Gray whale visual sightings from shore 2014-2015

Regina A. Guazzo, Scripps Institution of Oceanography

Dataset credit

National Oceanic and Atmospheric Administration, Southwest Fisheries
Science Center


Primary contact Regina Guazzo Naval Information Warfare Center Pacific
Data entry Ei Fujioka Duke University



During the eastern North Pacific gray whale 2014–2015 southbound
migration, acoustic call recordings, infrared blow detections, and visual
sightings were combined to estimate cue rates, needed to convert
detections into abundance. The gray whale M3 acoustic call rate was 2.3–24
calls/whale/day with an average of 7.5 calls/whale/day over the entire
migration (southbound and northbound) and showed a positive trend from
30 December–13 February. The infrared camera blow rate averaged 49
blows/whale/hour over 5–8 January. With a call rate model, we estimated
that 4,340 gray whales migrated south before visual observations began on
30 December, which is 2,829 more gray whales than used in the visual
abundance estimate. This finding highlights the usefulness of cue rates to
increase precision in abundance estimates. We suggest that visual
observers increase their survey effort to all of December to verify gray
whale abundance corrections. Probability of detection of a whale blow by
the infrared camera was the same at night as during the day. However,
probability of detection decreased beyond 2.1 km offshore, whereas visual
sightings revealed consistent whale densities up to 3 km offshore. We
suggest that future infrared camera surveys use multiple cameras
optimized for different ranges offshore.



Supplemental information

Visual Observation Location: 36 26' 23.61" N 121 55' 20.5" W

The sheet labeled "Effort" contains start and end times for observations in
both UTC and PST time zones. B indicates the observations were beginning
and E indicates the observations were ending. times are in Matlab's
datenum format: Days since January 0, 0000

The sheet labeled "Modeled Abundance" contains the estimated number of
whales that passed each day. Date is the Julian Date in Matlab's datenum
format: Days since January 0, 0000. The estimated number of whales each
day are given as a probability distribution. Median and the 95% highest
posterior density interval are reported. Methods are described by Durban
et al. 2015.

The original datasheet is included in the downloadable zipped file.




This section explains attributes included in the original dataset. OBIS-SEAMAP restricts the attributes available to the public to date/time, lat/lon and species names/counts only. Should you need other attributes described here, you are encouraged to contact the data provider.

Attributes described below represent those in the original dataset provided by the provider.
All attributes are included in the downloadable file (CSV or ESRI File Geodatabase) for "Complete Set of Dataset".

Attributes in dataset

Attribute (table column)Description
oidUnique ID number (generated by OBIS-SEAMAP)
speciesSpecies name recorded
sp_tsnTaxonomic Serial Number added by OBIS-SEAMAP
utc_timeJulian Time in Matlab datenum format, UTC time zone
local_timeJulian Time in Matlab datenum format, PST time zone
datetime_utcDate and time in UTC converted from utc_time
datetimeDate and time in local time zone converted from local_time
latitudeLatitude in decimal degrees
longitudeLongitude in decimal degrees
azimuthAzimuth to whale
rangeRange offshore in km
group_numberGroup identification number, each day starts again at 1
group_sizeEstimated number of whales in group
beaufortBeaufort sea state conditions
visibilityVisibility Conditions
directionDirection that the whales are traveling in
geomGeometry field added by OBIS-SEAMAP
Marine mammals3,958
Sea turtles0
Rays and sharks0
Other species0
Non spatial0
Non species0
Date, Begin2014-12-30
Date, End2015-02-13
Temporal prec.111111
Latitude36.41 - 36.46
Longitude-122.02 - -121.92
Coord. prec.6 decimal digits
Data typeAnimal sighting
Traveled (km)0
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Sharing policy CC-BY-NC (All)
Shared with OBIS
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