Volusia 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 and relative abundance 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 kts. 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 4–6 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 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 turtle sightings 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 Volusia County were flown twice a month from July 2002 to July 2004. FWC staff members were observers for these flights. The survey area includes the northern Volusia County border south along Indian River and along Spruce Creek to the southern Volusia County border.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，会借助航空分布调查来确定海牛（manatee）的季节分布与相对丰度。大多数调查使用四座高翼小型飞机（塞斯纳172或182）开展，飞行高度为500至1000英尺，飞行速度为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4至6小时，调查普遍以每两周一次的频率开展，持续两年。本调查聚焦于海牛及其主要食物来源海草所栖息的浅海近岸水域，以最大化海牛的统计数量。飞行航线呈与海岸线平行的弧形，当发现海牛时，飞机会盘旋直至统计出该群体内的所有个体数量。远海海域通常不在调查范围内。海豚与海龟的目击记录则为偶发采集。所有航空调查数据均先记录于纸质地图，之后录入地理信息系统（GIS）形状文件（shapefile）以开展空间分析。地理信息系统（GIS）是一种可对数据进行空间可视化并开展空间分析的计算机软件系统。沃卢西亚县的调查于2002年7月至2004年7月期间，每月开展两次飞行调查。本次飞行调查的观察员均为FWC工作人员。调查范围北起沃卢西亚县北部边界，沿印第安河向南延伸，并经斯普鲁斯溪至沃卢西亚县南部边界。