Tomoka River 1985 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 five hours long and are most commonly flown every two weeks for six months. 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 Volusia County (Tomoka River) were flown twice a month from May to November 1985. Staff from FWC, USFWS Sirenia Project, Brevard County and Hobe Sound NWR were observers for these flights. This survey was flown as a part of a larger study that included six east coast counties divided into five survey segments from north to south; Volusia and N. Brevard counties were within segment 1. The survey area includes the Tomoka Basin and Tomoka River.来自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采用航空分布调查，以探明海牛（manatee）的季节性分布规律。绝大多数调查采用四座小型高翼飞机（赛斯纳172或182型）作为执行平台，飞行高度设定为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行器。单次飞行时长通常为5小时，标准执行频次为每两周一次，持续时长共计6个月。本次调查以最大化海牛计数精度为目标，重点覆盖全州范围内海牛及其主要食物来源海草的栖息区域——近岸浅水环境。飞行航线呈与海岸线平行的曲线状，当观测到海牛时，飞机会环绕盘旋，直至完成对该群体个体数量的统计。通常不会对远海水域开展调查。对于偶然观测到的海豚与海龟，亦会一并记录。所有航空调查数据均先记录于纸质地图，随后录入地理信息系统（Geographic Information System, GIS）的形状文件（shapefile）中以开展空间分析。地理信息系统是一类可实现数据空间可视化并开展空间分析的计算机软件系统。1985年5月至11月期间，针对沃卢西亚县（托莫卡河）的调查执行频次为每月两次。本次飞行的观察员来自FWC、美国鱼类和野生动物管理局（USFWS）海牛目项目组、布雷瓦德县以及霍比桑德国家野生动物保护区。本次调查为一项更大规模研究的组成部分：该研究覆盖佛罗里达州东海岸6个县，并自北向南划分为5个调查区段，沃卢西亚县与北布雷瓦德县隶属于第一区段。本次调查区域涵盖托莫卡流域与托莫卡河。