Fish and benthic community surveys in the Lihou Reef National Nature Reserve (Coral Sea)

Fish and benthic communities were surveyed on five reefs within the Lihou Reef National Nature Reserve between 15-18 March 2004. The reefs surveyed were Anne Cay, Georgina Cay, Lorna Cay, Middle Cay and Turtle Cay. In choosing survey reefs, consideration was given to the likelihood of the reefs being revisited. For this reason reefs were chosen with sand cays, where previous bird and turtle work had been conducted, and preferably where there was a reasonable anchorage. Also included were reefs visited in 1984 by Ayling and Ayling who conducted the only previously documented survey of Lihou Reef (Ayling AM, Ayling AL (1985) Coral Sea Surveys. Unpublished Report to Australian National Parks and Wildlife Service, Canberra).Restrictions were placed on diving, due to the remote location of the Reserve and surveys were limited to depths of around 9 metres. Weather conditions were not ideal for working on these exposed reefs, with a large swell on most days and winds in excess of 20 knots much of the time. A Cyclone Watch (which formally became Cyclone Grace on 21 March) on the afternoon of 18 March meant that the field trip had to be cut short by several days. Species level data and crude abundance estimates of the benthic communities were obtained using a rapid visual assessment protocol (RAP). Video transect surveys were used to obtain rigorous abundance estimates of biota at a finer taxonomic resolution.Species composition data and crude abundance estimates of the fish communities were obtained using a timed swim, rapid visual census method. Visual census transects provided more rigorous density estimates of a select group of species and a solid baseline for future monitoring surveys.Thirteen species of Holothuria (bêche-de-mer), crown of thorns starfish (COTS) and giant clams (Tridacna gigas and Tridacna derasa) were surveyed along transects, using manta tow, snorkel swims and SCUBA searches.SCUBA searches, along transects, were used to provide information on numbers of COTS in defined size classes, COT scars, Drupella (a coral eating snail) and other sources of coral mortality including coral bleaching and coral disease.Two temperature loggers were also deployed at Turtle Cay, Lihou Reef.
The surveys were undertaken to provide a baseline against which future changes can be assessed and to allow the present 'status' of the reefs in the Reserve to be compared with other reef systems where similar surveys have been conducted.
The Lihou Reef National Nature Reserve (Reserve) is one of two protected areas in the Coral Sea Region. The Reserve is located some 400 kilometres east of Townsville, Queensland. The Reserve was declared on 16 August 1982 and the first plan of management prepared under the National Parks and Wildlife Conservation Act 1975, came into effect in 1989. The Coringa-Herald National Nature Reserve and Lihou Reef National Nature Reserve Management Plan states that the reef system is to be managed as a strict nature reserve - World Conservation Union (IUCN) category Ia. Such reserves are primarily for scientific research to ensure habitats, ecosystems, and native species are preserved in as undisturbed a state as possible. The Reserve also forms part of the National Representative System of Marine Protected Areas (NRSMPA).

2004年3月15日至18日期间，研究团队对利胡礁国家自然保护区（Lihou Reef National Nature Reserve）内的5座礁体开展了鱼类与底栖生物群落调查。本次调查涉及的礁体包括安沙洲（Anne Cay）、乔治娜沙洲（Georgina Cay）、洛娜沙洲（Lorna Cay）、中沙洲（Middle Cay）与海龟沙洲（Turtle Cay）。

本次调查礁体的遴选充分考量了后续重访该位点的可行性，因此优先选取了已开展过鸟类与海龟相关研究、且具备良好锚泊条件的沙礁礁体。此外，本次调查还纳入了1984年艾林夫妇（Ayling AM、Ayling AL）曾到访过的礁体——此前仅有的公开利胡礁调查记录正是由该二人完成（Ayling AM, Ayling AL, 1985. 珊瑚海调查：提交至堪培拉澳大利亚国家公园与野生动物服务处的未刊报告）。

由于保护区地处偏远，潜水作业存在诸多限制，本次调查仅开展于约9米水深范围内。本次作业的暴露礁体区域天气条件不佳：多数时段存在强涌浪，且风速多超过20节。3月18日下午发布的气旋预警（该预警于3月21日正式升级为格雷斯气旋（Cyclone Grace））导致本次野外作业被迫提前数日结束。

底栖生物群落的物种层级数据与粗略丰度估算，采用快速视觉评估方案（RAP）完成采集；视频样带调查则用于获取更高分类学分辨率下的生物类群严谨丰度估算值。鱼类群落的物种组成数据与粗略丰度估算，则通过计时游速快速视觉普查法完成采集。视觉普查样带可针对特定类群提供更为精准的密度估算结果，同时为后续监测调查搭建可靠的基准基线。

本次沿样带采用蝠鲼拖曳法、浮潜及水肺搜索（SCUBA searches）方式，对13种海参属（Holothuria，俗称海黄瓜/ bêche-de-mer）、长棘海星（Crown of Thorns Starfish，简称COTS）及砗磲（Tridacna gigas与Tridacna derasa）开展了调查。沿样带开展的水肺潜水调查，还用于统计特定尺寸分级下的长棘海星数量、长棘海星侵害疤痕、棘冠螺（Drupella，一种食珊瑚螺类）以及包括珊瑚白化与珊瑚病害在内的其他珊瑚死亡诱因相关数据。

本次调查还在利胡礁的海龟沙洲部署了2台温度记录仪。

本次调查旨在构建基准基线，用于评估后续的生态变化，并可将保护区内礁体的当前“状态”与其他开展过同类调查的礁体系统进行对比。

利胡礁国家自然保护区是珊瑚海区域仅有的2处保护区之一，该保护区位于昆士兰州汤斯维尔市以东约400公里处。保护区于1982年8月16日正式设立，依据1975年《国家公园与野生动物保护法》编制的首版管理计划于1989年生效。《科林加-赫尔德国家自然保护区与利胡礁国家自然保护区管理计划》明确，该礁体系统将按照严格自然保护区——世界自然保护联盟（International Union for Conservation of Nature，简称IUCN）Ia类标准进行管理。此类保护区的核心功能为科学研究，以确保栖息地、生态系统与本土物种尽可能处于未受干扰的保存状态。该保护区同时为国家海洋保护区代表性体系（National Representative System of Marine Protected Areas，简称NRSMPA）的组成部分。