Surveys to locate juvenile crown-of-thorns starfish (Acanthaster planci) on the Great Barrier Reef

In 1989, reefs in the central GBR were surveyed to locate high density populations of larger (5-15 cm) juvenile crown-of-thorns starfish (Acanthaster planci). Preliminary surveys were undertaken at two inshore reefs (Hayman Island and Reef No. 20-019) in October 1989. During November 1989, searches were carried out at different depths at 45 sites on 12 reefs. The reefs surveyed were 19-123, 19-124, 19-131, 19-138, Bait, Bowden, Davies, Hope, Little, Oublier, Rafter and Stanley.All reefs surveyed were relatively small and had supported large numbers of starfish during the 1970s. At the time of survey they either supported large numbers of adult starfish or were located immediately to the south of the main concentration of reefs with outbreaks. A range of reef types across the continental shelf were surveyed. The perimeter of each reef was surveyed by manta tow to identify sites with relatively high live coral cover and small areas of dead coral then 3 or 6 sites were selected for more intensive SCUBA swim searches.SCUBA searches were undertaken by divers along 4 depth contours at each site: reef crest/flat, 5m, 10m and 15m. Where this was impractical, the divers swam parallel to each other and covered the maximum practical depth range between the crest and the base of the reef slope. The four divers swam slowly along their respective depth contours for a set period of twenty minutes, covering a distance of approximately 100m. Whilst swimming, each diver scanned approximately 1m either side of the swim path looking for any small starfish or evidence of their presence. All small areas of recently dead coral were closely examined and if no starfish were found, then an attempt was made to determine the cause of mortality. The following observations were recorded during each 20 minute swim search: number of adult crown-of-thorns starfish, number and size of juvenile (Additional dives were undertaken at night on Stanley and Bait Reefs, in areas where numerous small coral scars had been recorded during the day. These involved 5 divers who searched for juveniles within an area approximately 100x50m, over a 90 minute period.
Surveys were undertaken to locate high density populations of juvenile crown-of-thorns starfish (Acanthaster planci), which could be used in further studies of recruitment, predation and population dynamics of the juvenile stage this starfish.
Only 14 juvenile starfish were found in the 1989 survey.Observations have been expanded since 1989 and some aspects have been incorporated into the ongoing AIMS Long Term Monitoring Program - refer to the separate metadata record on 'Agents of coral mortality'.

1989年，研究人员对大堡礁（Great Barrier Reef, GBR）中部的珊瑚礁开展调查，以寻找体型介于5~15厘米的高密度幼体长棘海星（Acanthaster planci，crown-of-thorns starfish）种群。1989年10月，研究人员在两座近岸珊瑚礁（海曼岛礁与20-019号礁）完成预调查。同年11月，研究人员在12座珊瑚礁的45个采样点开展不同水深的搜索作业。本次调查覆盖的珊瑚礁包括19-123、19-124、19-131、19-138、贝特礁（Bait）、鲍登礁（Bowden）、戴维斯礁（Davies）、霍普礁（Hope）、利特尔礁（Little）、乌布利耶礁（Oublier）、拉夫特礁（Rafter）与斯坦利礁（Stanley）。
所有被调查的珊瑚礁均规模较小，且在20世纪70年代曾承载过大量长棘海星种群。调查开展时，这些礁体要么仍拥有高密度的成年长棘海星，要么紧邻暴发虫害的珊瑚礁主集群南侧。研究人员对大陆架上的多种珊瑚礁类型进行了调查。研究人员采用帆式拖曳普查法（manta tow）对每座珊瑚礁的周边区域进行勘查，以筛选出活珊瑚盖度较高、死珊瑚分布面积较小的点位，随后从中选取3至6个点位开展更为精细的水肺潜水（SCUBA）泳道搜索作业。
潜水员在每个点位沿4条深度等高线开展搜索：礁冠/礁坪、5米、10米与15米水深。若该方案不可行，则潜水员会以平行泳道前进，覆盖礁坡从礁冠到坡底的最大可行水深范围。4名潜水员以缓慢速度沿各自的深度等高线行进，持续20分钟，行进距离约为100米。行进过程中，每名潜水员会对泳道两侧各约1米的区域进行扫描，以寻找小型长棘海星或其活动痕迹。对所有近期出现的小型死珊瑚区域均进行了细致排查；若未发现海星，则尝试确定珊瑚死亡的诱因。在每次20分钟的泳道搜索过程中，需记录以下观测数据：成年长棘海星的数量，幼体长棘海星的数量与体型。此外，研究人员在斯坦利礁与贝特礁的日间调查中发现多处小型珊瑚疤痕区域，随后在夜间开展了额外潜水作业：5名潜水员在约100×50米的区域内开展搜索，持续时长90分钟，以寻找幼体长棘海星。
本次调查旨在寻找高密度的幼体长棘海星种群，以支撑该物种幼体阶段的补充、捕食与种群动态等后续研究。1989年的本次调查仅发现了14只幼体长棘海星。自1989年起，相关观测工作得到了拓展，部分内容已纳入澳大利亚海洋科学研究所（AIMS）长期监测项目——相关细节可查阅题为《珊瑚死亡诱因》（Agents of coral mortality）的独立元数据记录。