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Susitna-Watana Hydroelectric Project Document
ARLIS Uniform Cover Page
Title:
SuWa 244
Cook Inlet beluga whale study (Study 9.17), 2014 Cook Inlet beluga whale
prey study implementation, technical memorandum
Author(s) – Personal:
Author(s) – Corporate:
LGL Alaska Research Associates, Inc.
AEA-identified category, if specified:
September 26, 2014 technical memorandum filings
AEA-identified series, if specified:
Series (ARLIS-assigned report number): Existing numbers on document:
Susitna-Watana Hydroelectric Project document number 244
Published by: Date published:
[Anchorage, Alaska : Alaska Energy Authority, 2014] September 2014
Published for: Date or date range of report: Alaska Energy Authority
Volume and/or Part numbers:
Final or Draft status, as indicated:
Attachment E
Document type: Pagination:
Technical memorandum 23 p.
Related work(s): Pages added/changed by ARLIS:
Cover letter to this report: Susitna-Watana Hydroelectric
Project, FERC Project no. 14241-000; Second set of 2014
technical memoranda for Initial Study Plan meetings. (SuWa
239)
Attachments A-D (SuWa 240-243) and F-G (SuWa 245-246)
Added cover letter
Notes:
All reports in the Susitna-Watana Hydroelectric Project Document series include an ARLIS-
produced cover page and an ARLIS-assigned number for uniformity and citability. All reports
are posted online at http://www.arlis.org/resources/susitna-watana/
September 26, 2014
Ms. Kimberly D. Bose
Secretary
Federal Energy Regulatory Commission
888 First Street, N.E.
Washington, D.C. 20426
Re: Susitna-Watana Hydroelectric Project, Project No. 14241-000
Second Set of 2014 Technical Memoranda for Initial Study Plan Meetings
Dear Secretary Bose:
As the Alaska Energy Authority (AEA) explained in its September 17, 2014 filing
with the Federal Energy Regulatory Commission (Commission or FERC) for the
proposed Susitna-Watana Hydroelectric Project, FERC Project No. 14241 (Project), the
June 3, 2014 Initial Study Report (ISR) provided for AEA to prepare certain technical
memoranda and other information based on 2014 work. In accordance with Commission
Staff direction, on September 17, 2014, AEA filed and distributed the first set of
technical memoranda and other information generated during the 2014 study season.
With this letter, AEA is filing and distributing the second set of technical
memoranda generated during the 2014 study season, as described below. As part of its
continued implementation of the study plan, AEA expects to file a third set of technical
memoranda prior to October 1, 2014.
This second set of technical memoranda includes:
• Attachment A: Geomorphology Study (Study 6.5) - Updated Mapping of
Aquatic Macrohabitat Types in the Middle Susitna River Segment from 1980s
and Current Aerials Technical Memorandum. This technical memorandum
updates the Middle Susitna River Segment portion of the aquatic macrohabitat
mapping results previously provided in the technical memorandum titled
Mapping of Aquatic Macrohabitat Types at Selected Sites in the Middle and
Lower Susitna River Segments from 1980s and 2012 Aerials (Tetra Tech
2013a).
• Attachment B: Geomorphology Study (Study 6.5) - Mapping of Geomorphic
Features and Turnover within the Middle and Lower Susitna River Segments
from 1950s, 1980s, and Current Aerials Technical Memorandum. This
technical memorandum updates the geomorphic mapping and assessment of
channel change that were initially provided in Mapping of Geomorphic
2
Features and Assessment of Channel Change in the Middle and Lower Susitna
River Segments from 1980s and 2012 Aerials (Tetra Tech 2013a). The initial
technical memorandum provided the results from tasks identified in Revised
Study Plan Study 6.5 Section 6.5.4.4. This update extends the previous 30
year analysis between the 1980s and 2012 by an additional 30 years with
aerial photography from the 1950s, and also provides a short term analysis of
geomorphic changes by comparing 2012 with 2013 aerial photography.
• Attachment C: Fluvial Geomorphology Modeling below Watana Dam Study
(Study 6.6) - Decision Point on Fluvial Geomorphology Modeling of the
Susitna River below PRM 29.9 Technical Memorandum. This technical
memorandum describes the decision of whether to extend the downstream
limit of the 1-D bed evolution model below Susitna Station at PRM 29.9.
• Attachment D: Fluvial Geomorphology Modeling Below Watana Dam (Study
6.6) - Winter Sampling of Main Channel Bed Material Technical
Memorandum. The overall purpose of this technical memorandum is to
quantify main channel bed material gradations at selected sites in the Upper,
Middle, and Lower Susitna River Segments. The data obtained from this
study serves as input for the 1-D and 2-D bed evolution modeling efforts
being conducted under the Fluvial Geomorphology Modeling Study (Study
6.6).
• Attachment E: Cook Inlet Beluga Whale Study (Study 9.17) - 2014 Cook Inlet
Beluga Whale Prey Study Implementation Technical Memorandum. This
technical memorandum summarizes activities implementing the Cook Inlet
Beluga Whale Study (Study 9.17) conducted in 2014 that tested methods to
document Cook Inlet Beluga Whale prey and prey habitat in the Susitna River
delta.
• Attachment F: River Productivity Study (Study 9.8) - 2013 Initial River
Productivity Results Technical Memorandum. This technical memorandum
provides a preliminary review and summary of 2013 river productivity sample
results based on laboratory data received after the ISR submittal in June 2014.
• Attachment G: River Productivity Study (Study 9.8) - 2014 Field Season River
Productivity Progress Report Technical Memorandum. This technical
memorandum presents an update on activities conducted during the Spring
field sampling event in June 2014, which was focused on data collection to
support the needs of the trophic modeling and stable isotope analysis
objectives of the River Productivity Study.
3
AEA appreciates the opportunity to provide this additional information to the
Commission and licensing participants, which it believes will be helpful in determining
the appropriate development of the 2015 study plan as set forth in the ISR. If you have
questions concerning this submission please contact me at wdyok@aidea.org or (907)
771-3955.
Sincerely,
Wayne Dyok
Project Manager
Alaska Energy Authority
Attachments
cc: Distribution List (w/o Attachments)
Attachment E
Cook Inlet Beluga Whale Study (Study 9.17) - 2014 Cook Inlet Beluga Whale Prey Study
Implementation Technical Memorandum
Susitna-Watana Hydroelectric Project
(FERC No. 14241)
Cook Inlet Beluga Whale Study
(Study 9.17)
2014 Cook Inlet Beluga Whale Prey
Study Implementation
Technical Memorandum
Alaska Energy Authority
Prepared by
LGL Alaska Research Associates, Inc.
September 2014
TECHNICAL MEMORANDUM 2014 COOK INLET BELUGA WHALE PREY STUDY IMPLEMENTATION
TABLE OF CONTENTS
1. Background ........................................................................................................................5
2. Methods ...............................................................................................................................5
2.1 Split-Beam Sonar Surveys for Beluga Prey .......................................................6
2.2 Visual Surveys for CIBW and other Marine Mammals.....................................7
3. Results .................................................................................................................................7
3.1 Survey Effort .....................................................................................................7
3.2 Sonar Surveys for Beluga Prey ..........................................................................8
3.3 Marine Mammal Observations .........................................................................9
3.3.1 CIBW Sighting Analysis................................................................. 9
3.3.2 Detailed Accounts of each CIBW Sighting .................................. 10
3.3.3 Accounts of Seal Sightings ........................................................... 11
3.4 Marine Mammal Distribution and Prey ...........................................................11
4. Literature Cited ...............................................................................................................12
LIST OF TABLES
Table 1. CIBW prey surveys in the Susitna River Delta in 2014. ................................................ 13
Table 2. Mean fish density (number of fish per hectare) and standard error, count of fish
detected, and mean fish length (cm) by survey. .................................................................... 13
Table 3. CIBWs observed both during surveys and during transits to the survey area in 2014. .. 14
Table 4. Seals observed during surveys and during transits to the survey area in June, 2014. .... 14
LIST OF FIGURES
Figure 1. Landing craft used for surveys. The mounted transducer is on the port side of the
vessel forward of the wheelhouse. ........................................................................................ 15
Figure 2. CIBW prey surveys in the Susitna River Delta in 2014. Five of the surveys occurred
during high tide (lines closer to the mouth of the Susitna River), and four occurred during
low tides (longer lines further from the river mouth). .......................................................... 15
Figure 3. Water depth in meters corrected for MLLW in the Susitna River Delta in 2014. Depth
between data points was interpolated using the kriging formula in ArcGIS 10.2. Depths
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TECHNICAL MEMORANDUM 2014 COOK INLET BELUGA WHALE PREY STUDY IMPLEMENTATION
near the Little Susitna River and at the southern portion of the survey area were calculated
using few data points and should be interpreted with caution. ............................................. 16
Figure 4. Fish densities at low and high tidal stages .................................................................... 16
Figure 5. Density of prey (fish per hectare) for all surveys in the Susitna River Delta in 2014.
Highest densities of fish were detected near the edge of the exposed mudflats during low
tide. ........................................................................................................................................ 17
Figure 6. Mean water depth (m) of fish, mean depth of water at the time of fish detection, and
mean depth of water of each survey by tidal stage. .............................................................. 17
Figure 7. Marine mammals observed during surveys and transits to the survey area in 2014.
Observation locations depicted were corrected for distance and location relative to the
vessel during post-season data processing using ArcGIS 10.2. ............................................ 18
Figure 8. Number of CIBW groups and number of CIBW individuals observed during surveys
and transits to the survey area in 2014. ................................................................................. 18
Figure 9. Mean number of individuals per group of CIBWs in the Susitna River Delta in June,
2014. ...................................................................................................................................... 19
Figure 10. Color composition of CIBW groups observed in the Susitna River Delta in June,
2014. Due to the effort of the vessel to maintain distance from CIBW groups, group
composition data are not reliable for distant sightings. See Detailed Accounts of each CIBW
Sighting for more information. ............................................................................................. 19
Figure 11. Behavioral composition of CIBW groups observed in the Susitna River Delta in June,
2014. Due to the effort of the vessel to maintain safe distance from CIBW groups,
behavioral data are not reliable for distant sightings. See Detailed Accounts of each CIBW
Sighting for more information. ............................................................................................. 20
Figure 12. Fish density detected, number of CIBW individuals, and number of harbor seal and
unidentified seal individuals observed in the Susitna River Delta in 2014. ......................... 20
Figure 13. CIBW, harbor seal, and unidentified seal sightings on days with high fish density
(June 02, June 28, July 02, July 16, and July 22). Numbers indicate the location of multiple
records of the same sighting. ................................................................................................ 21
Figure 14. CIBW, harbor seal, and unidentified seal sightings on days with low fish density (June
14, June 23, June 29, and July 21). Numbers indicate the location of multiple records of the
same sighting. ....................................................................................................................... 21
Figure 15. CIBW sightings and fish density on July 16, 2014. Numbers indicate the location of
multiple records of the same sighting. .................................................................................. 22
Figure 16. Fish density and distance of vessel from CIBWs for Sighting ID 38. As fish density
increased, distance from CIBWs decreased. Vessel engines were off and vessel was drifting
when closest whales were ~250 m away. ............................................................................. 22
Figure 17. CIBW sightings, harbor seal sightings, and fish density on July 22, 2014. Numbers
indicate multiple records of the same sighting...................................................................... 23
Figure 18. Harbor seal sightings and fish density on June 02, 2014. ........................................... 23
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TECHNICAL MEMORANDUM 2014 COOK INLET BELUGA WHALE PREY STUDY IMPLEMENTATION
LIST OF ACRONYMS, ABBREVIATIONS, AND DEFINITIONS
Abbreviation or Symbol Definition
CIBW Cook Inlet beluga whale
NMFS National Marine Fisheries Service
MMPA Marine Mammal Protection Act
GPS Global Positioning System
m meters
mm millimeter
ft foot
ha hectare
msec millisecond
kHz kilohertz
dB decibels
~ approximately
> greater than
< less than
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TECHNICAL MEMORANDUM 2014 COOK INLET BELUGA WHALE PREY STUDY IMPLEMENTATION
1. BACKGROUND
As stated in RSP 9.17, the goals of the Cook Inlet Beluga Whale (Delphinapterus leucas; CIBW)
study are to (1) provide current, fine scale information on CIBW distribution and movements
within the Susitna River delta, (2) correlate these data with information on the ecology and
habitat parameters of CIBW prey species, including eulachon (Thaleichthys pacificus) and
Pacific salmon (Onchorynchus spp.), and (3) record incidental observations of all marine
mammals sighted during beluga whale studies. Three specific objectives were identified:
1. Document CIBWs and other marine mammals in the Susitna River delta, focusing on
CIBW distribution and upstream extent;
2. Document CIBW group size, group composition, and behavior within the Susitna
River delta; and
3. Develop a model to describe the relationships between river flows, water surface
elevation, and CIBW foraging habitats in the Susitna River.
This technical memo summarizes activities conducted in 2014 that tested methods to document
CIBW prey and prey habitat in the Susitna River delta. Vessel-based surveys were used as a
platform to collect data on beluga prey species as well as data from marine mammal sightings
including distribution, behavior, and group composition. Split-beam sonar was used to collect
prey data while marine mammal observers collected environmental and marine mammal sighting
data. Marine mammal observers also directed vessel activities to remain in compliance with the
Marine Mammal Protection Act (MMPA).
2. METHODS
Vessel surveys were carried out using a ~9 m landing craft launched from the Port of Anchorage
(Figure 1). Surveys were designed to follow the shoreline between the Little Susitna River and
the Beluga River in a “zig-zag” pattern. A sonar technician and two marine mammal observers
from LGL participated in each survey, in addition to a skipper. The sonar technician operated
and monitored data collected by a split-beam sonar (mounted at ~1 m depth on the port side of
the vessel) which recorded information on fish and water depth.
Data collected during each survey included:
1. A continuous trackline from a GPS.
2. The data stream from the split-beam sonar including a continuous log of depth.
3. Environmental conditions every 30 minutes or more frequently if conditions changed
(i.e., sightability increased or decreased), and
4. Observations of beluga whales and other marine mammals.
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TECHNICAL MEMORANDUM 2014 COOK INLET BELUGA WHALE PREY STUDY IMPLEMENTATION
2.1 Split-Beam Sonar Surveys for Beluga Prey
The sonar system used to collect prey data was a BioSonics DT-X® split-beam echo-sounder.
The echo-sounder was programmed to transmit at 206 kHz, which is outside the range of beluga
whale hearing (Castellote et al. 2014). The data collection threshold for the system was set to -70
dB with a -10 dB power reduction level. The sample rate for the transducer was 12 pings per
second. The pulse duration was set to 0.2 msec. Data were geo-referenced with a GPS and the
locational information was collected simultaneously with the hydroacoustic sample data. The
acoustic system was calibrated using a standard (36 mm diameter) tungsten carbide calibration
sphere. The calibration sphere was lowered to about 2 m below the transducer, positioned in the
beam, and several thousand pings were recorded to estimate target strength of the sphere. The
post-calibration analysis indicated that the target strength was about 1.3 dB lower than the
expected target strength for the calibration sphere. As a result, an offset of +1.3 dB was applied
to the entire data set.
Acoustic data were processed using Echoview software v5.40. For targets detected 2.5 to 25 m
in depth, echo tracking was used to combine individual echoes into fish tracks. The tracks were
filtered by off axis angle to include only those tracks within 12 degrees of the center of the beam.
The effective beam width then varied by fish depending on the fish size relative to the analysis
threshold of -60 dB.
For each transect, fish density values were estimated as follows: each observed fish was
weighted by the effective width of the beam at the range of the fish. The weighted fish count
was then summed over each transect and divided by the transect length using the formula:
i
j j
i l
bD
∑
=
1
where Di is the fish density (fish/m2) of transect i, the summation is over all fish j observed in
transect i, bj is the beam diameter (m) at range of fish j, and li is the length (m) of transect i.
Density estimates were then expressed as fish per hectare.
We assumed Love’s (1977) equation for all aspects was representative of the target strength
distribution:
TS = 20 log L – 69.23 (all aspects);
where TS = target strength in decibels; and L = fork length in centimeters.
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TECHNICAL MEMORANDUM 2014 COOK INLET BELUGA WHALE PREY STUDY IMPLEMENTATION
2.2 Visual Surveys for CIBW and other Marine Mammals
Two observers conducted visual scans using unaided eyes and 7x50 binoculars while the vessel
conducted the surveys. Observers were primarily responsible for early detection of CIBW in the
survey area and then providing guidance to the vessel skipper to operate the vessel in such a way
as to avoid disturbance.
Environmental data were collected at the beginning and end of each survey, and once every 30
minutes during the survey, or if conditions affecting visibility changed rapidly. Environmental
data were collected using custom-built data entry software (“PSOTracker”). The following data
were collected:
• time, location, speed, heading, and leg of survey;
• sea state, visibility, and sun glare; and
• presence of other vessels in the vicinity of the survey area.
Sighting data were collected using a combination of “PSOTracker” and paper datasheets.
Information was recorded at the beginning, end, and at five minute intervals during each marine
mammal sighting. PSOTracker was used to capture a timestamp and GPS coordinates at the
beginning of a sighting and generate a unique Sighting ID. When new information about the
sighting needed to be recorded, a new record was created using PSOtracker to record a new
timestamp, coordinates, and a unique Record ID. Paper datasheets were used to record the
following information for each sighting:
• Sighting ID, Record ID, time and location from PSOTracker;
• Water depth at vessel and vessel heading;
• Species, group size, age/size categories;
• Location, bearing, and distance from vessel;
• Primary and secondary behaviors;
• Apparent reaction to vessel (e.g., none, avoidance, approach, etc.) and behavioral
pace; and
• Group formation (e.g., parallel, echelon) and inter-individual distance
3. RESULTS
3.1 Survey Effort
Nine surveys were at least partially completed in 2014 (Table 1). Two surveys were
substantially reduced due to weather, one survey was reduced due to CIBW presence in the area,
and six surveys were complete. No surveys were attempted from June 3 through June 12 to
avoid conflicting with National Marine Fisheries Service (NMFS) aerial surveys of CIBW
abundance.
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TECHNICAL MEMORANDUM 2014 COOK INLET BELUGA WHALE PREY STUDY IMPLEMENTATION
Surveys took place during low tide (n=4) and during high tide (n=5; Table 1). Surveys were
designed to follow the shoreline between the Little Susitna River and the Beluga River in a “zig-
zag” pattern and get as close as possible to the Susitna River mouth (Figure 2). One of the high
tide surveys was modified with the intent to identify, investigate, and characterize deep channels
near the river mouth. Water depth in areas surveyed ranged from ~4 ft to ~90 ft. During high
tide surveys, average recorded water depth was ~18 ft and the shallowest depth recorded was ~4
ft. During the low tide surveys, the average depth was ~40 ft and the shallowest depth recorded
was ~6 ft. Visibility was good for each survey, with occasional glare obstructing the view of
observers. Sea states in the survey area ranged from calm (glassy sea with small ripples) to ~5 ft
seas, at which point survey efforts were aborted. The final survey was nearly completed but
discontinued in response to concerns about CIBW presence in the area.
Two surveys were terminated before completion due to poor quality sonar data caused by
weather. Bathymetric data were good quality with minimal noise when collected during low sea
states; however, sea states >3 ft and the resulting turbidity and entrained air caused excessive
noise in the data. High sea states also create large gaps in the data as the pitch of the vessel can
raise the transducer partially out of the water.
3.2 Sonar Surveys for Beluga Prey
The sonar data stream included a continuous log of depth as well as presence of fish targets.
Deep channels were detected near the Little Susitna River and the Beluga River, but too few data
points were collected to create accurate bathymetry of those areas (Figure 3). Three possible
channels or holes were detected in the main body of the Susitna Delta during high tide surveys
(Figure 3), but were unable to be investigated extensively due to safety concerns. The eastern
channel is likely the deeper and larger of the identified channels. The edge of the flats, surveyed
during low tides, is characterized by a drop off and relatively flat plain that gradually increases in
depth in relation to distance from the mudflats. No substantial troughs were identified during
low tide surveys although gradual fluctuations in depth were detected.
Individual fish were detected during June and July surveys. The highest fish density as averaged
across the duration of each survey was on June 2nd, but in general, densities were lower in June
than July (Table 2). Fish densities were highest at low tidal stages (Figure 4). No relationship
between tidal stage and mean fish length is apparent. Mean fish length was somewhat greater
during June surveys (Table 2). Eighty-nine percent of fish detected were <15 cm in length.
While no large fish aggregations were identified, higher densities of fish were consistently
detected along the edge of the mudflats, while fewer fish were identified closer to the Susitna
River in channels and holes. Deep channel habitats and holes where fish might aggregate were
identified on high tide surveys, and one survey on July 21st was dedicated to exploring and
characterizing such troughs; however, few fish targets and no aggregations were found in these
channels and holes and mean fish density for this investigative survey was quite low (Table 2).
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TECHNICAL MEMORANDUM 2014 COOK INLET BELUGA WHALE PREY STUDY IMPLEMENTATION
Fish were consistently found in the center of the Susitna Flats and towards the west near Beluga
River; few fish were detected near the Little Susitna River (Figure 5). Fish were most reliably
detected during low tide within ~1000 m of the exposed Susitna mudflats. This area is
characterized by a deep, relatively flat plain sloping towards the inlet (Figure 3). Fish were
detected ~5 m from the bottom during low tide surveys and ~1 m from the bottom during high
tide surveys (Figure 6). The average bottom depth at the location of fish detections during high
tide was ~10 m shallower than the average depth at fish detections during low tide surveys. Fish
were detected at an average water depth of 16.3 m during low tide surveys, which was ~2 m
deeper than the average depth measured across all of the low tide surveys, which indicates that
fish were found more often in the deeper waters of those surveyed (Figure 6).
3.3 Marine Mammal Observations
CIBW, harbor seals, and unidentified seals were observed during surveys and during transit to
and from the survey site (Figure 7). Marine mammals were observed on every survey except
June 14th, which was aborted early due to weather. CIBWs were initially sighted at an average
of >1000 m away and closely monitored throughout the duration of the sighting to maintain
compliance with the MMPA. Observers requested multiple course alterations, reductions in
speed, and shut down of engines to avoid harassment of whales and seals hauled-out on
mudflats. Since the vessel frequently altered course to maintain a safe distance from marine
mammals during survey operations, sizes, colors, and behaviors were difficult to discern and
group composition and behavioral data are not reliable for distant sightings.
3.3.1 CIBW Sightings
Few CIBW sightings were recorded in June and these were of individual whales or small groups
(Figure 8). CIBW were sighted more consistently in July and in larger groups in late July
(Figure 8). The greatest number of groups was observed on July 2nd, and the greatest number of
individuals was observed on July 22nd. Average group size in late June and early July was ~5
individuals and in late July was ~67 individuals, although there was substantial variability in
group size in late July (Figure 9).
No discernable difference in group composition was seen during the season (Figure 10). For
sightings in which the stationary boat was approached by whales, which occurred 2 times, groups
were generally composed of white whales and large gray whales, with the exception of a sighting
on July 16th where one small, dark-gray whale was observed (Figure 10).
The pace of all observed CIBWs was described as sedate or moderate, with the exception of one
instance where belugas were observed chasing fish out of the water. The primary behavior of all
CIBWs sighted in June was swimming (Figure 11). The primary behavior of CIBWs sighted in
July included surface active, milling, travelling, and swimming. More coordinated group
behaviors were observed in late July than June or early July. CIBWs sighted in early July
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exhibited behaviors such as blowing, fluking, and swimming ~80% of the time (Figure 11). In
contrast, CIBWs observed in late July exhibited milling (~40%) and feeding or suspected feeding
(~20%; Figure 11). There were no observable reactions to the vessel during any of the beluga
sightings, including the two instances when whales approached the drifting vessel.
3.3.2 Detailed Accounts of each CIBW Sighting
CIBW were sighted three times in the month of June. Two of these sightings occurred in the
survey area and only one of them occurred during a survey (Table 3). The first CIBW sighting
(Sighting ID = 12) was observed near the Port of Anchorage on June 23rd and occurred while the
vessel was stationary making equipment adjustments. The second sighting (Sighting ID = 18)
occurred on June 28th near the eastern edge of the survey area while the vessel was in transit to
the start of the survey line. This group of five CIBWs was observed ~500 m to the side of the
vessel and heading away from the vessel. Given the distance and directional heading of the
whales, the survey vessel did not change course to further avoid the group. The third sighting
also occurred on June 28th (Sighting ID = 21). A group of 10 whales was observed ~300 m to
the side of the vessel, which was surveying on transect at <5 mph. Again, no change of course
was required to avoid the whales. Lighting conditions were poor at the time of the sighting, and
observers could not distinguish the color of the whales.
CIBWs were sighted during all four surveys in July. On July 2nd, five sightings of small groups
of beluga whales were observed. Two of the groups were observed while the vessel was in
transit to the start of the survey (Sighting IDs = 30, 31). The third sighting (Sighting ID = 32)
occurred while the vessel was present on a transect line, but stationary while sonar equipment
was being adjusted. The last two sightings on July 2nd (Sighting ID = 34, 35) occurred during
surveys.
CIBWs were sighted two times on July 16th, including a group of approximately 50 individuals
that were initially detected 2,000 m from the vessel as it was surveying (Sighting ID = 38). The
vessel altered course and abandoned the survey line when whales were ~400 m away. The vessel
then stopped and turned off its engines when belugas approached the vessel to within ~250 m.
Several whales approached as close as 10 m from the drifting vessel and appeared to be feeding.
One fish jumped out of the water with a whale in pursuit. There was no apparent reaction to the
vessel and CIBW behavior was consistent throughout the encounter. After the whales moved
>400 m away, the engine was restarted and the survey continued. The second sighting on July
16th (Sighting ID = 39) occurred during transit after the survey was completed. Several belugas
were seen ahead of the vessel and the vessel reduced speed, then stopped and turned off the
engines when whales were ~250 m from the vessel. Some individuals approached the stopped
vessel as close as 3 m, including one cow with a dark gray calf. Observers recorded that whales
appeared to be traveling past the vessel. Again, there was no apparent reaction to the vessel and
no behavioral changes were observed. The vessel resumed transit when the belugas were >300
m away.
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TECHNICAL MEMORANDUM 2014 COOK INLET BELUGA WHALE PREY STUDY IMPLEMENTATION
A single, distant sighting of a group of 45 individuals occurred on July 21st (Sighting ID = 40).
Due to the distance of the sighting, mostly white whales and a few large gray whales were
distinguished within the group.
Two sightings occurred on July 22nd. Whales were initially observed at ~2,500 m with a closest
point of approach of ~350 m (Sighting ID = 45). At ~350 m, the vessel altered course and
abandoned the survey line to maintain distance from the whales. Severe glare made group
composition impossible to determine. The second sighting was brief and distant, and only blows
were clearly visible (Sighting ID = 47).
3.3.3 Accounts of Seal Sightings
More sightings of seals occurred in June than July; however, larger groups were seen in July than
in June. Twenty six sightings of 34 individual harbor seals and unidentified seals occurred in
June and 7 sightings of 134 seals occurred in July (Table 4). It is likely that unidentified seal
sightings were harbor seals; however, the sightings were too brief or distant for the observers to
identify to species. The most common primary behavior of seals was look, followed by swim.
The most common reaction to the presence of the vessel was look, followed by no observable
reaction. Two of the seal sightings were of haul-outs on the mud flats during low tide. The
majority of the seals observed were described as sedate.
3.4 Marine Mammal Distribution and Prey
In general, on days when fish densities were high, marine mammal sightings were also high;
although this relationship appears stronger for CIBW than for seals (Figure 12). The major
exception to this trend is that the highest fish density was detected on June 2nd, but no CIBW
were observed in the Susitna River delta during that survey. Large groups of CIBW were first
detected in the Susitna River Delta on July 16th. Of the three days surveyed when belugas were
observed in large groups, two days (July 16th and July 22nd) also had high fish densities. There
was also a strong spatial relationship between fish density and CIBW sightings on these days
(see Figure 13 and descriptions below). This relationship did not appear to be present on days
with low to moderate fish density (Figure 14). It is important to note that data analyses from the
split-beam sonar can only describe the fish density along the vessel trackline and fish density at
distant CIBW sightings may have been much higher (or lower) than the average density near the
survey vessel.
On July 16th, the vessel altered course and shut off engines to avoid harassment of a group of
beluga whales traveling southwest along the mudflats (see Detailed Accounts of each CIBW
Sighting for more information). As belugas approached the drifting vessel (Record ID 2 in
Figure 15), fish density below the vessel increased dramatically (Figure 16). Fish density
reached the highest recorded value (~2,000 fish/ha) encountered during the 2014 season when
whales were <100 m from the vessel (Figure 16). CIBW behavior during this time was recorded
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as feeding or suspected feeding. Once the whales moved past the vessel (Record ID 4 in Figure
15), fish density had decreased to relatively low levels.
On July 22nd, the vessel altered course several times to maintain safe distance from a group of
beluga whales spread out across the survey area to the north of survey activities. Fish densities
increased as the vessel followed transect lines that neared the group of belugas and then
decreased as the vessel altered course and moved away from belugas (Figure 17). Primary
behavior for the group of belugas was “milling.”
Harbor seal sightings also occurred in areas of highest fish density. The survey on June 2nd had the
highest density of fish and the largest number of harbor seal sightings. Harbor seal sightings occurred in
the areas of highest fish density in the survey (Figure 18).
4. LITERATURE CITED
Castellote, M., T.A. Mooney, L. Quakenbush, R. Hobbs, C. Goertz, E. Gaglione. 2014.
Baseline hearing abilities and varibability in wild beluga whales (Delphinapterus leucas).
Journal of Experimental Biology. (217) 1682-1691.
Love, R. H. 1977. Target strength of an individual fish at any aspect. Journal of the Acoustical
Society of America 62:1397-1403.
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5. TABLES
Table 1. CIBW prey surveys in the Susitna River Delta in 2014.
Table 2. Mean fish density (number of fish per hectare) and standard error, count of fish detected, and mean fish length (cm) by survey.
Date
Tide at
Start
Tide at
End
Tidal
Stage
Duration
(h)
Fish
Detected
Belugas
Observed
June 02 2014 +27.4 +6.6 Low 4.8 Yes No
June 14 2014 +32.8 +32.2 High 1.0 No No
June 23 2014 +23.4 +25.9 High 1.8 Yes Yes
June 28 2014 +28.8 +24.2 High 2.8 Yes Yes
June 29 2014 +26.6 +28.8 High 2.0 Yes No
July 02 2014 +13.5 +4.9 Low 2.8 Yes Yes
July16 2014 +10.8 +0.1 Low 2.8 Yes Yes
July 21 2014 +22.8 +19.9 High 3.8 Yes Yes
July 22 2014 +11.0 +4.1 Low 2.9 Yes Yes
Date Tidal
Stage
Mean
Density*
Standard
Error Count Mean Fish
Length (cm)
June 01 2014 N/A N/A N/A N/A N/A
June 02 2014 Low 85.0 6.9 451 9.9
June 14 2014 High 0.0 0.0 N/A N/A
June 23 2014 High 2.6 2.6 1 3.0
June 28 2014 High 28.2 6.7 32 9.3
June 29 2014 High 2.4 1.4 3 8.3
July 02 2014 Low 40.8 5.5 107 5.6
July16 2014 Low 48.9 13.5 139 7.5
July 21 2014 High 4.7 2.6 6 4.5
July 22 2014 Low 53.8 6.9 187 6.6
* number of fish per hectare
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Table 3. CIBWs observed both during surveys and during transits to the survey area in 2014.
Table 4. Seals observed during surveys and during transits to the survey area in June, 2014.
Sighting ID Sighting
Date
Sighting
Time
During
Survey
Total Number
of Individuals
Initial Sighting
Distance (m)
Closest Point of
Approach (m)
12 6/23/2014 14:45 N 1 300 300
18 6/28/2014 06:44 N 5 500 500
21 6/28/2014 09:40 Y 10 300 300
30 7/2/2014 14:32 N 4 1000 750
31 7/2/2014 14:42 N 6 1500 1500
32 7/2/2014 14:55 N 3 400 400
34 7/2/2014 16:08 Y 7 1000 1000
35 7/2/2014 16:11 Y 4 700 700
38 7/16/2014 15:41 Y 50 2000 10
39 7/16/2014 18:00 N 75 400 3
40 7/21/2014 15:30 Y 45 3000 1000
45 7/22/2014 08:41 Y 150 2500 300
47 7/22/2014 09:52 Y 15 1000 750
Species
Total Number
of Sightings
Total Number
of Individuals
Harbor Seal 28 162
Unidentified Seal 5 6
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6. FIGURES
Figure 1. Landing craft used for surveys. The mounted transducer is on the port side of the vessel forward of the wheelhouse.
Figure 2. CIBW prey surveys in the Susitna River Delta in 2014. Five of the surveys occurred during high tide (lines
closer to the mouth of the Susitna River), and four occurred during low tides (longer lines further from the river mouth).
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Figure 3. Water depth in meters corrected for MLLW in the Susitna River Delta in 2014. Depth between data points was interpolated using the kriging formula in ArcGIS 10.2. Depths near the Little Susitna River and at the southern portion
of the survey area were calculated using few data points and should be interpreted with caution.
Figure 4. Fish densities at low and high tidal stages
61.9
8.3
0
10
20
30
40
50
60
70
80
90
Low Tide High TideMean fish per hectaren=1039n=1276
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Figure 5. Density of prey (fish per hectare) for all surveys in the Susitna River Delta in 2014. Highest densities of fish
were detected near the edge of the exposed mudflats during low tide.
Figure 6. Mean water depth (m) of fish, mean depth of water at the time of fish detection, and mean depth of
water of each survey by tidal stage.
11.0
4.5
16.3
5.6
14.5
6.6
0
5
10
15
20
25
Low Tide High TideMean depth (m)Mean depth of fish
Mean depth of bottom at fish
Mean survey bottom depth
n=42n=884
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Figure 7. Marine mammals observed during surveys and transits to the survey area in 2014. Observation
locations depicted were corrected for distance and location relative to the vessel during post-season data
processing using ArcGIS 10.2.
Figure 8. Number of CIBW groups and number of CIBW individuals observed during surveys and transits to the
survey area in 2014.
0
20
40
60
80
100
120
140
160
180
0
1
2
3
4
5
6
7
8
9
10
6/02 6/14 6/23 6/28 6/29 7/02 7/16 7/21 7/22Number of Groups ObservedNumber of Individuals ObservedSurvey Date
CIBW Groups
CIBW Individuals
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Figure 9. Mean number of individuals per group of CIBWs in the Susitna River Delta in June, 2014.
Figure 10. Color composition of CIBW groups observed in the Susitna River Delta in June, 2014. Due to the effort
of the vessel to maintain distance from CIBW groups, group composition data are not reliable for distant
sightings. See Detailed Accounts of each CIBW Sighting for more information.
0.0 5.3 4.8
67.0
0.0
20.0
40.0
60.0
80.0
100.0
120.0
140.0
Early June Late June Early July Late JulyMean Group Sizen=5n=0 n=3 n=5
63
38
49
25
50
37
13 13 13
0
20
40
60
80
100
Early June Late June Early July Late JulyPercentage of Individuals SightedDark Gray
Gray
White
Unknown
n=24n=0 n=16 n=335
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Figure 11. Behavioral composition of CIBW groups observed in the Susitna River Delta in June, 2014. Due to the
effort of the vessel to maintain safe distance from CIBW groups, behavioral data are not reliable for distant
sightings. See Detailed Accounts of each CIBW Sighting for more information.
Figure 12. Fish density detected, number of CIBW individuals, and number of harbor seal and unidentified seal
individuals observed in the Susitna River Delta in 2014.
20 20
20
100
40
20
20
20
40
0
10
20
30
40
50
60
70
80
90
100
Early June Late June Early July Late JulyPercentage of Groups SightedMilling
Feeding
Travel
Swim
Fluke
Blow
n=3n=0 n=5 n=5
0
20
40
60
80
100
120
140
160
180
0
10
20
30
40
50
60
70
80
90
6/02 6/14 6/23 6/28 6/29 7/02 7/16 7/21 7/22Fish per hectareNumber of Individuals ObservedSurvey Date
Fish Density
CIBW Individuals
Seal Individuals
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Figure 13. CIBW, harbor seal, and unidentified seal sightings on days with high fish density (June 02, June 28,
July 02, July 16, and July 22). Labels indicate the location of multiple records of the same Sighting ID.
Figure 14. CIBW, harbor seal, and unidentified seal sightings on days with low fish density (June 14, June 23,
June 29, and July 21). Labels indicate the location of multiple records of the same Sighting ID.
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Figure 15. CIBW sightings and fish density on July 16, 2014. Labels indicate the location of multiple records of
the same Sighting ID.
Figure 16. Fish density and distance of vessel from CIBWs for Sighting ID 38. As fish density increased,
distance from CIBWs decreased. Vessel engines were off and vessel was drifting when closest whales were
~250 m away.
0
500
1000
1500
2000
2500
0
500
1000
1500
2000
2500
07/16 14:24 07/16 15:36 07/16 16:48 07/16 18:00 Distance from CIBW Group (m)Fish per hectareFish Density
CIBW Sighting
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Figure 17. CIBW sightings, harbor seal sightings, and fish density on July 22, 2014. Labels indicate the location
of multiple records of the same Sighting ID.
Figure 18. Harbor seal sightings and fish density on June 02, 2014.
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