Hong Kong-Zhuhai-Macao Bridge Hong Kong Boundary Crossing Facilities-Reclamation Works

 

 

September – November 2013

Quarterly Report

Dolphin Impact Monitoring

 

 

 

 

 


TABLE OF CONTENTS

1. Introduction                                                                                                                       1

 

2. Objectives and Methodology                                                                                          2

2.1. Objectives of the Present Study                                                                                     2

2.2. Line-transect Vessel Surveys                                                                                         2

2.2.1 Baseline Survey Data and Data from Impact Monitoring                                             3

2.3. Photo-Identification                                                                                                          6

2.4. Data Analyses                                                                                                                 6

2.4.1. Distribution pattern analysis                                                                                          6

2.4.2. Encounter rate analysis                                                                                                6

2.4.3. Quantitative grid analysis on habitat use                                                                      6

2.4.4. Behavioural analysis                                                                                                     6

2.4.5. Ranging pattern analysis                                                                                              7

 

3. Results and Discussions                                                                                                 7

3.1. Summary of survey effort and dolphin sightings                                                             7

3.2. Distribution                                                                                                                       8

3.3. Encounter rate                                                                                                                 9

3.4. Group size                                                                                                                       10

3.5. Habitat use                                                                                                                       10

3.6. Mother-calf pairs                                                                                                              10

3.7. Activities and associations with fishing boats                                                                 10

3.8. Photo-identification work and individual range use                                                         11

4. Conclusions                                                                                                                      11

5. References                                                                                                                                    12

 

Tables

Table 1            The Dolphin Monitoring Transect Co-Ordinates for

HKBCF Monthly Monitoring                                                                           4

 

Table 2            A Comparison of Total Sightings Recorded in NEL

and NWL Areas During September–November 2011; 2012; 2013               8

 

Table 3            A Comparison of “On Effort” Sightings Recorded in NEL and

NWL Combined During September–November 2011; 2012; 2013   8

 

Table 4            A Comparison of “On Effort” Sightings Recorded in NEL and

NWL During September–November 2011; 2012; 2013                                 9

 

Table 5            A Comparison of Encounter Rates* in NEL and NWL Areas

During September–November 2011; 2012; 2013                                          9

 

Table 6            A Comparison of Sightings Group Size Averages Recorded

in NEL and NWL Areas During September–November 2011; 2012; 2013   10


Figures

Figure 1.          The Hong Kong Boundary Crossing (HKBCF) Reclamation Sites,

North Lantau, Hong Kong                                                                               1

 

Figure 2           Location of the Transect Lines for Baseline and Impact

Monitoring during HKBCF (modified to accommodate HKBCF)                   5

 

Figure 3           Distribution of Sightings Recorded During Impact Monitoring

Surveys for HKBCF (September 2013)                                                         13

 

Figure 4           Distribution of Sightings Recorded During Impact Monitoring

Surveys for HKBCF (October 2013)                                                              14

 

Figure 5           Distribution of Sightings Recorded During Impact Monitoring

Surveys for HKBCF (November 2013)                                                          15

 

Figure 6           Distribution of Sightings Recorded During Impact Monitoring

Surveys for HKBCF (September – November 2013)                                                16

 

Figure 7.          The Location of Dolphin Groups Numbering 5 and Above Individuals

(September – November 2013)                                                                     17

 

Figure 8           Sighting density SPSE (number of on-effort sightings per 100

units of survey effort) for September – November 2013                               18

 

Figure 9           Dolphin density DPSE (number of dolphins per 100 units of

survey effort) for September – November 2013                                           19

 

Figure 10.        Location of groups containing mother and calf pairs during

September – November 2013                                                                        20

 

Figure 11.        Activity Budget for Dolphin Behaviour September – November 2013          21

 

Figure 12.        The Location of Different Behavioural Activities

September – November 2013                                                                        22

 

 

ANNEXES

 

Annex I            Summary of Data from the Baseline Monitoring, September – November 2012 and September – November 2013 and Calculated Encounter Rates

 

Annex II           Impact Monitoring Survey Schedule and Details (September – November 2013)

 

Annex III          Impact Monitoring Survey Effort Summary (September – November 2013)

 

Annex IV         Impact Monitoring Sighting Database (September – November 2013)

 

Annex V          Methods Proposal for Density Surface Modelling and Power Analyses Related to the Hong Kong Zhuhai Macau Bridge (HZMB))

 

Annex VI         Photo ID Images (September – November 2013)

 

 


1. Introduction

In March 2012, construction for the Hong Kong-Zhuhai-Macao Bridge (HZMB) began in Hong Kong territorial waters.  In Hong Kong, the HZMB comprises three projects; the Hong Kong Boundary Crossing Facilities (HKBCF) Project; the Hong Kong Link Road (HKLR) Project and; the Tuen Mun-Chek Lap Kok Link (TM-CLKL) Project.  The HKBCF, the first of the HZMB projects to commence in Hong Kong, requires the total reclamation of approximately 149 hectares (ha); which consists of 130 ha for the HKBCF artificial island and 19 ha for the TM-CLKL southern landfall (Fig. 1).

 

HZMB WWW about_overview03_p01l

 

Figure 1.  The Hong Kong Boundary Crossing (HKBCF) Reclamation Sites, North Lantau, Hong Kong (http://www.hzmb.hk/eng/img/overview/about_overview03_p01l.jpg)

 

The EM&A Manuals and Environmental Permits (EP) associated with all three projects have special provision for Chinese white dolphins (CWD) as they occur regularly in the waters which will be affected by the HZMB development.  This report comprises the seventh quarterly (September – November 2013) summary of data associated with the impact monitoring conducted for contract HY/2010/02, HKBCF-Reclamation Works.  The format of this report follows as closely as possible the outline provided for the Baseline Monitoring Report.  The baseline monitoring was conducted at the same as this quarter thus three years of quarterly monitoring can be compared in this report; 2011; 2012 and 2013.  Where appropriate, information from previous reports, data provided by the Hong Kong Highways Department (HyD) and data from the Agriculture, Fisheries and Conservation Department (AFCD) Marine Mammal Annual Monitoring reports have also been incorporated[1]


 

2. OBJECTIVES AND METHODOLOGY

2.1. Objectives of the Present Study

The EM&A Manual for HZMB states that “A dolphin monitoring programme at North Lantau and West Lantau waters, in particular the dolphin sighting hotspots (e.g. Brothers Islands) and areas where juveniles have been sighted (e.g. West Lantau waters), should be set up to verify the predictions of impacts and to ensure that there are no unforeseen impacts on the dolphin population during construction phase“.  For HKBCF the study area known as West Lantau was not included in the site specific EM&A Manual for construction phase survey work.  As such, for HKBCF, vessel-based dolphin surveys to monitor impact are conducted in the areas known as Northeast Lantau (NEL) and Northwest Lantau (NWL).  These surveys are conducted twice monthly and for the duration of the construction phase of HKBCF.  The HZMB baseline study (incorporating HKBCF, TM-CLK and HKLR phases of the bridge development), indicates that the data gathered from these surveys are intended to monitor impacts by;

 

providing ongoing assessment of the spatial and temporal distribution patterns and habitat use of CWD during the construction phase of the HKBCF project.

 

identifying individual CWD by their natural marks, coloration and scars for comparison with the baseline data and to assess individual distribution patterns and habitat use.

 

comparing impact survey data to that gathered during the baseline data period so that any changes deemed to be of a significant nature can be assessed and mitigated appropriately. 

 

The baseline monitoring report includes distribution analysis, encounter rate analysis, behavioural analysis, quantitative grid analysis and ranging pattern analysis.  Protocols for data interpretation and analyses methods were provided in the baseline monitoring report.

 

2.2. Line-transect Vessel Surveys

The co-ordinates for the transect lines and layout map were provided by AFCD, however, these have been modified as the construction works at HKBCF has shortened one of the transect lines (Table 1; Figure 2).  The study area now incorporates 23 transects (totalling ~111km) which are surveyed twice per month by boat.  Line transect surveys should be conducted systematically and lines travelled in sequence (Buckland et al 2001).  When the start of a transect line is reached, “on effort” survey begins.  When the vessel is travelling between transect lines and to and from the study area, it is deemed to be “off effort”.  The transect line is surveyed at a speed of 7-8 knots (13-15 km/hr).  During some periods, tide and current flow in the study site exceeds 7 knots and thus the vessel travels at the same speed as the current during these periods.  A minimum of four marine mammal observers (MMOs) are present on each survey, rotating through four positions; observers (2), data recorder (1) and rest (1).  Rotations occur every 30 minutes or at the end of dolphin sightings.  The data recorder enters vessel effort, observer effort, weather and sightings information directly onto the programme Logger[2] and is not part of the observer team.  This is not standard line transect survey procedure, however, the baseline study was conducted this way thus it has been requested that only two observers be used for impact surveys.


When the boat is travelling along the transect line (“on effort”), observers search the area in front of the boat between 90° and 270° abeam (bow being 0°).  When a group of dolphins is sighted, position, bearing and distance data are recorded immediately onto Logger and, after a short observation, an estimate is made of group size[3].  This is an “on effort” sighting.  These input parameters are linked to the time-GPS-ships data which are automatically stored in Logger throughout the survey period.  In this manner, information on heading, position, speed, weather, effort and sightings are stored in an interlinked database which can be subsequently used in a variety of analytical software packages.

Once the vessel leaves the transect line, it is deemed to be “off-effort”.  The dolphins are approached with the purpose of taking high resolution images.  Then the vessel returns to the transect line at the point of departure and is again “on effort”.  If another group of dolphins is seen while travelling back to the transect line, or when with the first group of dolphins, the sightings are considered as “opportunistic” and noted accordingly. 

           

2.2.1    Baseline Survey Data and Data from Impact Monitoring

Data from the baseline was provided by the Highways Department (January 2013) and data has been reported monthly throughout the impact monitoring period. For ease of reference, these data have been summarised from that previously reported and encounter rate calculations are provided (Annex I).

 


New Transect Lines

Figure 2          Location of the Transect Lines for Baseline and Impact Monitoring during HKBCF (modified to accommodate HKBCF)


2.3. Photo-identification

When a dolphin(s) is sighted, the vessel leaves the transect line and slowly approaches the group or individual.  Attempts are made to photograph every individual sighted although close approaches to mother and calf pairs are not attempted.  A digital SLR camera (Nikon D90) using long lenses (Nikor 80-200mm and fixed length 300mm) are used to obtain high resolution images.  Effort is made to ensure consistency of image quality, e.g., no shadow and at an angle perpendicular to the dorsal fin.  Polarising filters are used to minimise glare.  In this manner, the best image clarity is achieved and image sorting and matching is more consistent.  Images are sorted according to clarity and presence/absence of identifying features (nicks/cuts/deformities/injury/pigmentation).  Only images deemed to be of suitable quality and as containing sufficient markings for unambiguous identification are included in the photo-identification catalogue. 

 

2.4. Data Analyses

2.4.1. Distribution pattern analysis

Dolphin sightings data are mapped in the Geographic Information System (GIS) ArcView© 10.1.

 

2.4.2. Encounter rate analysis

For this report, the baseline encounter rates were re-calculated using the revised data provided (as presented in Annex I) rather than quoting directly from the baseline report.  Calculation followed the EM&A Manuel methodology (“on-effort” sightings made during favourable weather and visibility conditions).

 

2.4.3. Quantitative grid analysis of habitat use

Quantitative grid analysis is performed by mapping both sighting and dolphin densities plotted onto 1kmx1km grid squares.  Only “on effort” sightings made while on a transect line and under favourable conditions should be included in grid analyses.  These densities are standardised by effort by calculating survey coverage in each line transect survey to determine the number of times the grid has been surveyed.  Densities are calculated using the following formulae;

 

SPSE and DPSE:

 

                        SPSE = (S/E x 100)/SA%

                        DPSE = (D/E x 100)/SA%

Where;

                        S= total number “on effort” sightings

                        D = total number dolphins from “on effort” sightings

                        E = total number units survey effort

                        SA% = percentage of sea area

 

2.4.4. Behavioural analysis

When dolphins are sighted during vessel surveys, their behaviour is observed. Different activities are categorised (i.e. feeding, traveling, surface active, associated with boats, unknown) and recorded in the sighting data form of Logger.  The sightings form is integrated with survey effort and positional data and can be subsequently mapped to examine distribution and behavioural trends.  All sightings data (“on-effort” and “opportunistic”) are used in this analysis.


2.4.5. Ranging pattern analysis

Home ranges for individual dolphins can be calculated using a variety of software (Worton 1989).  In the baseline monitoring report, the program Animal Movement Analyst Extension, created by the Alaska Biological Science Centre, USGS was used in conjunction with ArcView© 3.1 and Spatial Analyst 2.0.  Using the fixed kernel method, kernel density estimates and kernel density plots are created using all sightings.  In the baseline monitoring, data from other studies and from outside the baseline monitoring period were used to map individual ranges.  It is important to maximize the number of sightings used as kernel analyses cannot be conducted unless more than 20 independent sightings are made for an individual although it is recommended that a minimum of 70 resightings are used before kernel analyses has any accuracy (Wauters et al 2007; Kauhala and Auttila 2010).  AFCD Annual Reports use a minimum of 15 resightings for kernel analyses (AFCD 2012).  To date, too few data on individual dolphins exist from impact monitoring alone, i.e., 15 or more independent resightings per individual, to map utilisation densities using the fixed kernel method.  The most resightings for an individual dolphin in the baseline and impact monitoring period combined is thirteen (HZMB 054) split across baseline (seven sightings) and impact monitoring (6 sightings).  A comparison of baseline and impact sightings using kernel analyses will require longer term data collection.

 

3. RESULTS AND DISCUSSIONS

3.1. Summary of survey effort and dolphin sightings

From September – November, 12 vessel surveys were conducted in NEL and NWL survey areas (Annex II).  A total of 668.2 km of “on-effort” transect lines were conducted, of which 665.9km were under favourable conditions.  Therefore, 99.7% of vessel surveys were conducted under favorable conditions (Annex III).  Only those periods of “on-effort” survey conducted under favourable conditions were included in quantitative analyses.  During September – November 2013, 42 groups of dolphins, numbering 133 (min 131: max 143[4]) individuals, were sighted from the vessel surveys.  Of these, 28 groups were “on-effort” and the remaining 14 “opportunistic” (Annex IV). 

            Of the 42 sightings, 41 groups were located in NWL and 1 in NEL.  The baseline report, conducted during September-November 2011, notes a total of 44 groups, 34 of which occurred in NWL and 10 in NEL.  For period September – November 2012, a total of 71 groups were sighted, 53 of which were located in NWL and 18 in NEL. There are differences between the number of sightings made during baseline compared to the same period in 2012 and 2013.  For NEL, the number of groups almost doubled between baseline (2011) and September – November 2012 and then decreased markedly in September – November 2013.  For NWL, both September – November 2012 and 2013 recorded larger numbers of groups when compared to baseline monitoring (Table 2).  Maps depicting location of sightings which have not been corrected for effort or survey track length are included as Figs. 3;4;5;6. 


Table 2.  A Comparison of Total Sightings Recorded in NEL and NWL Areas During Sep – Nov 2011; 2012 and 2013

Monitoring Period

Total Dolphin Sighting in NWL

Total Dolphin Sighting in NEL

Number of Groups

Number of Groups

Sep – Nov 2011*

(Baseline Monitoring)

34

10

Sep – Nov 2012*

(HKBCF Third Quarter)

53

18

Sep – Nov 2013*

(HKBCF Seventh Quarter)

41

1

*  All Surveys conducted once per month

As per the EM&A manual, only “on effort” sightings can be used for some analyses therefore the combined number of “on effort” sightings for all three periods was compared There is an increase in the total number of “on effort” sightings between baseline monitoring (2011) and impact monitoring (2012) but a decrease below both previous totals in September – November 2013 (Table 3).  No correction for effort is made with these numbers, this is calculated in section 3.3.

 

Table 3.  A Comparison of “On Effort” Sightings Recorded in NEL and NWL Combined During Sep – Nov 2011; 2012 and 2013.

Monitoring Period

Groups of Dolphin sighted in NEL and NWL

Sep - Nov 2011                (Baseline Monitoring)

44

Sep – Nov 2012

(HKBCF Third Quarter)

52

Sep – Nov 2013

(HKBCF Seventh Quarter)

28

 

3.2. Distribution

During the both the baseline survey and the same period the following year, approximately three quarters of all “on effort” sightings were made in NWL.  For the period September – November 2013, however, no “on effort” sightings were made in NEL.  The similarity between the 2011 and 2012 periods is noted, however, there is no correction for effort (Table 4).  Throughout September – November 2013, the area of most use was the northern section of NWL, within and adjacent to the Shau Chau and Lung Kwu Chau Marine Park (SCLKCMP).  A few groups were recorded at the Tai O area and only two groups at the E edge of the airport platform.  Only one group was recorded in NEL at the east of the Brothers Islands (Fig. 6).  These areas are highlighted consistently throughout AFCD annual monitoring reports as well as during pre construction monitoring.  SCLKCMP is frequented all year round by dolphins and is perceived to be critical habitat whereas the use of NEL is regarded as more seasonal, however, the decrease in the number of groups occurring in NEL compared to the same season in previous years is noteworthy. 


 

Table 4.  A Comparison of “On Effort” Sightings Recorded in NEL and NWL During Sep – Nov 2011; 2012 and 2013.

Monitoring Period

No. of Dolphin Groups sighted in NWL

No. of Dolphin Groups sighted in NEL

Sep - Nov 2011          (Baseline Monitoring)

34

10

Sep – Nov 2012

(HKBCF Third Quarter)

39

13

Sep – Nov 2013

(HKBCF Seventh Quarter)

28

0

 

3.3. Encounter rate

As the survey periods have different transect lengths, variation in sightings occurrence was quantified by correcting for the different amount of effort (number and distance of transect lines surveyed, i.e., km spent “on-effort”), to obtain an encounter rate.  The baseline study (Sep-Nov 2011) reports that a total of 545.6km[5] of survey effort was conducted under favourable conditions in the NEL and NWL survey areas.  In NEL and NWL combined, 659.8km and 665.9km of track-line were conducted under favourable conditions during the periods September – November 2012 and 2013, respectively.  In NEL, there is a slight increase in encounter rate between baseline and the same period the following year, however, for the period September – November 2013, there is a marked decrease in encounter rate. i.e., 6.3 to 0.  For NWL, there is a continuous decline in encounter rate from the baseline period through the same period the next and subsequent years, i.e., 9.5 to 8.7 to 6.3 (Table 5).

 

Table 5.  A Comparison of Encounter Rates* in NEL and NWL Areas During September-November 2011; 2012 and 2013.

Monitoring Period

Encounter Rate NEL

Encounter Rate NWL (*)

Sept-Nov 2011

(Baseline Monitoring)

5.4

9.5

Sep – Nov 2012

(HKBCF Third Quarter)

5.9

8.9

Sep – Nov 2013

(HKBCF Seventh Quarter)

0

6.3

 

The AFCD Annual Reports describe variation in spatial distribution between areas and between seasons in NEL and NWL.  For the last sixteen years, it is reported that overall annual encounter rate for NEL varies between 1.6 and 6.2 and the annual encounter rate for NWL varies between 5.8 and 17.0.  The encounter rate for NWL for all three periods (September – November 2011; 2012; 2013) is within the annual limits recorded for this area previously.  For NEL, the encounter rates in September – November 2011 and 2012 are within the recorded annual norms for the area, however, the encounter rate of zero for the same period 2013 is not.  Historically, there have been both up and down movements within these limits, however, the general trend in yearly encounter rate for dolphins in all areas of Hong Kong is that of significant decline over the last decade and prior to new development projects in the Lantau area (AFCD 2013).  The known decline in the population, on top of the highly variable encounter rate noted historically, makes it problematic to discern any additional influence individual projects, such as HKBCF and others, may have on the dolphin population encounter rate.  As the impact of the work at HKBCF extends in addition to new dredging and other projects being initiated in NEL, it is likely that these activities have effected NEL encounter rates.

3.4. Group size

During September – November 2013, group size of all sightings varied from 1 to 12 individuals with an average of 3.2 in NWL and 1 in NEL.  For baseline monitoring, the NWL average group size was 4.5 and the NEL average group size was 3.5.  For the period September 2012, the NWL average group size was 3.1 and in NEL it was 3.6 (Table 6).  NEL shows a decreased number in groups size (although it is noted only one group was sighted in September – November 2013).  In NWL, groups sizes between September – November 2012 and 2013 are approximately the same although both are lower than the baseline monitoring.  A map depicting group size distribution shows that the two largest groups occurred at SCLKCMP and both of these groups contained calves (Fig. 7).

 

Table 6.  A Comparison of Sightings Group Size Averages Recorded in NEL and NWL Areas During Sep – Nov 2011; 2012 and 2013

Monitoring Period

Average Group Size (NWL)

Average Group Size (NEL)

Sep - Nov 2011          (Baseline Monitoring)

4.5

3.5

Sep – Nov 2012

(HKBCF First Quarter)

3.1

3.6

 

Sep – Nov 2013

(HKBCF Seventh Quarter)

3.2

1.0

 

 

As encounter rate and group size are both subject to variation, the use of other more powerful analyses may be more appropriate to discern differences over the shorter term, such as multi-variate analyses (Taylor et al 2007).  This is important so that project impact can be monitored over relevant time scales.  Alternative analyses have been proposed and developed using the first year of impact monitoring data and the methodology is attached (Annex V).  Considerable reformatting of baseline data and incorporation of environmental and habitat data from multiple sources is near completion and the models will be run over the next quarterly period [6]

 

3.5. Habitat use

Quantitative grid analyses indicates that the most often frequented areas in NWL were the SCLKCMP, the western limit of NWL and one area to the north of the Hong Kong International Airport (HKIA) platform.  In NEL, no “on effort” sightings occurred therefore no qualitative grid analyses can be conducted (Figs. 8; 9).  The grid analyses from this quarter shows a similar distribution in NWL to that published in the AFCD long term monitoring reports and the baseline monitoring report.  These areas of high use have been consistent in the long term and continue to be so.  The decrease in dolphin sightings between September – November 2013 and the two previous autumn seasons is noted.  It is also noted that the areas of DPSE and SPSE which were apparent in summer 2013 are also absent.

 

3.6. Mother-calf pairs

Seven of the groups sighted contained mother and calf pairs[7].  All groups were sighted in NWL (Fig. 10).  Calves comprised 6.7% of all dolphins sighted, much higher than that reported in the last quarterly report (2.5%).  Although calf mortality was highlighted in previous seasons, several new born dolphins have been sighted consistently in NWL this quarter.

 

3.7. Activities

Of the 42 groups sighted (using all sightings), 21 (50%) were engaged in feeding activities; three (7%) were travelling; 11 (26%) were feeding/travelling/surface active; two (5%) were milling (other) and it was not possible to define the behavior of five (12%) groups.  Feeding was the predominant activity during daylight hours in September – November 2013 with travelling/feeding/surface active (multiple) behaviours being the next most dominant behavioural category (Fig. 11).  In NWL, feeding occurred most often at east SCLKCMP and the western limits of NWL.  (Fig. 12).

 

3.8. Photo-identification work

The photo-identification catalogue was regularly updated and re-sightings of dolphins previously identified were recorded.  The project specific photo-identification catalogue for the impact monitoring period is presented in Annex VI.  Not all dolphins sighted have sufficient scarring, injury or pigmentation uniqueness to be unambiguously identified. During the baseline survey, 96 individuals were noted in the NEL, NWL and WL areas.  Of these, 57 were noted in the NEL and NWL area.  No new dolphins which have been identified in the last quarter are from the baseline study, however, several well known individuals have been recorded throughout September – November 2013.  There are five dolphins which have been sighted more than seven times, all of which are known from the AFCD catalogue (HZMB 002 [WL111]; HZMB 011 [EL01]; HZMB 041 [NL24]; HZMB 044 [NL98]; HZMB054 [CH34]).  Two of these well known individuals were not seen during the baseline study (HZMB 002 AND HZMB 044).  When both baseline and impact monitoring data is pulled, HZMB 54 has been seen the most in 14 different sighting groups.  HZMB 041 has been sighted 11 times; HZMB 002 has been sighted ten times, HZMB 044 has been sighted nine times and HZMB 011 has been sighted eight times.  Even when pooled with baseline data, the highest number of re-sightings is 14 (HZMB 054) and this does not consider independence of sightings, a critical assumption in kernel analyses.  (Annex VI; Table1).

 

4. CONCLUSION

The data from September – November 2013 shows some consistencies with the results reported in the same period 2011 (baseline) and 2012.  Habitat use, encounter rates, group size and behavioural trends all fall within those reported in AFCD Long Term Monitoring reports apart from the use of NEL which has dropped when compared to this season in previous years.  It is noted from the previous quarterly report which summaries the summer seasons for the last three years, there was an increase in seasonal usage of NEL.  Density distribution maps depicted key areas of frequent use within NWL, in particular, SCLKMP and Tai O.  Behavioural patterns were broadly similar, with feeding behavior predominating all months. .

            The decrease in encounter rate in NEL is noted although no link can be found between this and specific activities at HKBCF.  Although it is likely that the increase in HKBCF activities is having an effect on dolphin encounter rates in NEL (although not in the three months that preceded this quarter), it is also noted that a dredging project was started in November 2013 and new project works also were initiated in NEL during the autumn of 2013.  Increased activities in addition to the inherent variation apparent in dolphin distribution and habitat use make it challenging to discern specific sources of impact.  A significant decline in dolphin throughout the last ten years prior to construction commencement has also been published by AFCD (2013).  It is hoped that the fine scale density surface analysis presently being conducted will allow further light to be shed on the specific areas and environmental variables, including marine construction works, which impacts dolphin distribution throughout NEL and NWL.


References

 

Agriculture, Fisheries and Conservation Department (AFCD) 2012. Annual Marne Mammal Monitoring Programme April 2011-March 2012. ) The Agriculture, Fisheries and Conservation Department, Government of the Hong Kong SAR.

 

Buckland, S., Burnham, K., Laake, J., Borchers, D. and Thomas, L. 2001. Introduction to Distance Sampling.  Oxford University Press.

 

Connor, R. Mann, J., Tyack, P. and Whitehead, H. 1998. Social Evolution in Toothed Whales. Trends in Ecology and Evolution 13, 228-232

 

Gillespie, D., Leaper, R., Gordon, J. and Macleod, K. 2010.  An integrated data collection system for line transect surveys. J. Cetacean Res. Manage. 11(3): 217–227.

 

Kauhala, K. & Auttila, M. 2010: Estimating habitat selection of badgers - a test between different methods. - Folia Zoologica 59: 16-25.

 

Taylor, B., Martinez, M, Gerodette, T., Barlow, J and Hrovat, Y.  2007.  Lessons from Monitoring Trends in Abundance of Marine Mammals.  Marine Mammal Science 23(1):157-175.

 

Wauters, L., Preatoni, D., Molinari, A. and Tosi, G. 2007. Radio-tracking squirrels: Performance of home range density and linkage estimators with small range and sample size. Ecological Modelling 202(10):333-44

 

Worton, B. 1989.  Kernel Methods for Estimating Utilization Distribution in Home Range Studies. Ecology 70(I):164-8

 


Figure 3 Distribution of Sightings Recorded During Impact Monitoring Surveys for HKBCF (September 2013)

 

Figure 4 Distribution of Sightings Recorded During Impact Monitoring Surveys for HKBCF (October 2013)


 

Figure 5 Distribution of Sightings Recorded During Impact Monitoring Surveys for HKBCF (November 2013)

Figure 6. Distribution of Sightings Recorded During Impact Monitoring Surveys for HKBCF (September – November 2013)

Figure 7. The Location of Dolphin Groups Numbering 5 and Above Individuals (September – November 2013)


Figure 8. Sighting density SPSE (number of on-effort sightings per 100 units of survey effort) for September – November 2013.

Figure 9. Dolphin density DPSE (number of dolphins per 100 units of survey effort) for September – November 2013.


Figure 10.  Location of groups containing mother and calf pairs during September – November 2013.

 

 

Figure 11.     Activity Budget for Dolphin Behaviour September – November 2013.

 

Figure 12. The Location of Different Behavioural Activities June to August 2103


Annex I Summary of Data from the Baseline Monitoring and September – November 2012 and September – November 2013 (this study) and Calculated Encounter Rates

Date

Area 

Groups 

Trackline (KM) 

Encounter rate 

Sept – Nov 2011

(Baseline Monitoring)

NEL

10

175.7

5.4

Sept – Nov 2011

(Baseline Monitoring)

NWL

34

359.0

9.5

Sept-Nov 2012

(Third Quarter)

NEL

13

221

5.9

Sept-Nov 2012

(Third Quarter)

NWL

39

438.8

8.9

Sept-Nov 2013

(Seventh Quarter)

NEL

0

220.7

0

Sept-Nov 2013

(Seventh Quarter)

NWL

28

445.2

6.3

 


 

Annex II. Impact Monitoring Survey Schedule and Details (September – November 2013)

Date

Location

No. Sightings “on effort”

No. Sightings “opportunistic”

Total km “on effort”

17/09/2013

NE Lantau

0

0

33.5

19/09/2013

NW & NE Lantau

1

3

77.5

24/09/2013

NW Lantau

6

0

63.4

25/09/2013

NW & NE Lantau

0

0

47.6

15/10/2013

NW Lantau

6

3

59.7

17/10/2013

NW & NE Lantau

0

0

52.1

24/10/2013

NW Lantau

5

2

58.7

28/10/2013

NW & NE Lantau

0

0

51.8

01/11/2013

NE and NW Lantau

2

3

59.5

02/11/2013

NWL

1

3

52.2

07/11/2013

NWL

6

0

64.7

09/11/2013

NE and NW Lantau

1

0

47.5

Total

28

14

668.2

All effort in all sea states is listed


 

Annex III. Impact Monitoring Survey Effort Summary (September – November 2013)

Date

Area

Beaufort

Effort (km)

Season

Vessel

Type

17/9/2013

NEL

1

9.2

AUTUMN

HKDW

IMPACT

17/9/2013

NEL

2

15.6

AUTUMN

HKDW

IMPACT

17/9/2013

NEL

3

7.7

AUTUMN

HKDW

IMPACT

17/9/2013

NEL

4

1

AUTUMN

HKDW

IMPACT

19/9/2013

NEL

2

3.5

AUTUMN

HKDW

IMPACT

19/9/2013

NWL

1

10.6

AUTUMN

HKDW

IMPACT

19/9/2013

NWL

2

44.7

AUTUMN

HKDW

IMPACT

19/9/2013

NWL

3

18.7

AUTUMN

HKDW

IMPACT

24/9/2013

NWL

1

23.6

AUTUMN

HKDW

IMPACT

24/9/2013

NWL

2

19.4

AUTUMN

HKDW

IMPACT

24/9/2013

NWL

3

20.4

AUTUMN

HKDW

IMPACT

25/9/2013

NWL

1

7.6

AUTUMN

HKDW

IMPACT

25/9/2013

NWL

2

2.7

AUTUMN

HKDW

IMPACT

25/9/2013

NEL

1

20.3

AUTUMN

HKDW

IMPACT

25/9/2013

NEL

2

17

AUTUMN

HKDW

IMPACT

15/10/2013

NWL

1

35.8

AUTUMN

HKDW

IMPACT

15/10/2013

NWL

2

23.9

AUTUMN

HKDW

IMPACT

17/10/2013

NWL

1

1.1

AUTUMN

HKDW

IMPACT

17/10/2013

NWL

2

7.4

AUTUMN

HKDW

IMPACT

17/10/2013

NWL

3

6

AUTUMN

HKDW

IMPACT

17/10/2013

NEL

1

9.2

AUTUMN

HKDW

IMPACT

17/10/2013

NEL

2

20.5

AUTUMN

HKDW

IMPACT

17/10/2013

NEL

3

7.9

AUTUMN

HKDW

IMPACT

24/10/2013

NWL

1

12.2

AUTUMN

HKDW

IMPACT

24/10/2013

NWL

2

32.7

AUTUMN

HKDW

IMPACT

24/10/2013

NWL

3

13.7

AUTUMN

HKDW

IMPACT

24/10/2013

NWL

4

0.1

AUTUMN

HKDW

IMPACT

28/10/2013

NWL

1

4.9

AUTUMN

HKDW

IMPACT

28/10/2013

NWL

2

10.2

AUTUMN

HKDW

IMPACT

28/10/2013

NEL

1

14.6

AUTUMN

HKDW

IMPACT

28/10/2013

NEL

2

10.7

AUTUMN

HKDW

IMPACT

28/10/2013

NEL

3

11.4

AUTUMN

HKDW

IMPACT

11/1/2013

NEL

1

35.4

AUTUMN

HKDW

IMPACT

11/1/2013

NWL

1

14.6

AUTUMN

HKDW

IMPACT

11/1/2013

NWL

2

9.5

AUTUMN

HKDW

IMPACT

 

Annex III. Impact Monitoring Survey Effort Summary (September – November 2013) (con)

 

Date

Area

Beaufort

Effort (km)

Season

Vessel

Type

11/2/2013

NWL

2

26.7

AUTUMN

HKDW

IMPACT

11/2/2013

NWL

3

24.3

AUTUMN

HKDW

IMPACT

11/2/2013

NWL

4

1.2

AUTUMN

HKDW

IMPACT

11/7/2013

NWL

1

43.4

AUTUMN

HKDW

IMPACT

11/7/2013

NWL

2

21.3

AUTUMN

HKDW

IMPACT

11/9/2013

NEL

1

10

AUTUMN

HKDW

IMPACT

11/9/2013

NEL

2

21.2

AUTUMN

HKDW

IMPACT

11/9/2013

NEL

3

6.5

AUTUMN

HKDW

IMPACT

11/9/2013

NWL

1

3.7

AUTUMN

HKDW

IMPACT

11/9/2013

NWL

2

6.1

AUTUMN

HKDW

IMPACT

 


 

Annex IV. Impact Monitoring Sighting Database (September – November 2013)

Project

Contract

Date

Sighting No.

Time

Group Size

Area

Beaufort

PSD

Effort

Type

Latitude

Longitude

Season

Boat Assoc

HKBCF

HY/2010/02

9/19/2013

791

9:42

1

NEL

1

NA

Opp  

Impact

22.33573

113.9952

Autumn

No   

HKBCF

HY/2010/02

9/19/2013

792

11:31

1

NWL

2

NA

Opp  

Impact

22.35992

113.9283

Autumn

No   

HKBCF

HY/2010/02

9/19/2013

794

14:13

4

NWL

2

94

On   

Impact

22.39786

113.8874

Autumn

No   

HKBCF

HY/2010/02

9/19/2013

795

14:31

6

NWL

2

NA

Opp  

Impact

22.39240

113.8843

Autumn

No   

HKBCF

HY/2010/02

9/24/2013

798

9:19

5

NWL

1

243

On   

Impact

22.28493

113.8701

Autumn

No   

HKBCF

HY/2010/02

9/24/2013

799

10:02

1

NWL

1

279

On   

Impact

22.29694

113.8703

Autumn

No   

HKBCF

HY/2010/02

9/24/2013

800

10:15

2

NWL

1

30

On   

Impact

22.30655

113.8702

Autumn

No   

HKBCF

HY/2010/02

9/24/2013

802

10:42

2

NWL

2

78

On   

Impact

22.34161

113.8700

Autumn

No   

HKBCF

HY/2010/02

9/24/2013

803

13:33

1

NWL

1

221

On   

Impact

22.35825

113.8877

Autumn

No   

HKBCF

HY/2010/02

9/24/2013

804

14:41

4

NWL

3

85

On   

Impact

22.37340

113.8975

Autumn

No   

HKBCF

HY/2010/02

10/15/2013

812

9:48

2

NWL

2

365

On

Impact

22.33154

113.8662

Autumn

No

HKBCF

HY/2010/02

10/15/2013

813

9:51

1

NWL

2

347

On

Impact

22.32847

113.8704

Autumn

No

HKBCF

HY/2010/02

10/15/2013

814

9:53

1

NWL

2

7

On

Impact

22.32959

113.8702

Autumn

No

HKBCF

HY/2010/02

10/15/2013

815

10:11

3

NWL

1

61

On

Impact

22.33614

113.8703

Autumn

No

HKBCF

HY/2010/02

10/15/2013

817

10:43

1

NWL

1

NA

Opp

Impact

22.34800

113.8630

Autumn

No

HKBCF

HY/2010/02

10/15/2013

818

10:44

1

NWL

1

NA

Opp

Impact

22.34564

113.8637

Autumn

No

HKBCF

HY/2010/02

10/15/2013

819

11:15

6

NWL

1

64

On

Impact

22.37013

113.8700

Autumn

No

HKBCF

HY/2010/02

10/15/2013

820

12:15

8

NWL

1

50

On

Impact

22.40074

113.8776

Autumn

No

HKBCF

HY/2010/02

10/15/2013

821

16:33

3

NWL

2

NA

Opp

Impact

22.37510

113.9123

Autumn

No

HKBCF

HY/2010/02

10/24/2013

827

11:00

12

NWL

1

441

On

Impact

22.36340

113.8746

Autumn

No

HKBCF

HY/2010/02

10/24/2013

829

13:24

2

NWL

2

58

On

Impact

22.36996

113.8874

Autumn

No

HKBCF

HY/2010/02

10/24/2013

830

14:04

3

NWL

2

10

On

Impact

22.40109

113.8975

Autumn

No

HKBCF

HY/2010/02

10/24/2013

831

14:34

5

NWL

1

848

On

Impact

22.39506

113.8968

Autumn

No

HKBCF

HY/2010/02

10/24/2013

832

15:07

2

NWL

1

NA

Opp

Impact

22.39703

113.9011

Autumn

No

HKBCF

HY/2010/02

10/24/2013

833

15:11

2

NWL

1

NA

Opp

Impact

22.39688

113.8988

Autumn

No

HKBCF

HY/2010/02

10/24/2013

834

15:21

1

NWL

1

69

On

Impact

22.37427

113.8976

Autumn

No

Annex IV. Impact Monitoring Sighting Database (September – November) (con)

 

Project

Contract

Date

Sighting No.

Time

Group Size

Area

Beaufort

PSD

Effort

Type

Latitude

Longitude

Season

Boat Assoc

HKBCF

HY/2010/02

11/1/2013

837

13:34

2

NWL

1

NA

Opp  

Impact

22.35255

113.9363

Autumn

No   

HKBCF

HY/2010/02

11/1/2013

838

14:25

1

NWL

2

NA

Opp  

Impact

22.36760

113.9164

Autumn

No   

HKBCF

HY/2010/02

11/1/2013

839

15:26

4

NWL

1

112

On   

Impact

22.36538

113.9076

Autumn

No   

HKBCF

HY/2010/02

11/1/2013

841

16:17

1

NWL

2

173

On   

Impact

22.35673

113.9079

Autumn

No   

HKBCF

HY/2010/02

11/1/2013

842

17:08

5

NWL

2

NA

Opp  

Impact

22.32953

113.9332

Autumn

No   

HKBCF

HY/2010/02

11/2/2013

845

11:44

11

NWL

2

594

On   

Impact

22.34556

113.8780

Autumn

No   

HKBCF

HY/2010/02

11/2/2013

847

14:38

2

NWL

3

NA

Opp  

Impact

22.26560

113.8617

Autumn

No   

HKBCF

HY/2010/02

11/2/2013

849

15:01

5

NWL

3

NA

Opp  

Impact

22.25650

113.8488

Autumn

No   

HKBCF

HY/2010/02

11/2/2013

850

15:43

1

NWL

3

NA

Opp  

Impact

22.26079

113.8516

Autumn

No   

HKBCF

HY/2010/02

11/7/2013

853

9:08

6

NWL

1

141

On   

Impact

22.27083

113.8703

Autumn

No   

HKBCF

HY/2010/02

11/7/2013

854

9:46

2

NWL

1

109

On   

Impact

22.30234

113.8706

Autumn

No   

HKBCF

HY/2010/02

11/7/2013

855

10:38

6

NWL

2

76

On   

Impact

22.36685

113.8701

Autumn

No   

HKBCF

HY/2010/02

11/7/2013

856

12:13

3

NWL

1

169

On   

Impact

22.35167

113.8778

Autumn

No   

HKBCF

HY/2010/02

11/7/2013

857

15:31

2

NWL

2

65

On   

Impact

22.37546

113.9072

Autumn

No   

HKBCF

HY/2010/02

11/7/2013

858

16:31

1

NWL

1

13

On   

Impact

22.35391

113.9170

Autumn

No   

HKBCF

HY/2010/02

11/9/2013

860

10:49

1

NWL

2

24

On   

Impact

22.33698

113.9463

Autumn

No   

 


 

 

 

 

 

Annex V

 

METHODS PROPOSAL FOR DENSITY SURFACE MODELLING AND POWER ANALYSES RELATED TO THE HONG KONG-ZHUHAI-MACAO BRIDGE (HZMB)

 


 

 

 

OVERVIEW

This document outlines the proposed statistical analysis of data concerning the Chinese White Dolphin (CWD) found in and around the HZMB area. The proposal involves the analysis of baseline monitoring data and data collected during and post construction.

This proposal outlines statistical analyses for comparing differences in dolphin densities between baseline and impact monitoring - as per Section 9.5.3 of the Contract Specific EM & A Manual.

This document also serves a form of Statistical Analysis Plan (SAP) that permits vetting of the statistical methods. The technical details necessarily pre-suppose familiarity with statistical models, in particular Generalized Linear Models (GLMs) or Generalized Additive Models (GAMs).

ASSESSING THE DISTRIBUTION OF DOLPHINS IN THE SURVEYED AREA

The distribution of dolphins through space and time will be described by statistical models fitted to dolphin observation data. Relevant drivers of dolphin distributions, such as oceanographic features, will also be included in the modelling process. The modelling methods employed will be appropriate for the problem, representing the most recent developments in this area and currently accepted UK standards for species distribution modelling for the purposes of Environmental Impact Assessments. The methods are described briefly here.

Flexible modelling of animal distributions

In many surveyed sites, the way the animals distribute themselves can vary a great deal. For example, some areas (e.g. close to the coast) may require a very flexible modelling surface which can potentially change quickly with local features, while areas with deeper water may exhibit less local variability and require less flexibility. 

It is important to target model flexibility to ensure important local features are not missed and 'smoothed-out', such as areas in and around a potentially impacted site, and to ensure the spatial range of any local effects that do exist are not exaggerated. For instance, 'smoothing-out' local features will result in under-reporting of any impacts in and around the site(s) of interest and also result in extending the range of the impact into areas which are, in truth, unaffected.

Targeting model flexibility also helps ensure that some areas of the surface are not unduly variable, and therefore natural fluctuations in dolphin numbers are not mistaken for genuine changes in the underlying system. This is particularly relevant in impact studies where it is important not to falsely attribute natural variability in animal numbers to an impact effect.

The methods we propose to use for the HZMB data are 'spatially-adaptive' and allow model flexibility to be targeted. Additionally, these methods are developed with impact assessment in mind, to allow a particular focus on special areas of interest e.g. in and around the potentially impacted site. The methods proposed for the analysis reflect the most recent research in this area[8]. They were recently presented as an invited talk for the UK government and industry 'Sharing Good Practice' event for Scottish Natural Heritage (November, 2011)[9] and are currently being used to analyse an extensive international data set collected over 30 years as a part of the recent Joint Cetacean Protocol Project (JCP, commissioned by the UK government; JNCC)[10]. These methods have also been used successfully to model many renewable projects for a variety of large UK and international companies with stakes in renewables (Forewind, Centrica plc, Royal Haskoning), including one of the world's largest offshore wind farms[11].

As an example of modelling output, 'difference-maps' illustrating where statistically significant changes/redistribution of animals across a surveyed area can be supplied with reference to an impact site (Figure 1). This allows any differences over time to be geo-referenced, helping the end-user to exercise judgement about whether differences are both significant and related to the speculative impact. Maps of this nature will be extended to the current region (Figure 2).

Inclusion of Covariate data

Any readily available data that might be useful in the prediction of dolphin distributions can and should be considered for selection in these models. The utility of these covariates for predicting dolphin distributions can then be determined during the modelling phase. The covariates might include oceanographic features such as tidal flows and bathymetry, whose temporal & spatial resolution can be variable e.g. daily/ weekly /monthly. The finest available resolutions will be considered as a starting point; however the most sensible resolutions are also determined during the modelling process. For example, some covariate data may need to be coarsened to match the resolution of the dolphin observation data.

Covariates for consideration

The following outlines the available covariates for a priori consideration in the models, with justification. These may not be represented in the final model, subject to model selection results.

  • Time of day, day-of-year, month, year: These temporal measures will all be included as potential covariates in the model to capture patterns of dolphin distribution not evident in other covariates. For example, month has a tendency to capture seasonal variations in animal distributions; the time of day may capture diurnal patterns beyond tidal patterns.

 

  • Tidal state: marine animals typically show patterns of activity associated with tidal cycles. This can be due to changes in water depth, tidal flows, prey movements, etc. Suitable summaries of the tidal state will be considered in the pool of covariates.

 

  • Salinity/Turbidity/DO & DO saturation/pH: while these may not be directly influential on dolphins, they may present as proxies for prey distributions or habitats which influence dolphin distributions.

 

  • Depth: this frequently serves as a strong predictor of the distributions of marine animal distributions. There are many potential reasons for this e.g. in the case of diving animals this indicates the accessibility of the sea floor. It is also a strong indicator of particular prey species and is often indicative of the proximity of land masses.

 

  • Water temperature: as above, this is frequently a strong predictor of marine animal distributions, whether as a direct driver on the animals or via its effects on productivity and prey distributions.

 

  • Suspended solids: given the nature of the construction activities, patterns in animal distributions relating to solids in the water column will be of clear interest.

 

  • Details of construction activities per day: These are essential, as they will provide the basis of variables that code for potential construction–related impacts. These will be translated into an appropriate small set of categorical variables and potentially durations, depending on the available information.

 

 

Data resolution

The maximum native resolution will be used in the first instance where possible to retain the maximum information. The resolutions need not be matched either in time or space and can be post-processed where needed. The resolutions of the covariate data identified above are:

  • Native resolutions of the data….

 

The resolution of the data may be coarsened in some cases. This cannot be determined with certainty prior to analysis of the data, but the following scenarios are common based on previous work in this area:

  • Dolphin observation data is frequently very spatially and temporally sparse i.e. dominated by zero observations. The data may be condensed to quarter-hour to hour temporal resolution and some 100s of metre spatial resolution.

 

  • All subsequent covariate data will be formatted to match the dolphin observation data. For example, near-continuous time covariates, such as tide height, will be condensed to match the temporal resolution of the observations data.

 

Model structure/equations

To avoid unnecessary assumptions, the models proposed are:

  • adaptive in their systematic form,
  • have a range of potential error distributions,
  • can accommodate various types of non-independence in the errors.

The modelling process will involve the selection of model terms, optimisation of covariate-response functions and selection of models for stochastic components.

Hence, the specific model equation cannot be known with certainty prior to analysis. This is common to any modelling process that involves optimisation of complexity e.g. regression with model selection, GAMs with optimised smoothing terms. However the broad model structure can be considered, being a type of GAM fitted with GEEs.

Generalized Additive Models (GAMs)

Broadly we seek to estimate f, where the response is in some way functionally related to a set of covariates :

The actual observed response will consist of some inexplicable noise, modelled by some error distribution. The approach is similar to GLMs, so the mean response  is modelled on the scale of a link-function , with errors  being governed by probability density functions of the exponential family e.g. Gaussian, Gamma, Poisson or quasi- variants. In the current context,  may be the expected numbers or densities of dolphins, with the  being relevant covariates including spatial coordinates.

GLMs approximate the link-scale f with a simple linear form, , where  is the matrix of measured covariates and  the associated parameters to be estimated. GAMs differ by seeking to approximate f as a linear combination of smooths on the link-scale, whose individual forms are estimated from the data. As an indication:

Where we can have a range of marginal/single-covariate smooth terms , and multidimensional smooth terms , for groups of covariates , as required. The smooth terms may be very smooth, i.e. linear terms, meaning that GLMs are a special case. Categorical variables can be included as per ordinary GLMs, not included as smooths per se, but via dummy variables.

The fitting of this model operates under assumed error distributions, such as found in GLMs. The smooths themselves can be created in a variety of ways, with splines being commonplace. The complexity of the smooth terms is either set in advance or estimated. The various smooth terms to be included in the model will be subject to selection methods i.e. parsimonious models are selected with insignificant terms dropped.

GAMs are a well-established flexible modelling tool with extensive theoretical treatment – for example refer to Hastie & Tibshirani (1989) or Wood (2006).

Accounting for correlated data/errors

The models we propose to use for this analysis are designed for data collected across space and time, which is true of the type of survey data considered here. This methodology allows for reliable geo-referenced confidence intervals across the fitted surface - which can be interpreted as best and worst case scenarios for any changes over time. Specifically, the modelling framework involves Generalized Estimating Equations (GEEs[12]) to account for the spatio-temporal autocorrelation.

Most basic statistical modelling methods operate under the simple assumption of independence of errors. However many data collection scenarios will impose some correlation in the errors for these models, due to sampling in a patterned way through space and/or repeated measures on areas through time. The usual consequence of ignoring this correlation when fitting models, is that the variance estimates will be incorrect (typically too small as positive correlation is most common). This has a multitude of inferential consequences – in particular, covariates will be incorrectly determined as significance/insignificant. Generally the complexity of the models is incorrectly determined.

There are a variety of modelling methods to account for this, whereby the correlation structure of the errors is also specified and estimated. We favour here the use of GEEs, which produce empirical adjustments to the variance estimates and are robust to initial misspecification of the error correlation structure.

Any analysis applied to this type of data that does not account for correlated errors will provide spurious results. Most basic statistical tools operate under this assumption of the independence of errors, which while providing simple analyses, produces indefensible results.

Model assumptions

The model and fitting method indicated in section 0 are a form of Generalized Additive Model, fitted using Generalized Estimating Equations. These have been chosen to avoid unreasonable or unnecessary assumptions.

Assumptions of the systematic component

As indicated in section 0, the systematic component of the model consists of adaptive spline models for continuous covariates, or factors for categorical covariates. For the spatial component, the function used is a geodesic smoother with adaptive selection of knots and basis functions, as described in Scott-Hayward et al (2013). For the modelling of individual continuous covariates these are splines with adaptive knot selection, as described in Walker et al (2011). The range of functions that can be approximated by this scheme is very rich.

Common to other regression methods, it is assumed that important predictors are included in the model. However this is mitigated against, in part, by the inclusion of a spatial smoothing term. Un-measured covariates may be represented in by proxy, if they have spatial structure themselves. Failing to include important drivers in the model may produce models with poor predictive power.

The assumptions regarding the systematic component are minimal:

  • Due to the adaptive model specification, relatively little is assumed for the functional form of the relationship between the response and continuous covariates, beyond continuity and smoothness.

 

  • The level of complexity is correctly determined i.e. under- and over- fitting are to be avoided, which covariates are important and to be included, the level of smoothing applied. These are determined by various information criteria (AIC, QIC, BIC) and/or cross-validation.

 

  • It is assumed that the covariates are not excessively correlated with one another. These are checked as a matter of course, so high collinearity will be mitigated against.

Assumptions of the stochastic component

Common to GLMs, the models here permit a range of error distributions. The exact distribution assumed is determined during analysis, however the nature of the response suggests quasi-Poisson. The parameter estimates are therefore from maximising either likelihoods or quasi-likelihoods.

Taken collectively, the assumptions implied from our treatment of errors are minimal:

  • We do not assume independence of errors, which is a priori unlikely. The fitting of GEEs is known to be robust to the choice of working correlation structure, so while this is assumed to be correctly specified, it is not largely influential on the results.

 

  • We do assume that the choice of error distribution is correct, however there is a wide range of distributions to choose between and the choice is scrutinised.

Determination of impact

Definition of impact

Impact here is restricted to statistically significant differences in dolphin abundance or spatial distribution that are attributable to construction activities. Other definitions based on the magnitude of effect can be employed if such criteria exist. The models described here provide estimates of the size of effect, along with confidence intervals – these permit alternative impact assessments.

Impact will be sought via statistical models by:

  • Statistically significant changes in the absolute or relative abundance of dolphins within the study area, when comparing pre- to post-development data. This is after account has been taken of important covariates.

 

  • Statistically significant changes in the distribution of animals over the study area when comparing pre- to post-development data - again after the effect of important covariates has been accounted for. The model contains a spatial smoothing component, providing estimated surfaces and confidence intervals for the dolphin distributions through time, with other covariates partialled. Changes in dolphin distributions which are strongly associated with the areas of highest development activity will provide evidence of impact.

It is difficult to determine with certainty that a statistically significant change is due only to development activities. Any change in conditions coincident in time with the development, that is not included as a covariate in the model, serves as an alternative explanation. For example, a disease that is coincident with the development phase.

However, significant distributional changes that are coincident both temporally and spatially with the development will provide a compelling case. For example, if there is a significant shift in distribution around the development site at the same time as development, after other important covariates are accounted for.

Impact hypotheses

The nature of the questions, data and the statistical methods necessitated by these, precludes simple a priori hypotheses as might be presented for simple, inappropriate analysis. However some formalisation can be attempted.

  • The null hypothesis is one of no impact on the dolphin distribution, or abundance, attributable to development activities.

 

  • The alternative hypothesis is one of some impact on the dolphin distribution, or abundances, due to development activities.

 

The impact here is determined by statistically significant parameters, or changes parameters, that compare the pre- to post-development states. The models are subject to selection in light of the data, so their specific form cannot be known a priori.

Nonetheless, a simple variable can be included in the model, along with the model-selected covariates, that codes for different development states e.g. before/during/after. Significant changes in the general dolphin abundance will be detectible from tests and confidence intervals on these parameters.

Relatedly, the spatial smoothing method has a set of parameters that relate to locally restricted abundances. Tests and confidence intervals for these parameters over the development phases will also identify spatially explicit shifts in dolphin abundances.

More generally, parametric bootstraps will be employed to provide empirical confidence intervals for abundances and their spatial distribution, for the distinct development phases. Any shifts in abundance and distribution over these phases, that are not explicable by natural variation and other covariates, will suggest impacts.

 

 


 

AN ASSESSMENT OF THE POWER OF THE SURVEY (AND DATA) AT DETECTING CHANGE

As a part of this work, the power of the monitoring regime to detect real change in dolphin numbers can also be quantified, under a range of scenarios agreed with the client. For example, this might consist of determining the power to detect a general decline in animal numbers ranging over 5%-50% and/or a spatially restricted decline about the point source.

The power analysis will be carried out using a simulation based approach which includes relevant complexities in the data to ensure realistic results. Specifically, the simulations for power analysis are bespoke to quantify the power in detecting an 'impact' while addressing the following important features of the survey data:

a)      Non-linear relationships.

b)      Correlated and/or over dispersed observations.

c)       Spatially explicit impact/changes.

Briefly, the simulation-based power analysis works as follows:

  • A model for the species distribution, including any environmental covariates, is constructed.

 

  • This model, that has been developed on historical data, is assumed to hold true for the future monitoring periods, but with some general reduction in relative animal abundance (e.g. attributable to a specific impact).

 

  • Simulated data is generated from this process with noise consistent with the historical recordings.

 

  • The current modelling process is applied to the multiple sets of simulation data, but additionally estimating an impact effect.

 

  • Various sizes/types of impact are simulated, and detection of a statistically significant effect is sought from the models under scenarios of interest, for example under differing intensities of monitoring.

 

The inherent noise in the system may mean small installation effects might be difficult to detect over small time-periods, but these effects will become more detectable with more data. Large effects should be detectible sooner. The simulation process described allows quantification of the probability of detecting an effect, for various effect sizes and periods of additional monitoring.

 

Map_ver3

Figure 1: An example output showing the significant decreases (white horizontal lines) and significant increases (solid black crosses) post impact. In this particular case, the scale moves from a deep blue colour (which indicates a decrease in number) to a red colour (which indicates an increase in number) and the animals have moved out along the 10-15m contour in depth, post impact.

 

Figure 2: the region over which the methods will be applied, ultimately providing a model surface and infrerence similat to Figure 1. Model predictions can be provided on a range of resolutions.

 


 

References

Hardin, J. W. & Hilbe, J. (2003) Generalized Estimating Equations. Chapman & Hall/Crc Press.

Hastie, T. & Tibshirani, R. (1989) Generalized Additive Models. Volume 43 of Monographs on Statistics and Applied Probability. Chapman & Hall, 1990. ISBN                0412343908. 335pp.

Paxton, C., Mackenzie, M. L., Burt, L., Rexstad, E. & Thomas, L. (2011) Phase II Data Analysis Of Joint Cetacean Protocol Data Resource, Http://Jncc.Defra.Gov.Uk/Pdf/Jcp_Phase_Ii_Report.Pdf

Petersen, I. K., MacKenzie, M. L., Rexstad, E., Wisz, M. S. and Fox, A. D. (2011) Comparing Pre- And Post-Construction Distributions Of Long-Tailed Ducks Clangula Hyemalis In And Around The Nysted Offshore Wind Farm, Denmark : A Quasi-Designed Experiment Accounting For Imperfect Detection, Local Surface Features And Autocorrelation. Http://Hdl.Handle.Net/10023/2008

Scott-Hayward, L. A. S., Mackenzie, M. L. ,Donovan, C. R., Walker, C. & Ashe, E. (2013), Complex Region Spatial Smoother (Cress). Journal of Computational and Graphical Statistics. In press

Wood, S. (2006) Generalized Additive Models: An Introduction with R. Volume 66 of Texts in Statistical Science. Chapman and Hall/CRC Texts in Statistical Science Series. ISBN1584884746. 391 pp.


 

 

 

Annex VI

March 2012– November 2013

(and Baseline September – November 2011)

Photo Identification Information


 

Table 1. Sightings of Individually Identified Chinese White Dolphin (Sousa chinensis) between March 2012 – November 2013 and during the Baseline Survey (September - November 2011)

 

Identification Number

Baseline Identification Number

Date

(YYYY-MM-DD)

Sighting Number

Area Sighted

HZMB 114

 

2013-10-24

827

NWL

HZMB 113

 

2013-10-24

827

NWL

HZMB 112

 

2013-10-15

815

NWL

HZMB111

 

2013-10-15

815

NWL

HZMB 110

 

2013-10-15

812

NWL

HZMB 108

 

2013-08-30

780

NEL

HZMB 107

 

2013-08-21

770

NWL

HZMB 106

 

2013-08-21

769

NWL

HZMB 105

 

2013-07-08

711

NWL

HZMB 104

 

2013-07-08

711

NWL

HZMB 103

 

2013-07-08

711

NWL

HZMB 102

 

2013-07-08

706

NWL

HZMB 101

 

2013-07-08

706

NWL

HZMB 100

 

2013-07-08

706

NWL

HZMB 099

 

2013-06-13

2013-06-13

681

680

NWL

NWL

HZMB 098

NL104

2013-11-02

2013-11-02

2013-10-24

2013-07-08

2013-05-24

849

845

831

711

659

NWL

NWL

NWL

NWL

NWL

HZMB 097

 

2013-05-09

647

NWL

HZMB 096

 

2013-04-01

621

NWL

HZMB 095

 

2013-08-30

2013-06-25

2013-06-13

2013-04-01

780

697

682

621

NEL

NWL

NWL

NWL

Identification Number

Baseline Identification Number

Date

(YYYY-MM-DD)

Sighting Number

Area Sighted

HZMB 094

 

2013-06-26

2013-06-25

2013-03-18

703

698

601

NWL

NWL

NWL

HZMB 093

 

2013-05-24

2013-02-21

657

587

NWL

NWL

HZMB 092

 

2013-02-21

2013-02-15

589

581

NWL

NWL

HZMB 091

 

2013-02-15

579

NWL

HZMB 090

 

2013-06-25

2013-06-13

2013-02-15

697

682

579

NWL

NWL

NWL

HZMB 089

 

2013-02-15

579

NWL

HZMB 088

 

2013-02-15

579

NWL

HZMB 087

 

2013-02-15

579

NWL

HZMB 086

NL242

2013-05-09

2013-02-15

2011-10-10

642

579

Baseline

NWL

NWL

NWL

HZMB 085

 

2013-06-26

2013-02-15

703

579

NWL

NWL

HZMB 084

 

2013-02-14

575

NWL

HZMB 083

NL136

2013-03-28

2013-02-15

2013-01-28

2012-01-28

607

579

568

564

NWL

NWL

NWL

NWL

HZMB 082

 

2013-02-21

2013-02-15

2013-01-28

587

579

563

NWL

NWL

NWL

HZMB 081

 

2013-01-28

2013-01-28

559

557

NWL

NWL

Identification Number

Baseline Identification Number

Date

(YYYY-MM-DD)

Sighting Number

Area Sighted

HZMB 080

 

2013-01-28

556

NWL

HZMB 079

 

2013-01-28

556

NWL

HZMB 078

 

2013-02-15

2013-01-08

579

552

NWL

NWL

HZMB 077

 

2013-07-08

2012-12-11

706

541

NWL

NWL

HZMB 076

 

2013-07-08

2012-12-11

706

541

NWL

NWL

HZMB 075

 

2012-12-06

525

NEL

HZMB 074

 

2013-05-09

2013-04-01

2013-04-01

2013-02-21

2012-12-10

2012-12-06

647

623

621

594

529

525

NWL

NWL

NWL

NEL

NEL

NEL

HZMB 073

 

2013-05-09

2013-04-01

2013-04-01

2013-02-21

2012-12-10

2012-12-06

647

623

621

594

529

525

NWL

NWL

NWL

NEL

NEL

NEL

HZMB 072

 

2012-10-24

476

NWL

HZMB 071

 

 

2012-10-24

2012-10-12

475

466

NWL

NWL

HZMB 070

 

2012-10-24

476

NWL

 


 

 

Identification Number

Baseline Identification Number

Date

(YYYY-MM-DD)

Sighting Number

Area Sighted

HZMB 069

 

2013-08-21

2013-07-08

2012-10-24

774

711

476

NWL

NWL

NWL

HZMB 068

 

2013-11-01

2012-10-24

839

476

NWL

NWL

HZMB 067

 

2012-10-24

475

NWL

HZMB 066

 

NL93

2013-01-28

2012-12-11

2012-10-24

2012-10-12

559

537

475

466

NWL

NWL

NWL

NWL

HZMB 064

 

2013-05-09

2013-01-28

2012-10-24

2012-10-12

647

561

475

466

NWL

NWL

NWL

NWL

HZMB 063

 

2013-05-09

2012-10-12

647

466

NWL

NWL

HZMB 060

 

2012-09-18

447

NWL

HZMB 059

 

2013-02-21

2012-09-18

591

445

NWL

NWL

HZMB 057

 

2012-09-18

440

NWL

HZMB 056

 

2012-09-18

2012-09-05

442

433

NWL

NEL

HZMB 055

 

2012-09-04

425

NWL

 


 

Identification Number

Baseline Identification Number

Date

(YYYY-MM-DD)

Sighting Number

Area Sighted

HZMB 055

 

2012-09-04

425

NWL

HZMB 054

CH34

2013-11-07

2013-11-02

2013-10-24

2013-08-30

2013-07-08

2012-09-18

2012-09-05

2011-11-07

2011-11-05

2011-11-02

2011-11-01

2011-11-01

2011-10-28

2011-10-06

854

845

831

780

711

448

432

Baseline

Baseline

Baseline

Baseline

Baseline

Baseline

Baseline

NWL

NWL

NWL

NEL

NWL

NWL

NEL

NWL

NWL

NWL

NEL

NEL

NWL

NWL

HZMB 053

 

2012-09-04

425

NWL

HZMB 052

 

2012-09-04

423

NWL

HZMB 051

NL213

2013-05-09

2013-04-01

2013-02-15

2013-02-15

2013-01-28

2013-01-28

2012-09-04

644

622

582

581

559

556

422

NWL

NWL

NWL

NWL

NWL

NWL

NWL

HZMB 050

 

2013-02-15

2012-09-04

579

421

NWL

NWL

HZMB 049

 

2012-09-03

419

NWL

HZMB 048

 

2012-09-03

419

NWL

HZMB 047

 

2012-09-03

412

NWL

Identification Number

Baseline Identification Number

Date

(YYYY-MM-DD)

Sighting Number

Area Sighted

HZMB 046

 

2012-09-03

412

NWL

HZMB 045

 

2013-06-13

2013-02-15

2012-11-01

682

579

495

NWL

NWL

NWL

HZMB 044

NL98

2013-11-02

2013-11-01

2013-10-15

2013-05-09

2013-05-09

2013-04-01

2013-04-01

2013-02-15

2012-11-01

845

842

819

648

647

623

621

579

495

NWL

NWL

NWL

NWL

NWL

NWL

NWL

NWL

NWL

HZMB 043

 

2012-09-03

407

NWL

HZMB 042

NL260

2012-11-01

2011-11-07

495

Baseline

NWL

NWL

HZMB 041

NL24

2013-11-02

2013-05-09

2013-05-09

2013-04-01

2013-04-01

2013-02-15

2012-11-01

2011-11-06

2011-11-05

2011-11-05

2011-10-10

845

648

647

623

621

579

495

Baseline

Baseline

Baseline

Baseline

NWL

NWL

NWL

NWL

NWL

NWL

NWL

NEL

NWL

NWL

NWL

HZMB 040

 

2013-10-15

2013-07-08

2013-07-08

2013-02-21

2012-11-01

821

714

711

589

493

NWL

NWL

NWL

NWL

NWL

HZMB 038

 

2012-11-01

490

NWL

HZMB 037

 

2012-11-01

490

NWL

HZMB 036

 

 

2012-09-03

2012-11-01

407

490

NWL

NWL

Identification Number

Baseline Identification Number

Date

(YYYY-MM-DD)

Sighting Number

Area Sighted

HZMB 035

 

2013-02-15

2012-11-01

579

490

NWL

NWL

HZMB 034

 

2012-11-01

493

NWL

HZMB 028

 

2013-04-01

2012-08-06

625

373

NWL

NWL

HZMB 027

 

2013-02-15

2013-01-28

2013-01-28

2012-06-14

579

568

564

299

NWL

NWL

NWL

NWL

HZMB 026

 

2013-06-25

2013-05-09

2013-01-28

2012-06-13

697

642

561

295

NWL

NWL

NWL

NEL

HZMB 025

 

2013-02-22

2013-02-21

2012-12-06

2012-10-11

2012-06-13

596

591

525

457

295

NEL

NWL

NEL

NWL

NEL

HZMB 024

 

2013-03-18

2012-06-13

601

295

NWL

NEL

HZMB 023

 

2013-07-08

2013-07-08

2013-04-01

2013-02-21

2013-02-15

2012-07-10

715

711

619

589

579

330

NWL

NWL

NWL

NWL

NWL

NWL

HZMB 022

 

2013-10-24

2013-07-08

2013-07-08

2013-04-01

2013-02-21

2013-02-15

2012-07-10

827

715

711

619

589

579

330

NWL

NWL

NWL

NWL

NWL

NWL

NWL

HZMB 021

NL37

2012-07-10

2011-09-16

330

Baseline

NWL

NWL

Identification Number

Baseline Identification Number

Date

(YYYY-MM-DD)

Sighting Number

Area Sighted

HZMB 020

 

2012-07-10

330

NWL

HZMB 019

 

2012-07-10

330

NWL

HZMB 018

 

2013-05-09

2013-02-21

2012-12-10

2012-07-10

647

594

529

330

NWL

NEL

NEL

NWL

HZMB 017

 

2012-07-10

330

NWL

HZMB 016

 

 

2013-07-08

2012-12-11

2012-09-18

2012-09-04

2012-07-10

706

539

446

421

330

NWL

NWL

NWL

NWL

NWL

HZMB 015

 

2012-07-10

330

NEL

HZMB 014

NL176

2012-08-06

2012-06-13

2011-11-06

2011-11-01

2011-11-01

373

295

Baseline

Baseline

Baseline

NWL

NEL

NEL

NEL

NEL

HZMB 013

 

2012-05-28

281

NWL

HZMB 012

 

2012-05-28

281

NWL

 


 

Identification Number

Baseline Identification Number

Date

(YYYY-MM-DD)

Sighting Number

Area Sighted

HZMB 011

EL01

2013-02-22

2013-02-21

2013-02-14

2012-11-06

2012-09-19

2012-03-31

2011-11-02

2011-11-01

597

592

572

517

452

261

Baseline

Baseline

NEL

NEL

NEL

NEL

NWL

NEL

NWL

NEL

HZMB 009

 

2012-05-28

281

NWL

HZMB 008

 

2012-05-28

281

NWL

HZMB 007

NL246

2012-12-10

529

NEL

HZMB 006

 

2013-02-21

2012-12-11

2012-11-01

2012-03-29

594

539

495

250

NEL

NWL

NWL

NWL

HZMB 005

 

2013-11-09

2013-11-07

2013-10-15

2012-12-10

2012-08-06

2012-05-28

860

858

813

532

374

287

NWL

NWL

NWL

NWL

NWL

NWL

HZMB 004

 

2012-09-04

2012-03-31

421

262

NWL

NWL

HZMB 003

NL179

2014-10-15

2013-06-25

2012-12-10

2012-03-31

2011-11-06

2011-09-16

812

697

529

261

Baseline

Baseline

NWL

NWL

NEL

NWL

NEL

NWL

Identification Number

Baseline Identification Number

Date

(YYYY-MM-DD)

Sighting Number

Area Sighted

HZMB 002

 

WL111

2013-11-01

2013-10-15

2013-09-24

2013-02-14

2012-12-11

2012-12-11

2012-10-12

2012-10-24

2012-05-28

2012-03-29

839

819

798

573

536

535

466

475

281

250

NWL

NWL

NWL

NWL

NWL

NWL

NWL

NWL

NWL

NWL

HZMB 001

WL46

2013-08-21

2013-06-13

2013-04-01

2013-02-14

2012-03-29

771

681

617

573

250

NWL

NWL

NWL

NWL

NWL

 

CH98

2011-11-02

Baseline

NWL

 

NL11

 

2011-11-02

2011-11-07

Baseline

Baseline

NWL

NWL

 

NL12

2011-11-02

Baseline

NWL

 

NL33

 

2011-09-23

2011-11-01

2011-11-05

2011-11-07

Baseline

Baseline

Baseline

Baseline

NWL

NEL

NWL

NWL

 

NL37

2011-09-16

Baseline

NWL

 

NL46

2011-10-28

Baseline

NWL

 


 



[2] Logger is purpose built software which automatically collects and stores GPS data and contains a user configurable interface for the manual entry of the data required for line transect and other cetacean research studies (Gillespie et al 2010).

[3] Group size is defined as an aggregation of dolphins within 100m of each other involved in similar behaviour (Connor et al 1998).

[4] During sightings a minimum, maximum and best estimate of group size is noted; the range stated represents the minimum and maximum numbers estimated)

[5] Updated data set provided April 2013

[6] The provision of data from multiple government agencies and the private sector is acknowledged

[7] Please note: the monthly report for October 2013 erroneously reported no calves were seen during this month. There were four sightings of calves during this month.

[8] Scott Hayward, L. A. S. , Mackenzie ,M. L. , Donovan, C R , Walker, C. & Ashe, E. (2013), Complex Region Spatial Smoother (Cress). Journal of Computational and Graphical Statistics. In press

[9] http://www.snh.gov.uk/docs/a609642.pdf

[10] Paxton, C., Mackenzie, M. L., Burt, L.,  Rexstad, E. & Thomas, L. (2011) Phase II Data Analysis Of Joint Cetacean Protocol Data Resource, Http://Jncc.Defra.Gov.Uk/Pdf/Jcp_Phase_II_Report.Pdf

[11] Comparing Pre- and Post-Construction Distributions of Long-Tailed Ducks Clangula Hyemalis in and Around the Nysted Offshore Wind Farm, Denmark : A Quasi-Designed Experiment Accounting for Imperfect Detection, Local Surface Features and Autocorrelation. Http://Hdl.Handle.Net/10023/2008

[12]   Hardin, J. W.  and Hilbe, J., Generalized Estimating Equations. 2003. Chapman & Hall/CRC Press.