Data for: The use of macroalgal habitats by juvenile rabbitfishes on an inshore reef

Background:Macroalgal beds are increasingly recognised as nursery habitats for coral reef fish, however, the extent to which they are used as a source of food and/or a refuge from predation remain largely unexplored. Here, we investigate the distribution, feeding behaviour, diet, and predation risk for juvenile rabbitfish in macroalgal habitats on Orpheus Island, Great Barrier Reef.

Methods:Data was collected through belt transects and point intercept transects. Behavioural feeding observations were conducted to assess primary dietary targets of juvenile S. doliatus within macroalgal habitats. A minimum of 50 focal observations were conducted within macroalgal habitats on the reef flat at each of the three sites, with all feeding observations being conducted between 0900h and 1600h. After locating a juvenile S. doliatus (i.e., between 10-50mm TL), a diver would estimate the total length (TL) of the individual to the nearest 0.1cm then wait 30 seconds to ensure the fish had acclimated to the diver presence prior to commencing the observation period. Each individual would then be followed for an additional 1-2 minutes (mean = 1.3 minutes) during which the number of bites, and the substratum of each bite was recorded. To supplement the behavioural feeding observations, a total of 16 juvenile S. doliatus between 23-45mm TL were collected from the reef flat using a hand net, barrier net, and a dilute clove oil solution (1:10 clove oil to ethanol). Additionally, 16 juvenile S. canaliculatus, and two juvenile S. spinus between 23-55mm TL were collected opportunistically using a hand net, barrier net, and a dilute clove oil solution. The standard and total length of each juvenile fish collected was measured to the nearest 0.1cm using callipers. Using a dissection microscope the entire alimentary tract of each individual was removed and carefully uncoiled, and the content of the stomach removed and placed into a small petri dish. The stomach content was then carefully spread across the petri dish and a photo was taken of the stomach content at 7-14x magnification. A series of random points were then overlaid on each photo with a minimum of 20 points overlaying dietary content. The dietary item found directly under each point was identified to the lowest taxonomic level. Algal material was identified to genus (where possible) or algal function group (following Steneck and Dethier 1994). Consequently, dietary items were placed into one of six categories: Sargassum, foliose algae, corticated terete algae, filamentous algae, unidentified algae and detritus. Proportion of diet was then calculated by dividing the count of each category by the total count of all categories.

This data record contains:
5 csv and 3 excel files:

one with count and size data of small fish (10cm) from two time series
one with benthic point intercept data from two time series
one of focal feeding observations and proportion of bites taken on substrates
one with proportions of gut content from juvenile rabbitfishes (3 species: S. doliatus, S. canaliculatus, S. spinus)
one with proportions of gut content from juvenile and adult rabbitfishes (3 species: S. doliatus, S. canaliculatus, S. spinus)
one with proportions of gut content from juvenile S. doliatus
one with data from focal feeding observations of only S. doliatus

Files available and archived in Open Document Format (.ods)
Software/equipment used to create/collect the data: R Studio version 4.4.0; Microsoft Excel Version 16.89.1
Software/equipment used to manipulate/analyse the data: R studio

研究背景：大型藻床（macroalgal beds）作为珊瑚礁鱼类的育苗栖息地已日益受到学界认可，但其作为食物来源和/或躲避捕食的庇护所的利用程度仍未得到广泛探索。本研究针对大堡礁奥费斯岛（Orpheus Island）大型藻栖息地下的幼体兔鱼，调查其分布、摄食行为、食性及捕食风险。

研究方法：数据通过带状样带法（belt transects）与点截距样带法（point intercept transects）采集。开展摄食行为观察以评估大型藻栖息地下幼体带纹篮子鱼（S. doliatus）的主要摄食目标。在三个样点的礁坪大型藻栖息地中，各开展至少50次焦点取样观察，所有摄食观察均于09:00至16:00间进行。定位幼体带纹篮子鱼（体长10~50mm TL）后，潜水员先估算其总长度（total length, TL）至0.1cm精度，随后等待30秒以确保鱼类适应潜水员的存在，再启动观察期。随后对每条个体追踪1~2分钟（平均1.3分钟），记录咬食次数及每次咬食的底质类型。
为补充摄食行为观察数据，使用手网、拦网与稀释丁香油-乙醇溶液（体积比1:10）从礁坪采集16尾体长23~45mm的幼体带纹篮子鱼。此外，通过手网、拦网与稀释丁香油-乙醇溶液偶捕获得16尾体长23~55mm的幼体斑篮子鱼（S. canaliculatus）及2尾幼体棘篮子鱼（S. spinus）。使用游标卡尺测量所有采集幼鱼的标准长度与总长度，精度至0.1cm。借助解剖显微镜（dissection microscope）取出每条个体的完整消化道并小心展开，剥离胃内含物置于培养皿中。将胃含物均匀铺展于培养皿后，以7~14倍放大倍率拍摄照片。在每张照片上叠加至少20个随机落点，识别每个落点正下方的食物类群至最低分类学层级。藻类材料尽可能鉴定至属级，或遵循Steneck与Dethier 1994的分类标准归入藻类功能群。最终将食物类群划分为六大类别：马尾藻属（Sargassum）、叶状藻类（foliose algae）、具皮层圆柱状藻类（corticated terete algae）、丝状藻类（filamentous algae）、未鉴定藻类及碎屑（detritus）。通过将每类食物的计数除以总计数，计算各类别在食性中的占比。

本数据集包含：
5个CSV格式文件与3个Excel格式文件，具体如下：
1. 包含两个时间序列采集的、体长10cm左右小型鱼类的数量与体长数据
2. 包含两个时间序列的底栖点截距调查数据
3. 包含焦点摄食观察记录及底物咬食占比数据
4. 包含3种幼体兔鱼（带纹篮子鱼S. doliatus、斑篮子鱼S. canaliculatus、棘篮子鱼S. spinus）的胃含物占比数据
5. 包含3种兔鱼（带纹篮子鱼S. doliatus、斑篮子鱼S. canaliculatus、棘篮子鱼S. spinus）的幼体与成体胃含物占比数据
6. 包含幼体带纹篮子鱼的胃含物占比数据
7. 仅包含带纹篮子鱼的焦点摄食观察数据

所有文件以开放文档格式（Open Document Format, .ods）归档。
数据采集与创建所用软件/设备：R Studio 4.4.0版本；微软Excel 16.89.1版本。
数据处理与分析所用软件/设备：R Studio。