MMS Low Altitude Survey 1980-1983

Minerals Management Service

This dataset is from the marine mammal and seabird surveys of central and northern California studies: Central/northern California - low aerial [birds and mammals] study code: CL, Contract number: 14-12-0001-29090, Principal investigator: Thomas P. Dohl, Center for Marine Studies, University of California, Santa Cruz

Time period: February 1980 through June 1983
Study area: Shelf, slope, and offshore waters to a distance of 100 nm off the California coast from Point Conception to the California-Oregon boundary.

Methodology: Offshore transect surveys were flown twice-monthly at two different altitudes (200 ft and about 750-1,000 ft ASL) along approximately 40 east-west transect lines extending an average of 60 nm offshore. The transects sampled on a given survey were selected randomly from a set of 92 standard (predetermined) lines spaced at intervals of 5’ of latitude. Standard transects provided systematic coverage of shelf, slope, and offshore waters in the study area. Sightings of seabirds, pinnipeds, and sea otters were recorded only on low-altitude surveys. Sightings of cetaceans and turtles were recorded on both low- and high-altitude surveys. Seabird sightings were recorded only on the shaded side of the aircraft within a strip transect of 50 m width. Marine mammal and turtle sightings were recorded within an unbounded corridor on both high- and low-altitude surveys, but only the shaded side of the aircraft was searched on the low-altitude surveys. Cross-legs connecting standard transects were searched only on high-altitude surveys. Offshore cross-legs were searched on both sides of the aircraft, while only the nearshore side was searched on cross-legs along the coast. Declination angle was measured and noted for each marine mammal/turtle sightings and later used to calculate a probability density function of frequency with right-angle sighting distance. Navigation was by Loran and VLF-Omega.

Databases produced: Three databases of sightings at sea were produced by these studies (data on numbers of seabirds and pinnipeds on land were also collected but are not addressed in the present study). These include: 1) sightings of cetaceans and turtles recorded on 36 high-altitude aerial surveys, 2) sightings of cetaceans, pinnipeds, sea otters, and turtles recorded on 36 low-altitude aerial surveys, and 3) sightings of seabirds on 36 low-altitude aerial surveys. Each sighting database is accompanied by files providing the search effort on transect and environmental characteristics of the waters surveyed (e.g., sea surface temperature).

To determine species composition, distribution, abundance, and seasonal variation for marine mammal and seabird populations, provide a description of habitat use, and identify areas of special biological importance to these populations in the central and northern California study area.

[2020-09-30] The following invalid species names were corrected according to the Integrated Taxonomic Information System (ITIS).
Branta nigricans: Branta nigricans (175013) => Branta bernicla nigricans (714723)
Bonaparte's Gull: Larus philadelphia (176839) => Chroicocephalus philadelphia (824040)
Caspian Tern: Sterna caspia (176924) => Hydroprogne caspia (176935)
Sterna elegans: Sterna elegans (176925) => Thalasseus elegans (176931)
Great Egret: Casmerodius albus (174810) => Ardea alba (554135)
Manx Shearwater: Puffinus puffinus puffinus (174556) => Puffinus puffinus (174555)
Red Phalarope: Phalaropus fulicaria (554376) => Phalaropus fulicarius (176734)
Royal Tern: Sterna maxima (176922) => Thalasseus maximus (824142)
Larus tridactyla (176874) => Rissa tridactyla (176875)
Brachyramphus hypoleuca (176999) => Synthliboramphus hypoleucus (177011)
Larus sabini (176865) => Xema sabini (176866)
Phalacrocorax olivaceus (174722) => Phalacrocorax brasilianus brasilianus (824220)

Overview

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.
Only minimum required attributes are visible and downloadable online. Other attributes may be obtained upon provider's permission.

Attributes in dataset

Attribute (table column)	Description
id	ID
study	Study code
platform	Platform code
on_	On (Y) or off (N) effort
effdate	effort date
date_0	Date in original format
date	Date of the observation
time_0	Time in original format
time	Time of the observation
species	Species name
species_code	Species code
number	Group size
lat	Latitude in decimal degrees
lon	Longitude in decimal degrees
width	Width of the transect
newborns	Number of calves
males	Number of males
females	Number of females
age	Age
sex	Sex
plumage	Plumage
assoc	Association
direction	Direction
group_	Group size
behavior	Behavior code
altitude	Altitude in feet
decline	Decline
distance	Distance
perpdist	definition not provided
reldir	definition not provided
distcode	definition not provided
comment	Comments
weather	Weather code
clouds	Cloud code
wind	Wind
seastatus	Sea status
glaredir	Glare direction
glare	Glare
seatemp	Sea temperature (-99: not available)
record	Record No.
geom	Geometry field added by OBIS-SEAMAP
oid	Unique ID number (generated by OBIS-SEAMAP)