To support the increased use of natural gas in Hong Kong from 2020 onwards, Castle Peak Power Company Limited (CAPCO) and The Hongkong Electric Co., Ltd. (HK Electric) have identified that the development of an offshore liquefied natural gas (LNG) receiving terminal in Hong Kong using Floating Storage and Regasification Unit (FSRU) technology (‘the Project’) presents a viable additional gas supply option that will provide energy security through access to competitive gas supplies from world markets. The Project involves the construction and operation of an offshore LNG import facility to be located in the southern waters of Hong Kong, a double berth jetty, and subsea pipelines that connect to the gas receiving stations (GRS) at the Black Point Power Station (BPPS) and the Lamma Power Station (LPS). In accordance with the Updated EM&A Manual of the Project, marine mammal monitoring has been conducted covering baseline, construction and post-construction periods.

Further to the completion of the marine-based construction works in October 2022, post-construction marine mammal monitoring was conducted between November 2022 and October 2023 for vessel-based line transect survey and between November 2022 and December 2023 for passive acoustic monitoring (PAM). A total of 103 groups of 250 Finless Porpoises (FPs) were sighted among the three survey areas between November 2022 and October 2023. The monthly variations in combined encounter rates during the post-construction monitoring period indicated that FP occurrences peaked in November 2022, with another peak between February 2023 and April 2023, which are broadly in line with the understanding of seasonal variation in distribution of FP in Hong Kong waters with peak season during winter and spring (December – May) in southern waters. For the PAM results collected between November 2022 and December 2023, the mean porpoise detection positive minutes (DPM) per day ranged from 80.1 to 245.4 for the five deployment locations.

The change in distribution of the finless porpoises between the baseline, construction and post-construction monitoring was evaluated. The number of sightings and number of FPs were found to be higher during post-construction monitoring (23 groups of 78 FPs) when comparing with the same monitoring period (i.e. June to November) of baseline monitoring (18 groups of 35 FPs) and construction monitoring (19 groups of 62 FPs). A few FP sightings were recorded near the Jetty during post-construction phase, indicating the return of FPs around the Jetty upon cessation of the disturbance. The PAM results also showed a return of porpoise usage to a level similar to the baseline period around the Jetty during the post-construction monitoring period.

Overall, unacceptable impacts on marine mammals due to the Project were not detected, which aligns with the EIA study predictions.

1. Introduction

1.1 Background

To support the increased use of natural gas in Hong Kong from 2020 onwards, Castle Peak Power Company Limited (CAPCO) and The Hongkong Electric Co., Ltd. (HK Electric) have identified that the development of an offshore liquefied natural gas (LNG) receiving terminal in Hong Kong using Floating Storage and Regasification Unit (FSRU) technology (‘the Project’) presents a viable additional gas supply option that will provide energy security through access to competitive gas supplies from world markets. The Project will involve the construction and operation of an offshore LNG import facility to be located in the southern waters of Hong Kong, a double berth jetty, and subsea pipelines that connect to the gas receiving stations (GRS) at the Black Point Power Station (BPPS) and the Lamma Power Station (LPS).

The Environmental Impact Assessment (EIA) Report for the Project was submitted to the Environmental Protection Department (EPD) of the HKSAR Government in May 2018. The EIA Report (EIAO Register No. AEIAR-218/2018) was approved by EPD and the associated Environmental Permit (EP) (EP-558/2018) was issued in October 2018.

An application for Further Environmental Permits (FEPs) was made on 24 December 2019 to demarcate the works between the different parties. The following FEPs were issued on 17 January 2020 and the EP under EP-558/2018 was surrendered on 5 March 2020.

n the double berth jetty at LNG Terminal under the Hong Kong LNG Terminal Limited (HKLTL), joint venture between CAPCO and HK Electric (FEP-01/558/2018/A) ([1]⁾ – construction commenced on 27 November 2020;

n the subsea gas pipeline for the BPPS and the associated GRS in the BPPS under CAPCO (FEP-03/558/2018/B) ([2]⁾ – construction commenced on 23 September 2020; and

n the subsea gas pipeline for the LPS and the associated GRS in the LPS under HK Electric (FEP-02/558/2018/A)⁽[3]⁾– construction commenced on 13 December 2020.

The location of these components is shown in Figure 1.1.

This Post-Construction Marine Mammal Monitoring Report is prepared in accordance with the requirements as set out in the Updated EM&A Manual of the Project.

1.2 Structure of the Report

The remainder of the report is structured as follows:

n Section 2 details the monitoring locations, monitoring methodology and the monitoring results; and

n Section 3 provides the conclusion of this post-construction marine mammal monitoring.

2. Marine Mammal Monitoring

In order to determine the efficacy of the recommended mitigation measures and provide verification of impact prediction/ evaluation of results, marine mammal monitoring was conducted using vessel-based line transect survey and passive acoustic monitoring (PAM) method according to the Updated EM&A Manual.

2.1 Monitoring Methodology

2.1.1 Vessel-based Line Transect Survey

Vessel-based marine mammal survey by means of systematic line-transect boat survey was undertaken to examine the distribution and encounter rate of Finless Porpoise (FP) in southern Lantau where a majority of Project construction works would take place. Survey transects covering three survey areas for line-transect boat surveys, namely Southwest Lantau (SWL), Southeast Lantau (SEL) and Lamma (LM), are presented in Figure 2.1.

The transect boat survey was conducted from a 15m inboard vessels (with an open upper deck above the pilothouse, providing a mostly unobstructed 180° view of the area ahead of the vessel), weather permitting (Beaufort 0-5, no heavy rain, and visibility > 1,200m). The marine mammal observer (MMO) team conducted searches and observations from the flying bridge area, 4-5m eye height above the water surface. In order to ensure the quality of the data and allow consistency with the long-term AFCD database, and take consideration of the sea conditions of the monitoring site, a team of three qualified and trained MMOs made up the survey team.

As the vessel transits the transect lines at a relatively constant speed of 13-15km hr^-1, the primary MMO searched for marine mammals continuously through 7 X 50 marine binoculars. A second MMO searched with unaided eye and filled out data sheets. Both MMOs searched ahead of the vessel, between 270° and 90° (in relation to the bow, which is defined as 0°). MMOs rotated positions approximately every 30 minutes. An additional MMO was on the boat, who rotated into position to give observers a rest after each hour of search effort to minimise fatigue.

Effort data collected during on-effort monitoring periods included time and position for the start and end of search effort, vessel speed, sea state (Beaufort scale), visibility, and distance travelled in each series (a continuous period of search effort). When marine mammals were sighted, the survey team would end the survey effort and fill out a sighting sheet. The vessel would divert from its course to approach the marine mammal group for group size estimation, behavioural observations, and collection of identification photos. The sighting sheet included information on initial sighting angle and distance, position of initial sighting, sea state, group size and composition, and behaviour, such as response to the survey vessel and associations with vessels. Position, distance travelled, and vessel speed were obtained from a hand-held Global Positioning System (GPS) unit. The perpendicular distance (PSD) of the marine mammal group to the transect line was later calculated from the initial sighting distance and angle.

All records of marine mammal sightings were collated, compiled and integrated with Geographic Information System (GIS). Positions of sightings together with group sizes, activities and calf occurrence were plotted on figures for illustration of spatial and temporal patterns of porpoise distribution, if any. The method for line transect analysis of porpoise encounter rate followed the established approach for AFCD long-term marine mammal monitoring ⁽[4]⁾. It should be noted that as FP are cryptic and difficult to identify as unique individuals with no useful natural markings, the potential of double counting could not be eliminated and hence rendering any abundance or density estimation confounded with serious violation of assumption under the line-transect survey method; therefore such analysis was not proposed to be completed for FP, which is the same approach adopted for the AFCD long-term marine mammal monitoring.

Further to the completion of the marine-based construction works in October 2022, vessel-based line transect marine mammal surveys were conducted for 12 months between November 2022 and October 2023 with each transect line surveyed twice per month during post-construction monitoring.

2.1.1.1 Distribution Pattern Analysis

The line-transect survey data was integrated with a Geographic Information System (GIS) to visualize and interpret different spatial and temporal patterns of FP distribution using their sighting positions collected from vessel surveys. Location data of porpoise groups were plotted on map layers of Hong Kong using a desktop GIS (ArcView© 3.1) to examine their distribution patterns in detail. The dataset was also stratified into different subsets to examine distribution patterns of porpoise groups with different categories of group sizes, activities, fishing boat associations and young calves.

2.1.1.2 Encounter Rate Analysis

Since the line-transect survey effort was uneven among different survey areas and across different months of the study period, the encounter rates of FP in terms of number of on-effort sightings per 100 km of survey effort, and total number of porpoise sighted on-effort per 100 km of survey effort) were calculated in each survey area in relation to the amount of survey effort conducted. The encounter rate could be used as an indicator to determine areas of importance to porpoises within the survey areas.

Only survey data collected under Beaufort 2 or below condition would be used for encounter rate analysis of FP ^([5]). Formula for encounter rate is provided below:

Encounter Rate of Number of Porpoise Sightings (STG)

Encounter Rate of Number of Porpoises (ANI)

2.1.2 Passive Acoustic Monitoring

Underwater PAM surveys were conducted to monitor porpoise usage of southern Lantau waters over 24 hours under all weather conditions. Specific C-POD (Cetacean-Porpoise Detector) devices were used to record vocalizations of echolocating toothed whales and dolphins, in particular FP by detecting the trains of echolocation sounds they produced. C-PODs were deployed at five locations on the seabed within and in the vicinity of the LNG Terminal site, including three monitoring locations near the LNG terminal site (i.e. Locations 2-4), one monitoring location at east of Tai A Chau (i.e. Location 1) and one monitoring location at southeast of Shek Kwu Chau (i.e. Location 5) (Figure 2.2). During each deployment, the C-POD unit serial numbers as well as the time and date of deployments were recorded. Information including the GPS positions and water depth at each of the deployment locations were also obtained. The records downloaded from the C-PODs were examined to identify vocalisation of FP. Analysis was undertaken to obtain information on FP, including:

n Number of clicks: calculated per hour to detect diel patterns, and per day to determine activity level at a site;

n Detection positive minutes (DPM): indicates the total amount of minutes where at least one click train was detected within a one minute time period, to measure the duration the FP spent in an area;

n Duration of click trains: provides an indication of the average density of FP at a site; and

n Encounter rates: represents the number of porpoise echolocation click train (>5 clicks) encounters per hour of acoustic measurement with the C-POD.

Any spatial or temporal trends (especially the 24-hour activity patterns) in changes of the above parameters were determined.

2.1.2.1 Analysis of PAM Data

For detailed data analyses, the raw click data on the C-POD was first converted by the CPOD.exe software to “CP1” files. The click data was then processed using the KERNO classifier to identify click trains and their likely sources, and to reject weak boat sonar. The classified click trains were recorded in a “CP3” file.

The integrity of data record was first checked, and the period of adequate deployment and correct operation were identified. Visual validation was then performed to assess the overall rate of false positive detection positive minutes (DPM) as identified by the KERNO classifier. This validation method was based on the characteristics of clicks, multi-path clusters, and trains. Additional criteria based on the characteristics of the ambient noise regime could also be used, particularly in relation to boat sonar and sediment transport noise, which could generate a large number of ultrasonic “clicks”.

Notably, the level of false positives is not some consistent fraction of true positives, but is determined by the prevalence of the sources that are liable to be misclassified as dolphin clicks, such as boat sonar and sediment transport noise. Moreover, it should be recognized that the cause of a substantial proportion of the “false positive porpoises” was actually true porpoises, but were rejected simply because they were not distinctive enough to meet the stringency of these criteria.

After the visual validations, the DPMs could then be assessed as the parameter for porpoise occurrences at each deployment location. The DPM was chosen to calculate the total number of minutes where at least one click train was detected within a one-minute period, in order to measure the amount of time porpoises spend in an area.

Using DPM could eliminate the possibility of counting individual click trains produced by more than one porpoise, as the number of animals detected is unknown. The DPM is also useful for detecting diel and seasonal patterns of porpoise occurrences in order to determine the level of habitat utilization by both species at the various deployment locations.

2.1.3 Action and Limit Levels for Marine Mammal Monitoring (Applicable for Construction Phase)

The Action and Limit Levels for marine mammal monitoring are established for the construction phase of the Project using encounter rate calculated from the six-month baseline vessel-based line transect surveys from the three survey areas as a whole in accordance with the Updated EM&A Manual. The combined baseline encounter rate was used to compare with the encounter rate obtained during construction phase monitoring calculated from last three month’s monitoring data (i.e. running quarterly value). This approach would allow natural seasonal fluctuations in FP encounter rate to be accounted for, and allow data to be reviewed every month such as appropriate remedial actions could be taken timely if the threshold values are triggered. The established Action and Limit Levels for the construction phase marine mammal monitoring are provided in Table 2.1. The Event and Action Plan for the construction phase marine mammal monitoring is provided in Table 2.2.

Table 2.1 Action and Limit Levels for Marine Mammal Monitoring

Monitoring Area	Action Level	Limit Level
SWL, SEL and LM as a whole	Running quarterly STG < 1.12 & ANI < 2.18	Two consecutive running quarterly STG < 1.12 & ANI < 2.18

Notes:

^a STG = Encounter Rate of Number of Porpoise Sightings

^b ANI = Encounter Rate of Number of Porpoises

^c Action / Limit Levels will be triggered if both STG and ANI fall below the criteria

Table 2.2 Event and Action Plan for Marine Mammal Monitoring

Event	Action
Event	ET	IEC	Contractor(s)	Project Proponents
Action Level exceeded	1. Check monitoring data and repeat data analysis to confirm findings; 2. Review available AFCD data and relevant EM&A data to check if the exceedance is due to natural variation or works related; 3. Identify potential source(s) of impact; 4. Inform the IEC, Project Proponents and Contractor; 5. Increase site inspection and audit frequency to ensure all the marine mammal protective and/or precautionary measures are properly implemented.	1. Check monitoring data and analysis and investigation by ET; 2. Conduct additional site inspection and audit with ET to ensure all the marine mammal protective and/or precautionary measures are properly implemented and advise Project Proponents the audit results and findings accordingly.	1. Inform the Project Proponents and confirm notification of the non-compliance in writing; 2. Conduct site inspection and audit with the ETL and IEC; 3. Ensure all the marine mammal protective and/or precautionary measures are properly implemented.	1. Discuss the need for increased site inspection and audit frequency proposed by ET with IEC and the Contractor; 2. Check the audit results and findings from ET and IEC.
Limit Level exceeded	1. Check monitoring data and repeat data analysis to confirm findings; 2. Review available AFCD data and relevant EM&A data to check if the exceedance is due to natural variation or works related; 3. Identify potential source(s) of impact; 4. Inform the IEC, Project Proponents and Contractor; 5. Increase site inspection and audit frequency to ensure all the marine mammal protective and/or precautionary measures are properly implemented; 6. Review previous occurrence of non-compliance events to investigate if there is a longer term trend that needs attention; 7. ET to discuss and confirm with Project Proponents, IEC and Contractor on the need for further mitigation measures (e.g. consider controlling and, if necessary suspending marine works associated with the suspected source of impact).	1. Check monitoring data and analysis and investigation by ET; 2. Conduct additional site inspection and audit with ET to ensure all the marine mammal protective and/or precautionary measures are properly implemented and advise Project Proponents the audit results and findings accordingly; 3. Discuss and confirm further mitigation measures with Project Proponents, ET and Contractor; 4. Supervise / audit the implementation of further mitigation measures and advise Project Proponents the results and findings accordingly.	1. Inform the Project Proponents and confirm notification of the non-compliance in writing; 2. Conduct site inspection and audit with the ETL and IEC; 3. Ensure all the marine mammal protective and/or precautionary measures are properly implemented; 4. Discuss and confirm further mitigation measures with the ETL, IEC and Project Proponents; 5. Carry out further measures when advised by ET and agreed by Project Proponents and IEC.	1. Discuss the need for increased site inspection and audit frequency proposed by ET with IEC and the Contractor; 2. Check the audit results and findings from ET and IEC; 3. Discuss and confirm further mitigation measures with the ET, IEC and Contractor; 4. Supervise the implementation of further mitigation measures.

2.2 Monitoring Results

2.2.1 Vessel-based Line Transect Survey

2.2.1.1 Line-Transect Survey Effort

During the 12 months of post-construction monitoring surveys conducted between November 2022 and October 2023 after completion of the marine-based construction works in October 2022, a total of 72 line-transect surveys were conducted among the three survey areas in SWL, SEL and LM. The detailed monitoring schedule is shown in Annex A. Details of these survey effort data are presented in Annex B.

A total of 5,154.78 km of survey effort was collected from the line-transect vessel surveys, which included 1,677.35 km in SWL, 1,634.17 km in SEL and 1,834.26 km in LM (Annex B). The total survey effort conducted on primary and secondary lines among these three survey areas were 4,286.48 km and 868.30 km, respectively. 67.4% of the total survey effort was conducted in condition of Beaufort Sea State 2 or below with good visibility, and such data can be used for the encounter rate analysis of FP. No other major activities that might affect the results were recorded during the surveys.

2.2.1.2 Finless Porpoise Sightings

For the 12-month post-construction monitoring period, a total of 103 groups of 250 FPs were sighted among the three survey areas and 101 groups of 248 FPs were sighted during on-effort search (Annex C). Among these FP sightings, a total of 82 groups of 218 FPs were sighted at Beaufort 2 or below (Annex C), which can be utilized for encounter rate analysis.

2.2.1.3 Distribution and Habitat Use of Finless Porpoise

Throughout the post-construction monitoring period, FP were regularly sighted in all three survey areas of SWL, SEL and LM (Figure 2.3) and they were mainly recorded at both western and eastern sides of Tai A Chau, and the waters between Siu A Chau and Shek Kwu Chau (especially at the juncture of SWL and SEL survey areas). On the contrary, FPs rarely occurred at the western portion of SWL waters, the inshore waters to the south of Lantau Island (except a handful of sighting made near Shui Hau Peninsula), as well as the offshore waters to the south of Shek Kwu Chau (Figure 2.3). Furthermore, FP sightings made in the western side of LM survey area were quite scattered, but it appeared that they occurred more often at the offshore waters than inshore waters in LM survey area. Several FP sightings were made near the Project area.

The FP sighting distribution with different group sizes is shown in Figure 2.4. The group sizes of FP occurred during the post-construction monitoring period ranged from 1 to 16 animals, with an overall mean of 2.4 ± 2.49. The majority of FP groups were very small, with 71.8% of porpoise groups composed of 1-2 animals, and 87.3% of porpoise groups composed of fewer than five animals (Annex C). On the contrary, there were ten groups with 5-9 animals per group, and three groups with more than 10 animals per group (Annex C). The very small groups of 1-2 porpoises largely resembled their overall distribution for the post-construction monitoring period. On the other hand, the medium-sized groups with 3-4 porpoises per group were scattered around the Soko Islands (mainly on the southern side), near Shek Kwu Chau and Pui O Wan and the offshore waters in SEL and LM survey areas. Notably, the larger groups of porpoises were mostly located at the southern side of Tai A Chau, and between Shek Kwu Chau and Siu A Chau (Figure 2.4). The exceptionally large group of porpoises were located to the northeast of Siu A Chau, between Siu A Chau and Shek Kwu Chau, and between Shek Kwu Chau and Cheung Chau.

2.2.1.4 Encounter Rates of Finless Porpoise

The combined encounter rates of FP from SWL, SEL and LM during the 12-month post-construction monitoring period was 2.36 sightings per 100 km of survey effort. The monthly variations in combined encounter rates during the post-construction monitoring period indicated that FP occurrences peaked in November 2022, with another peak between February 2023 and April 2023 (Table 2.3).

Table 2.3 Monthly and Quarterly STG and ANI for Finless Porpoise

Survey Period	On-effort (km)	No. of Sighting	No. of Porpoise	STG	ANI
Nov 2022	116.27	4	19	3.44	16.34
Dec 2022	249.03	7	13	2.81	5.22
Jan 2023	305.74	7	10	2.29	3.27
Feb 2023	381.36	13	37	3.41	9.70
Mar 2023	271.00	16	40	5.90	14.76
Apr 2023	234.50	8	19	3.41	8.10
May 2023	308.75	8	21	2.59	6.80
Jun 2023	279.36	3	5	1.07	1.79
Jul 2023	365.41	1	3	0.27	0.82
Aug 2023	327.61	3	7	0.92	2.14
Sep 2023	317.93	9	24	2.83	7.55
Oct 2023	315.39	3	20	0.95	6.34
Overall (Nov 2022-Oct 2023)	3472.35	82	218	2.36	6.28

Notes:

^a Only data collected at Beaufort 2 or below were included for encounter rate analysis.

2.2.2 Passive Acoustic Monitoring

2.2.2.1 Summary of Passive Acoustic Monitoring Data Collection

C-POD units were deployed at five locations (see Figure 2.2 for the locations) during the post-monitoring period from 9 November 2022 to 6 December 2023 after completion of the marine-based construction works in October 2022. All units from the five deployment locations were recovered and refurbished for data download. The mean porpoise detection positive minutes (DPM) per day ranged from 80.1 to 245.4 for the five deployment locations. The summaries of deployment data are presented in Table 2.4 below, with detection statistics of FP included in Annex D.

Table 2.4 Summary of PAM Data for each Location

Location	Description
Location 1 (East of Tai A Chau)	The C-POD units were deployed for 282.9 days during the period of 9 November 2022 to 25 November 2023. Data could not be retrieved between 26 February and 4 May 2023, 22 August and 20 September 2023 as well as after 25 November 2023 due to equipment failure. Porpoise activity was recorded on most monitoring days (99.7%), with mean porpoise DPM per day to be 144.8.
Location 2 (FSRU-W)	The C-POD units were deployed for 319.1 days during the period of 9 November 2022 to 5 December 2023. The C-POD unit was lost during the period of 10 July 2023 to 20 September 2023. Porpoise activity was recorded on all monitoring days (100%), with mean porpoise DPM per day to be 237.8.
Location 3 (FSRU-E)	The C-POD units were deployed for 391.1 days during the period of 9 November 2022 to 5 December 2023. Porpoise activity was recorded on all monitoring days (100%), with mean porpoise DPM per day to be 245.4.
Location 4 (FSRU-N)	The C-POD units were deployed for 341.0 days during the period of 10 November 2022 to 17 October 2023. Data could not be retrieved after 17 October 2023 due to equipment failure. Porpoise activity was recorded on most monitoring days (92.4%), with mean porpoise DPM per day to be 183.0.
Location 5 (Shek Kwu Chau)	The C-POD units were deployed for 329.0 days during the period of 9 November 2022 to 25 November 2023. Data could not be retrieved between 10 December 2022 and 10 February 2023 due to equipment failure. Porpoise activity was recorded on most monitoring days (99.4%), with mean porpoise DPM per day to be 80.1.

2.2.2.2 Evaluation of Detection Errors, Loss of Click Detections and Boat Sonar

Visual validation was used to assess the overall rate of false positive porpoise DPM as identified by the KERNO classifier. Such false positives were found to be 0-2% (with 95% confidence level) across the monitoring locations (Annex D). Inspection of the sampled porpoise DPM found that the majority of false positives were most likely due to misclassified boat sonar noise.

Notably, the minute click limit can be exceeded in very noisy environments, meaning that no further clicks will be detected until the start of the next minutes. However, no time was lost at all five monitoring locations. Moreover, boat sonar was detected throughout the five monitoring locations, and this was generally around 50 kHz.

2.2.2.3 Temporal Variations in Finless Porpoise Occurrences

Variations in porpoise activity per day were observed at all five locations (Figure 2.5). At Location 1 (East of Tai A Chau), much higher porpoise activity was detected in February 2023 as well as in late September to October 2023. In contrast, such activity dropped noticeably between mid-June and mid-July, and in November 2023. Both Location 2 (FSRU-W) and Location 3 (FSRU-E) showed similar patterns in porpoise activities with several peaks detected between March and May 2023. At Location 3 (FSRU-E) with no interrupted period of data collection, there were several larger peaks between February and September 2023. Higher porpoise activity was detected between January and May 2023 at Location 4 (FSRU-N). In contrast, Location 5 (Shek Kwu Chau) recorded the least porpoise activity amongst the five locations.

2.2.2.4 Diel Patterns on Finless Porpoise Occurrences

The diel patterns of FP occurrences at the five deployment locations are presented in Figures 2.6-2.7. All five locations generally showed a decline in porpoise activity from late morning to the middle of the day to some extent. Similar diel patterns were observed in Locations 2 - 4 (i.e. locations near the LNG terminal site) with peaks at early morning (around 6-7 am) and early evening (around 6-7 pm). Location 1 (East of Tai A Chau) and Location 5 (Shek Kwu Chau) were observed to have higher porpoise activity during night-time.

2.3 Evaluation

For vessel-based line transect monitoring, the sightings of FP for the three monitoring phases (baseline, construction and post-construction) are presented in Figure 2.8. The results showed that FP were sighted in all the three survey areas (i.e. SWL, SEL and LM) during the three monitoring phases with sightings mainly recorded at both western and eastern sides of Tai A Chau, and the waters between Siu A Chau and Shek Kwu Chau (especially at the juncture of SWL and SEL survey areas). In addition, a few FP sightings were recorded near the Jetty during post-construction phase, indicating the return of FPs around the Jetty upon cessation of the disturbance. The findings are generally in line with the EIA prediction that marine mammals are expected to avoid the vicinity of the works areas and would return to the areas upon cessation of the disturbance. Based on the literature review, it is understood that seasonal variation in distribution is evident for FP in Hong Kong ^{([6])([7])([8])}. FPs were reported to be more commonly sighted in southern waters (i.e. waters off South Lantau and Lamma) during winter (December-February) and spring (March-May), while in summer (June-August) and autumn (September-November) they occurred more often in eastern waters ^([9])([10]). The 12-month post-construction monitoring showed that higher encounter rates of FP were recorded during winter and spring (December – May) which are broadly in line with the understanding of seasonal variation in distribution of FP in Hong Kong waters with peak season during winter and spring (December – May) in southern waters. The number of sightings and number of FPs were found to be higher during post-construction monitoring (23 groups of 78 FPs) when comparing with the same monitoring period (i.e. June to November) of baseline monitoring (18 groups of 35 FPs) and construction monitoring (19 groups of 62 FPs) ^([11]). Based on the vessel-based line transect survey results from the baseline, construction and post-construction monitoring, there is no evidence of unacceptable impacts on change in marine mammal distribution, abundance and usage pattern in the wider Hong Kong waters due to the construction of the Project.

For the PAM results, the mean porpoise DPM per day at the five deployment locations generally followed similar pattern amongst the baseline, construction and post-construction monitoring, with higher mean porpoise DPM per day recorded near the Jetty (i.e. Location 2, Location 3 and Location 4) during baseline (ranged from 207.1 to 241.5) and post-construction (ranged from 183.0 to 245.4) monitoring, and lower mean porpoise DPM per day recorded during construction monitoring (ranged from 80.3 to 137.9). This indicates that porpoise activities near the Jetty were lower during the construction phase, and then porpoise activities returned to a level similar to the baseline period during the post-construction phase. Diel patterns were found to be similar amongst the baseline, construction and post-construction monitoring with a decline in porpoise activity from late morning to the middle of the day to some extent. There is no observable change of diel patterns throughout the three monitoring phases. Based on the PAM results from the baseline, construction and post-construction monitoring, it is observed that there is a return of porpoise usage to a level similar to the baseline period around the Jetty during the post-construction monitoring period.

Overall, unacceptable impacts on marine mammals due to the Project were not detected, which aligns with the EIA study predictions.

3. Conclusion

In accordance with the Updated EM&A Manual of the Project, post-construction marine mammal monitoring was conducted between November 2022 and December 2023 upon completion of marine construction activities for the Project.

A total of 103 groups of 250 FPs were sighted among the three survey areas between November 2022 and October 2023. The monthly variations in combined encounter rates during the post-construction monitoring period indicated that FP occurrences peaked in November 2022, with another peak between February 2023 and April 2023, which are broadly in line with the understanding of seasonal variation in distribution of FP in Hong Kong waters. For the PAM results collected between November 2022 and December 2023, the mean porpoise DPM per day ranged from 80.1 to 245.4 for the five deployment locations.

Overall, unacceptable impacts on marine mammals due to the Project were not detected, which aligns with the EIA study predictions.

([1]) Application for variation of an environmental permit for FEP-01/558/2018 was undertaken and the latest FEP (FEP-01/558/2018/A) was issued on 6 November 2020.

([2]) Application for variation of an environmental permit for FEP-03/558/2018/A was undertaken and the latest FEP (FEP-03/558/2018/B) was issued on 25 August 2021.

([3]) Application for variation of an environmental permit for FEP-02/558/2018 was undertaken and the latest FEP (FEP-02/558/2018/A) was issued on 22 December 2020.

([4])Samuel K.Y. Hung (2015) Monitoring of Marine Mammals in Hong Kong Waters (2014-15): Final Report (1 April 2014 to 31 March 2015). Submitted to the Agriculture, Fisheries and Conservation Department of the Hong Kong SAR Government Tender Re.: AFCD/SQ/177/13

([5]) Samuel K.Y. Hung (2018) Monitoring of Marine Mammals in Hong Kong Waters (2018-19): Final Report (1 April 2018 to 31 March 2019). Submitted to the Agriculture, Fisheries and Conservation Department of the Hong Kong SAR Government Tender Re.: AFCD/SQ/197/17

([6]) Jefferson, T. A. and Braulik, G. T. 1999. Preliminary report on the ecology of the finless porpoise in Hong Kong waters. IBI Reports 9: 41-54.

([7]) Jefferson, T. A., Hung, S. K., Law, L., Torey, M. and Tregenza, N. 2002. Distribution and abundance of finless porpoises in Hong Kong and adjacent waters of China. Raffles Bulletin of Zoology, Supplement 10:43-55.

([8]) Hung, S. K. 2005. Monitoring of finless porpoise (Neophocaena phocaenoides) in Hong Kong waters: final report (2003-05). An unpublished report submitted to the Agriculture, Fisheries and Conservation Department, 95 pp.

([9]) Jefferson, T. A., Hung, S. K., Law, L., Torey, M. and Tregenza, N. 2002. Op cit.

([10]) Hung, S. K. 2005. Op cit.

([11]) It should be noted that construction phase marine mammal monitoring was conducted in December 2020 and July to November 2021. The data collected in July to November 2021 are presented for comparison.