
indicate exceedance of relevant criteria.
Levels
of Dissolved Oxygen
Dissolved oxygen (DO) concentration may be reduced with increased SS in the water column in combination with other effects. Elevated SS reduces light penetration, lowers the rate of photosynthesis by phytoplankton (primary producers) and thus lowers the rate of oxygen production in the water column. Elevated SS can also cause an increase in energy retention from sunlight, resulting in higher water temperature and thus the potential for lower oxygen levels as oxygen is more soluble in cold water. Such condition may particularly cause an adverse effect on fish larvae and juveniles, as high oxygen demand is essential for these stages to support high metabolic rates for development.
High
levels of nutrients such as inorganic
nitrogen in seawater can cause rapid increase in phytoplankton abundance, on occasions to the point
where an algal bloom occurs. An intense
bloom of algae can lead to sharp decrease in the level of DO.
This decrease will initially occur in the surface water, and gradually
in deeper water as dead algae fall to the lower portion of the water column and
being decomposed at the bottom. Anoxic conditions may result if DO
concentrations are initially low
or are not replenished. This may result in the mortality of
fish, especially juveniles, due to oxygen depletion.
From the results of Water Quality Impact
Assessment, the predicted minimum
depth-averaged and bottom layer
DO levels at the fish culture zones for Scenarios 1 to 7 are presented in Appendix 3.9. The maximum decrease in DO is predicted to be 0.01 mg L-1 at
Ma Wan FCZ and insignificant DO depletion at Lo Tik Wan, Sok Kwu Wan and Cheung
Sha Wan FCZs. The non-compliance of minimum depth-averaged DO levels at the fish culture zones within
Total Inorganic Nitrogen, Unionised Ammonia and Ammoniacal
Nitrogen
The predicted maximum depth-averaged and bottom layer total inorganic
nitrogen (TIN) at the fish culture zones presented in Appendix 3.9 indicated that exceedances for TIN were recorded at Lo
Tik Wan, Sok Kwu Wan and Cheung Sha Wan FCZs. The TIN exceedances, especially
in the
The potential release of unionised ammonia
(UIA) and increase in ammoniacal nitrogen concentration during the dredging
activities may cause indirect disturbance to fisheries resources and direct
loss of fisheries resources due to toxic effects. The toxic effect will increase with an
increase in pH value and with warmer temperature. According to the water
quality prediction, UIA concentration (with the excision of S2) at all the fish
culture zones indicated no exceedance of WQO (annual mean concentration exceed
0.021mg L-1) will occur during construction phase (Table 3.35). Thus the potential impact
of increase UIA concentration on culture fisheries is anticipated to be acceptable.
Regarding compliance with WQO UIA annual
average criteria of 0.021 mg/L, marginal exceedances are predicted based on the annual average results,
with 0.034 mg L-1 at B2 (Approach Beach) and 0.028 mg L-1
at B3 (Ting Kau)(Table 3.35). However, these coastal waters are not the major
fisheries production area with medium low adult fish production with reference
to Port Survey 2006 findings (AFCD, 2009b) and hence no significant impact to
fisheries production is expected.
When comparing results with the water
quality assessment guideline under the Consultancy Study on Fisheries and
Marine Ecological Criteria for Impact Assessment (City U’s CCPC 2001), it is
noted that the predicted total ammoniacal nitrogen concentrations (Table A3.12b of Appendix 3.12) at Approach Beach and Ting Kau Beach during dry
season ranged from 0.70 to 0.86 mg L-1 and are all below 0.16 mg/L
during wet season for all scenarios. It is shown that there is a seasonal
variation in terms of total ammoniacal nitrogen prediction representing higher
predicted value during the dry season than the averaged level throughout the
year (Table A3.12b of Appendix 3.12). The higher seasonal
values are compared with the recommended criterion for maximum concentration
(1.2 mg L-1) for 80% protection of fisheries and marine biota from
acute effect (City U’s CCPC 2001) and are all below the criterion, indicating
the potential adverse effect on capture fisheries in marine waters surrounding
the proposed dredging area is anticipated to be insignificant.
Table 6.4: Summary of Dissolved
Oxygen and Total Inorganic Nitrogen for the worst case
among Scenarios 1-7
|
Fish Culture Zone |
Season |
Minimum Depth-averaged DO level (mgL-1) |
Minimum DO level at bottom layer (mgL-1) |
Maximum TIN concentration (mgL-1) |
|
Ma Wan |
Dry Season |
5.5 |
5.7 |
0.2908 |
|
Wet Season |
3.6 |
2.7 |
0.3706 |
|
|
Non-compliance? |
Yes† |
No |
No |
|
|
Lo Tik Wan |
Dry Season |
6.2 |
6.2 |
0.1400 |
|
Wet Season |
3.7 |
2.7 |
0.2100 |
|
|
Non-compliance? |
Yes† |
No |
Yes* |
|
|
Sok Kwu Wan |
Dry Season |
6.2 |
6.2 |
0.1400 |
|
Wet Season |
3.7 |
2.7 |
0.2100 |
|
|
Non-compliance? |
Yes† |
No |
Yes* |
|
|
Cheung Sha
Wan |
Dry Season |
6.0 |
6.1 |
0.2500 |
|
Wet Season |
4.4 |
4.1 |
0.5000 |
|
|
Non-compliance? |
Yes† |
No |
Yes* |
* Due to the non-compliance of the background TIN levels with the WQO.
† Due to the
non-compliance of the background depth-averaged DO levels with the WQO during
wet season.
Potential Contaminant Release During Dredging
The potential release of contaminants during
dredging may cause toxic effect to the fisheries resources. The potential for
release of contaminants from the marine mud during dredging is inferred from
the results of the elutriate tests summarised in Table 3.26 under Section 3.7.1.6. In summary,
the measured levels of all the PCBs, PAHs and chlorinated pesticides were below
the detection limit. It was noted that the effects of exceedance of arsenic
concentration are transient, and the mixing zone is confined to 100m, further
than that, there would be no exceedance. As the nearest FCZ at Ma Wan is
approximately 5km from the nearest dredging boundary, any release of heavy
metals during dredging will be rapidly diluted by the large volume of marine
water within the dredging site. According to the elutriate test results, it was
concluded that the potential impacts of release of heavy metals and organics
due to seabed disturbance on all FCZs are negligible.
6.2.2.1
Maintenance
Dredging
The
isopachytes show that there is no
significant of siltation within
most of the Study Area, other than for some isolated high spots adjacent to the
berth boxes. Maintenance dredging will therefore only
be considered when removal of local high spot is required to maintain the
navigation depth.
As the future maintenance dredging will be
on a much smaller scale than compared to the capital dredging works (which was
acceptable from a fisheries perspective), and in view of the fact that the
Project area is not the prime fishery operation area, the potential impacts on
fisheries resources and fishing operations are considered to be negligible
during periods of maintenance dredging.
6.3 Assessment of Fisheries Impacts
The
fisheries impacts identified in Section 6.5 during and after the dredging works were evaluated in accordance with Annex 9 of the EIAO-TM and presented in Table 6.5 and Table 6.6 respectively.
Table 6.5: Evaluation of Potential Fisheries Impacts during Construction Phase
|
Criteria |
Loss of Fishing Ground |
Disruption of Fishing Operation |
Changes in Water Quality |
|
Nature of Impact |
Temporary loss of
fishing ground; reversible and short-term
during the construction period. |
Temporary and
short-term in phases. |
Temporary and short-term during the construction phase. |
|
Size of Affected Area |
Around 446ha of seabed will be dredged, in
which 220ha of the total area are within the Principal Fairways. Around 226ha
dredging area is outside the Principal Fairways but within the |
Around 446ha of seabed will be dredged, in
which 220ha of the total area are within the Principal Fairways. Around 226ha
dredging area is outside the Principal Fairways but within the |
Localised to the
dredged areas and the waters in close
vicinity; no FCZ will
be impacted. |
|
Loss of Fisheries Resources/Production |
Constitutes a
small proportion of total fisheries resources/ production in |
Constitutes a
small proportion of total fisheries production in |
Constitutes a
small proportion of total fisheries resources/ production in |
|
Destruction and disturbance of nursery and spawning grounds are identified in the vicinity of the
project area |
No important nursery and spawning
grounds are identified in the vicinity of the Project area. No
destruction or disturbance of
areas of fisheries importance is expected
due to dredging works. |
||
|
Impact on fishing activity |
The area to be affected is of low fisheries production and value. Impacts to fishing activities in the area due to temporary loss of fishing ground are not expected to be significant due to the small area physically disrupted in phases, the short time frame of disturbance and the high mobility of the fishes that will move to adjacent waters. |
A small number of vessels of length less than 15m will be affected, as the confinement of dredging area will be in phases, the short duration and the major portion of the works are within Principal Fairway that fishing operation is restricted. |
Impacts to fishing activities in the area due to indirect disturbance of water quality are expected to be localised and in short-term. The dominance of water pollution tolerant species (i.e. Rabbit Fish) and the high mobility of fish (i.e. moving to adjacent waters) will result low impact on fishing activities during construction. |
|
Impact on aquaculture activity |
No direct impact on culture fisheries is anticipated as no fish culture zone is within the proposed dredging area. |
No direct impact on marine fish culture activity is identified for the FCZs are away from the proposed works area. |
No significant impact on marine fish culture activity is
identified due to compliance of SS
elevation and no significant change in DO level. No algal bloom or red tide
caused by the project is predicted. The impacts of toxic unionised ammonia
and contaminant release due to dredging are considered negligible. |
Table 6.6: Evaluation of Potential Fisheries Impacts during Operation Phase
|
Criteria |
Disturbance
Impact due to Maintenance Dredging |
|
Nature of Impact |
No impact on the fisheries is anticipated after the dredging works cease; Impact due to infrequent trimming works will be occasional, temporary, short-term and reversible. |
|
Size of Affected Area |
Only a specific and confined
small area will be
affected. |
|
Loss of Fisheries Resources/Production |
Loss of fisheries resources/production will be negligible due to the small area to be affected. |
|
Destruction and disturbance of nursery and spawning grounds |
No important nursery and spawning grounds are identified. No destruction or disturbance of areas of fisheries importance is expected. |
|
Impact on fishing activity |
The impact on fishing activity due to the occasional trimming works
will be low and short-term,
as the Project area is not
the prime fishing ground, only very small
number of fishermen or fishing vessels will be affected. |
|
Impact on aquaculture activity |
No significant impact on culture fisheries is anticipated for the minor works and distances from the FCZs. |
6.4 Mitigation of Adverse Environmental Impacts
Mitigation measures recommended in the Water Quality Impact Assessment chapter (refer to Section 3.8)
for minimizing water quality impacts
(including control of the speed of all construction vessels within the
works area to prevent propeller wash from stirring up the seabed sediments; barges / dredgers to be fitted with tight fitting seals
to their bottom openings to prevent leakage of material; and barges or
hopper not to be filled to a
level that will cause the overflow of materials or polluted water during
loading or transportation, the
use of a frame type silt
curtain to surround the dredgers and
reduction of dredging rates at specific location during dry season) will also minimize any adverse
environmental impact to fisheries. Therefore, no fisheries-specific
mitigation measures are required during the
proposed dredging works.
The potential cumulative impact of change in
water quality on fisheries due to this Project and concurrent projects
described in Section 2.8 of this Study were
assessed in Section 3.7.1.2. With
reference to the water quality modelling results in Appendix
3.8 of Section 3, the cumulative impact especially for
the elevation of SS levels would be minimal for all the FCZs. The
implementation of water quality mitigation measures including closed grab
dredger and frame type silt curtain could further reduce the SS level to
minimal. In view of the location of the concurrent projects will be more
than 7km from the Project area,
minimal cumulative impacts on fisheries is
expected from these projects.
6.6 Evaluation of Residual Fisheries Impacts
No
adverse significant residual
impact due to the proposed dredging
works is expected after the implementation of the mitigation measures to
control water quality impacts.
6.7 Environmental Monitoring and Audit
The
implementation of the water quality mitigation
measures stated in Section 3.8 shall
be checked as part of the environmental monitoring and audit procedures during
the construction period as presented in the stand-alone Environmental
Monitoring and Audit Manual.
Monitoring of water quality parameters including Dissolved Oxygen (DO),
Dissolved Oxygen Saturation (DO%), temperature, turbidity, salinity, suspended
solid (SS), should be conducted at the
four fish culture zones (Ma Wan, Lo Tik Wan, Sok Kwu Wan and Cheung Sha Wan
FCZs) during the course of the marine construction works as part of the routine
impact monitoring. 24 hours monitoring is also suggested at the monitoring
stations of the four FCZs to undertake continuous measurements of DO,
temperature and turbidity to supplement the routine monitoring activities in
case where an action/limit exceedance is evidence. Details of the monitoring requirement,
locations and frequency are presented in the stand-alone Environmental
Monitoring and Audit Manual for Water Quality Section.
Reviews
of existing information on capture and
culture fisheries within the proposed
dredging area and Study Area has been undertaken. The findings showed that both capture and culture fisheries resources
are relatively low and the fisheries activities are infrequent within the area
to be dredged.
The dredging area is situated within the
Principal Fairways and the
Impacts to capture fisheries due to
temporary loss of fishing ground and short term disruption of fisheries
operation are predicted to be minor owing to the low frequency of fishing
operation in the proposed dredging area. Indirect water quality impact to the
FCZs was assessed with references to the Water Quality Modelling results, which
indicated that the SS elevations are compliant with the Water Quality
Objectives as well as the maximum SS criterion of 50 mg/L at FCZs. The
exceedance of total inorganic nitrogen concentration is due to the high ambient
concentration as recorded by the routine monitoring of EPD. Additionally, the non-compliance of DO levels
during wet season is due to the
non-compliance of the ambient depth-averaged DO levels with the WQO. However,
the changes in total inorganic nitrogen concentration and DO level during the
construction phase in the FCZs are predicted to be insignificant. The
exceedances of UIA predicted at coastal waters around the gazetted beaches at
Rambler Channel are anticipated to have insignificant impact to fisheries. The potential release of contaminants during
dredging is considered to be negligible for the rapid dilution effect and the
far distance of the FCZs from the nearest dredging boundaries. Therefore the
potential impact to the FCZs and fisheries due to the change of water quality
in construction phase is predicted to be negligible. Potential impacts on
fisheries during the operation phase are negligible as maintenance
dredging will only be in small scale
and confined to the areas for the removal of local high spots due to the
siltation rate to the dredged seabed is predicted to be very low.
The potential cumulative impact of change in
water quality on fisheries due to this Project and concurrent projects were
assessed in the Water Quality Impact Assessment. With reference to the water
quality modelling results, the
cumulative impact especially for the elevation of SS levels are predicted to be
minimal for all the FCZs. The implementation of water quality mitigation
measures including closed grab dredger and frame type silt curtain could
further reduce the SS level to minimal. In view of the fact the location
of concurrent projects are more than
7km from the Project area,
minimal cumulative impacts on fisheries are
predicted.
General good site practices and mitigation
measures recommended for controlling water quality to acceptable levels are also
expected to be effective in minimizing the impact to capture and
culture fisheries during the
construction phase. With the implementation of water quality monitoring
programme during the construction phase including routine monthly water quality
monitoring and 24 hours monitoring for dissolved oxygen, temperature and
turbidity at the four fish culture zones, no specific mitigation measure for
fisheries impact is required.
AECOM.
(2009). Tuen Mun – Chek Lap Kok Link -
Investigation: EIA Report.
Prepared for Highways Department of HKSAR Government.
AFCD. (2009a).
Departmental Annual Report. Retrieved
December 2, 2009, from http://www.afcd.gov.hk/ english/publications
AFCD. (2009b). Port Survey 2006. Retrieved December
2, 2009, from http://www.afcd.gov.hk/english/
fisheries/fish_cap/fish_cap_latest/fish_cap_latest.html
AFCD.
(2010a). Capture Fisheries. Retrieved
May 10, 2010, from http://www.afcd.gov.hk/english/
fisheries/fish_cap/fish_cap.html
AFCD.
(2010b). Aquaculture. Retrieved
May 10, 2010, from http://www.afcd.gov.hk/english/
fisheries/fish_aqu/fish_aqu.html
CityU
CCPC. (2001). Consultancy Study on
Fisheries and Marine Ecological Criteria for Impact Assessment. Submitted
to Agriculture, Fisheries and Conservation Department of HKSAR Government.
CPSL.
(2002). Consultancy Study on Marine
Benthic Communities in
EPD. (2009). Marine Water Quality
in Hong Kong 2008.
ERM.
(1998). Fisheries Resources and Fishing
Operations in
Maunsell. (2003). Outlying