BROADHAVEN BAY MARINE MAMMAL OBSERVATIONS FINAL REPORT 2009

Microsoft Word - Final MMO report 14-1 LDdwab.docCONTENTS 1 Introduction .................................................................1
4 Conclusions...............................................................12
5 Acknowledgements...................................................13
Tables Table 2.1: Acoustic specifications of ROV-mounted sonar systems for MV Manta
III and MV Highland Rover, employed in Broadhaven Bay between 13 May and 8 June 2009 (source: Allseas, 2008)..................................................... 4
Table 2.2: Acoustic specifications of ROV-mounted sonar systems for MV Mærsk Advancer, employed in Broadhaven Bay between 19 August and 6 October 2009 (source: Mærsk, 2010) .......................................................... 6
Table 3.1: Total marine mammal observation (MMO) effort in hours, total construction vessel effort in hours, and construction vessel effort as a proportion of MMO effort.............................................................................. 8
Table 3.2: Marine mammal species composition of sightings made by on-effort (on-duty) observers throughout 205-day survey period (10 May–14 October 2009)............................................................................................................ 9
Table 3.3: Respective species category sightings as percentage of total survey sightings (all categories) – sightings made by on-effort (on-duty) observers throughout 205-day survey period (10 May–14 October 2009).................... 9
Table 3.4: Number of individuals in each species category as percentage of total survey individuals (all categories) – sightings made by on-effort (on-duty) observers throughout 205-day survey period (10 May–14 October 2009). 10
Figures Figure 2.1: Trailing suction hopper dredger MV HAM 311 .................................. 2 Figure 2.2: Backhoe dredger Razende Bol ......................................................... 3 Figure 2.3: Survey boat, MV Niamh Áine ............................................................ 3 Figure 2.4: Survey ship, MV Manta III................................................................. 4 Figure 2.5: Survey ship, MV Highland Rover ...................................................... 5 Figure 2.6: Rock-trenching ship, MV Mærsk Advancer ....................................... 6 Figure 2.7: Rock-dumping ship, MV Tertness ..................................................... 7 Figure 3.1: Seasonal and interannual sightings comparisons, 2008 and 2009 . 11
Broadhaven Bay Marine Mammal Observations 2009
RSK Environment Ltd 1 RSK/He/P40036/36/08 rev00
1 Introduction RSK Environment Ltd has been engaged by Shell Exploration and Production Ireland Ltd (SEPIL) to provide various environmental services during the construction period for the Corrib offshore gas pipeline.
This final (summary) report has been compiled to comply with the 2009 Environmental Management Plan (Nearshore Works - Landfall and Pipeline Pull-in Environmental Management Plan (EMP) COR-14-SH-018/Rev03), as part of which, SEPIL has been required to provide monthly reports of cetaceans observed by marine mammal observers (MMOs) who have been onboard vessels during the construction works.
MMOs were required to be present on vessels at the commencement of noise- generating activities (geophysical survey and dredging operations) under the code of practice agreed between SEPIL and the National Parks and Wildlife Service (NPWS). Records were made of any marine mammals seen before or during construction operations (which were delayed if marine mammals were sighted within 1000m of any noise-generating vessels before they started work), and reported monthly.
This final report provides a summary of the previous seven monthly reports (April–October) for 2009.
The series of reports have been submitted to the Department of Communications, Energy and Natural Resources (DCENR), and copied to NPWS.
2 Materials and Methods Figure 2.1 shows the 94.54m length overall (LOA) trailing suction hopper dredger (TSHD) MV HAM 311, from which MMOs conducted watches between 10 May and 23 June 2009. This vessel dredged the trench for the Corrib gas pipeline throughout Broadhaven Bay at a speed over the ground of approximately one to two knots. The HAM 311 trailed a suction pipe when dredging, and loaded dredge spoil into a self-contained hopper. The hopper was emptied at a designated spoil site, which was employed as a temporary storage area only, as the spoil was used for subsequent backfilling purposes.
Figure 2.1: Trailing suction hopper dredger MV HAM 311
Figure 2.2 shows the 50.33m LOA backhoe dredger Razende Bol, from which MMOs conducted watches between 13 May and 26 August 2009. Owing to its relatively shallow draft this vessel dredged the landfall and near-shore section of the trench for the Corrib gas pipeline in Broadhaven Bay. The Razende Bol comprised an excavator on a pontoon, which was floated onto location, whereupon the legs or ‘spudcans’ were jacked down onto the seabed to create a stable dredging platform. The Razende Bol loaded its spoil into split-hopper barges, which were then emptied at the designated temporary spoil storage location.
Figure 2.2: Backhoe dredger Razende Bol
Figure 2.3 shows the 11.58m LOA survey boat, Niamh Áine, from which MMOs conducted watches between 14 May and 1 September 2009. The boat was equipped with side-mounted multi-beam sonar to acoustically survey the seabed topography and monitor the progress of dredging operations. The vessel surveyed the seabed throughout Broadhaven Bay at a typical bottom speed of one to two knots. As a precaution, prior to continuous operation, the multi-beam sonar was initially powered on and off over a 20-minute period, known as a ‘soft-start’, and intended to act as a warning signal and allow any marine mammals present to move away from the noise source. However, the multi-beam operating frequency of 450kHz (with unavailable intensity) is beyond the known audible/hearing range of any marine mammal species.
Figure 2.3: Survey boat, MV Niamh Áine
Figure 2.4 shows the 82.4m LOA hydrographical survey vessel, MV Manta III, from which an MMO conducted watches between 31 May and 8 June 2009. The ship deployed a remotely operated vehicle (ROV), equipped with underwater cameras and sonar, in order to visually and acoustically survey the seabed topography and negotiate an optimal pipeline route that avoided obstructions (e.g. rocky outcrops) from Broadhaven Bay, seaward to outwith the SAC boundary. When the ROV was deployed, the MV Manta III typically followed a fixed course using dynamic positioning (DP) thrusters at a bottom speed of 0.20–0.45 knots. Activation of the ROV’s sonar operations were subject to the 20-minute soft-start procedure, and Table 2.1 lists relevant acoustic specifications for the five ROV-mounted sonar systems, including source frequencies and intensities.
Figure 2.4: Survey ship, MV Manta III
Table 2.1: Acoustic specifications of ROV-mounted sonar systems for MV Manta III and MV Highland Rover, employed in Broadhaven Bay between 13 May and 8 June 2009 (source: Allseas, 2008)
Type Make and model Frequency Intensity
Obstacle avoidance sonar
Dual multi-beam echosounders
Reson SeaBat 7125 400kHz 220dB re 1µPa at 1m range
Altimeter Kongsberg 1007 200kHz 210dB re 1µPa at 1m range Doppler velocity log RDI Workhorse
Navigator DVL 1200kHz 214dB re 1µPa at 1m range
USBL positioning transponder/responder
19–36kHz 188–206dB re 1µPa at 1m range
Figure 2.5 shows the 71.8m LOA hydrographical survey vessel, MV Highland Rover, from which an MMO conducted watches between 25 June and 19 July
2009. The MV Highland Rover deployed an ROV to visually and acoustically survey the progress of the pipe-laying vessel, MV Solitaire, from Broadhaven Bay, seaward to outwith the SAC boundary. The ROV’s operations were subject to the 20-minute soft-start procedure, and Table 2.1 lists relevant acoustic specifications for the five ROV-mounted sonar systems.
Figure 2.5: Survey ship, MV Highland Rover
Figure 2.6 shows the 90.3m LOA rock-trenching vessel, MV Mærsk Advancer, from which an MMO conducted watches between 19 August and 6 October 2009. The MV Mærsk Advancer trenched the exposed sections of pipeline in Broadhaven Bay, and deployed an ROV to visually and acoustically survey its progress. The ROV’s sonar operations were subject to the 20-minute soft-start procedure, and Table 2.2 lists relevant acoustic specifications for the five ROV- mounted sonar systems.
Figure 2.6: Rock-trenching ship, MV Mærsk Advancer
Table 2.2: Acoustic specifications of ROV-mounted sonar systems for MV Mærsk Advancer, employed in Broadhaven Bay between 19 August and 6 October 2009 (source: Mærsk, 2010)
Type Make and model Frequency Intensity
Obstacle avoidance sonar
Dual multi-beam echosounders
Reson SeaBat 8125 455 kHz 180dB re 1µPa at 1m range
Bathymetry unit c/w altimeter
500kHz Unavailable, but beyond wildlife’s audible range
Doppler velocity log Navigator (Teledyne) Workhorse RDI
1200kHz Unavailable, but beyond wildlife’s audible range
USBL positioning transponder/responder
19kHz– 36kHz
185-190dB re 1µPa at 1m range
Figure 2.7 shows the 129.4m LOA flexible fall-pipe/bulk carrier vessel, or ‘rock- dumping’ vessel, MV Tertness, from which an MMO conducted watches between 22 September and 14 October 2009. The MV Tertness buried the exposed sections of pipeline that could not be trenched in Broadhaven Bay, and deployed a ROV to visually and acoustically survey its progress. The ROV’s sonar was subject to the 20-minute soft-start procedure; however, the multi-beam operating frequency of 450kHz (with unavailable intensity) is beyond the known audible/hearing range of any marine mammal species.
Figure 2.7: Rock-dumping ship, MV Tertness
3 Results
3.1 Synopsis of monitoring Table 3.1 shows that MMO effort comprised a total of 1434 hours and construction vessels operated for a total of 996.7 hours, which equates to around 70% of the total MMO effort.
Table 3.1: Total marine mammal observation (MMO) effort in hours, total construction vessel effort in hours, and construction vessel effort as a proportion of MMO effort
Vessel(s) MMO effort (hrs)
Vessel effort as % of MMO effort
MV Ham 311 83.5 57.5 69 Razende Bol 583.8 455.5 78 MV Niamh Áine 278.1 192 69 MVs Manta III & Highland Rover 207.4 136 66 MV Mærsk Advancer 202.4 125.5 62 MV Tertness 78.8 30.5 39
Total 1434 996.7 70
3.2 Total survey sightings Throughout the entire 205-day monitoring period from 10 May to 14 October 2009, there were 186 sightings; these are listed chronologically in the seven monthly reports. Table 3.2 provides summaries of these sightings and the number of individuals per sighting. The data analyses for this report consider known observed number of individuals only. Therefore, the maximum possible estimate is provided for completeness only, as MMOs did record this additional information.
Table 3.2: Marine mammal species composition of sightings* made by on-effort (on-duty) observers throughout 205-day survey period (10 May– 14 October 2009)
Species category No. of sightings
Minimum or known no. of individuals
Maximum possible estimate of individuals
Phocoena phocoena (common porpoise) 2 2 2 Tursiops truncatus (bottlenose dolphin) 12 139 170 Delphinus delphis (common dolphin) 5 73 82 Orcinus orca (killer whale) 1 2 2 Unidentified dolphin 8 96 100 Unidentified dolphin or porpoise 1 1 1 Balaenoptera acutorostrata (minke whale) 2 1 1 Unidentified whale 5 5 6 Halichoerus grypus (grey seal) 96 100 100 Phoca vitulina (common seal) 7 7 7 Unidentified seal 44 45 45 Cetorhinus maximus (basking shark) 1 1 1 Mola mola (ocean sunfish) 2 2 2
Totals 186 474 519 * Note that the term ‘sighting’ can comprise an individual or a cluster (group) of animals ‘Unidentified’ = sighting was distant and/or brief, which prevented identification of species
Table 3.3 lists respective species category sightings as a percentage of total survey sightings (all categories).
Table 3.3: Respective species category sightings* as percentage of total survey sightings (all categories) – sightings made by on-effort (on-duty) observers throughout 205-day survey period (10 May–14 October 2009)
Species category No. of sightings Percentage of total survey sightings (186)
Phocoena phocoena 2 1.1 Tursiops truncatus 12 6.5 Delphinus delphis 5 2.7 Orcinus orca 1 0.5 Unidentified dolphin 8 4.3 Unid. dolphin or porpoise 1 0.5 Balaenoptera acutorostrata 2 1.1 Unidentified whale 5 2.7 Halichoerus grypus 96 51.6 Phoca vitulina 7 3.8 Unidentified seal 44 23.7 Cetorhinus maximus 1 0.5 Mola mola 2 1.1
* Note that the term ‘sighting’ can comprise an individual or a cluster (group) of animals ‘Unidentified’ = sighting was distant and/or brief, which prevented identification of species
Table 3.3 shows that Halichoerus grypus (grey seal) was the most sighted species in 2009, which coincides with the results reported in 2008, as this species comprised approximately 50% of the sightings during both years.
Table 3.4 lists respective species category individuals as a percentage of total survey individuals (all categories).
Table 3.4: Number of individuals in each species category as percentage of total survey individuals (all categories) – sightings* made by on-effort (on-duty) observers throughout 205-day survey period (10 May–14 October 2009)
Species category No. of individuals
Percentage of total survey individuals (474)
Phocoena phocoena 2 0.4 Tursiops truncatus 139 29.3 Delphinus delphis 73 15.4 Orcinus orca 2 0.4 Unidentified dolphin 96 20.3 Unid. dolphin or porpoise 1 0.2 Balaenoptera acutorostrata 1 0.2 Unidentified whale 5 1.1 Halichoerus grypus 100 21.1 Phoca vitulina 7 1.5 Unidentified seal 45 9.5 Cetorhinus maximus 1 0.2 Mola mola 2 0.4
* Note that the term ‘sighting’ can comprise an individual or a cluster (group) of animals ‘Unidentified’ = sighting was distant and/or brief, which prevented identification of species
The majority of the MMOs working throughout 2009 were equipped with professional SLR cameras and telephoto lenses. The series of figures in Appendix 1 (A-1 to A-4) show the marine mammal sightings that presented the best opportunities for photography during the 2009 marine mammal monitoring.
3.3 Seasonal and annual comparisons During 2009, as reported in the final monthly (October) report, there were nine sightings in May, which compares with 103 in June, 30 in July, 24 in August, 13 in September, and 7 in October. Sightings in May comprised at least 5 different species, which compares with at least 5 in June, at least 4 in July, at least 4 in August, at least 4 in September, and at least 4 in October. The results support existing records of abundance and diversity in the region.
With the exception of the relatively higher numbers of sightings in June – which coincided with favourable weather and sea-state conditions, and therefore increased construction activities and associated MMO effort – no obvious seasonal patterns can be established. During all other months, weather and sea-state conditions periodically precluded construction activities and associated MMO effort, and therefore resulted in limited sightings data with which to attempt comparisons. Furthermore, construction activities ranged from different types of dredging and surveying, pipe-laying, rock trenching and rock dumping, none of which are directly comparable in terms of any potential acoustic and/or physical disturbance. Therefore, sightings between vessels that may have varying environmental impacts are also not directly comparable. Nevertheless, as a proxy indicator of seasonal and interannual comparability,
monthly sightings totals were plotted against monthly effort totals, from both 2008 and 2009, as per Figure 3.1.
Figure 3.1 shows a clear correlation between increased sightings and increased MMO effort. In 2008, most sightings were made during August and, in 2009, most sightings were made during June, the respective months in each year that coincided with the most favourable weather conditions.
Ongoing scientific research is trying to establish whether other factors, specifically oceanographic conditions and migratory prey patterns, are also closely correlated with marine mammal sightings.
Seasonal and interannual sightings comparison
0
20
40
60
80
100
120
Month
M M
O e
ffo rt
No. of sightings 2008 No. of sightings 2009 MMO effort (hrs) 2008 MMO effort (hrs) 2009
Figure 3.1: Seasonal and interannual sightings comparisons, 2008 and 2009
4 Conclusions
• There were 186 sightings in 2009, composed of at least 474 individuals.
• There were 13 species, categorised as follows: ‘Phocoena phocoena’ (harbour porpoise), ‘Tursiops truncatus’ (bottlenose dolphin), ‘Delphinus delphis’ (common dolphin), ‘Orcinus orca’ (killer whale), ‘Unidentified dolphin’, ‘Unidentified dolphin or porpoise’, ‘Balaenoptera acutorostrata’ (minke whale), ‘Unidentified whale’, ‘Halichoerus grypus’ (grey seal), ‘Phoca vitulina’ (common seal), ‘Unidentified seal’, ‘Cetorhinus maximus’ (basking shark), and ‘Mola mola’ (ocean sunfish).
• During 2008 and 2009, Halichoerus grypus (grey seal) was the most sighted species, comprising approximately 50% in both years.
• Monthly sightings total were highest during August in 2008 and June in 2009, coinciding with the most favourable weather conditions, increased construction activities and associated MMO effort.
5 Acknowledgements This marine mammal monitoring has provided a good indication of the species likely to be encountered during the summer months in Broadhaven Bay and may help to elucidate ongoing scientific research within the region.
The use of MMOs provides a strong indication of the stakeholders’ commitments towards responsible environmental stewardship and awareness of marine mammals.
The operator’s representatives, superintendents and vessel crews provided their full cooperation and regarded marine mammal mitigation measures with the utmost sincerity.
APPENDIX 1: SELECTED MARINE MAMMAL SIGHTINGS FROM 2009 MONITORING
Figure A-1. Common dolphin sighting (Sighting #1 11/05/2009)
Figure A-2. Bottlenose dolphin sighting (Sighting #16 02/06/2009)

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BROADHAVEN BAY MARINE MAMMAL OBSERVATIONS FINAL REPORT 2009

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