4    Fisheries Impact Assessment

 

4.1    Introduction

 

This Section of the EIA Report presents the findings of an assessment of the impact of construction and operation of the proposed South Brothers Facility on existing fisheries resources, fishing operations and fish culture activities based on the Project Description (Part 2, Section 1) and the findings of the Water Quality Impact Assessment (Part 2, Section 2).?A series of fisheries sensitive receivers were identified in the Study Area from a review of baseline information as follows:

 

   Fish Culture Zone at Ma Wan;

   The seasonal spawning ground in northwestern waters; and,

   The two artificial reef complexes (Airport and Marine Park).

 

The focus of the impact assessment will be on these sensitive receivers.

 

4.2    Fisheries Impact Assessment Methodology

 

A desktop literature review (Part 1, Section 4) was conducted in order to establish the fisheries importance of the area within and surrounding the South Brothers Facility.? Information from the water quality assessment was used to determine the size of the study area as that potentially affected by perturbations to water quality parameters (Part 2, Section 2).?This area became the Study Area for this fisheries impact assessment.?The importance of potentially impacted fishing resources and fisheries operations identified within the Study Area was assessed using the EIAO-TM.?The potential impacts due to the construction and operation of the South Brothers Facility have been assessed (following the EIAO-TM Annex 17 guidelines) and the impacts evaluated (based on the criteria in EIAO-TM Annex 9).

 

4.3    Identification of Environmental Impacts

 

As discussed in Part 2, Section 1 the proposed South Brothers Facility will consist of three purposely dredged seabed pits.?The pits will be dredged sequentially prior to backfilling with contaminated mud and capping with uncontaminated mud.? Impacts associated with the South Brothers Facility are thus divided into those occurring during the dredging of pits and those during backfilling with contaminated mud and capping with uncontaminated mud.?Following this assessment the potential for residual impacts and cumulative impacts associated with concurrent projects, or through the combination of the above works, are discussed.

 

4.3.1    Backfilling

 

Impacts to the fisheries resources and sensitive receivers potentially arising from backfilling operations at the South Brothers Facility are as follows:

 

Changes in Water Quality

 

Impacts to water quality through both grab and trailer disposal backfilling operations have been discussed in Part 2, Section 2.?Through detailed water quality modelling it has been identified that backfilling operations will cause an increase in suspended solid concentrations in the water column.?Due to the greater loss rates associated with trailer disposal backfilling works, predicted concentrations calculated for these works have been used in the assessment as they thus represent a worst-case scenario.

 

Suspended Solids

 

Suspended sediment (SS) fluxes occur naturally in the marine environment, consequently fish have evolved behavioural adaptations to tolerate increased SS load (eg, clearing their gills by flushing water over them).?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 life cycle.?

 

Ma Wan Fish Culture Zone (FCZ):?Water quality modelling results presented in Part 2, Section 2 have shown that the maximum SS elevation at the FCZ as a result of backfilling operations is < 1 mg L-1.?These values do not exceed tolerance reported in adult fish at values below 125 mg L-1 ([1]), or the guideline values identified for fisheries and selected marine ecological sensitive receivers as part of the recent study for AFCD (50 mg L-1 - based on half of the no observable effect concentrations) ([2]).?Impacts to the Ma Wan FCZ as a result of the backfilling works are thus unlikely to occur as the increases in SS are expected to be negligible.

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Seasonal Spawning Ground: ?/span>SS concentrations predicted to exceed the WQO are expected to stay within relatively close proximity to backfilling operations (Part 2, Section 2).?As the South Brothers Facility lies outside the area that is generally considered to be a seasonal spawning area for commercial fisheries resources, which makes up the majority of central northwest Lantau waters, impacts to these seasonal spawning grounds are expected to be low.?In addition, it is worth noting that where relatively high concentrations of SS have been identified as having the potential to occur through backfilling operations, these are generally not predicted to occur in the surface layer, where most fish larvae, eggs and fry are likely to be found post-spawning.

 

Artificial Reefs:?The predicted elevations of SS concentrations at the ARs within the Marine Park as a result of backfilling operations are very low and compliant with the WQO (bottom layer = < 1 mg L-1 (dry season)).?Impacts, however, at the AR within the Airport Exclusion Zone are expected to occur.? SS elevations at this sensitive receiver have been predicted from the backfilling works cause an elevation of 21 mg L-1 (wet season).?Although these impacts exceed the WQO it should be noted that these predictions have been made at the bottom layer.?When the depth average elevations are examined (Annex A) it can be seen that the maximum depth average elevations are < 10 mg L-1 in both the wet and dry seasons.?These elevations, although above the WQO (annual of 5.7 mgL-1), are not expected to cause unacceptable impacts as such variations in SS values are observed throughout the year in this area.?Consequently, any species present on the ARs are expected to be tolerant of such SS elevations.?

 

Dissolved Oxygen

 

Depletions of DO as a result of backfilling activities have been predicted to be non-detectable and compliant with the relevant WQOs (Part 2, Section 2).?It is, thus, expected that unacceptable impacts to the fisheries resources in the vicinity of the South Brothers Facility will not occur.

 

Nutrients

 

Modelling results have indicated that the levels of nutrients are not predicted to increase appreciably from background conditions during the backfilling operations.? It is thus expected that unacceptable impacts to fisheries resources in the vicinity of the South Brothers Facility will not occur.

 

Contaminants

 

Aside from the effects of SS, DO and nutrient release on the water column backfilling operations have the potential for release of contaminants during disposal activities.? Contaminant impacts to fisheries may arise as a result of:

 

   accumulation of contaminants in the tissue of fish and invertebrates resulting in sublethal effects which may affect behaviour, reproduction and increasing susceptibility to disease; and

   increased mortality, and sub lethal effects to, eggs, larvae and juvenile species, as these are particularly sensitive to elevated contaminant concentrations.

 

Contaminants that accumulate in commercially important fish species may ultimately impact human health.? Investigation of this potential expected elevations in the body burden values of marine organisms as a result of backfilling operations at the South Brothers Facility has been determined through a bioaccumulation assessment (Annex B).?Predictions in the water quality assessment have indicated that the release of contaminants during backfilling operations at the South Brothers Facility will cause only minor elevations in the immediate vicinity of the pits.?Consequently, the bioaccumulation assessment has indicated that elevations in body burden levels are expected to be minor.?The implications of these elevations to the health of the Indo-Pacific Humpback Dolphin, Sousa chinensis, and human health through consumption of these organisms are discussed in Part 2, Section 5 and Annex C.

 

In addition to the above, it is important to note that a review of long term biomonitoring data collected in the East of Sha Chau area has indicated that current disposal operations are not resulting in an increase in contaminants in target species tissue levels ([3]).?As such, backfilling operations in the South Brothers Facility are also not expected to result in unacceptable impacts to fisheries resources with regard to contaminant loading.?

 

Vessel Traffic

 

Backfilling operations at the South Brothers Facility will introduce plant into an area where they do not occur frequently at present.?This has the potential to interfere with fishing vessel use of the area.? Information from the Port Survey has indicated that small vessels such as P4s mainly use the area ([4]).?Given that these vessels are highly mobile it is not expected that the marine vessels will interfere with the fishing activities of the small vessel operators in this area.

 

4.3.2    Dredging

 

Impacts to the fisheries resources and sensitive receivers potentially arising from dredging operations at the South Brothers Facility are as follows:

 

Habitat Loss

 

The construction of the South Brothers Facility will result in the direct temporary loss of approximately 164 ha, or 4.2%, of active AFCD Fishing Zones within northwestern Lantau waters.?Based on information presented in Part 1, Section 4, this would result in a temporary loss of 21,911 kg yr-1 adult fisheries production and 105 kg yr-1 of fry fisheries production, equating a 2.7 % and 0.5 % of the Fishing Zones production, respectively.?These numbers are considered to be low.?No unacceptable impacts to the annual fishery as a result of dredging operations at the South Brothers Facility are therefore considered to occur through dredging operations.

 

It should be noted that once dredging, filling and capping works associated with the South Brothers Facility are completed, the seabed and hydrodynamic regime is expected to restore to their original condition.?A review of long term monitoring in and around the existing capped pits at East of Sha Chau has demonstrated that within a relatively short period of time, recolonisation of sediments occurs returning the site to a pre-dredged state ([5]) ([6]).?Initially capped pits will be colonised by infaunal opportunists and during the early stages of recovery and diversity is expected to be low.?However, as more competitive species begin to colonise, the diversity of the infaunal, epifaunal benthic assemblages and demersal fisheries resources will increase until it returns to pre-dredged conditions.

 

Changes in Water Quality

 

Suspended Solids

 

Ma Wan Fish Culture Zone (FCZ):?Water quality modelling results presented in Part 2, Section 2 have shown that the maximum SS elevations at the FCZ as a result of dredging operations is < 1 mg L-1, which is well within the acceptable range and is not expected to cause adverse impacts.

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Seasonal Spawning Ground: ?/span>SS concentrations predicted to exceed the WQO are expected to stay within relatively close proximity to dredging operations (Part 2, Section 2).?As described for backfilling operations, the South Brothers Facility lies outside the seasonal spawning ground and impacts to the surface layer of the water column are minimal, therefore, impacts to the seasonal spawning ground are expected to be of low severity.

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Artificial Reefs:?Predicted elevations of SS concentrations at ARs as a result of dredging operations are very low and compliant with the WQO (Marine Park AR: maximum = < 1 mg L-1 (dry season); Airport Exclusion Zone AR: maximum = < 1 mg L-1 (wet season)).?As such, no impacts to fisheries resources at the ARs as a result of dredging operations are expected to occur.

 

Vessel Traffic

 

Dredging operations at the South Brothers Facility will introduce plant into an area where they do not occur frequently at present.?As discussed under the assessment of backfilling operations, information from the Port Survey indicate that small vessels such as P4s mainly use the area.?Given that these vessels are highly mobile it is not expected that the marine vessels will interfere with the fishing activities of the small vessel operators in this area.

 

4.3.3    Capping

 

Impacts to the fisheries resources and sensitive receivers potentially arising from capping operations at the South Brothers Facility are as follows:


Changes in Water Quality

 

Suspended Solids

 

Ma Wan Fish Culture Zone (FCZ):?Water quality modelling results presented in Part 2, Section 2 have shown that the maximum SS elevations at the FCZ as a result of capping operations is < 1 mg L-1, which is well within the acceptable range and is not expected to cause adverse impacts.

 

Seasonal Spawning Ground: ?/span>SS concentrations predicted to exceed the WQO are expected to stay within relatively close proximity to capping operations (Part 2, Section 2).?As described under Section 4.3.1, the South Brothers Facility lies outside the area that is to be a seasonal spawning area for commercial fisheries resources and elevations in SS are not expected to occur in the surface layer, where most fish larvae, eggs and fry are likely to be found post-spawning, therefore, impacts to the seasonal spawning ground are expected to be of low severity.

 

Artificial Reefs:?Predicted elevations of SS concentrations at the ARs within as a result of capping operations are very low and compliant with the WQO (Marine Park AR: maximum = < 1 mg L-1 (dry season); Airport Exclusion Zone AR: maximum = 1.3 mg L-1 (wet season)).? As such, no impacts to fisheries resources at the ARs as a result of capping operations are expected to occur.

 

Dissolved Oxygen

 

Depletions of DO as a result of capping activities have been predicted to be non-detectable and compliant with the relevant WQOs (Part 2, Section 2).? It is, thus, expected that unacceptable impacts to the fisheries resources in the vicinity of the South Brothers Facility will not occur.

 

Nutrients

 

Modelling results have indicated that the levels of nutrients are not predicted to increase appreciably from background conditions during the capping operations.? It is thus expected that unacceptable impacts to fisheries resources in the vicinity of the South Brothers Facility will not occur.

 

Vessel Traffic

 

Capping operations at the South Brothers Facility will introduce plant into an area where they do not occur frequently at present.?As discussed under the assessment of backfilling operations, information from the Port Survey indicate that small vessels such as P4s mainly use the area.?Given that these vessels are highly mobile it is not expected that the marine vessels will interfere with the fishing activities of the small vessel operators in this area.

 

4.4    Assessment of Environmental Impacts

 

From the information presented above, the fisheries impact associated with the South Brothers Facility is considered to be low.?An evaluation of the impact in accordance with Annex 9 of the EIAO-TM is presented below.

 

          Nature of impact:?Low severity direct impacts will occur to fisheries resources within the pit boundaries of the South Brothers Facility.?Low severity indirect impacts as a result of the dredging, backfilling and capping operations are predicted to occur in the vicinity of the pits as result of minor perturbations to water quality.
          Size of affected area:?The construction of the South Brothers Facility will result in the direct temporary loss of approximately 164 ha, or 4.2%, of active AFCD Fishing Zones within northwestern Lantau waters.?Upon completion of backfilling and capping the natural seabed will be restored and the fishing area reinstated.
          Size of fisheries resources / production:?The construction of the South Brothers Facility will result in the direct temporary loss of 21,911 kg yr-1 adult fisheries production and 105 kg yr-1 of fry fisheries production, equating a 2.7 % and 0.8 % of the Fishing Zones production, respectively.?These numbers are considered to be low.?
          Destruction and disturbance of nursery and spawning grounds:?The central northwestern waters off Lantau have previously been identified as a seasonal spawning ground for commercially important species.?The construction and operation of the South Brothers Facility is predicted to cause minor disturbances to the spawning area as the pit boundaries lie outside of the spawning area and impacts to the surface layer, where most fish larvae, eggs and fry are likely to be found post-spawning, are minimal. Impacts can, therefore, be considered as of low magnitude ([7]).
          Impact on fishing activity:?The South Brothers Facility will be constructed and operated in area used by small-scale fishermen operating P4 type vessels.?Impacts arisings from the facility are largely confined to the facility area, which occupies only 4.2 % of the area of fishing zones it lies within.
          Impact on aquaculture activity:?Based on the Water Quality Objectives and AFCD criteria, the Ma Wan FCZ is not predicted to be impacted by either SS elevations, DO depletions or nutrient elevations as a result of the South Brothers Facility.

 

4.5    Mitigation of Adverse Environmental Impacts

 

In accordance with the guidelines in the EIAO-TM on fisheries impact assessment the general policy for mitigating impacts to fisheries, in order of priority, are avoidance, minimization and compensation.
Impacts to fisheries resources and fishing operations have largely been avoided during construction and operation of the South Brothers Facility through constraints on backfilling and dredging activities.?These constraints were recommended in Part 2, Section 2 to control water quality impacts to within acceptable levels and are also expected to control impacts to fisheries resources.? Hence, no fisheries-specific mitigation measures are required during construction and operation of the South Brothers Facility.

 

4.6    Residual Fisheries Impacts

 

The only residual impact identified that may affect commercial fishing operations as a result of the construction and operation of the South Brothers Facility is the disturbance to fishing activities during the lifetime of the mud disposal facility.? However, the severity of this residual impact is predicted to be no greater than during previous or ongoing mud disposal activities at the Contaminated Mud Disposal Facility at East of Sha Chau which have been shown through a review of long term fisheries resources data to have no detectable adverse impacts to fisheries ([8]).

 

4.6.1    Cumulative Impacts

 

The water quality impact assessment section has presented a discussion on the impacts of cumulative activities on water quality.?Cumulative impacts to fisheries resources and fishing operations may arise from concurrent dredging, backfilling or development projects in the area.?In addition, cumulative impacts through the combination of dredging, backfilling and capping operations within the South Brothers Facility have the potential to occur.?

It is apparent that the elevations of SS are higher when concurrent activities are examined as opposed to when backfilling or dredging is examined separately.

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          Elevations at the Ma Wan FCZ not predicted to exceed 2 mg L-1 (dry season) which is within the tolerance criteria discussed above and consequently, acceptable;

          The majority contributor to the cumulative impact results appears to be Type 1, or Type 1 (dedicated), disposal operations at the North Brothers MBA.?Should operational controls be employed to manage disposal operations they should focus on operations at the North Brothers MBA. ?/span>Operations within the proposed South Brothers Facility, ie dredging, backfilling and capping were shown to be able to proceed concurrently in an environmentally acceptable manner.

          Under the cumulative scenario, the AR within the Airport Exclusion Zone has the potential to experience maximum elevations of SS of < 3 mg L-1 (wet season – barge disposal).?As such, no exceedances of the WQO are expected to occur.

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4.7    Environmental Monitoring and Audit

 

The construction and operation of the proposed South Brothers Facility has been shown to proceed at rates that maintain environmental impacts to within acceptable levels.?Actual impacts during the works will be monitored by through a detailed Environmental Monitoring and Audit (EM&A) programme.? Full details of the EM&A programme are presented in the EM&A Manual which has been based on the on-going and previous monitoring programmes conducted at the Contaminated Mud Disposal Facility at East of Sha Chau.?This programme will provide management actions and supplemental mitigation measures to be employed should impacts arise, thereby ensuring the environmental acceptability of the South Brothers Facility.

 

4.8    Conclusions

 

Reviews of existing information on commercial fisheries resources and fishing operations located within the Study Area have been undertaken.?Information from a study on fishing operations in Hong Kong and the AFCD Port Surveys indicate that fisheries production values in the vicinity of the South Brothers Facility vary but are medium to low.

 

The construction and operation of the South Brothers Facility may give rise to fisheries impacts from disturbances to benthic habitats, changes in water quality and contaminant release.?Disturbances to benthic habitats are predicted to be confined within the pit boundaries of the South Brothers facility, and recolonisation of sediments is expected to occur following completion of works.?As changes in water quality are minimal and transient, adverse impacts to fisheries resources are not predicted to arise.?Assessment of contaminant release has indicated that the concentrations will be minimal and well within the relevant criteria.

While no special mitigation measures are required for fisheries resources, mitigation measures recommended to reduce impacts to water quality are also expected to mitigate any impacts to fisheries resources.


 



([1]) ?? Binnie Consultants Limited (1994)?Marine Ecology of the Ninepin Islands.?For the Fill Management Department., Hong Kong SAR Government.

([2])???City University of Hong Kong (2001) Consultancy Study on Fisheries and marine Ecological Criteria for Impact Assessment (Agreement No. CE 62/98).?Final Report.?For the Agriculture, Fisheries and Conservation Department, Hong Kong SAR Government.

([3]) ?? ERM - Hong Kong, (2004)?Detailed Site Selection Study for a Proposed Contaminated Mud Disposal Facility within the Airport East/East of Sha Chau (Agreement No. CE 12/2002 (EP)) - Environmental Monitoring Data Review.?For the Civil Engineering Department, Hong Kong SAR Government.

([4]) ?? Agriculture, Fisheries and Conservation Department (1998) Port Survey 1996/1997.

([5]) ?? ERM - Hong Kong, (2004)?Detailed Site Selection Study for a Proposed Contaminated Mud Disposal Facility within the Airport East/East of Sha Chau (Agreement No. CE 12/2002 (EP)) - Environmental Monitoring Data Review.?For the Civil Engineering Department, Hong Kong SAR Government.

([6]) ?? Qian PY, Qiu JW, Kennish R and Reid C (2003)? Recolonization of benthic infauna subsequent to capping of contaminated dredged material in East Sha Chau, Hong Kong.? Estuarine, Coastal and Shelf Science 56: 819-831.

([7]) ?? ERM - Hong Kong, Ltd (1998)?Fisheries Resources and Fishing Operations in Hong Kong.? Final Report.?For the Agriculture, Fisheries and Conservation Department, Hong Kong?/span>SAR Government.

([8]) ?? ERM - Hong Kong (2004)? Op cit.