Aerial Survey Counts of Harbor Seals in Lake Iliamna, Alaska, 1984-2013 (NODC Accession 0123188)

This dataset provides counts of harbor seals from aerial surveys over Lake Iliamna, Alaska, USA. The data have been collated from three previously published sources (Mathisen and Kline 1992; Small 2001; ABR Inc. Environmental Research and Services 2011) and newly available data from the NOAA Alaska Fisheries Science Center and the Newhalen Tribal Council. The survey years range between 1984 and 2013. Counts are reported as summed totals across all identified waypoints in the lake for each survey date. The NOAA National Marine Mammal Laboratory (NMML) (Alaska Fisheries Science Center, Seattle, Washington, USA) conducted aerial surveys of Iliamna Lake between 2008 and 2013. Surveys were conducted as part of annual harbor seal survey effort and in collaboration with local community participants and researchers at the University of Alaska. Surveys were flown using high wing, twin engine aircraft (Aero Commander 680, 690 or a de Havilland Twin Otter). Survey altitude was generally 330 m and at an aircraft speed of 120 kts. Surveys were performed seasonally for most years between 2008 and 2013. Surveys were timed so that one survey was conducted while the lake was mostly frozen (Late March/early April), one during pupping (mid July), and often several during the August molt, when the greatest number of seals typically haul out on shore. Surveys were flown, weather allowing, in the mid- to late-afternoon, when the number of seals hauled out was expected to be highest. Aircraft flight track was recorded by GPS and all seals sighted were digitally photographed using a high resolution digital SLR camera with a telephoto zoom lens (up to 400mm). Time, date, latitude, longitude, and altitude were automatically saved into the image metadata or georeferenced post survey using the GPS track and software. The total number of seals hauled out were counted from the digital photographs and recorded for each identified site. Pups were determined by their smaller size, and close proximity (less than 1 body length; either nursing or laying right next) to a larger seal. Pups were no longer recorded beyond about mid-August when many have been weaned and cannot reliably be distinguished from other non-adult seals. In 2009, a collaborative effort between NMML and researchers from the Newhalen Tribal Council (Newhalen Tribal Council 2009) provided 10 additional surveys and similar techniques were used. The raw survey count data from these surveys was provided to NMML. Aerial surveys were authorized under a Marine Mammal Protection Act General Authorization (LOC No. 14590) issued to the NMML. Between 2005 and 2007, ABR, Inc. Environmental Research and Services conducted a series of aerial surveys for harbor seals in Iliamna Lake (ABR Inc. Environmental Research and Services 2011). In addition, earlier counts from surveys conducted by ADFG (Small 2001) and a 1991 census by Mathisen and Kline (Mathisen and Kline 1992) were incorporated into the dataset to expand the historical reach. Geographic coordinates were provided (or, when not provided, determined based on descriptions or phyiscial maps) for each survey site and these sites were compared and merged with locations identified by NMML. In some cases, sites in very close geographic proximity were combined into a single site. The iliamna_totalcounts file provides counts (n=96) and observed weather conditions for each survey date. Both total number of adult seals (adulttotal) and total number of identified pups (puptotal) are provided when available. puptotal is recorded as NA when adults and pups were not distinguished. In these cases, the adulttotal value is presumed to include pups. In addition to the seal count inforamtion, each record includes observed weather variables (airtemp (in ranges of degrees F), windspeed (in ranges of miles per hour), winddirection (cardinal), and descriptive categories for skycondition and precip). The datetime values correspond to local Alaska time.本数据集提供了美国阿拉斯加州伊利亚姆纳湖（Lake Iliamna）航空调查所得的港海豹（harbor seal）数量统计数据。该数据集整合了三份已发表文献的数据（Mathisen与Kline，1992；Small，2001；ABR公司环境研究与服务部，2011），以及美国国家海洋和大气管理局（National Oceanic and Atmospheric Administration, NOAA）阿拉斯加渔业科学中心（Alaska Fisheries Science Center）与纽哈伦部落委员会（Newhalen Tribal Council）最新公开的数据。调查年份跨度为1984年至2013年。每份调查日期对应的统计值为全湖所有已识别航点的海豹总数求和结果。 美国国家海洋和大气管理局国家海洋哺乳动物实验室（National Marine Mammal Laboratory, NMML）（隶属于美国华盛顿州西雅图市阿拉斯加渔业科学中心）于2008年至2013年间开展了伊利亚姆纳湖的航空调查。本次调查作为年度港海豹调查工作的一部分，与当地社区参与者及阿拉斯加大学的研究人员合作开展。调查采用上单翼双引擎飞机执行，机型包括Aero Commander 680、690或德哈维兰双水獭（de Havilland Twin Otter）。调查飞行高度通常为330米，飞行速度为120节（knots）。2008年至2013年的多数年份中，调查按季节开展。调查时间安排如下：一次在湖面大部分封冻时（3月末/4月初），一次在产崽期（7月中旬），通常还会在8月换毛季开展多次调查——此时多数港海豹会上岸栖息，数量达到峰值。若天气允许，调查安排在午后至傍晚时段开展，此时上岸栖息的海豹数量预计最多。飞机飞行轨迹由GPS记录，所有观测到的海豹均使用搭载长焦变焦镜头（最大焦距400mm）的高分辨率数码单反相机进行数字化拍摄。拍摄时间、日期、纬度、经度与高度信息会自动保存至图像元数据中，或在调查结束后通过GPS轨迹与相关软件进行地理配准。 科研人员从数字化拍摄的照片中统计上岸栖息的海豹总数，并为每个已识别的调查站点记录统计结果。幼崽通过体型更小、与成年海豹距离过近（小于1倍体长，处于哺乳或紧挨成年海豹的状态）来识别。8月中旬之后，多数幼崽已断奶，无法与其他亚成体海豹可靠区分，因此不再单独记录幼崽数量。2009年，国家海洋哺乳动物实验室与纽哈伦部落委员会的研究人员合作开展了10次补充调查，采用了相同的调查方法（Newhalen Tribal Council，2009）。本次调查的原始统计数据已提交至国家海洋哺乳动物实验室。本次航空调查依据《海洋哺乳动物保护法》通用授权（授权编号LOC No.14590）开展，授权对象为国家海洋哺乳动物实验室。 2005年至2007年间，ABR公司环境研究与服务部在伊利亚姆纳湖开展了一系列港海豹航空调查（ABR Inc. Environmental Research and Services，2011）。此外，数据集还纳入了阿拉斯加鱼类与狩猎部（Alaska Department of Fish and Game, ADFG）开展的调查早期统计数据（Small，2001），以及Mathisen与Kline于1991年开展的普查数据（Mathisen与Kline，1992），以扩展数据集的历史时间跨度。每个调查站点均提供了地理坐标（若未提供，则根据描述或实体地图确定坐标），并将这些站点与国家海洋哺乳动物实验室识别的站点进行比对与合并。部分地理距离极近的站点会被合并为单个站点。 iliamna_totalcounts文件提供了每份调查日期对应的统计数据（共96条）与观测到的天气状况。若条件允许，数据集会同时提供成年海豹总数（adulttotal）与已识别幼崽总数（puptotal）。若无法区分成年海豹与幼崽，则puptotal字段记为NA（不可用）。此种情况下，adulttotal字段的数值默认包含幼崽数量。除海豹统计信息外，每条记录还包含观测到的气象变量：气温（以华氏度区间表示，airtemp）、风速（以英里/小时区间表示，windspeed）、风向（以方位基点表示，winddirection），以及天空状况与降水的描述类别（skycondition与precip）。记录的日期时间均采用阿拉斯加当地时间。