MMS High Altitude Survey 1980-1983

Original provider: Minerals Management Service Dataset credits: Minerals Management Service Abstract: This dataset is from the marine mammal and seabird surveys of central and northern California studies: Central/northern California - high aerial [Cetaceans] study Code: CH, Contract number: 14-12-0001-29090, Principal investigator: Thomas P. Dohl, Center for Marine Studies, University of California, Santa Cruz 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).原始提供方：矿产管理服务局（Minerals Management Service） 数据集贡献方：矿产管理服务局 摘要：本数据集源自加利福尼亚州中部与北部海域的海洋哺乳动物及海鸟调查研究：加州中北部高空[鲸类（Cetaceans）]研究代码：CH，合同编号：14-12-0001-29090，首席研究员：托马斯·P·多尔（Thomas P. Dohl），加州大学圣克鲁兹分校海洋研究中心。 研究区域：覆盖从康塞普西翁角至加州-俄勒冈州界的加州近岸海域，包含陆架、陆坡及离岸100海里范围内的远海水域。 调查方法：本研究采用近海断面抽样调查方案，沿约40条东西向断面线以两种飞行高度（海拔200英尺及约750-1000英尺（Above Sea Level，ASL））每月开展两次飞行调查，单条断面平均离岸距离达60海里。单次调查所用断面从92条标准预设断面中随机抽取，标准断面以5分纬度间隔布设，可系统覆盖研究区域内的陆架、陆坡及远海水域。 海鸟、鳍足类及海獭的目击记录仅在低空飞行调查中获取；鲸类与海龟的目击记录则在高低空调查中均有记录。海鸟目击仅记录于航空器背光侧的50米宽度条带断面范围内。高低空调查中，海洋哺乳动物与海龟的目击记录均采集于无边界廊道内，但低空调查仅对航空器背光侧进行搜索。连接标准断面的跨向航线仅在高空调查中开展搜索：远海跨向航线需对航空器两侧均进行搜索，而沿海岸线的跨向航线仅搜索近岸一侧。 每次海洋哺乳动物/海龟目击事件均记录了磁偏角，后续用于结合直角目击距离计算频率概率密度函数。导航采用罗兰（Loran）与甚低频-奥米加（VLF-Omega）导航系统。 生成数据库：本研究共生成3份海上目击数据库（同期还收集了陆地上的海鸟与鳍足类数据，但本研究未涉及该部分内容），具体包括：1）36次高空航空调查中记录的鲸类与海龟目击数据；2）36次低空航空调查中记录的鲸类、鳍足类、海獭与海龟目击数据；3）36次低空航空调查中记录的海鸟目击数据。每份目击数据库均附带相关文件，提供断面调查作业量及调查海域的环境特征数据（如海水表面温度）。