OCS Study 

BOEM 2012-015 

 

Seismic Survey Mitigation Measures 

and Marine Mammal Observer Reports 

U.S. Department of the Interior 

Bureau of Ocean Energy Management 

Gulf of Mexico OCS Region 
U.S. Department of the Interior

Bureau of Ocean Energy Management 

Gulf of Mexico OCS Region 

OCS Study 

BOEM 2012-015 

Seismic Survey Mitigation Measures 

and Marine Mammal Observer Reports 

Authors 

M.J. Barkaszi 

M. Butler 

R. Compton 

A. Unietis 

B. Bennet 

Prepared under BOEM Contract 

M08PC20051 

by 

GeoCet Group, LLC 

411 North Sam Houston Parkway East 

Suite 400 

Houston, TX 77060 

Published by 

New Orleans

June 2012 
iii

DISCLAIMER

This report was prepared under contract between the Minerals Management Service (MMS, now 

the Bureau of Ocean Energy Management [BOEM]) and GeoCet Group, LLC. This report has 

been technically reviewed by BOEM, and it has been approved for publication. Approval does 

not signify that the contents necessarily reflect the views and policies of BOEM, nor does 

mention of trade names or commercial products constitute endorsement or recommendation for 

use. It is, however, exempt from review and compliance with BOEM editorial standards. 

REPORT AVAILABILITY

This report is available on CD from the Bureau of Ocean Energy Management, Gulf of Mexico 

OCS Region, for $15.00, and free of charge as a pdf file downloaded from the BOEM Web site. 

Copies can also be viewed at selected Federal Depository Libraries. The addresses are listed 

below. 

To order a CD, use the Gulf of Mexico OCS Region contact information below and reference 

OCS Study BOEM 2012-015. To download a pdf copy, use the Environmental Studies Program 

Information System (ESPIS) and search on the study report number. In the near future, you will 

also be able to get this report also from the National Technical Information Service. 

U.S. Department of the Interior

Bureau of Ocean Energy Management

Gulf of Mexico OCS Region 

Public Information Office (MS 5034) 

1201 Elmwood Park Blvd.

New Orleans, Louisiana 70123-2394 

Phone: (504) 736-2519, 1-800-200-GULF 

Fax: (504) 736-2620

U.S. Department of Commerce

National Technical Information Service

5301 Shawnee Rd. 

Springfield, Virginia 22312 

Phone: (703) 605-6000, 1-800-553-6847 

Fax: (703) 605-6900 

Website: http://www.ntis.gov/

CITATION

Barkaszi, M.J., M. Butler, R. Compton, A. Unietis, and B. Bennet. 2012. Seismic survey 

mitigation measures and marine mammal observer reports. U.S. Dept. of the Interior, 

Bureau of Ocean Energy Management, Gulf of Mexico OCS Region, New Orleans, LA. 

OCS Study BOEM 2012-015. 28 pp + apps. 
v 

TABLE OF CONTENTS

Page

LIST OF FIGURES .................................................................................................................... vii

LIST OF TABLES ....................................................................................................................... ix

1.0. EXECUTIVE SUMMARY ................................................................................................... 1

2.0. INTRODUCTION ................................................................................................................. 2

3.0. METHODOLOGY ................................................................................................................ 4

3.1. Data Collection and Recording ...................................................................................... 4

3.2. Data Entry ....................................................................................................................... 6

3.3. Data Analysis ................................................................................................................. 6

4.0. RESULTS ............................................................................................................................... 7

4.1. Seismic Operation Records ............................................................................................ 7

4.2. Sighting Records ............................................................................................................ 8

4.2.1. Distance from the Seismic Source .................................................................. 13

4.2.2. Sighting Duration ............................................................................................ 15

4.2.3. Behavioral Observations ................................................................................. 16

4.3. Observer Survey Effort ................................................................................................ 20

4.3.1. Sighting Rate ................................................................................................... 21

5.0. MITIGATION...................................................................................................................... 22

6.0. PASSIVE ACOUSTIC MONITORING ............................................................................ 23

7.0. DISCUSSION ....................................................................................................................... 23

8.0. REFERENCES .................................................................................................................... 27

APPENDICES

Appendix A: Location and Effort (Observer Effort) Form ............................................... A-1 

Appendix B: Record of Operations (Survey) Form .......................................................... B-1 

Appendix C: Record of Sighting (Sighting) Form ............................................................ C-1 

Appendix D: Notice to Lessees 2007-G02 ........................................................................ D-1 
vii

LIST OF FIGURES

Page

Figure 1. Gulf of Mexico regional map depicting BOEM planning areas. ................................ 3

Figure 2. BOEM protraction areas within the Gulf of Mexico OCS. ........................................ 5

Figure 3. Distribution of cetacean and sea turtle sightings. ..................................................... 10

Figure 4. Comparison of the distance to the seismic source during full power and 

silence. ...................................................................................................................... 14

Figure 5. Comparison of the distance to the seismic source during mitigation and 

silence. ...................................................................................................................... 14

Figure 6. Comparison of median sighting duration during full power and silence. ................. 15

Figure 7. Comparative behavioral responses of the “all cetaceans” group during full 

power and silence. .................................................................................................... 16

Figure 8. Comparative behavioral responses of the “all cetaceans” group during 

mitigation and silence. .............................................................................................. 17

Figure 9. Comparative behavioral reponses of the “all cetaceans” group during 

ramp-up and silence. ................................................................................................. 17

Figure 10. Comparison of sightings frequency during full power and silence. ......................... 22
ix

LIST OF TABLES

Page

Table 1. Data Completeness Summary from All Survey Report Forms .................................. 8

Table 2. Species Sighting Summaries by Lowest Identified Taxonomic Group .................... 11

Table 3. Kruskal-Wallis Analysis of Variance Results for the Closest Approach to 

the Seismic Source (n.s.: not significant) ................................................................ 13

Table 4. Krustal-Wallis Analysis of Variance Results for Sighting Duration 

(n.s.: not significant) ................................................................................................. 15

Table 5. Chi-squared Results for Grouped Behaviors by Seismic Status (Greyed 

areas not included within analysis due to low sample size.) .................................... 18

Table 6. Chi-squared Results for Individual Behaviors .......................................................... 19

Table 7. Krustal-Wallis Analysis of Variance Results for Sighting Rate/1,000 Hours 

(n.s.: not significant) ................................................................................................. 21
1 

1.0. EXECUTIVE SUMMARY

• Mitigation observation data were collected during seismic survey operations in 

the Gulf of Mexico (GOM), United States of America (USA) between December 

2002 and December 2008 under Notice to Lessees (NTL) 2007-G02 and earlier 

versions. The required submissions included observer effort, record of operations 

and sighting report data forms within each biweekly report. 

• A total of 1,440 bi-weekly reports were received by the Bureau of Ocean Energy 

Management (BOEM), formerly the Minerals Management Service (MMS), for 

seismic surveys; a total of 194,273 visual survey hours were recorded. 

• Visual observations yielded 3,963 complete sighting records; approximately 

28,000 individual animals were represented in the records. 

• Cetaceans comprised 3,335 (85%) of these records with 20 species identified. Sea 

turtles comprised the remaining 579 (15%) records with five species identified. 

The most common cetacean encountered was the sperm whale, Physeter 

macrocephalus (N=1,136 records); the most common small cetacean identified 

was the pantropical spotted dolphin (Stenella attenuata), (N=740 records). 

• There were 32,939 ramp-ups recorded within all bimonthly reports. Of these 

records 65% were fully complete or nearly complete so that ramp-up activity and 

compliance were clearly discernible. Of the ramp-ups recorded, 90% were 

between 20 and 40 minutes in duration, as required by the NTL. 

• Of the daytime ramp-up records 86% had data complete enough to discern 

compliance with the pre-firing survey requirement. Only 3% of the pre-firing 

surveys were less than the required 30 minute duration. 

• There were 32 delays in ramp-ups due to the presence of protected species in the 

exclusion zone during the 30 minutes immediately prior to ramp-up. Of these 

delays, 24 (75%) were due to dolphins, four (12.5%) due to sea turtles, and four 

(12.5%) due to sperm whales. 

• There was a total of 18.5 hours of down time attributed to ramp-up delays. 

• There were 144 occurrences of whales visually detected in the exclusion zone that 

resulted in a shutdown of airguns. Of the required 144 shutdown events, 

139 (97%) were due to sperm whales. 

• The average downtime resulting from shutdowns was 58 minutes and there was a 

total of 125.74 hours of down time attributed to shutdowns. 

• Shut down frequency for sperm whales was 0.71 shutdowns per 1,000 hours of 

observation, resulting in an estimated 1 shutdown for every 1,500 hours 

(or roughly 125 days) of daylight survey operations, assuming observations are 

conducted during all daylight hours regardless of gun operations. 

• The mean dolphin sighting frequency decreased 9% during airgun ramp-up 

procedures when compared to airgun silence. However, dolphin sighting 

frequency during minimum source firing sightings was equal to that during gun 
2 

silence. Dolphin sighting frequency when airguns were at full power increased 

14% when compared to silent mode. 

• The minimum distance of dolphins to airguns increases from silent, to ramp-up, to 

mitigation, and full power. At full power, the mean closest approach of dolphins 

to airgun arrays was 90% further away than during silent status. 

2.0. INTRODUCTION

The Outer Continental Shelf (OCS) region of the United States Gulf of Mexico (GOM) is one of 

the world’s most active hydrocarbon exploration and production areas. A major element of the 

continuing work in this region is the use of deep-water seismic surveys in order to identify 

potential hydrocarbon resources. Marine seismic surveys involve the use of a seismic sound 

source (typically an “airgun array”) which generates sounds which propagate through the water 

column and the seafloor; sound reflected and refracted by geological boundaries is recorded for 

interpretation (Kearey et al. 2002). Seismic airgun arrays produce a predominantly 

low-frequency sound, though the production of high frequency sound has also been 

demonstrated (Goold and Fish 1998). The sound impulse is repeated at intervals of about 

10 seconds (dependent on the water depth and geological target depth); a survey is generally 

several weeks to several months in duration. 

There is growing concern that sound from anthropogenic sources such as seismic surveys has the 

potential to impact marine wildlife, and in particular cetaceans, which use sound to 

communicate, navigate, and hunt (Richardson et al. 1995; Hatch and Wright 2007). The 

dominant sound frequencies produced by airgun arrays (<200 Hz) overlap with those used by 

mysticetes, while the high frequency content of the sound impulse overlaps with frequencies 

used by odontocetes (Richardon et al. 1995). A growing body of research has documented a 

wide range of behavioral responses of cetaceans and other marine fauna to sound sources, with 

any potential for long term consequences unknown (Richardson et al. 1995, Gordon et al. 2003). 

The potential for causing temporary physical damage to auditory systems has been 

experimentally demonstrated, and hypotheses have been put forward regarding the behaviorally 

mediated stranding of animals (Finneran et al. 2005; Jepson et al. 2003). Sound perception 

varies widely between marine species and therefore, there is no single model or agreement for 

source impacts to all marine mammal and sea turtle species for all circumstances. Behavioral 

responses to sound have been suggested for marine mammals at sound pressures ranging from 

90 dB re 1μPa to 200 dB re 1μPa (Baily et al. 2010). Southall et al. (2007) suggests using a 

sound level of 230 dB re 1μPa as the onset of permanent threshold shifts to cetaceans. 

In light of concerns regarding the potential impacts of underwater sound from seismic surveys, a 

number of countries have implemented mitigation measures designed to minimize the potential 

for disturbance and injury to marine species (Compton et al. 2007). The Bureau of Ocean

Energy Management (BOEM) conveys regulations to offshore operators via the Notice to 

Lessees (NTL), which mandates standard operating procedures necessary to comply with the 

Endangered Species Act (ESA) and the Marine Mammal Protection Act (MMPA). Mitigation is 

required for all geophysical survey operators working in waters greater than 200 meters

throughout the GOM and in all water depths in the Eastern Planning Area (Figure 1). The 
3 

regulations follow NTL 2007-G02 (and previous versions): Implementation of Seismic Survey 

Mitigation Measures and Protected Species Observer Program.

1

Figure 1. Gulf of Mexico regional map depicting BOEM planning areas. 

The mitigation measures are designed to minimize potential noise impacts to protected marine 

species through visual monitoring, ramp-up procedures, maintenance of an exclusion zone 

around surveying vessels, operational shut-down protocols, and regulatory reporting. The 

mitigation measures require the following:

• Use of three trained observers on board all source vessels, with maximum 

observer hours established at a continuous four hours with a 2-hour break and 

no single observer working greater than 12 hours over a 24-hour period. 

• Observers must monitor an exclusion zone of 500 meters around the center of 

the airgun array and the area within the immediate vicinity of the vessel.

• Operators must ramp-up the survey array from silence to full power over a 

time period between 20 and 40 minutes. 

• Observers must maintain continuous watches during all airgun operations 

during daylight hours. 

• Operators may reduce the source level of the airgun array, using the same shot 

interval as the seismic survey, to maintain a minimum source level of 160 dB 

during turns and unscheduled maintenance. 

 

1 This NTL was superceded by Joint NTL 2012-G02 on January 1, 2012. Available from 

http://boem.gov/Regulations/Notices-To-Lessees/Notices-to-Lessees-and-Operators.aspx. 
4 

• Cetaceans are grouped into the regulatory categories of Whales, which 

includes all Mysticete whales, sperm whales (Physeter macrocephalus), dwarf 

and pygmy sperm whales (Kogia spp.), and all species of beaked whales 

(Ziphius, Mesoplodon); and Dolphins which includes all other Odontocetes. 

• The start of airguns must be delayed until the exclusion zone is free of marine 

mammals and sea turtles for 30 minutes. 

• Airguns must be shut off if a whale enters the zone within 500 meters of the 

airgun source. 

• Reports must be submitted to BOEM on the first and 15th of each month. 

Data collected in biweekly reports were compiled in three data forms. These data forms emulate 

the Joint Nature Conservancy Committee (JNCC) forms for seismic surveys and were modified 

for Gulf of Mexico operations; these included: Observer Effort (Location and Effort), Survey 

Report (Record of Operations), and Sighting Report (Record of Sighting). Standardized data 

forms, however, were not required but the required information itself provided to BOEM in the 

forms was standardized; thus, observer providers submitted varying forms with the same data 

requirements.

Previous analyses have been conducted on datasets collected by marine mammal observers 

(MMOs) working under guidelines issued by the JNCC in the United Kingdom (Stone and 

Tasker, 2006; Stone, 1997; 1998; 2000; 2001; 2003a; 2003b). This report represents the 

compilation of visual observer data collected within the GOM OCS region over six years, 

between December 2002 and December 2008, by way of compliance reports submitted to 

BOEM. The observer data were used to examine compliance levels with NTL guidelines, and 

investigate the potential effects of seismic operations on marine species.

3.0. METHODOLOGY 

3.1. DATA COLLECTION AND RECORDING

Observers recorded all field data during observations and submitted biweekly reports to BOEM 

in electronic format. Reports were submitted on the first and 15th of each month; therefore, 

multiple reports were submitted for the same seismic project depending on the duration of that 

project. Some GOM seismic projects last months to years and thus will have multiple reports 

from multiple observers over the course of the project.

A total of 1,440 bi-weekly reports were received by BOEM for seismic surveys conducted in the 

GOM between December 2002 and December 2008. Bi-weekly reports were reviewed and data 

from each of the three forms within the reports were entered into databases.

The Location and Effort (Observer Effort) form summarized the location and duration of visual 

surveys as well as the physical observation conditions encountered by the observer 

(Appendix A). Survey location was recorded using latitude and longitude coordinates as well as 

the BOEM protraction blocks and numbers (Figure 2). Protraction areas and the observation 

hours were used for statistical analysis rather than a linear distance of surveys due to the fact that 

track line data were not required on the effort forms. Distribution of effort was calculated using 
5 

the difference between start and end of time of watch, and assigned that time in units of minutes 

to the start block ID. Where multiple effort records were available for the same start block 

across the six years, the minutes from all records were summed in order to get the total minutes 

in that block. 

Figure 2. BOEM protraction areas within the Gulf of Mexico OCS. 

The Record of Operations (Survey) form was used to record all ramp-up times and durations; 

pre-ramp-up visual survey times; documentation of protected species during the pre-ramp-up 

visual surveys; and any mitigation actions (delays or shut downs) that were required for NTL 

compliance (Appendix B). Data from the Record of Operations were used to summarize 

frequency and duration of ramp-ups and compliance regularity of ramp-ups and mitigation 

actions. Airgun activity was recorded as full power, ramp-up, mitigation firing, or silent. 

Ramp-up of airguns is a mitigation used to minimize noise impacts to marine mammal and sea 

turtle species. The reasoning behind using ramp-ups, also called soft-starts, is to “warn” 

individuals who may be in the highest risk zone for noise impacts by starting at a lower power 

source and incrementally increasing source power to survey strength, thereby allowing 

individuals time to move away from the sound source before being subjected to the maximum 

sound levels. All ramp-up start and end times were recorded on the Record of Operations forms. 

Under the NTL: ramp-up should be initiated and ended within the time constraints of 

20-40 minutes; no ramp-ups can take place from silence during darkness or during incompatible 

visual observation conditions; and ramp-ups cannot be initiated only to establish mitigation 
6 

shooting or to avoid a later ramp-up (Epperson 2007). In the case of non-visual conditions 

(darkness or fog), a ramp-up may occur only if a constant source has maintained at least 160 dB 

re 1 μPa-m (rms) and has been operated continuously since the cessation of full power shooting. 

In that case, ramp-up is conducted from the minimum source level up to full power in the 

20-40 minute time constraint. 

The Record of Sighting (Sighting) form was used to record each protected species (individual or 

group) that was detected during all visual surveys (Appendix C). Species were recorded 

regardless of their location in relation to the exclusion zone and during all operations whether 

guns were firing or not. There were occasions when no protected species were observed; 

therefore, not every submitted report contained sighting records. The Sighting form documented 

species identification and behavior information, the spatial relation of the animal to the vessel 

and sound source, gun operations during the sighting period, location information, observation 

conditions, and any required mitigation actions. 

3.2. DATA ENTRY

The transfer of data from the bi-weekly Protected Species Observer reports to a Microsoft 

Excel® spreadsheet was done separately by a group of data entry personnel according to the 

three standard forms found within the observer reports. The personnel compiling the database 

signed non-disclosure agreements with BOEM. The majority of reports contained all three 

forms; however, the biweekly reports were not uniform in structure. The biweekly reports had 

varied inputs and information in the earlier years of the program and began to become more 

consistent in the latter years. 

The standard forms were used as a template to collect data from previous reports because they 

corresponded with the majority of the consistent data. The majority of the Protected Species 

Observer reports were in a pdf format; only a few reports were in Microsoft Word or Excel®. 

Data entry personnel copied and pasted or hand typed the exact data found within the reports 

over to the Excel® spreadsheet with the exception of the latitude and longitude fields. The 

format of the latitudes and longitudes were adjusted if needed so that they provided a decimal 

conversion in the subsequent columns. This was done so that all positional information was in a 

consistent format for analysis. Other fields contained various inputs such as symbols, words, 

numbers or a combination thereof. To prevent potential bias, unintentional changing of data or 

interpretation of data during data entry phase the other fields were copied over to the Excel 

database exactly as they were entered in the reports. 

For example, some start times for monitoring had an input of “continuous monitoring” instead of 

a specific time, thus the words “continuous monitoring” were entered into the database instead of 

interpreting the potential times that monitoring may have begun. Data entry was examined for 

errors after each report was entered and then again once all the data was compiled into one 

spreadsheet. The data was primarily inspected for potential errors in typing because many of the 

entries in the database were entered by hand.

3.3. DATA ANALYSIS

Data from three airgun firing modes comprising ramp-up, mitigation, and full power were 

analyzed separately and each compared against sightings during which airguns were silent. 
7 

Sightings of different species groups were analyzed separately for Baleen whales, Delphinids, 

sperm whales, and sea turtles. An analysis was undertaken for all cetaceans combined 

(excluding sea turtles).

Data analyses were comprised of two core methodologies. The first was the analysis of sightings 

collated by block identification for use in determining sightings frequency per 1,000 hrs effort 

per block, average sightings duration per block, and the average closest distance of approach of 

animals to airguns per block. The data were not normally distributed and Kruskal-Wallis 

analysis of variance was used to determine the significance of different firing modes on sightings 

frequency, duration, and closest distance of approach for each species group. In order to remove 

geographical bias the block data was aggregated at the level of Protraction Area and, where areas 

contained either only firing or only silent for any firing mode/species group, the blocks from 

these areas were removed from the dataset before running the Kruskal-Wallis analysis.

The second methodology comprised analyzing individual sightings events for analysis of animal 

behavior in response to airgun firing modes. Data were not normally distributed and 

Chi-Squared analysis was used to determine differences in the frequencies of recorded behavior 

between each airgun firing mode in turn against silent. Geographical bias was removed by 

aggregating sightings at the level of Protraction Area and, where areas contained sightings 

occurring either only during firing or only during silent for any firing mode/species group, the 

sightings from these areas were removed before running the Chi-Squared analysis. 

The behavior categories analyzed included Blow, Bow Riding, Feeding, Logging, Porpoising, 

Surfacing, Swimming below the Surface, and Other. A minimum of five sightings per behavior 

category were required for inclusion of that behavior in the analysis. An initial analysis was run 

per species category comparing behavior frequency distributions across all behavior categories. 

A second more detailed analysis was then undertaken for Delphinids and sperm whales 

comparing each specific behavior against all other behaviors so that the significance of changes 

in the frequency of individual behaviors could be determined between firing modes. 

4.0. RESULTS

4.1. SEISMIC OPERATION RECORDS

Survey Report forms were used to record pre ramp-up survey times, start and end of ramp-ups, 

delays or shutdowns for protected species, and general survey activity. There were 

32,939 ramp-up records documented in the Survey Report forms. Different compliance 

categories showed different levels of completeness in the data records (Table 1). Information 

that was specifically listed in the NTL as required on the record of operations data forms and 

were included on the sample data forms referenced in NTL 2007-G02 showed completion rates 

higher than data that would inherently assist in compliance consideration but was not specifically 

required in the NTL. A high percentage of data records that were complete enough to determine 

compliance in the duration of the ramp-up (96%) and the duration of the pre-ramp-up survey 

(86%). Sixty-five percent of these records were completed in a way that day or night start of the 

ramp-up was clearly discernible. However, duration of minimum source firing had to be derived 

from data input and this showed a completion rate of only 18% in the record. 
8 

Table 1. 

Data Completeness Summary from All Survey Report Forms

Analysis Topic Number of Records Complete 

for Analysis Topic

Percentage of Records 

Complete for Analysis Topic

Ramp-up duration 31,512 96%

Mitigation gun firing duration 6,063 18%

Day or night ramp-up start 21,546 65%

Thirty-minute pre-shooting survey compliance 10,702 86%

Individual vessels ramped-up between zero to 20 times within a 24-hour period, with an average 

of 2.53 ramp-ups within a 24-hour operating period per vessel. Fifty-seven percent of all 

ramp-ups recorded took place during daylight hours with the remaining 43% conducted during 

non-visual conditions (night-time or poor weather) and were conducted from the mitigation 

source. There are occasions on the vessels where night-time ramp-ups were not recorded; 

therefore, this may be an underestimation of the actual percentage of ramp-ups taking place 

during darkness. From the data form structure it was not possible to determine how many rampups were initiated from silence compared with how many were initiated from a minimum source. 

Ramp-ups from silence during darkness are not permitted. 

Ramp-ups are required to be 20-40 minutes in duration. The Survey forms clearly require entry 

of the ramp-up duration, which is reflected in the high number of accurate data records for this 

activity. Ninety-six percent of the Survey Report records contained data that clearly discerned 

ramp-up time compliance. Of these complete records, 90% were between the required 20 and 

40 minute duration. Short ramp-ups were noted for other operational activities such as gun 

testing, noise files, aborted ramp-ups, and shut downs for protected species. There were 

195 (0.5% total ramp-ups) events that were less than 20 minutes and had no other operational 

explanation within the data form and, therefore, would not be in compliance with ramp-up 

requirements. There were 143 (<0.5%) ramp-up events that were greater than 40 minutes and 

contained no operational explanation. There were 262 concise records (<1%) of vessels ramping 

up only to the mitigation source, which would not be in compliance with the NTL. This number 

may be slightly underrepresented because data forms did not specify gun power at final ramp-up 

and a ramp-up to the mitigation source is often not possible; instead, the mitigation source is 

turned on and represents minimum power levels. This action is not in compliance; the mitigation 

source is to be used between full power survey lines, not as a means to allow a later ramp-up. 

Eighty-six percent of the daytime ramp-up records had data complete enough to discern 

compliance with the pre-firing 30-minute survey requirement. Three percent of the surveys were 

less than the required 30 minute duration. 

4.2. SIGHTING RECORDS

There were 3,963 complete sighting reports for protected species submitted in biweekly reports. 

Sighting reports with records of “unidentified cetacean” (N = 17) were not used in the analyses. 

Unidentified dolphins, whales, and turtles with an identification level of “best guess” or below 

were removed from analysis (N=32). Identification changes were made on some sighting reports 

after review of descriptive data and/or photographs (N=18). Some of these involved a change 
9 

from Sei (Balaenoptera borealis) and Fin (Balaenoptera physalus) whales to Bryde’s whales 

(Balaenoptera edeni). All other changes placed the identified species into a more general 

taxonomic category that did not change the overall group in which the species would be 

identified for analysis.

A preliminary analysis of individual observer effort and sightings frequency was undertaken to 

help identify any anomalous records. There were no anomalous MMO records in relation to 

sightings frequency per observer. Observer identification on the data forms do not specifically 

indicate whether or not the observer is a third party contractor or a trained crew member; 

however, a very low number of crew members performed MMO duties in the GOM during this 

period (Barkaszi, personal communication 2011). 

Observers were required to identify species to the lowest taxonomic group possible and to state 

their certainty of identification (sure, most likely, best guess). Observers scored the certainty of 

identification using criteria listed on the individual data forms. These scores were tallied into the 

following categories: 1 = Best Guess, 2 = Most Likely, 3 = Sure. Overall, 67% of the 

identifications were classified as “Sure”, while 13% were classified as “Most Likely” and 20% 

classified as “Best Guess”. Most sightings were identified to species level (87%); family was the 

next most common taxonomic group identified (10%). 

A total of 3,914 sighting records (98%) were used in the final sighting analyses (Figure 3). 

Approximately 28,000 individual animals were identified in these sighting records. Cetaceans 

comprised 3,335 (85%) of these records with 20 species identified. Sea turtles comprised the 

remaining 579 (15%) records with five species identified. 

The most common cetacean encountered was the sperm whale, Physeter macrocephalus, 

(N=1,136 records); the most common small cetacean identified was the pantropical spotted 

dolphin (Stenella attenuata), (N=740 records) (Table 2).

Not all sighting reports recorded the number of individuals or adults and juveniles. Only those 

records that contained complete information on the number of individuals were used in the 

analysis of juvenile presence. Sea turtles showed the greatest percentage of juveniles recorded

(47.2%). These were all single individuals and no carapace measurements were recorded. 

Approximately 27% of dolphin groups reported included juveniles, with an average of four 

juveniles per group (when recorded). Sperm whales were the only whales that had juveniles 

reported, with 20.9% having juveniles as part of their group. The average number of juveniles 

seen with any sperm whale group was 1.37. 

Group sizes for all species also varied. Sea turtles had the smallest average group size (1.04), 

while dolphins were reported in groups of one to over 200, with an average group size of 

15.9 individuals. Sperm whale groups ranged in size from one to 16 with an average group size 

of 2.63. 
10 

Figure 3. Distribution of cetacean and sea turtle sightings. 
11

Table 2. 

Species Sighting Summaries by Lowest Identified Taxonomic Group

NTL 

Category Family Genus Species Common Name

Number of 

Sighting 

Records 

Represented

Number of 

Individuals 

Recorded

Mean Group 

Size

Mean Closest 

Distance from 

Airguns 

(meters)

Sighting 

Frequency 

per 1,000 

Hours

WHALE 30 36 1.8 2597.0 0.15

Balaenopteridae Balaenoptera 6 6 1.0 1290.0 0.03

Balaenoptera brydei Bryde’s Whale 6 9 1.8 1436.6 0.03

Kogiidae Kogia breviceps or sima Pygmy or Dwarf 

Sperm Whale 20 59 3.2 773.6 0.10

Physeteridae Physeter macrocephalus Sperm Whale 1136 2554 2.5 1777.1 5.84

Ziphiidae Ziphius or

Mesoplodon spp Beaked Whale 11 14 2.0 1575.0 0.05

DOLPHIN

Delphinidae 328 1693 11.5 1140.0 1.68

Feresa attenuata Pygmy Killer 

Whale 44 442 13.8 577.6 0.22

Globicephala macrorhynchus Shortfinned Pilot 

Whale 174 1566 12.5 734.9 0.89

Grampus griseus Risso’s Dolphin 31 189 7.0 754.2 0.15

Lagenodelphis hosei Fraser’s Dolphin 16 187 16.0 751.2 0.08

Orcinus orca Killer Whale 5 20 5.0 1110.0 0.02

Peponocephala electra Melonheaded 

Whale 42 719 22.4 724.6 0.21

Pseudorca crassidens False Killer Whale 46 285 8.3 1044.1 0.23

Stenella spp Stenellid Dolphin 34 553 23.0 1196.7 0.17
12

Table 2.

Species Sighting Summaries by Lowest Identified Taxonomic Group (continued)

NTL 

Category Family Genus Species Common Name

Number of 

Sighting 

Records 

Represented

Number of 

Individuals 

Recorded

Mean Group 

Size

Mean Closest 

Distance 

From 

Airguns 

(meters)

Sighting 

Frequency 

per 1,000 

Hours

DOLPHIN

Stenella attenuata Pantropical 

Spotted Dolphin 740 10429 18.6 497.4 3.79

Stenella clymene Clymene Dolphin 69 1015 18.8 659.6 0.35

Stenella coeruleeoalba Striped

Dolphin 12 169 24.1 1431.9 0.06

Stenella frontalis Atlantic Spotted 

Dolphin 53 566 13.4 234.4 0.27

Stenella longirostris Spinner Dolphin 77 1162 19.0 933.5 0.39

Steno bredanensis Rough-toothed 

Dolphin 103 1055 12.1 428.9 0.53

Tursiops truncatus Bottlenose Dolphin 352 2644 8.4 353.9 1.81

TURTLE

Chelonidae 53 53 1.0 166.4 0.27

Caretta caretta Loggerhead Turtle 233 239 1.0 149.7 1.19

Chelonia mydas Green Turtle 127 130 1.0 178.6 0.65

Eretmochelys imbricata Hawksbill Turtle 18 19 1.0 153.0 0.09

Lepidochelys kempii Kemps Ridley 

Turtle 55 55 1.0 169.9 0.28

Dermochelyidae Dermochelys coriacea Leatherback Turtle 93 93 1.0 243.7 0.47
13 

4.2.1. Distance from the Seismic Source

The median closest distance of approach to the seismic source was compared between active 

seismic source conditions and silence. Table 3 summarizes the Kruskal-Wallis analysis of 

variance results. All species groups were found to occur at statistically significant greater 

distances from the seismic source during times of full power source operation when compared to 

silence (Kruskal-Wallis, p<0.05), as can be seen from Figure 4. A similar pattern can be seen 

during mitigation source operation, though the differences are reduced (Figure 5). This 

difference remains statistically significant for the “all cetaceans” group, Delphinids, and sea 

turtles only (Kruskal-Wallis, p<0.05). When comparing the distance to source between ramp-up 

and silence, the sample sizes are very low. A significant difference was found for “baleen 

whales” (Kruskal-Wallis, p<0.05), though, with a sample size of 15, this result is questionable. 

Table 3. 

Kruskal-Wallis Analysis of Variance Results for the Closest Approach to the Seismic Source 

(n.s.: not significant)

 Species Group N z Median p 

Full Power vs. Silent

All Cetaceans 1591 9.92 900 0.000

Baleen Whales 39 2.49 1000 0.013

Delphinids 1049 9.54 500 0.000

Sperm Whales 495 3.25 180 0.001

Turtles 342 3.23 100 0.001

Mitigation vs. Silent

All Cetaceans 577 3.35 540 0.001

Baleen Whales 6 1.01 1000 n.s.

Delphinids 386 3.77 400 0.000

Sperm Whales 172 1.00 1091 n.s.

Turtles 82 3.12 150 0.002

Ramp-up vs. Silent

All Cetaceans 417 -0.10 363 n.s.

Baleen Whales 15 2.09 1750 0.036

Delphinids 281 -0.34 250 n.s.

Sperm Whales 120 -0.46 1063 n.s.

Turtles 52 0.95 90 n.s.
14 

0

200

400

600

800

1000

1200

1400

1600

1800

2000

Baleen Whale Delphinid Sperm Whale Turtle All Cetaceans

Species group

Median distance to sighting (m)

Full Power

Silent

Figure 4. Comparison of the distance to the seismic source during full power and silence. 

0

200

400

600

800

1000

1200

1400

1600

1800

2000

Baleen Whale Delphinid Sperm Whale Turtle All Cetaceans

Species group

Median distance to sighting (m)

Mitigation

Silent

Figure 5. Comparison of the distance to the seismic source during mitigation and silence. 
15 

4.2.2. Sighting Duration

Comparing the median sighting duration for each active seismic source conditions against silence 

showed sighting duration for both “Delphinids” and the “all cetaceans” species groups to be 

significantly longer during full power than during silence (Kruskal-Wallis, p<0.05), as 

summarized in Table 4, and illustrated in Figure 6. No further differences were statistically 

significant either for other species groups or lower volume active source conditions. 

Table 4. 

Krustal-Wallis Analysis of Variance Results for Sighting Duration 

(n.s.: not significant)

Species N z Median p 

Full Power vs. Silent

All Cetaceans 1324 2.33 11 0.020

Baleen Whales 20 0.83 5 n.s.

Delphinids 879 2.62 11 0.009

Sperm Whales 419 0.13 10 n.s.

Turtles 250 -0.15 1 n.s.

Mitigation vs. Silent

All Cetaceans 468 0.92 10 n.s.

Baleen Whales 6 1.46 20 n.s.

Delphinids 322 0.31 10 n.s.

Sperm Whales 137 1.00 12.5 n.s.

Turtles 70 -0.44 1 n.s.

Ramp-up vs. Silent

All Cetaceans 325 0.97 12.5 n.s.

Baleen Whales 6 1.46 20 n.s.

Delphinids 225 0.99 13 n.s.

Sperm Whales 92 -0.50 13 n.s.

Turtles 40 0.43 1 n.s.

0

5

10

15

20

25

Baleen Whale Delphinid Sperm Whale Turtle All Cetaceans

Species group

Median Duration (min)

Full Power

Silent

Figure 6. Comparison of median sighting duration during full power and silence. 
16 

4.2.3. Behavioral Observations

A lack of consistent recording of behaviors limited the sample size for species groups and for 

behavior types. By combining the behaviors and assessing whether there was a difference in 

response, rather than a specific type of response, it was possible to establish that there were 

statistically significant differences in behavior between times when the seismic source was active 

compared with when it was silent. Baleen whales were excluded from all behavioral analyses 

due to low sample size (N=15). 

For all other species groups, when comparing full power source operations with silence, there are 

statistically significant differences between the responses of those groups. This can be seen in 

behaviors such as blowing and bow-riding, which are more prevalent during periods of silence. 

When the seismic source was at full power, surface behaviors including logging, porpoising, and 

surfacing are more prevalent (Figure 7). 

0%

5%

10%

15%

20%

25%

30%

35%

40%

Sw imming

Below

Surface

Blow Bow Riding Breaching Feeding Logging Other Porpoising Surfacing

Behavior

Percentage of sightings

Full Power

Silent

Figure 7. Comparative behavioral responses of the “all cetaceans” group during full power and 

silence.

This pattern is repeated for comparisons of both mitigation and ramp-up with silence, illustrated 

in Figure 8 and Figure 9. The differences are statistically significant for both mitigation and 

ramp-up when compared with silence, though small sample size limited the inclusion of sperm 

whales and sea turtles in the analysis.
17 

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

Sw imming

Below

Surface

Blow Bow

Riding

Breaching Feeding Logging Other Porpoising Surfacing

Behavior

Percentage of sightings

Mitigation

Silent

Figure 8. Comparative behavioral responses of the “all cetaceans” group during mitigation and 

silence.

0%

5%

10%

15%

20%

25%

30%

35%

Sw imming

Below

Surface

Blow Bow

Riding

Breaching Feeding Logging Other Porpoising Surfacing

Behavior

Percentage of sightings

Ramp Up

Silent

Figure 9. Comparative behavioral reponses of the “all cetaceans” group during ramp-up and 

silence.
18 

Sample size was sufficiently large enough to allow further analysis of individual behaviors for 

delphinids during all seismic source conditions, and for sperm whales during full power and 

mitigation, as summarized in Table 5. Complete dolphin records showed that 58% were within 

the exclusion zone. Out of these 1,248 records, 1,044 records had some behavior noted. In these 

records, 33% included bow-riding behavior. Of the 23 dolphin records that resulted in ramp-up 

delays, 61% were recorded bow-riding. 

Table 5. 

Chi-squared Results for Grouped Behaviors by Seismic Status 

(Greyed areas not included within analysis due to low sample size.) 

Species Group

Airgun Activity

Swimming 

below Surface

(%)

Blow (%) 

Bow Riding

(%) 

Breeching (%)

Feeding (%)

Logging (%) 

Other (%) 

Porpoising (%) 

Surfacing (%) 

2 n d.f. p 

Full power

All Cetaceans

Full 3 15 8 8 3 12 1 16 34 202.

79

13

75 8 0.000

Silent 4 17 21 5 2 7 2 13 30

Delphinids

Full 5 2 13 12 4 4 1 26 33 180.

26

83

6 7 0.000

Silent 5 3 30 6 3 0 2 18 31

Sperm Whales

Full 1 37 0 1 0 25 0 0 35 24.4

4 

48

3 2 0.000

Silent 0 48 0 2 23 0 0 27

Turtles

Full 42 0 0 0 0 18 1 0 38 135.

69

30

8 2 0.000

Silent 18 0 0 0 0 16 0 66

Mitigation

All Cetaceans Mitigation 4 5 9 7 2 11 2 19 40 49.1

1 

20

4 8 0

Silent 2 17 21 5 2 8 2 13 30

Delphinids Mitigation 5 1 13 8 3 2 3 25 40 25.1

9 

14

3 5 0.000

Silent 3 3 30 7 3 0 2 18 31

Sperm Whales Mitigation 19 0 6 0 37 0 0 38 14.3

6 49 2 0.001

Silent 0 46 0 2 0 24 0 0 28

Turtles Mitigation 35 0 0 0 0 17 0 0 48

7.93 46 2 0.019

Silent 19 0 0 0 0 17 0 0 64

Ramp-up

All Cetaceans Ramp-Up 0 10 12 12 7 0 22 32

9.96 36 4 0.041

Silent 2 18 20 5 2 8 2 12 30

Delphinids Ramp-Up 0 0 17 17 7 3 0 30 27

8.46 27 3 0.037

Silent 4 0 31 7 4 1 3 18 32

Sperm Whales Ramp-Up 0 33 0 0 0 22 0 0 449 Silent 0 47 0 2 0 23 0 0 28

Turtles Ramp-Up 38 0 0 0 0 13 0 0 508 

Silent 18 0 0 0 0 18 0 0 64

There are significant differences in delphinid behaviors for all listed in Table 6 when the seismic 

source is active compared with silence, including greater incidences of porpoising, breaching, 

and surfacing, and a much lower incidence of bow-riding. When the source is at full power, 

sperm whales are surfacing more often, although there are fewer records of blowing behavior at 

full power. 
19 

Table 6. 

Chi-squared Results for Individual Behaviors

Species 

Group

Behavior 

Category Airgun Activity Behavior 

Frequency

2 n d.f. p 

Full power

Delphinids

Blow Full Power 2% 6.07 836 1 0.014 Silent 3%

Bow Riding Full Power 13% 109.81 836 1 0.000 Silent 30%

Breaching Full Power 12% 58.87 836 1 0.000 Silent 6%

Feeding Full Power 4% 6.11 836 1 0.013 Silent 3%

Porpoising Full Power 26% 36.50 836 1 0.000 Silent 18%

Surfacing Full Power 33% 4.36 836 1 0.037 Silent 31%

Sperm 

Whales

Blow Full Power 37% 21.86 483 1 0.000 Silent 48%

Logging Full Power 25% 1.39 483 1 0.239 Silent 23%

Surfacing Full Power 35% 16.89 483 1 0.000 Silent 27%

Mitigation 

Delphinids

Bow Riding Mitigation 13% 24.01 143 1 0.000 Silent 30%

Breaching Mitigation 8% 0.29 143 1 0.587 Silent 7%

Feeding Mitigation 3% 0.01 143 1 0.943 Silent 3%

Porpoising Mitigation 25% 4.43 143 1 0.035 Silent 18%

Surfacing Mitigation 40% 5.38 143 1 0.020

Silent 31%

Sperm 

Whales

Blow Mitigation 19% 14.17 49 1 0.000 Silent 46%

Logging Mitigation 37% 5.70 49 1 0.017

Silent 24%

Surfacing Mitigation 38% 3.60 49 1 0.058

Silent 28%

Ramp-up

Delphinids

Bow Riding Ramp-up 17% 3.28 27 1 0.070 Silent 31%

Breaching Ramp-up 17% 4.21 27 1 0.040 Silent 7%

Porpoising Ramp-up 30% 2.67 27 1 0.102 Silent 18%

Surfacing Ramp-up 27% 0.53 27 1 0.467 Silent 32%
20 

Delphinids follow a similar pattern during mitigation as they do during full power source 

operation. During ramp-up, delphinids breach more often. Sperm whales have a similar 

observed reduction in blowing during mitigation, but spend more time logging at the surface. 

Low sample size excluded sperm whales from analysis of behaviors during ramp-up operations. 

4.3. OBSERVER SURVEY EFFORT

There were 194,273 total hours of visual surveying recorded over the five-year period. To 

estimate the amount of observer effort under each gun operation mode, we used only the location 

and effort information for data entries in which sightings occurred (26,482 hours) because 

detailed gun operation information was not recorded on the Location and Effort forms. 

Sixty-three percent of the survey effort was conducted during full power airgun firing, 2% took 

place during ramp-up, 10% took place during minimal source firing, and 23% took place during 

gun silence. The remaining 2% is made up of gun testing and unspecified gun operations. 

The BOEM uses Official Protraction Diagrams (OPD) for geographic mapping of the Outer 

Continental Shelf (OCS) regions. A standard OPD is one degree in latitude by two degrees in 

longitude (USDOI BOEMRE 2010). Protraction diagram sheet names relate to land features, or 

to hydrographic features contained within the limits of the diagram (USDOI BOEMRE 2010). 

Actual seismic survey track lines and visual survey track lines in a Geographical Position System 

(GPS) format were not available; therefore, survey effort was calculated using the OPD and OCS 

block numbers of the visual survey start entry on the Location and Effort form and the total 

survey time for that entry attributed to that single block. Survey effort was recorded for 52 OPD 

areas within the GOM region; however, 90% of all survey effort took place in just 11 OPD areas: 

Mississippi Canyon, Green Canyon, Walker Ridge, Keathley Canyon, Garden Banks, Atwater 

Valley, The Elbow, Alaminos Canyon, East Breaks, Ewing Bank, and Lloyd Ridge. 

The greatest amount of survey effort took place in the Mississippi Canyon (29%) and Green 

Canyon (20%) OPD areas, and made up nearly 50% of all survey effort over the five year data 

collection period. Species sighting frequency followed some trends in survey effort; however, 

Green Canyon and Atwater Valley showed a pronounced greater percentage of all protected 

species sightings than the percent survey effort. Conversely, Mississippi Canyon showed a 

lower percentage of all protected species sightings than average from the total survey effort. 

Three of the OPD areas, Atwater Valley, Sigbee Escarpment, and Desoto Canyon, showed a 

sighting frequency greater than the average across the surveyed GOM. Mississippi Canyon, an 

area noted for frequent and regular sperm whale observations, showed a lower than average 

sighting frequency for sperm whales even though this area represented the second highest 

number of sperm whale sightings (N=180). Green Canyon had the highest number of sperm 

whale sighting records (N=234), dolphin sighting records (N=485) and sea turtle sighting records 

(N=130); however, sighting rates for these species were closer to the overall average than some 

of the other areas. Sighting rates within each area do not take into account seasons, surveys over 

multiple years compared with shorter time periods, or other geospatial variables. 
21 

4.3.1. Sighting Rate

Using the total survey effort of 194,273 hours, the overall sighting frequency for protected 

species was 20.15 sighting records per 1,000 hours of observation. The overall sighting 

frequency for sperm whales was 5.84 sperm whale sighting records per 1,000 observation hours. 

Sighting rates for gun operations were calculated per unit effort (1,000 hours of observation) 

using only the location and effort information for data entries in which sightings occurred, and 

compared between among seismic source conditions: full power, mitigation, ramp-up and 

silence. Table 7 summarizes Kruskal-Wallis analysis of variance results. The combined results 

for “all cetaceans” show a statistically significant variation in sighting rate, with a higher 

sighting rate during full power than silence (Kruskal-Wallis, p<0.05), as shown in Table 7 and 

Figure 10. 

Table 7. 

Krustal-Wallis Analysis of Variance Results for Sighting Rate/1,000 Hours

(n.s.: not significant)

 Species Group N z Median p 

Full Power vs. Silent

All Cetaceans 1650 2.33 92 0.020

Baleen Whales 40 0.37 83 n.s.

Delphinids 1096 1.68 94 n.s.

Sperm Whales 506 1.66 92 n.s.

Turtles 359 -0.17 84 n.s.

Mitigation vs. Silent

All Cetaceans 606 0.93 91 n.s 

Baleen Whales 17 -1.26 60 n.s

Delphinids 411 0.22 88 n.s

Sperm Whales 175 1.26 94 n.s

Turtles 90 -0.12 82 n.s

Ramp-up vs. Silent

All Cetaceans 448 0.07 84 n.s.

Baleen Whales 16 0.34 71 n.s.

Delphinids 306 -0.06 82 n.s.

Sperm Whales 124 -0.02 84 n.s.

Turtles 60 -1.63 70 n.s.
22 

0

10

20

30

40

50

60

70

80

90

100

Baleen Whale Delphinid Sperm Whale Turtle All Cetaceans

Species group

Median Sightings per 1000 hours

Full Power

Silent

Figure 10. Comparison of sightings frequency during full power and silence. 

5.0. MITIGATION

There were 32 delays in ramp-ups due to the presence of protected species in the exclusion zone 

during the 30 minutes immediately before ramp-up. Of these delays, 24 (75%) were due to 

dolphins, four (13%) due to sea turtles, and four (13%) due to sperm whales. There is a required 

30-minute waiting period after a protected species had been sighted within the exclusion zone, 

which allows for a full 30 minutes of visual clearance before any airguns are started. Downtime 

in operations due to ramp-up delays ranged from four minutes to 87 minutes, with an average 

delay time of 33 minutes. A total of 18.5 hours down time was attributed to ramp-up delays. 

There were 194 occurrences of whales spotted in the exclusion zone; 144 (72.4%) resulted in a 

shutdown of airguns. The remaining 50 sightings within the exclusion zone occurred during 

silence in gun operations. Of the required shutdown events, 139 (97%) were due to sperm 

whales. The remaining five shutdowns were due to Kogia spp. (N=2) and Bryde's whales, 

Balaenoptera brydei (N=2), and one unidentified whale (N=1). The average downtime resulting 

from shutdowns was 58 minutes and there was a total of 125.74 hours of down time attributed to 

shutdowns. 

At the time of shutdown, airgun operations were at full power 112 times (76.3%), minimum 

(mitigation) sourcing 24 times (15.9%), and six ramp-up/gun testing (4.1%). The remaining 

2 shutdowns recorded were one that was voluntary to go to other operations and one that 

coincided with the end of a survey line by which there was no loss in production. 

Shut down frequency for sperm whales was 0.71 shutdowns per 1,000 hours of observation, an 

estimated one shutdown for every 1,500 hours (or roughly 125 days) of daylight survey 
23 

operations, assuming observations are conducted during daylight hours regardless of gun 

operations. 

Two voluntary shutdowns were implemented when dolphins entered the exclusion zone of a 

vessel. One shutdown was during minimum source firing whereby operations could be ramped 

up again later and the other was during a ramp-up whereby the survey line was still a number of 

hours away and ramp-up could be conducted later. One voluntary shutdown of guns was 

implemented when a sea turtle was spotted in the exclusion zone during gun testing. Gun testing 

was resumed at a later time. In addition to these voluntary cessations of airgun firing, a number 

of operators implemented voluntary “turtle pauses” whereby guns would be stopped for a series 

of shots to allow the gun array to be silent as it passed the last visual location of the turtle but did 

not result in lost seismic survey data. Voluntary shot pauses were recorded 95 times for sea 

turtles in the exclusion zone. 

A 30-minute wait period is required after any shutdown due to whales in the exclusion zone. 

Therefore, the minimum delay time for any mitigation-required shutdown is 30 minutes. 

However, two operational delays were under the 30 minute minimum (13 minutes and 

29 minutes). No explanations were provided to account for the two shortened waiting periods. 

All other shutdown delays ranged from 30 minutes to slightly over 13 hours (when a shut down 

occurred immediately before darkness and guns could not be re-started until daylight conditions 

allowed visual observations). 

6.0. PASSIVE ACOUSTIC MONITORING

Passive acoustic monitoring (PAM) is an optional technology; it is allowable under the NTL and 

can be used by seismic operators to reduce the chances of operational downtime during darkness 

or inclement weather. Use of PAM is voluntary but it does afford the operator additional 

opportunities for ramp-up from silence and eliminates the need for visual conditions to clear the 

vessel for starting operations. There were 54 acoustic detection records over the five-year 

period. None of the data from acoustic detections were used in the analyses unless there was a 

corresponding visual sighting record. 

7.0. DISCUSSION 

Completeness in recording and reporting is evident from the data submitted indicating that the 

submission periods and methodologies lend themselves to high compliance reporting standards. 

In terms of actual compliance data, there appears to be high levels of compliance by operators 

and observation personnel in regard to ramp-up times, pre-watch conditions, and mitigation 

actions. However, portions of the data used in this report were derived from recorded data that 

were not required by regulations or on standardized data forms. For example, the high amount of 

observation time that took place during gun silence was due mainly to the scope of work laid out 

by observer contractors and not by NTL regulations (Barkaszi, personal communication 2011). 

Additionally, mitigation measures such as the use of minimum source firing is not expressly 

monitored on the standardized data forms; therefore, the times and use of this procedure cannot 

be adequately determined for compliance.

Source array volume is not consistent across all geophysical surveys in the Gulf of Mexico. 

Source volume is not a required data collection item and therefore cannot be analyzed within the 
24 

statistical parameters of this document. Typical volumes of individual air-guns used by the 

geophysical industry can range from 20 in3 to 800 in3. Strings of airguns are used within an 

array so that a typical survey involves between 12 and 48 guns, with a sum volume in the range 

of 3,000-8,000 in3 during full power firing. The source volume is normally reduced to a single 

airgun for mitigation firing to maintain a minimal source output as defined in the NTL. Other 

variability in received source levels is derived from newer techniques in survey design. Rather 

than using a single source vessel to transect a survey area, multi-vessel surveys became more 

common in 2006-2007 and have become a standard practice in recent years. The multiple vessel 

configurations as used in wide azimuth or rich azimuth surveys can use two to six source vessels 

in varying patterns to survey the area simultaneously. All data collection is vessel-specific; 

therefore, no distinction has been made between single vessel and multi-vessel surveys within 

the data analysis. These vessels typically work within a one to two kilometer range from one 

another; therefore, sightings tend to be duplicated across the vessel fleet. Regulations, however, 

require that each vessel maintain independence in all operational and sighting records and, 

therefore, all sighting information is treated independently.

There was a high level of compliance with regard to shut-down requirements and ramp-up 

delays. Between 2002 and 2003 over 730,000 track line miles of 3D seismic surveys were 

permitted in GOM waters greater than 200 meters (Continental Shelf Associates, Inc. 2004). On 

average, the BOEM administers 100 seismic permits per year. Given these levels of permitted 

activities, and the nearly 200,000 hours of observer effort, operational down time due to 

mitigation measures represented a small proportion of overall survey time. 

Sea turtles demonstrate the closest mean distance to air gun arrays reported by observers. This is 

likely due the fact that only turtles close to the vessel are most visible to observers. There is little 

known about the impact of seismic operations, and noise in general, on sea turtles. However, the 

close exposure distances and the fact that all sea turtles are listed under the Endangered Species 

Act (ESA), make this group a potential concern in the regulatory environment. The current NTL 

requires a 30 minute waiting period before starting any airguns if a sea turtle is spotted within the 

exclusion zone. There is also extensive use of voluntary shutdowns for sea turtles when they are 

detected in the exclusion zone during airgun firing; however, there is no requirement to do so 

under the NTL. 

Sighting duration was found to be longer during times of full power seismic source operation 

when compared with silence, for both the “delphinid” species group and “all cetaceans” group. 

Looking at each of these measures; sighting rate, distance from seismic source and sighting 

duration, there is no consistency of significance for any one species group, other than the 

combined “all cetaceans” group. This may indicate a lack of clear response from any one 

species group, or a limitation in terms of sample size. Taking the “all cetaceans” group, an 

indication from the results is that there is spatial avoidance both laterally (greater sighting 

distances from the active seismic source), and vertically (increased sighting frequency and 

duration). A comparison of each behavior and sighting factor with seismic source status 

indicates that the differences are most pronounced for full power source operation. While a 

similar pattern in sighting rate or closest distance of approach might be apparent at lower seismic 

source volumes (mitigation and ramp-up), there are less statistically significant results. The 

sighting rates for all individual cetacean groups was higher while the seismic source was active, 

compared to silence, with the combined “all cetaceans” group being significant. This contrasts 
25 

with previous findings, where the sighting rate of small odontocetes (T. truncatus, 

Lagenorhyncus spp., D. delphis, S. coeruleoalba, P. phocoena) was found to decrease 

significantly when the seismic source was active, whereas no differences for other groups were 

observed (Stone and Tasker 2006). 

Each species group was found to be sighted at significantly greater distances from the seismic 

source during full power compared with silence, illustrating a level of spatial avoidance to the 

seismic source. This finding concurs with previous findings, in which a number of small 

odontocete species and a combined “all mysticetes” group were found to occur at significantly 

greater distances from large volume seismic sources (Stone and Tasker 2006). These results, 

however, diverge somewhat from the controlled exposure experiments (CEE) conducted by the 

Sperm Whale Seismic Study (SWSS) (Jochens et al. 2008). In the SWSS CEE studies, the 

direction of movement in eight tagged sperm whales was determined over a series of 30-minute 

intervals during pre-exposure, ramp-up, and full-array firing. Results showed no horizontal 

avoidance to airgun exposure of <150 dB re 1 μPa (rms). These sound exposure levels were 

reached by whales that were 1.4 – 12.6 kilometers from the source array. Similar analysis 

showed that the direction of movement of the eight sperm whales did not change at the onset of 

gradual ramp-up at ranges of 7.3 – 12.5 kilometers or during full power firing at ranges between 

1.5 and 12.6 kilometers. The CEE studies also looked at diving and foraging rates in the eight 

tagged whales. These experiments showed that seven of the eight whales continued deep 

foraging diving during controlled acoustic exposure; however, one whale, which had the closest 

approach by the source array, rested at the surface for an interval of over four hours. This rest 

period was twice as long as the 10 other resting bouts of ≤ two hours during pre -exposure that 

were observed for this animal during the study. It dove immediately following the final airgun 

transmission. The SWSS report suggests that the animals’ behavior may be a response to the 

airgun sounds and that the sperm whale had chosen to rest at the surface until airgun exposure 

ceased. The average closest distance for sperm whales reported in our data was 1.7 kilometers

which is at the lower end of the range for the eight sperm whales studied. Given the fact that the 

closest sperm whale in the SWSS CEE studies did appear to exhibit more surface behavior than 

the other seven whales, it is a comparable result to the findings of increased surface behavior of 

sperm whales during active gun operations in the observer data. Increased surface behaviors 

may therefore be more of an indication of sperm whale avoidance of airgun noise exposure than 

changes in direction. 

For lower volumes (ramp up and mitigation firing) the differences in sighting distance are less 

pronounced and are also limited by sample size. During mitigation operation, “all cetaceans” 

occurred at greater distances during source operation, though no individual species groups did. 

The significant result for baleen whales during ramp-up operation is based on a sample size of 

only six sightings, so is clearly not representative of any wider trend in relation to that species 

group and ramp-up operations. Due to the overlap of the peak frequencies of the seismic source 

array and those used by baleen whales, this group has been considered most vulnerable 

(Richardson et al. 1995). The dataset presented here, which is representative of the cetacean 

diversity of the GOM, makes thorough analysis of any potential effects on this group of species 

largely impossible. Baleen whale numbers for the Gulf of Mexico are low, due to the fact that 

there is only one regularly occurring mysticete, Bryde’s whale, in the Gulf. Population estimates 

for B. brydei in the northern GOM range from 15 to 40; the lower estimate is typically used as 
26 

the most current information; therefore, the low sighting rates for baleen whales in this GOM 

data set is not unexpected. 

The sperm whale is regarded as the umbrella species for regulations in the Gulf of Mexico. They 

are the most abundant large cetacean in the GOM and have a larger population estimate than the 

most common GOM baleen whale. Unlike other odontocetes in the GOM which are protected 

only under the Marine Mammal Protection Act (MMPA), the sperm whale is also listed as 

endangered under the ESA. Evidence may indicate that sperm whale hearing is not impacted by 

the predominant low frequency impulse of airguns, but there is some evidence that 

anthropogenic sound, including seismic surveys, can alter behavior in sperm whales 

(International Whaling Commission 2007). As such, the most recent NOAA-NMFS Biological 

Opinion (2007) requires that protection measures for sperm whales are implemented during 

seismic surveys in the GOM.

Of note, however, are the statistically significant observations relating to delphinid species. 

Considered as being less likely to be impacted by operations using primarily low frequency 

sources, this data has demonstrated that delphinids show spatial avoidance, display more surface 

behaviors such as breaching and porpoising, and are less likely to display bow-riding behavior. 

Assessing observer data has demonstrated a high level of compliance with regard to 

implementing specific mitigation measures in order to minimize the potential impacts of sound 

on protected species. While the data has demonstrated a number of short-term behavioral 

effects, the consequences in the long-term remain unknown, highlighting the need for precaution. 

It is also clear that the data have limitations regarding the collection, interpretation and analysis 

of behavioral observations in relation to their use in impact assessment. Nevertheless, the data 

presented here provides a unique insight into the responses of protected species in the GOM in 

relation to commercial seismic activity.
27 

8.0. REFERENCES

Bailey, H., B. Senior, D. Simmons, J. Rusin, G. Picken, and P.M. Thompsen. 2010. Assessing 

underwater noise levels during pile-driving at an offshore windfarm and its potential effects on 

marine mammals. Marine Pollution Bulletin. 60:888-897. 

Compton, R., L. Goodwin, R. Handy, and V. Abbot. 2007. A critical examination of worldwide 

guidelines for minimising the disturbance to marine mammals during seismic surveys. Marine Policy. 

doi:10.1016/j.marpol.2007.05.005. 

Continental Shelf Associates, Inc. 2004. Geological and geophysical exploration for mineral resources 

on the Gulf of Mexico Outer Continental Shelf final programmatic environmental assessment. 

US Department of the Interior, Minerals Management Service, Gulf of Mexico OCS Region, New 

Orleans, LA. OCS EIS/EA MMS 2004-054. 

Epperson, D. 2007. Initial guidance regarding NTL 2007-G02 (26 Apr. 2007). E-mail communication

26 April 2007. 

Finneran, J.J., D.A. Carder, C.E. Schulndt, and S.H. Ridgeway. 2005. Temporary threshold shift in 

bottlenose dolphins (Tursiops truncatus) exposed to mid-frequency tones. Journal of the Acoustical 

Society of America. 118(4):2696-2705. 

Goold, J.C. and P.J. Fish. 1998. Broadband spectra of seismic survey air-gun emissions, with reference 

to dolphin auditory thresholds. Journal of the Acoustical Society of America. 103(4):2177-2184. 

Gordon, J., D. Gillespie, J. Potter, A. Frantzis, M.P. Simmonds, R. Swift, and D. Thompson. 2003. A 

review of the effects of seismic surveys on marine mammals. Marine Technology Society Journal. 

37(4):16-34. 

Hatch, L.T. and A.J. Wright. 2007. A brief review of anthropogenic sound in the oceans. International 

Journal of Comparative Psychology. 20:121-133. 

International Whaling Commission. 2007. Report of the scientific committee. Annex K. Report of the 

Standing Working Group on Environmental Concerns. Journal of Cetacean Research and 

Management. 9:227-296. 

Jepson, P.D., M. Arbelo, R. Deaville, I.A.P. Patterson, P. Castro, J.R. Baker, E. Degollada, H.M. Ross, 

P. Herraez, A.M. Pocknell, F. Rodriguez, F.E. Howiell, A. Espinosa, R.J. Reid, J.R. Jaber, V. Martin, 

A.A. Cunningham, and A. Fernandez. 2003. Gas-bubble lesions in stranded animals: Was sonar 

responsible for a spate of whale deaths after an Atlantic military exercise? Nature. 425(6958):575-76. 

Jochens, A., D. Biggs, K. Benoit-Bird, D. Engelhaupt, J. Gordon, C. Hu, N. Jaquet, M. Johnson, 

R. Leben, B. Mate, P. Miller, J. Ortega-Ortiz, A. Thode, P. Tyack, and B. Würsig. 2008. Sperm 

whale seismic study in the Gulf of Mexico: Synthesis report. U.S. Dept. of the Interior, Minerals 

Management Service, Gulf of Mexico OCS Region, New Orleans, LA. OCS Study MMS 2008-006. 

341 p. 

Kearey, P., M. Brooks, and I. Hill. 2002. An introduction to geophysical exploration, 3rd ed. Oxford: 

Blackwell Science Ltd.

Richardson, W.J., C.R. Greene, C.I. Malme, and D.H. Thomson. 1995. Marine mammals and noise. San 

Diego: Academic Press. 

Southall, B.L., A.E. Bowles, W.T. Ellison, J.J. Finneran, R.L. Gentry, C.R. Greene, Jr, D. Kastak, 

D.R. Ketten, J.H. Miller, P.E. Nachtigall, W.J. Richardson, J.A. Thomas, and P. Tyack. 2007. 

Marine mammal noise exposure criteria: Initial scientific recommendations. Aquatic Mammals. 

33:411-521. 
28 

Stone, C.J. 1997. Cetacean observations during seismic surveys in 1996. JNCC Report No. 228 

Stone, C.J. 1998. Cetacean observations during seismic surveys in 1997. JNCC Report No. 278. 

Stone, C.J. 2000. Cetacean observations during seismic surveys in 1998. JNCC Report No. 301 

Stone, C.J. 2001. Cetacean observations during seismic surveys in 1999. JNCC Report No. 316. 

Stone, C.J. 2003a. Cetacean observations during seismic surveys in 2000. JNCC Report No. 322. 

Stone. C.J. 2003b. The effects of seismic activity on marine mammals in UK waters, 1998-2000. JNCC 

Report, No. 323. 

Stone, C.J. and M.L. Tasker. 2006. The effects of seismic airguns on cetaceans in UK waters. Journal of 

Cetacean Research and Management. 8(3):255-263. 

U.S. Department of the Interior, Bureau of Ocean Energy Management, Regulation and Enforcement. 

2010. Official protraction diagrams; BOEMRE lease sales. Available from:

http://www.gomr.boemre.gov/homepg/lsesale/map_arc.html. 1 April 2010. 

U.S. Department of the Interior, Minerals Management Service. 2007. Notice to Lessees and Operators 

(NTL) of Federal Oil, Gas, and Sulphur Leases in the Outer Continental Shelf, Gulf of Mexico OCS 

region: Implementation of seismic survey mitigation measures and protected species observer 

program. Available from: http://www.gomr.boemre.gov/homepg/regulate/regs/ntls/2007NTLs/07-

g02.pdf. OMB Control Number: 1010-0151. 
A-1 

Appendix A

 

Location and Effort (Observer Effort) Form
A-3

RPS GeoCet PROTECTED SPECIES RECORDING FORM

EFFORT

Regulatory reference number Vessel name

Project number Effort page number

Date

Visual 

or 

PAM

Observers' 

initials

Start of watch End of watch Wind 

speed

(knots)

Wind 

direction

Beaufort 

sea 

state

Swell 

(m)

Visibility

(km)

Glare 

severity Time Latitude Longitude Depth

(m) Time Latitude Longitude Depth(m)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 
B-1 

Appendix B

 

Record of Operations (Survey) Form
B-3 

R

PS GeoCet PROTECTED SPECIES RECORDING FORM

OPERATIONS

Regulatory reference number Vessel name

Project number Page number

Date

Time preshooting 

monitoring 

began

Time 

monitoring 

ended

Time PAM 

began

Time 

PAM 

ended

Was it day 

or night

In

period 

prior

to

firing?

Reason for 

firing

s = survey

t = test

x = test 

followed 

immediatel

y 

by survey

Time

soft start/

ramp-up 

began

Time

soft start/ 

ramp-up 

ended

Time

of

start

of

line/

test

Time

Of

End

of

line/

test

Time 

mitigation 

gun 

enabled/

source 

output 

reduced

Time all 

airguns/

source 

stopped

Was

any 

mitigation 

action 

required?

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 
C-1 

Appendix C

 

Record of Sighting (Sighting) Form 
C-3 

RPS GeoCet

PROTECTED SPECIES RECORDING FORM

DETECTION

Date Project number Time at first 

detection (UTC)

Time at last 

detection (UTC)

Visual detection 

number

Acoustic detection 

number

 

Regulatory reference number Vessel name Survey type Observer(s)

 

Detection was made Detection was first made

 

Latitude of vessel Longitude of vessel Bearing of vessel (degrees) Water depth (metres)

 

Swell height

(metres)

Beaufort sea state Precipitation Visibility (km) Cloud cover (%) Glare severity and 

direction

 

Common name Scientific name Certainty of identification

 

Total number Number of adults Number of juveniles Bearing to animal(s) when first 

detected (degrees)

Range to animal(s) when first 

detected (metres)

 

Description (include features such as overall size; shape of head; colour 

and pattern; size, shape, and position of dorsal fin; height, direction, and 

shape of blow; etc.)

Visual sighting and/or Acoustic detection details (note behavior, 

especially changes in relation to gun activity and distance from gun 

array)

 

Direction of travel / first approach (relative to vessel) Initial compass heading 

(degrees)

Final compass heading 

(degrees)

 

Closest distance of animals to 

airguns/source (metres)

Closest distance of animals to 

vessel (metres)

Source activity at initial 

detection

Source activity at final detection

 

Time at closest approach (UTC) Distance during soft start (m) Source mitigation action(s) 

required

Strike avoidance maneuvers 

required First Closest Last

 

 Total duration of mitigation 

action(s) (HH:MM)

Total duration of production 

loss due to mitigation (HH:MM)

 Other notes or comments

 
D-1 

Appendix D

 

Notice to Lessees 2007-G02
D-3 

OMB Control Number: 1010-0151 

OMB Expiration Date: December 31, 2011 

UNITED STATES DEPARTMENT OF THE INTERIOR 

MINERALS MANAGEMENT SERVICE (MMS) 

GULF OF MEXICO (GOM) OCS REGION 

NTL No. 2007-G02 Effective Date: February 7, 2007 

NOTICE TO LESSEES AND OPERATORS (NTL) OF FEDERAL OIL, GAS, AND 

SULPHUR LEASES IN THE OUTER CONTINENTAL SHELF, 

GULF OF MEXICO OCS REGION 

This NTL supersedes and replaces NTL No. 2004-G01. It does not introduce any new types of 

mitigation measures; however, it clarifies how you should implement seismic survey mitigation 

measures, including ramp-up procedures, the use of a minimum sound source, airgun testing and 

protected species observation and reporting. The measures contained herein apply to all on-lease 

surveys you conduct under 30 CFR 250 and all off-lease surveys you conduct under 30 CFR 251. 

Implementation of Seismic Survey Mitigation Measures and Protected Species Observer 

Program 

Background 

The use of an airgun or airgun arrays while conducting seismic operations may have an impact on 

marine wildlife, including marine mammals and sea turtles. Some marine mammals, such as the 

sperm whale (Physeter macrocephalus), and all sea turtles that inhabit the GOM are protected under 

the Endangered Species Act (ESA). All marine mammals are protected under the Marine Mammal 

Protection Act (MMPA). 

In order to protect marine mammals and sea turtles during seismic operations, the National Marine 

Fisheries Service (NMFS) requires seismic operators to use ramp-up and visual observation 

procedures when conducting seismic surveys. Procedures for ramp-up, protected species observer 

training, visual monitoring and reporting are described in detail in this NTL. These mitigation 

measures apply to geophysical activities conducted under lease terms, for all seismic survey 

operations conducted in waters deeper than 200 meters (656 feet) throughout the GOM and, in the 

GOM waters east of 88.0° W. longitude, for all seismic survey operations conducted regardless of 

water depth. Performance of these mitigation measures is also a condition of the approval of 

applications for geophysical permits. You must demonstrate your compliance with these mitigation 

measures by submitting to MMS certain reports detailed in this NTL. 
D-4 

Definitions 

Terms used in this NTL have the following meanings: 

1. Airgun 

2. 

means a device that releases compressed air into the water column, creating an 

acoustical energy pulse with the purpose of penetrating the seafloor. 

Ramp-up 

3. 

means the gradual increase in emitted sound levels from an airgun array by 

systematically turning on the full complement of an array’s airguns over a period of time. 

Visual monitoring 

4. 

means the use of trained observers to scan the ocean surface visually for the 

presence of marine mammals and sea turtles. These observers must have successfully 

completed a visual observer training program as described below. The area to be scanned 

visually includes, but is not limited to, the exclusion zone. Visual monitoring of an exclusion 

zone and adjacent waters is intended to establish and, when visual conditions allow, maintain 

a zone around the sound source and seismic vessel that is clear of marine mammals and sea 

turtles, thereby reducing or eliminating the potential for injury. 

Exclusion zone means the area at and below the sea surface within a radius of 500 meters 

surrounding the center of an airgun array and the area within the immediate vicinity of the 

survey vessel. Each survey vessel must maintain its own unique 

5. 

exclusion zone. 

Whales 

6. 

mean all marine mammals in the GOM except dolphins (see definition below) and 

manatees. This includes all species of baleen whales (Suborder Mysticeti), all species of 

beaked whales (Ziphius cavirostris and Mesoplodon sp.), sperm whales (Physeter 

macrocepahalus), and pygmy and dwarf sperm whales (Kogia sp.). Of the baleen whales, 

only the Bryde’s whale (Balaenoptera edeni) is expected to be present in the northern GOM 

and is considered uncommon. This species has primarily been sighted in water depths less 

than 200 m in the eastern GOM. Sightings of other baleen whale species are highly unlikely. 

Dolphins mean all marine mammal species in the Family Delphinidae. In the GOM, this 

includes, among others, killer whales, pilot whales, and all of the “dolphin” species. 

Ramp-up Procedures 

The intent of ramp-up is to warn marine mammals and sea turtles of pending seismic operations and 

to allow sufficient time for those animals to leave the immediate vicinity. Under normal conditions, 

animals sensitive to these activities are expected to move out of the area. For all seismic surveys, 

including airgun testing, use the ramp-up procedures described below to allow whales, other marine 

mammals, and sea turtles to depart the exclusion zone before seismic surveying begins. 

Measures to conduct ramp-up procedures during all seismic survey, including airgun testing, 

operations are as follows: 

1. Visually monitor the exclusion zone and adjacent waters for the absence of marine mammals 

and sea turtles for at least 30 minutes before initiating ramp-up procedures. If none are 

detected, you may initiate ramp-up procedures. Do not initiate ramp-up procedures at night or 

when you cannot visually monitor the exclusion zone for marine mammals and sea turtles if 

your minimum source level drops below 160 dB re 1 μPa-m (rms) (see measure 5). Altering 

the vessel’s course to shallower water depths (< 200m in the Central and Western Planning 

Areas) to circumvent ramp-up requirements of the 200 meter isobath will be considered 

noncompliant. 
D-5 

2. Initiate ramp-up procedures by firing a single airgun. The preferred airgun to begin with 

should be the smallest airgun, in terms of energy output (dB) and volume (in

3

). 

3. Continue ramp-up by gradually activating additional airguns over a period of at least 

20 minutes, but no longer than 40 minutes, until the desired operating level of the airgun 

array is obtained. 

4. Immediately shut down all airguns ceasing seismic operations at any time a whale is detected 

entering or within the exclusion zone. You may recommence seismic operations and ramp-up 

of airguns only when the exclusion zone has been visually inspected for at least 30 minutes to 

ensure the absence of marine mammals and sea turtles. 

5. You may reduce the source level of the airgun array, using the same shot interval as the 

seismic survey, to maintain a minimum source level of 160 dB re 1 μPa-m (rms) for the 

duration of certain activities. By maintaining the minimum source level, you will not be 

required to conduct the 30-minute visual clearance of the exclusion zone before ramping 

back up to full output. Activities that are appropriate for maintaining the minimum source 

level are: (1) all turns between transect lines, when a survey using the full array is being 

conducted immediately prior to the turn and will be resumed immediately after the turn; and 

(2) unscheduled, unavoidable maintenance of the airgun array that requires the interruption of 

a survey to shut down the array. The survey should be resumed immediately after the repairs 

are completed. There may be other occasions when this practice is appropriate, but use of the 

minimum source level to avoid the 30-minute visual clearance of the exclusion zone is only 

for events that occur during a survey using the full power array. The minimum sound source 

level is not to be used to allow a later ramp-up after dark or in conditions when ramp-up 

would not otherwise be allowed. 

Protected Species Observer Program 

Visual Observers 

Visual observers who have completed a protected species observer training program as described 

below are required on all seismic vessels conducting operations in water depths greater than 200 

meters (656 ft) throughout the GOM. Visual observers are required on all seismic vessels conducting 

operations in OCS water depths less than 200 meters (656 ft.) in the GOM waters east of 88.0° W. 

longitude. At least two protected species visual observers will be required on watch aboard seismic 

vessels at all times during daylight hours (dawn to dusk) when seismic operations are being 

conducted, unless conditions (fog, rain, darkness) make sea surface observations impossible. If 

conditions deteriorate during daylight hours such that the sea surface observations are halted, visual 

observations must resume as soon as conditions permit. Operators may engage trained third party 

observers, may utilize crew members after training as observers, or may use a combination of both 

third party and crew observers. During these observations, the following guidelines shall be 

followed: (1) other than brief alerts to bridge personnel of maritime hazards, no additional duties may 

be assigned to the observer during his/her visual observation watch (if conditions warrant more 

vigilant look-outs when navigating around or near maritime hazards, additional personnel must be 

used to ensure that watching for protected species remains the primary focus of the on-watch 

observers), (2) no observer will be allowed more than 4 consecutive hours on watch as a visual 

observer, (3) a “break” time of no less than 2 hours must be allowed before an observer begins 

another visual monitoring watch rotation (break time means no assigned observational duties), and 

(4) no person (crew or third party) on watch as a visual observer will be assigned a combined watch 

schedule of more than 12 hours in a 24-hour period. Due to the concentration and diligence required 
D-6 

during visual observation watches, operators who choose to use trained crew members in these 

positions may select only those crew members who demonstrate willingness as well as ability to 

perform these duties. 

Training 

All visual observers must have completed a protected species observer training course. MMS will not 

sanction particular trainers or training programs. However, basic training criteria have been 

established and must be adhered to by any entity that offers observer training. Operators may utilize 

observers trained by third parties, may send crew for training conducted by third parties, or may 

develop their own training program. All training programs offering to fulfill the observer training 

requirement must: (1) furnish to MMS, at the address listed in this NTL, a course information packet 

that includes the name and qualifications (i.e., experience, training completed, or educational 

background) of the instructor(s), the course outline or syllabus, and course reference material; 

(2) furnish each trainee with a document stating successful completion of the course; and (3) provide 

MMS with names, affiliations, and dates of course completion of trainees. 

The training course must include the following elements: 

I. Brief overview of the MMPA and the ESA as they relate to seismic acquisition and protection of 

marine mammals and sea turtles in the GOM, 

II. Brief overview of seismic acquisition operations in the GOM, 

III. Overview of seismic mitigation measures (NTLs) and the protected species observer program in 

the GOM, 

IV. Discussion of the role and responsibilities of the protected species observer in the GOM, 

including: 

a) Legal requirements (why you are here and what you do), 

b) Professional behavior (code of conduct), 

c) Integrity, 

d) Authority of protected species observer to call for shut-down of seismic acquisition 

operations, 

e) Assigned duties, 

1) What can be asked of the observer, 

2) What cannot be asked of the observer, 

f) Reporting of violations and coercion, 

V. Identification of GOM marine mammals and sea turtles, with emphasis on whales, 

VI. Cues and search methods for locating marine mammals, especially whales, and sea turtles, 

VII. Data collection and reporting requirements: 

a) Forms and reports to MMS via email at protectedspecies@mms.gov 

b) Whale in exclusion zone/shut-down report within 24 hours. 

on the 1st 

and 15

th 

of each 

month, 

Visual Monitoring Methods 

The observers on duty will look for whales, other marine mammals, and sea turtles using the naked 

eye and hand-held binoculars provided by the seismic vessel operator. The observers will stand 

watch in a suitable location that will not interfere with navigation or operation of the vessel and that 

affords the observers an optimal view of the sea surface. The observers will provide 360o 

coverage 

surrounding the seismic vessel and will adjust their positions appropriately to ensure adequate 
D-7 

coverage of the entire area. These observations must be consistent, diligent, and free of distractions 

for the duration of the watch. 

Visual monitoring will begin no less than 30 minutes prior to the beginning of ramp-up and continue 

until seismic operations cease or sighting conditions do not allow observation of the sea surface 

(e.g., fog, rain, darkness). If a marine mammal or sea turtle is observed, the observer should note and 

monitor the position (including lat./long. of vessel and relative bearing and estimated distance to the 

animal) until the animal dives or moves out of visual range of the observer. Make sure you continue 

to observe for additional animals that may surface in the area, as often there are numerous animals 

that may surface at varying time intervals. At any time a whale is observed within an estimated 

500 meters (1,640 feet) of the sound source array (“exclusion zone”), whether due to the whale’s 

movement, the vessel’s movement, or because the whale surfaced inside the exclusion zone, the 

observer will call for the immediate shut-down of the seismic operation, including airgun firing (the 

vessel may continue on its course but all airgun discharges must cease). The vessel operator must 

comply immediately with such a call by an on-watch visual observer. Any disagreement or 

discussion should occur only after shut-down. When no marine mammals or sea turtles are sighted 

for at least a 30-minute period, ramp-up of the source array may begin. Ramp-up cannot begin unless 

conditions allow the sea surface to be visually inspected for marine mammals and sea turtles for 

30 minutes prior to commencement of ramp-up (unless the method described in the section entitled 

“Experimental Passive Acoustic Monitoring” is used). Thus, ramp-up cannot begin after dark or in 

conditions that prohibit visual inspection (fog, rain, etc.) of the exclusion zone. Any shut-down due 

to a whale(s) sighting within the exclusion zone must be followed by a 30-minute all-clear period and 

then a standard, full ramp-up. Any shut-down for other reasons, including, but not limited to, 

mechanical or electronic failure, resulting in the cessation of the sound source for a period greater 

than 20 minutes, must also be followed by full ramp-up procedures. In recognition of occasional, 

short periods of the cessation of airgun firing for a variety of reasons, periods of airgun silence not 

exceeding 20 minutes in duration will not require ramp-up for the resumption of seismic operations 

if: (1) visual surveys are continued diligently throughout the silent period (requiring daylight and 

reasonable sighting conditions), and (2) no whales, other marine mammals, or sea turtles are 

observed in the exclusion zone. If whales, other marine mammals, or sea turtles are observed in the 

exclusion zone during the short silent period, resumption of seismic survey operations must be 

preceded by ramp-up. 

Reporting 

The importance of accurate and complete reporting of the results of the mitigation measures cannot 

be overstated. Only through diligent and careful reporting can MMS, and subsequently NOAA 

Fisheries, determine the need for and effectiveness of mitigation measures. Information on observer 

effort and seismic operations are as important as animal sighting and behavior data. In order to 

accommodate various vessels’ bridge practices and preferences, vessel operators and observers may 

design data reporting forms in whatever format they deem convenient and appropriate. Alternatively, 

observers or vessel operators may adopt the United Kingdom’s Joint Nature Conservation Committee 

forms (available at their website www.jncc.gov.uk). At a minimum, the following items should be 

recorded and included in reports to the MMS: 
D-8 

Observer Effort Report

• Vessel name, 

: Prepared for each day during which seismic acquisition operations are 

conducted. Furnish an observer effort report to MMS on the 1st 

and the 15

th 

of each month that 

includes: 

• Observers’ names and affiliations, 

• Survey type (e.g., site, 3D, 4D), 

• MMS Permit Number (for “off-lease seismic surveys”) or OCS Lease Number 

(for “on-lease seismic surveys”), 

• Date, 

• Time and lat./long. when daily visual survey began, 

• Time and lat./long. when daily visual survey ended, 

• Average environmental conditions while on visual survey, including 

Wind speed and direction, 

Sea state (glassy, slight, choppy, rough or Beaufort scale), 

Swell (low, medium, high or swell height in meters), 

Overall visibility (poor, moderate, good). 

Survey Report

• Vessel name, 

: Prepared for each day during which seismic acquisition operations are conducted 

and the airguns are being discharged. Furnish a survey report to MMS on the 1st 

and the 15

th 

of each 

month during which operations are being conducted that includes: 

• Survey type (e.g., site, 3D, 4D), 

• MMS Permit Number (for “off-lease seismic surveys”) or OCS Lease Number 

(for “on-lease seismic surveys”), 

• Date, 

• Time pre-ramp-up survey begins, 

• What marine mammals and sea turtles were seen during pre-ramp-up survey? 

• Time ramp-up begins, 

• Were whales seen during ramp-up? 

• Time airgun array is operating at the desired intensity, 

• What marine mammals and sea turtles were seen during survey? 

• If whales were seen, was any action taken (i.e., survey delayed, guns shut down)? 

• Reason that whales might not have been seen (e.g., swell, glare, fog), 

• Time airgun array stops firing. 

Sighting Report

• Vessel name, 

: Prepared for each sighting of a marine mammal (whale or dolphin) or sea turtle 

made during seismic acquisition operations. Furnish a sighting report to MMS on the 1st 

and the 

15

th

of each month during which operations are being conducted that includes: 

• Survey type (e.g., site, 3D, 4D), 

• MMS Permit Number (for “off-lease seismic surveys”) or OCS Lease Number (for 

“on-lease seismic surveys”), 

• Date, 

• Time, 

• Watch status (Were you on watch or was this sighting made opportunistically by you or 

someone else?), 
D-9 

• Observer or person who made the sighting, 

• Lat./long. of vessel, 

• Bearing of vessel, 

• Bearing and estimated range to animal(s) at first sighting, 

• Water depth (meters), 

• Species (or identification to lowest possible taxonomic level), 

• Certainty of identification (sure, most likely, best guess), 

• Total number of animals, 

• Number of juveniles, 

• Description (as many distinguishing features as possible of each individual seen, 

including length, shape, color and pattern, scars or marks, shape and size of dorsal 

fin, shape of head, and blow characteristics), 

• Direction of animal’s travel – compass direction, 

• Direction of animal’s travel – related to the vessel (drawing preferably), 

• Behavior (as explicit and detailed as possible; note any observed changes in behavior,) 

• Activity of vessel, 

• Airguns firing? (yes or no), 

• Closest distance (meters) to animals from center of airgun or airgun array (whether 

firing or not). 

Note: If this sighting was of a whale(s) within the exclusion zone that resulted in a shut-down of 

the airguns, include in the sighting report the observed behavior of the whale(s) before shut-down, 

the observed behavior following shut-down (specifically noting any change in behavior), and the 

length of time between shut-down and subsequent ramp-up to resume the seismic survey (note if 

seismic survey was not resumed as soon as possible following shut-down). Send this report to MMS 

within 24 hours of the shut-down. These sightings should also be included in the first regular 

semi-monthly report following the incident. 

Additional information, important points, and comments are encouraged. All reports will be 

submitted to MMS on the 1st and the 15th of each month (with one exception noted above). 

Forms should be scanned (or data typed) and sent via email to protectedspecies@mms.gov. 

Please note that these marine mammal and sea turtle reports are in addition to any reports you submit 

under NTL No. 98-20, dated September 15, 1998, and NTL No. 2005-G07, effective July 1, 2005, 

and all progress and final reports required as a condition of your geophysical permit. 

Borehole Seismic Surveys 

Borehole seismic surveys differ from surface seismic surveys in a number of ways, including the use 

of much smaller airgun arrays, having an average survey time of 12-24 hours, utilizing a sound 

source that is not usually moving at 4-5 knots, and requiring the capability of moving the receiver in 

the borehole between shots. Due to these differences, the following altered mitigations apply only to 

borehole seismic surveys: 

• During daylight hours, when visual observations of the exclusion zone are being 

performed as required in this NTL, borehole seismic operations will not be required 

to ramp-up for shutdowns of 30 minutes or less in duration, as long as no whales, 

other marine mammals, or sea turtles are observed in the exclusion zone during the 

shutdown. If a whale, other marine mammal, or sea turtle is sighted in the exclusion 
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zone, ramp-up is required and may begin only after visual surveys confirm that the 

exclusion zone has been clear for 30 minutes. 

• During nighttime or when conditions prohibit visual observation of the exclusion zone, 

ramp-up will not be required for shutdowns of 20 minutes or less in duration. For 

borehole seismic surveys that utilize passive acoustics during nighttime and periods 

of poor visibility, ramp-up is not required for shutdowns of 30 minutes or less. 

• Nighttime or poor visibility ramp-up is allowed only when passive acoustics are used to 

ensure that no whales are present in the exclusion zone (as for all other seismic 

surveys). Operators are strongly encouraged to acquire the survey in daylight hours 

when possible. 

• Protected species observers must be used during daylight hours, as required in this 

NTL, and may be stationed either on the source boat or on the associated drilling rig 

or platform if a clear view of the sea surface in the exclusion zone and adjacent 

waters is available. 

• All other mitigations and provisions for seismic surveys as set forth in this NTL will 

apply to borehole seismic surveys. 

• Reports should reference OCS Lease Number, Area/Block and Borehole Number. 

Experimental Passive Acoustic Monitoring 

Whales, especially sperm whales, are very vocal marine mammals, and periods of silence are usually 

short and most often occur when these animals are at the surface and may be detected using visual 

observers. However, sperm whales are at the greatest risk of potential injury from seismic airguns 

when they are submerged and under the airgun array. Passive acoustic monitoring appears to be very 

effective at detecting submerged and diving sperm whales, and some other marine mammal species, 

when they are not detectable by visual observation. MMS strongly encourages operators to 

participate in an experimental program by including passive acoustic monitoring as part of the 

protected species observer program. Inclusion of passive acoustic monitoring does not relieve an 

operator of any of the mitigations (including visual observations) in this NTL with the following 

exception: Monitoring for whales with a passive acoustic array by an observer proficient in its use 

will allow ramp-up and the subsequent start of a seismic survey during times of reduced visibility 

(darkness, fog, rain, etc.) when such ramp-up otherwise would not be permitted using only visual 

observers. If you use passive acoustic monitoring, include an assessment of the usefulness, 

effectiveness, and problems encountered with the use of that method of marine mammal detection in 

the reports described in this NTL. A description of the passive acoustic system, the software used, 

and the monitoring plan should also be reported to MMS at the beginning of its use. 

Paperwork Reduction Act 

The PRA (44 U.S.C. Chapter 35) requires us to inform you that we collect the information 

described in this NTL to ensure that you conduct operations in a manner that will not jeopardize 

threatened or endangered species or destroy or adversely modify critical habitat that has been 

designated for those species. We protect all proprietary information submitted according to the 

Freedom of Information Act and 30 CFR 250.196. An agency may not conduct or sponsor a 

collection of information unless it displays a currently valid Office of Management and Budget 

(OMB) control number. You are not obligated to respond until the OMB has approved this 
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collection of information. We estimate the total hour burden to be 751 hours and the total “nonhour cost” burden to be $1,854,080. Direct comments regarding the burden, or any other aspect 

of this information collection, to the Information Collection Clearance Officer, Mail Stop 5438, 

Minerals Management Service, 1849 C Street, NW, Washington, DC 20240. 

In addition, this NTL refers to information collection requirements under 30 CFR 250, subpart B. 

The OMB has approved all of the information collection requirements in these regulations and 

assigned OMB Control Number 1010-0151. 

Contact 

Any questions regarding this NTL should be submitted in writing to: 

protectedspecies@mms.gov. Submittals by mail may be directed to: 

Minerals Management Service Gulf of Mexico OCS Region Attention: Environmental Sciences Unit 

(MS 5430) 1201 Elmwood Park Blvd. New Orleans, LA 70123-2394 

[original signed by] 

Chris C. Oynes Regional Director 
The Department of the Interior Mission

As the Nation’s principal conservation agency, the Department of the Interior has 

responsibility for most of our nationally owned public lands and natural 

resources. This includes fostering the sound use of our land and water 

resources, protecting our fish, wildlife and biological diversity; preserving the 

environmental and cultural values of our national parks and historical places; and 

providing for the enjoyment of life through outdoor recreation. The Department 

assesses our energy and mineral resources and works to ensure that their 

development is in the best interests of all our people by encouraging stewardship 

and citizen participation in their care. The Department also has a major 

responsibility for American Indian reservation communities and for people who 

live in island communities. 

The Bureau of Ocean Energy Management 

The Bureau of Ocean Energy Management (BOEM) works to manage the 

exploration and development of the nation's offshore resources in a way that 

appropriately balances economic development, energy independence, and 

environmental protection through oil and gas leases, renewable energy 

development and environmental reviews and studies.