Feeding behaviours and lengths of coral reef fishes obtained via stereo-video in Eilat, Gulf of Aqaba, Red Sea

DOI

We used remote underwater stereo-video footage to assess the feeding behaviour of benthic herbivorous fishes on a degraded model coral reef.Sampling took place on the reef in front of the Inter-University Institute for Marine Sciences (IUI) (29°30'7.0"N, 34°55'3.7"E) in Eilat (Israel, Gulf of Aqaba) between 8th and 14th of March 2018. In preparation for the surveys, calibrated stereo-video setups, each consisting of 2 GoPro (4 x Hero 5 and 2 x Hero 4) cameras, were mounted on a total of 3 racks (Neuswanger et al. 2016; doi:10.1139/cjfas-2016-0010). For each sampling day, racks were sequentially installed at a depth of between 2 to 3 m and set to record continuously. Setting up the cameras was the sole purpose of a dive to minimize the disturbance caused to the site. Sites were chosen based on the criteria that a variety of grazable substratum (not just live coral) must be present, as there are a range of micro-habitats within the grazable substrate for fishes that require specific categorisation (Green & Bellwood, 2009; https://repository.library.noaa.gov/view/noaa/926). Therefore, sites with a heterogenous mixture of available benthic substrate cover such as live coral and epilithic algal turf (EAT) on standing dead coral, bare rocks, coral rubble and sand were generally preferred. Because grazing rates in surgeonfishes are highest during midday, the majority of our filming was; conducted between 11:00 – 15:00 (Montgomery et al. 1989 (doi:10.1016/0022-0981(89)90127-5); Fouda and El-Sayed 1994). The analysable video was accumulated from 15 rack placements and comprised 22.9 hrs of footage in total.At the beginning of each recording, we placed a 1 x 1 m PVC quadrat in front of the cameras. We quantified the substrate cover of each quadrat by taking a long shot photograph. These images were uploaded to the program SketchAndCalc Version 1.1.2 (iCalc Inc), in which the 1 x 1 m quadrat was calibrated so each transformed image contained roughly the same number of cells. This equated to ~1000 cells per image, each being around 5 cm². The images with the canvas imprinted upon them were subsequently exported and annotated with each form of substratum having a corresponding colour. Annotated cells were counted and relative substrate cover (in %) was calculated.We then proceeded to measure fish total length (mm), bite rate (bites per min), and the distance between each consecutive bite (bite distance, in mm) only within the delimited quadrat area during the entirety of the recorded video footage. In total, we identified 28 different fish species (from 13 families). We calculated individual fish mass according to the following formula: mass = aTL^b^, where a and b for each species were informed from FishBase (www.fishbase.org). The initial 15-min of each video, however, were discarded to allow for surgeonfishes to resume normal behaviour after the quadrat was removed and divers left the site (Acanthuridae dataset). To calculate abundances across all species, only the subsequent 45-min of recording were used for analysis (All species dataset). The time at which a single fish entered the quadrat to take bites from substrates until the time when it exited constituted a feeding event. For each feeding event, all bites were collated and then standardized to obtain bites per minute. Further, for each feeding event we averaged the distances between consecutive bites to obtain bite distance. We conducted all measurements in VidSync Version 1.661 (Neuswanger et al. 2016; doi:10.1139/cjfas-2016-0010). For the two surgeonfish species we calculated Manly's feeding ratios (Manly et al. 2002; doi:10.2307/5247), which illustrate an individual's use of each substrate category (number of bites) in relation to the availability of substrate type across the entire reef.

Identifier
DOI https://doi.pangaea.de/10.1594/PANGAEA.932686
Metadata Access https://ws.pangaea.de/oai/provider?verb=GetRecord&metadataPrefix=datacite4&identifier=oai:pangaea.de:doi:10.1594/PANGAEA.932686
Provenance
Creator Lilkendey, Julian; Meares, Michael; Zhang, Jingjing; Sabetian, Armagan
Publisher PANGAEA - Data Publisher for Earth & Environmental Science
Publication Year 2021
Rights Data access is restricted (moratorium, sensitive data, license constraints)
OpenAccess false
Representation
Language English
Resource Type Dataset
Format text/tab-separated-values
Size 4841 data points
Discipline Earth System Research
Spatial Coverage (34.917W, 29.502S, 34.919E, 29.505N); Red Sea/Gulf of Aqaba
Temporal Coverage Begin 2018-03-08T16:30:00Z
Temporal Coverage End 2018-03-14T11:08:00Z