Indian River County 2002-2004 Manatee Distribution Survey Observations

Aerial distributional surveys are used by marine mammal biologists from FWC and other agencies to determine the seasonal distribution of manatees. Most surveys are conducted from small, four-seat, high-winged airplanes (Cessna 172 or 182) flying at a height of 500-1000 ft at a speed of 70-90 knots. Small helicopters may be used instead of fixed wing aircraft in urban areas or where waters are particularly opaque and hovering may be required. Flights are usually three to five hours long and are most commonly flown every two weeks for two years. The surveys are designed to maximize the manatee counts by concentrating on shallow nearshore waters where manatees and their primary food source, sea grasses, are located. Flight paths curve along parallel to the shoreline, and the airplane circles when manatees are spotted until a count of the number of animals in each group is obtained. Offshore waters are usually not surveyed. Dolphin and sea turtles are recorded opportunistically. All aerial data are recorded on paper maps and entered into a GIS shapefile for spatial analysis. GIS is a computer software system for representing data spatially and for conducting spatial analyses. Surveys of Indian River County surveys were flown twice a month from July 2002 to July 2004 by FWC staff memebers. Survey area included the Atlantic Coast, Intracoastal Waterway and small tributaries of Indian River County.佛罗里达鱼类与野生动物保护委员会（FWC）及其他机构的海洋哺乳动物生物学家，借助航空分布调查来确定海牛的季节分布格局。多数调查采用小型四座高翼飞机（赛斯纳172或182型）执行，飞行高度为500至1000英尺，飞行速度70至90节。在城市区域或水体透明度极低、需要悬停作业的场景中，可使用小型直升机替代固定翼飞机。单次飞行时长通常为3至5小时，调查周期普遍为两年，每两周执行一次飞行任务。本次调查聚焦海牛及其主要食物海草栖息的浅海近岸水域，以最大化海牛的统计数量。飞行航线沿海岸线平行弯曲延伸，当发现海牛时，飞机会盘旋直至完成该群体个体数量的统计。远海海域通常不纳入调查范围。海豚与海龟的观测记录采用机会性采集方式。所有航空调查数据均先记录于纸质地图，随后导入地理信息系统（GIS）形状文件（shapefile）以开展空间分析。地理信息系统（GIS）是一类可实现数据空间可视化与空间分析的计算机软件系统。印第安河县的航空调查任务由FWC工作人员于2002年7月至2004年7月期间执行，每月开展两次飞行调查。调查范围涵盖印第安河县的大西洋沿岸区域、沿海内陆航道（Intracoastal Waterway）以及小型支流水域。