Dataset: seal_counts_2008

Name: Visual estimates of seal abundance from aerial surveys conducted by a Cessna-185 in the San Juan Islands, Salish Sea in 2008 (Seal_response_to_prey project)
Published: 2012-11-16
Keywords: oceans

Cite This Dataset

Spatial Extent: N:48.789 E:-122.3957 S:48.2098 W:-123.1835

Project:

Responses of Seals and Sea Lions to Increased Rockfish Density (Seal_response_to_prey)

Lead Principal Investigator:

Alejandro Acevedo-Gutierrez (Western Washington University, WWU)

Co-Principal Investigator:

Jeffrey F Bromaghin (United States Geological Survey, USGS)

Steven J Jeffries (Washington Department of Fish and Wildlife)

John M Kennish (University of Alaska, Anchorage, UAA)

Monique M Lance (Washington Department of Fish and Wildlife)

Philip S. Levin (National Marine Fisheries Service, NMFS)

BCO-DMO Data Manager:

Shannon Rauch (Woods Hole Oceanographic Institution, WHOI BCO-DMO)

Version:

16 Nov 2012

Version Date:

2012-11-16

Validated:

Yes

Current State:

Final no updates expected

Visual estimates of seal abundance from aerial surveys conducted by a Cessna-185 in the San Juan Islands, Salish Sea in 2008 (Seal_response_to_prey project)

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Description

Number of seals counted during several aerial surveys of the Salish Sea during July and August of 2008. Data are also available from 2007 surveys.

Related publications: (Both available from Alejandro Acevedo's lab website.)
Howard, S. 2009. Seasonal energy budgets to model energy use and prey consumption in harbor seals (Phoca vitulina) in the San Juan Islands, WA. MSc thesis, Department of Biology, Western Washington University, Bellingham, WA.
Hardee, S. 2008. Movements and home ranges of harbor seals (Phoca vitulina) in the Georgia Basin: implications for marine reservinland waters of the Pacific Northwest. MSc thesis, Department of Biology, Western Washington University, Bellingham, WA.

Methods & Sampling

Following protocol from Jeffries et al. (2003), with collaboration from the Washington Department of Fish and Wildlife, surveys were flown in a Cessna 185 at 200 to 300 m, moving at 90 kt, on two or three consecutive days during moderately low tides. Flights were made over the region moving with the tide, to cover the entire area within +/- 2 h from low tide. Visual counts were taken on sites with < 25 seals and digital photographs and visual counts were taken concurrently at sites with > 25 animals, using a Nikon D100 with a 200 mm lens. The time was documented on the survey log for all haul-out counts, haul-out estimates and photographs. Surveys were conducted under permit 782-1702 awarded to the Washington Department of Fish and Wildlife by the Office of Protected Resources.

Selection of flight times was not only dependent on tidal conditions but also on time of day. If one chooses tidal heights that are extremely low, there is a risk that the survey underestimates the number of seals in the region because normal haul-out sites may be inaccessible (Jeffries, pers. comm.). Additionally, fog may become problematic for flying if the tide window, especially in August, is too early in the morning. These factors were taken into account when selecting the survey dates.

Tide times on dates of aerial surveys are as follows:
Date       Tide Station        Tide Time     Tide Height (ft)
07/17/08 Port Townsend     10:12             -1.7
07/18/08 Port Townsend     10:49             -1.8
07/18/08 Seattle                  11:48            -1.6
07/31/08 Port Townsend      09:44            -2.6
07/31/08 Seattle                  10:39            -2.9
08/01/08 Port Townsend      10:32            -2.4
08/14/08 Port Townsend      09:14            -0.9
08/15/08 Port Townsend      09:52            -1.0

References:
Jeffries SJ, Huber HR, Calambokidis J, Laake J (2003) Trends and status of harbor seals in Washington State: 1978-1999. Journal of Wildlife Management 67:208-219. Available online from Washington Department of Fish and Wildlife.
Huber HR, Jeffries SJ, Brown RF, DeLong RL, Van Blaricom G (2001) Correcting aerial survey counts of harbor seals (Phoca vitulina richardsi) in Washington and Oregon. Marine Mammal Science 17:276-293. DOI: 10.1111/j.1748-7692.2001.tb01271.x

Data Processing Description

The estimation of seal population size based on haul-out counts requires a correction factor to account for seals in the water at the time of the survey (Huber et al. 2001, Jeffries et al. 2003), however, correction factors have NOT been applied to these data.

BCO-DMO made the following edits to the dataset:
- Blanks and 'NA' were replaced with 'nd' to indicate 'no data';
- Parameter names were modified to conform with BCO-DMO conventions;
- day, month, and year were separated from original date column;
- Abbreviated species names were replaced with the full species names;
- Corrected typos in the year column from '2009' to '2008';
- lat and lon were added based on the site_code (2007 site_codes are the same locations as 2008).

Data Files

File
seal_counts_2008.csv (Comma Separated Values (.csv), 53.87 KB) MD5:72535028c0ca4c0387d01ae142a587f0 Primary data file for dataset ID 3707

More Information about this dataset

Funding Sources

Funding Source	Award Number
NSF Division of Ocean Sciences	OCE-0550443

Deployments

Deployment	Synonyms	Start Date	Platform	Investigator
Aerial_Survey_2008_SRtP		2008-07-17	Cessna-185	Alejandro Acevedo-Gutierrez (Chief Scientist)	data info

Instruments

Camera

Supplied Description:

Photos were taken using a Nikon D100 with a 200 mm lens.

Instrument Type

Generic Name: Camera

Acronym: camera

Community Identifier: http://vocab.nerc.ac.uk/collection/L05/current/311/

Generic Description:

All types of photographic equipment including stills, video, film and digital systems.

Parameters

Date and time formats are described in python strftime() syntax.

Supplied Name	Supplied description	Supplied Units	Standard Name
date	Month, day, and year in mmddyy format (local time).	mmddyy	date_local
month	2-digit month of year, local time.	mm (01 to 12)	month_local
day	2-digit day of month, local time.	dd (01 to 31)	day_local
year	4-digit year (local time).	YYYY	year
site_code	Numeric identifier for the sampling site.	unitless	Site_ID
lat	Latitude; North = positive. (Added by BCO-DMO; assumes site_codes used in 2008 are the same locations as 2007.)	decimal degrees	lat
lon	Longitude; West = negative. (Added by BCO-DMO; assumes site_codes used in 2008 are the same locations as 2007.)	decimal degrees	lon
time_local	Local time when the survey occurred, in hours and minutes, 24-hour clock.	HH:MM	time_local
species	Name of the species: Phoca vitulina = Harbor seal Mirounga angustirostris = Northern elephant seal Eumetopias jubatus = Steller sea lion	text	species
est_total	Estimated total number of seals.	unitless	no_bcodmo_term
est_pups	Estimated number of pups.	unitless	no_bcodmo_term
count_total	Total number seals, corrected using photos if available.	unitless	count
count_pups	Number of pups, corrected using photos if available.	unitless	count
photo	TRUE = photo was taken; FALSE = no photo was taken.	unitless	no_bcodmo_term
photo_no	The photograph identification number, if a photo was taken.	unitless	no_bcodmo_term
count_type	1 = hauled out; 2 = in the water.	unitless	no_bcodmo_term
count_q_flag	Count quality flag: 1 = slides countable; 2 = slides blurry or similar problem but countable; 3 = seals disturbed after photo or count; 4 = major disturbance (by plane) before plane or count; 5 = major disturbance (other than plane); 6 = slides not countable or estimate >50 and no slides; 7 = miscellaneous reason for concern about count or estimate.	unitless	q_flag
comment	Remarks/comments about the observation.	text	comment

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Dataset: seal_counts_2008