St. Johns, Flagler, & Volusia counties 1991-1993 Manatee Distribution Survey Observations

Aerial distribution 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 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 six 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 around the state 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 St. Johns, Flagler and Volusia County were flown twice a month from March 1991 to November 1993. FWC staff members were observers for these flights. The survey area includes the coastal, estuarine, and riverine waters of St. Johns, Flagler and Volusia counties. The St. Johns River or tributaries were not included. The survey extended from the Duval-St. Johns county line south to Mosquito Lagoon at the Volusia-Brevard county line. The water bodies included in the survey are Tolomato, Guana, Matanzas, San Sebastian, Tomoka and Halifax rivers; Turnbull Bay and Salt Run; Spruce Creek and Palm Coast canal systems.佛罗里达鱼类和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，会开展航空分布调查以探明海牛的季节性分布规律。绝大多数调查使用小型四座高翼飞机（赛斯纳172或182）执行，飞行高度维持在500至1000英尺，航速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，可改用小型直升机替代固定翼飞机。单次飞行时长通常为6小时，调查频率多为每两周一次，持续周期为两年。本调查聚焦该州周边海牛及其主要食物来源海草所在的浅海近岸水域，以最大化海牛计数效率。飞行航线呈与海岸线平行的曲线，发现海牛时，飞机会盘旋直至完成该群体个体数量的计数。远海海域通常不纳入调查范围。海豚与海龟的目击情况将被机会性记录。所有航空调查数据均记录于纸质地图，并被录入地理信息系统（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。1991年3月至1993年11月期间，针对圣约翰斯县、弗莱格勒县与沃卢西亚县的调查以每月两次的频率开展，本次飞行的观测员均为FWC工作人员。调查范围涵盖圣约翰斯县、弗莱格勒县与沃卢西亚县的沿岸、河口及河流水域，但圣约翰斯河及其支流未被纳入。调查范围北至杜瓦尔县与圣约翰斯县县界，南至沃卢西亚县与布雷瓦德县县界的蚊子潟湖。本次调查涵盖的水体包括托洛马托河、瓜纳河、马坦萨斯河、圣塞瓦斯蒂安河、托莫卡河与哈利法克斯河；特恩布尔湾与盐流水道；斯普鲁斯溪与棕榈海岸运河系统。