Lee County 1994-1995 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 4-5 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 Lee County were flown twice a month from October 12, 1994 to November 15, 1995. FWC staff members were observers for these flights. The survey area includes most of the rivers and coastal waters of Lee County. The major bodies of water include Caloosahatchee and Orange Rivers, San Carlos and Estero Bays, Matlacha Pass and Pine Island Sound. Many undeveloped areas that are under state or federal management were part of the study area.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，会借助航空分布调查来确定海牛的季节性分布范围。多数调查采用四座小型高翼飞机（塞斯纳172或182）开展，飞行高度设定为500至1000英尺，飞行速度为70至90节。在城区、水体浑浊且需要悬停作业的区域，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5小时，且连续两年内每两周开展一次调查飞行。本次调查以最大化海牛观测数量为目标，重点覆盖全州范围内海牛及其主要食物来源海草栖息的近岸浅水区。飞行航线沿平行于海岸线的弧形延伸，发现海牛后飞机会盘旋停留，直至完成对每一群海牛的个体数量统计。远海水域通常不在调查范围内。观测过程中偶遇的海豚与海龟会被顺带记录。所有航空观测数据均会记录于纸质海图，随后录入地理信息系统（Geographic Information System, GIS）形状文件以开展空间分析。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。1994年10月12日至1995年11月15日期间，李县的调查飞行每月开展两次。本次飞行的观测员均为FWC工作人员。本次调查的覆盖范围包含李县境内绝大多数河流与近岸海域。主要水域包括卡卢萨哈奇河、奥兰治河、圣卡洛斯湾、埃斯特罗湾、马特拉查水道以及派恩岛湾。诸多由州级或联邦机构管理的未开发区域也被纳入本次研究范围。