5                    FISHERIES impact

 

Introduction

 

5.1              Based on a literature review of fisheries information within the assessment area and in the vicinity of the project site, this section provides a description of the baseline conditions. An assessment of potential impacts on fisheries resources associated with the construction of the jetty has been undertaken, and further study and mitigation measures recommended where appropriate.

 

Environmental Legislation and Standards

 

5.2              This section makes reference to the following Hong Kong Government ordinances regulations, guidelines and standards and international conventions when identifying fisheries activities, and assessing impacts of the proposed jetty development on the fisheries resources and activities in the assessment area.

 

Fisheries Protection Ordinance (Cap. 171)

 

5.3              It promotes the conservation of fish and other forms of aquatic life within the waters of Hong Kong and regulates fishing practices to prevent activities detrimental to the fishing industry.

 

Marine Fish Culture Ordinance (Cap 353)

 

5.4              It designates and protects fish culture zones (FCZs) from injury to fish and pollution of waters.

 

Water Pollution Control Ordinance (Cap. 358)

 

5.5              It sets limits to water quality parameters in various water control zones.

 

Technical Memorandum on Environmental Impact Assessment Process (EIAO TM)

 

5.6              It provides guidance on the methodology for fisheries impact assessment in Hong Kong. Annex 9 of the Technical Memorandum sets out criteria for evaluating fisheries impact while Annex 17 denotes the guidelines for fisheries impact assessment.

 

Assessment Methodology and Criteria

 

5.7              A desktop literature review was conducted to establish the baseline conditions of the physical environment and the fisheries resources in the assessment area. The impact assessment follows the criteria and guidelines for evaluating and assessing fisheries impact as stated in Annexes 9 and 17 of the EIAO TM, respectively.

 

 

 

 

 

 

 

 

Baseline Conditions

 

5.8              Mariculture and fishing activities that are detrimental to the ecology of Marine Parks are strictly prohibited.  Other fishing activities conducted by bona fide fishermen are controlled through a permit system (AFCD, 2000).  Artificial reefs have been deployed at the southwest of the Sha Chau and Lung Kwu Chau Marine Park. 

 

5.9              The assessment area falls within the North Western Water Control Zone.  The Environmental Protection Department (EPD) conducts regular marine water quality monitoring in the area and the most relevant monitoring station to the assessment area is NM5.  A summary of the monitoring data for the year 2000 at station NM5 is presented in Table 3.2.   The mean values of all water quality parameters showed compliance with the respective Water Quality Objective (WQO) apart from depth-averaged total inorganic nitrogen.

 

5.10          Available existing fisheries information from other studies in Hong Kong waters were  reviewed as the baseline reference, and the key relevant findings are presented below.

 

5.11          Based on AFCD’s Port Survey 96/97, the waters of Hong Kong are divided into 189 fishing areas.  The fishing area in the immediate vicinity of the Marine Park is Area 33, Lung Kwu Sha Chau.

 

5.12          There were approximately 257 fishing vessels operating in the Sha Chau Lung Kwu Chau fishing area, compared with the territory’s total of 2,619.  Of the fishing vessels operating in the fishing area, about 50% were bigger than 15m.   Tables 5.1 and 5.2 present the production and top ten adult fish at the Lung Kwu Sha Chau fishing area.

 

Table 5.1 Production in Lung Kwu Sha Chau fishing area (all fishing vessels)

 

Fishing Area

Area (Ha)

Adult fish production in kg

(% of total HK production)

Rank

(Production per Ha)

Lung Kwu Sha Chau  (0033)*

3,616.46

651,700

(3.7%)

82

Total of Hong Kong (189 fishing areas)

181790.97

17,681,243

-

*              Fry fish production not recorded

 

Table 5.2 Top ten adult fish caught at Lung Kwu Sha Chau Fishing Area

 

Name

 

Ranked by Adult Fish Weight

1

2

3

4

5

Lung Kwu Sha Chau

 

MIXSPP

(mixed fish)

CARKAL1

(Caranx kalla)2 shrimp scad3

CLUPUN

(Clupanodon punctatus)

gizzard shad

SARJUS

(Sardinella jussieu)

sardine

TRIHAU

(Trichiurus Haumela)

hairtail

 

6

7

8

9

10

 

MUGAFF

(Mugil affinis)

 

mullet

ARGSPP

(Argyrosomus spp)

croaker

COLLUC

(Collichthys lucida)

lion head

DECLAJ

(Decapterus lajang)

scad

STOSPP

(Stolephorus spp)

anchovy

Note: 1. species code              2. species name       3. common name

 

5.13          Of the 651,700 kg fish caught, i.e. about 3.7% of total production, the catch was composed mainly of adult fish.  The rank production of the assessment area was 82 out of the total 189 fishing areas.   The fish species caught were also common in Hong Kong waters as shown in Table 5.2. ERM (1997 and 1998) also found that croaker was one of the abundant fish families captured, in terms of weight and number, in the Marine Park area.

 

5.14          ERM (1997) found that the total demersal catch yield was about 35,000g with the productivity 0.093gm-1 at Lung Kwu Chau-Sha Chau area when compared with the total production 1,019,396g and an average production of 0.15 gm-1.  The demersal fisheries production was ranked 13 out of a total 19 survey stations between March and September 1996.  These results indicate that the fishing resources at LKC would be considered low to moderate. 

 

Identification of Environmental Impacts

 

Construction Phase

 

5.15          Impacts to fisheries resources include habitat loss due to construction of jetty and dredging of the approach channel.  Other impacts to fisheries resources and fishing operations during the construction phase include sediment release associated with the dredging activities.  Potential impacts to water quality from sediment release are listed below:

 

Operation Phase

 

5.16          Maintenance dredging of the approach channel will be required and would have similar impact as construction dredging. 

 

Evaluation of Impacts

 

5.17          Based on the blockwork design, the loss of natural seabed is approximately 0.03ha due to the construction of jetty.  Therefore, the direct impacts to fisheries resources and fishing operation include habitat loss due to the dredging associated with the dredging work is regarded as low.

 

5.18          Dredging of the approach channel will be required during the construction phase.  The impact is anticipated to be insignificant due to the area is of low fisheries value as shown in Table 5.1 and the dredging is small scale and temporary.

 

5.19          One of the main water quality parameters under consideration is elevation in suspended solids (SS) during the dredging works which at high levels would clog gills and affect turbidity. Eggs and fry fish are most susceptible to increased SS. Assessment of potential impacts of dredging on fisheries has been undertaken using the results from the sediment plume modelling.  Water quality impacts on dissolved oxygen (DO) obtained from the water quality impact assessment of the area has also been considered for the fisheries impact assessment.

 

Increased concentrations of suspended solids (SS)

 

5.20          Suspended sediment fluxes occur naturally in the marine environment and consequently fish have evolved behavioural adaptations to tolerate increased SS loads, including clearing their gills by flushing water over them.  Where SS levels become excessive, fish will move to clearer waters.  Susceptibility generally decreases with age, with eggs the most vulnerable and the adults the least sensitive to effects from sediments.  Other factors such as the rates and duration of SS elevations will interact with life stage sensitivity to influence the type and extent of impact upon fish.

 

5.21          Based on water quality modelling predictions where mitigative silt curtains are deployed, and the short duration of dredging activities, the suspension of sediment into the water column by dredging will not have a significant impact on fisheries resources. In general, sedimentation rates off east Lung Kwu Chau would be elevated only slightly by less than 0.01 Kg m2 day-1 and no more than 0.1 Kg m2 day-1 in a small pocket in the mixing zone.  Similarly, turbidity is not predicted to be elevated to levels that would be deleterious to fisheries.  During mitigated dredging, the sediment plumes will be very narrow (20-60 m) and the SS concentrations in general are predicted to be only slightly elevated (1-4 mg/L) (see Section 3).

 

Decrease in DO concentrations

 

5.22          The relationships between SS and DO are complex, with increased SS in the water column combining with a number of other effects to reduce DO concentrations in the water column.  Elevated SS (and turbidity) reduces light penetration, lowers the rate of photosynthesis by phytoplankton (primary productivity) and thus lowers the rate of oxygen production in the water column.  Elevated SS can also cause increased energy retention from sunlight, resulting in higher temperatures, and hence the potential for lower oxygen levels as oxygen is more soluble in cold water.  This has a particularly adverse effect on the eggs and larvae of fish, as at these stages of development high levels of oxygen in the water are required for growth due to high metabolic rates.

 

5.23          As demonstrated by the water quality modelling (see section 3), there are not predicted to be significant reductions in DO levels which could impact fisheries resources.

 

Operation Phase

 

5.24          Fisheries impacts during the operation phase may include increase vessel traffic and human disturbance other than appointed personnel for maintenance of DVOR/DME station on the island. Adverse impact to fisheries activities is not anticipated. 

 

5.25          The rubble mounds foundation of the jetty may increase the colonisation of fish.  The impact of maintenance dredging will be substantially less intensive than the construction phase which, as previously discussed, would not result in any significant impact on fisheries resources.

           

Mitigation Measures

 

5.26          According to the EIAO TM, the order of priority for mitigating impacts should be avoidance, minimisation and compensation. In view of the short-term construction and dredging work for the Project, it is predicted that no major fisheries impacts will be associated with the Project.  Mitigation measures recommended in Section 3 and Section 4 will ensure no significant impact on fisheries resources

 

 

Conclusions

 

5.27          Preliminary literature review has been conducted to establish the baseline conditions of the assessment area. Water quality monitoring records revealed that nearby waters were generally clear with moderate surface dissolved oxygen level and inorganic nutrients. Parameters such as suspended solids and dissolved oxygen have been considered for fisheries impact assessment.

 

5.28          Sediment plume modelling results indicate that sedimentation rates or turbidity levels in the Assessment Area’s waters are not elevated to levels that would impact fisheries. Provided that mitigation measures recommended to protect water quality (Section 3) are fully implemented, specific mitigation measures to protect fisheries resources are not necessary.

 

 

References

 

1.      AFCD (2000)  http://www.info.gov.hk/afcd.

2.      AFCD (1998) Port Survey 96/97.

3.      ERM (1996) Aviation Fuel Receiving Facility at Sha Chau: Detailed Design Basis Supplementary EIA.

4.      ERM (1997) EIA Study for Disposal of Contaminated Mud in the East Sha Chau Marine Borrow Pit.

5.      ERM (1998) Fisheries Resources and Fishing Operations in Hong Kong Waters.