7               dolphin north-south movement

 

7.1               A total of 180 hours and 51 minutes were spent during the 30 days of theodolite tracking effort at Sham Wat Station (Figure 6) to examine dolphin movement and behaviour from December 29, 2012 through January 30, 2013.  90.2% of effort was conducted in favourable weather condition.

 

7.2               Dolphins were successfully tracked from shore on 15 of 30 days of effort, and a total of 89 dolphin groups were tracked.  In addition, 12 dolphin group tracks on six days of successful tracking between April 2011 and August 2012 (collected by HKCRP outside the baseline monitoring period) was included in the data analysis to augment the data set.  These historical data were collected in the same manner as those collected in the 30-day baseline period, and the pooling of both sets of data can increase the sample size for statistical analysis during the baseline phase and is beneficial to understand and quantify any responses during construction.

 

7.3               Major findings from the analysis of the above data are summarized as follows:

·       Dolphin behaviour and movement change dependent upon natural (time of day, size of group) and anthropogenic (vessel presence) factors

·       Dolphins swim faster along a straighter path and breathe less frequently when multiple vessels are present at one time than when no vessels are present.  This can be understood as a single snapshot in time: if there are more boats present when the snapshot is taken, the dolphins are likely to be swimming faster.

·       As the number and variety of vessels encountered during a track increases, dolphins swim slower, make more turns, and breathe more frequently.  This can be understood as a longer period of time instead of a snapshot moment: as the sum total of boats that interact with the dolphins increase over time, the dolphins swim more slowly.

·       Dolphins change aspects of their behaviours relative to vessels

·       Dolphins are more likely to feed in the presence of fishing vessels.  If feeding behaviour is assisted by vessel presence (particularly the presence of fishing vessels), it is possible that the presence of multiple vessels inhibits this process.

·       It is possible that vessel noise from multiple vessels exceeds a threshold tolerance level for the dolphins, and bored piling and related vessel activity during construction has the potential to have the same effect.

·       The numerical summary of the monitoring results is presented in Tables 7.1 and 7.2.

 

Table 7.1        Values of all response variables in the presence and absence of vessels by time of day, size of group, and maximum number of vessels present

 

Speed (km/hr)

Reorientation rate (degrees/surfacing)

Linearity

Inter-breath interval (sec)

Vessels absent

3.60

50.3

0.618

51.2

    Morning

3.46

45.4

0.676

53.9

    Afternoon

3.80

57.2

0.536

47.3

    Individual

3.39

46.9

0.733

57.2

    Group

3.91

55.2

0.455

42.6

 

Vessels present

3.77

50.5

0.577

43.3

    Morning

3.74

49.9

0.606

45.0

    Afternoon

3.93

52.7

0.454

36.2

    Individual

3.42

50.8

0.542

45.0

    Group

4.26

50.0

0.625

41.1

    1 vessel

3.91

48.8

0.572

36.9

    2 vessels

3.74

55.8

0.559

53.6

    3 vessels

4.26

45.8

0.689

62.5

 

Table 7.2        Proportion of time spent in each behavioural state in the absence and presence of vessels within 500 m 

Behavioural state

Vessels absent

Vessels present

z-value

p-value

Feeding

0.23

0.44

-2.882

0.004

Milling

0.20

0.21

-0.164

0.870

Resting

0.08

0.03

1.593

0.111

Travelling

0.48

0.32

2.202

0.028

Results and significance of the z-test for two proportions indicate if behaviour significantly changes when vessels are present.  Significant differences are indicated by bold text.

 

Event and Action Plan

 

7.4               It is proposed to take all baseline data into account, including times with no apparent anthropogenic activities near the dolphins, various vessel activities, and time of day and other variables for formulating the Action and Limit Levels of the Event and Action Plan:

 

·       Departures of any the response variables between baseline and construction phases with a 20% difference should trigger the Action Level. 

·       Departures of any of the response variables between baseline and construction phases with a 40% difference should trigger the Limit Level and immediate action will be required. Such evaluation should be conducted shortly after the 30-day construction monitoring period.

·       The abovementioned percentage reduction approach to set the Action and Limit Levels has taken into consideration of the influencing factors (e.g. time of the day, group size, vessel activities) that may affect the baseline condition on dolphin movement and behaviour.

·       The detailed Event and Action Plan is presented in Table 7.3.

Table 7.3        Event and Action Plan on Dolphin Movement and Behaviour

EVENT

ACTION

ET Leader

IEC

SO

Contractor

Action Level

With the numerical values presented in Tables 7.1-7.2, any of the response variable for dolphin movement patterns (speed, inter-breath interval, reorientation rate & linearity) and behaviour (proportion of time spent in each behavioural state) recorded in the construction phase monitoring is 20% higher or lower than that recorded in the baseline monitoring, action level should be triggered

 

1. Repeat statistical data analysis to confirm findings;

2. Review all available and relevant data to ascertain if differences are as a result of natural variation or seasonal differences;

3. Identify source(s) of impact;

4. Inform the IEC, SO and Contractor;

5. Check monitoring data;

6. Carry out audit to ensure all dolphin protective measures are implemented fully and additional measures be proposed if necessary

 

1. Check monitoring data submitted by ET and Contractor;

2. Discuss monitoring with the ET and the Contractor;

 

 

1. Discuss with the IEC the repeat monitoring and any other measures proposed by the ET;

2. Make agreement on measures to be implemented.

 

1. Inform the SO and confirm notification of the non- compliance in writing;

2. Discuss with the ET and the IEC and propose measures to the IEC and the SO;

3. Implement the agreed measures.

 

Limit Level

With the numerical values presented in Tables 7.1-7.2, any of the response variable for dolphin movement patterns (speed, inter-breath interval, reorientation rate & linearity) and behaviour (proportion of time spent in each behavioural state) recorded in the construction phase monitoring is 40% higher or lower than that recorded in the baseline monitoring, limit level should be triggered

 

1. Repeat statistical data analysis to confirm findings;

2. Review all available and relevant data to ascertain if differences are as a result of natural variation or seasonal differences;

3. Identify source(s) of impact;

4. Inform the IEC, SO and Contractor;

5. Check monitoring data;

6. Carry out audit to ensure all dolphin protective measures are implemented fully and additional measures be proposed if necessary

7. Discuss additional dolphin monitoring and any other potential mitigation measures (e.g. consider to temporarily stop relevant portion of construction activity) with the IEC and Contractor.

 

 

1. Check monitoring data submitted by ET and Contractor;

2. Discuss monitoring with the ET and the Contractor;

3. Review proposals for additional monitoring and any other measures submitted by the Contractor and advise ER accordingly.

 

1. Discuss with the IEC the repeat monitoring and any other measures proposed by the ET;

2. Make agreement on measures to be implemented.

 

1. Inform the SO and confirm notification of the non- compliance in writing;

2. Discuss with the ET and the IEC and propose measures to the IEC and the SO;

3. Implement the agreed measures.

Abbreviations: ET – Environmental Team, IEC – Independent Environmental Checker, SO – Supervising Officer

 

7.5              Detailed methodology, results and discussion can be found in the Land-based Dolphin Behaviour and Movement Monitoring Baseline Monitoring Report in Appendix F.