Cross shelf variation in assemblages of Lutjanidae and Lethrinidae in the central Great Barrier Reef

In March 1993, fish traps were deployed on three reefs located across the continental shelf in the central Great Barrier Reef. One reef was nearshore (Pandora Reef), approximately 10 km from the coast; one on the midshelf (Rib Reef), approximately 50 km offshore; and one on the outershelf (Myrmidon), approximately 100 km offshore.Traps were deployed day and night on the protected leeward slopes of the midshelf and outershelf reefs in depths of 15-40 m, and on the leeward slopes of the nearshore reef in depths of 10-15 m (maximum depth of nearshore reefs). Traps were set in a random manner, at a minimum distance of 50 metres apart and ranged up to a few hundred metres apart in order to reduce possible overlap in the capture fields of adjacent traps. A total of 48 trap sets (2 days, 2 nights of sampling with 12 traps) were completed on the outershelf, 24 trap sets (1 day, 1 night of sampling) were completed on the midshelf and 36 trap sets (1 day, 2 nights of sampling) were completed inshore.'Day' set traps were set between 05:30 h and 08:30 h and were hauled from 16:30 h onwards, with sorting and processing usually completed by 18:30 h. Soak times during the day varied from 9 to 11 h. 'Night' set traps were set between 16:30 h and 18:30 h, left overnight and were hauled from 05:30 h onwards, with sorting and processing of trap catches usually completed by 08:30 h. 'Night' soak times varied from 12 to 14 h.The catch of each trap was identified to species, measured to the nearest millimetre, then tagged and released.
This study was undertaken to examine and quantify the distribution and abundance of species of the Lutjanidae (snappers) and Lethrinidae (emperors), given the extremely variable physical environmental conditions occurring across the continental shelf in the central Great Barrier Reef region.

1993年3月，研究人员在大堡礁（Great Barrier Reef）中部横跨大陆架的三座珊瑚礁上布设了鱼笼。其中一座为近岸礁：潘多拉礁（Pandora Reef），距海岸约10公里；一座为陆架中部礁：里布礁（Rib Reef），离岸约50公里；最后一座为陆架外缘礁：默米登礁（Myrmidon），离岸约100公里。
鱼笼在陆架中部和外缘礁的保护背风坡布设，水深区间为15至40米；在近岸礁的背风坡布设时，水深为10至15米（近岸礁的最大水深）。所有鱼笼均采用随机方式布设，相邻鱼笼间距不小于50米，最大间距可达数百米，以此降低相邻鱼笼捕获区域重叠的可能性。
陆架外缘礁累计完成48组鱼笼布设，采用12个鱼笼开展2天2夜的采样工作；陆架中部礁完成24组鱼笼布设，对应1天1夜的采样周期；近岸区域完成36组鱼笼布设，对应1天2夜的采样周期。
日间布设的鱼笼于05:30至08:30之间完成布设，于16:30后起笼，渔获分拣与处理工作通常于18:30前完成，日间鱼笼水下布放时长为9至11小时。夜间布设的鱼笼于16:30至18:30之间完成布设，整夜放置，于次日05:30后起笼，渔获分拣与处理通常于08:30前完成，夜间鱼笼水下布放时长为12至14小时。
每个鱼笼的渔获均被鉴定至物种水平，测量精度精确至1毫米，随后进行标记并放流。
鉴于大堡礁中部大陆架区域的物理环境条件存在极强的变异性，本研究旨在调查并定量分析笛鲷科（Lutjanidae，鲷类）与裸颊鲷科（Lethrinidae，皇帝鱼）物种的分布与丰度。