Dataset: seal_counts_2007

Name: Visual estimates of seal abundance from aerial surveys conducted by a Cessna-185 in the San Juan Islands, Salish Sea in 2007 (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 2007 (Seal_response_to_prey project)

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Description

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

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;
- Added day, month, and year columns using dates in original data provided.

Data Files

File
seal_counts_2007.csv (Comma Separated Values (.csv), 80.48 KB) MD5:995eb1ce0bd73cb3ad1392694650f330 Primary data file for dataset ID 3706

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_2007_SRtP		2007-03-20	Cessna-185	Alejandro Acevedo-Gutierrez (Chief Scientist)	data info

Instruments

Camera

Supplied Description:

Photos were taken with 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.	mmddyy	date
month	2-digit month of year.	mm (01 to 12)	month
day	2-digit day of month.	dd (01 to 31)	day
year	4-digit year.	YYYY	year
site	Name of the haulout/sampling site.	text	site
site_code	Numeric identifier for the sampling site.	unitless	Site_ID
lat	Latitude; North = positive.	decimal degrees	lat
lon	Longitude; West = negative.	decimal degrees	lon
region	Region identification number.	unitless	region
count_total	Total number of seals.	unitless	count
count_non_pup	Number of seals, excluding pups.	unitless	count
count_pups	Number of pups.	unitless	count

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Dataset: seal_counts_2007