Colour change and colour phases in Lethrinidae with insights into ecology
Data files
Nov 09, 2023 version files 120.59 KB
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Lethrinidae_colour_change_MaxN_v2.xlsx
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Lethrinidae_colour_change_Metadata_v2.xlsx
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README.md
Abstract
This dataset was collected using seabed stereo-baited remote underwater video systems (Stereo-BRUVS). Seabed stereo-BRUVS consist of two GoPro cameras mounted 80 cm apart on a horizontal base bar, each converging at an angle of four degrees to a common focal point. A galvanised steel mesh bait cage containing ~1 kg of crushed pilchards Sardinops sagax is attached to the end of a 1.5-m-long bait arm. Seabed stereo-BRUVS are deployed at least 200 m apart for a minimum of 60 minutes.
All videos were analysed using Eventmeasure software. Video processing commenced once seabed stereo-BRUVS had settled on the seabed, for a period of 60 minutes. All animals entering the field of view were identified to the lowest possible taxonomic level, and abundance was estimated using the conservative abundance metric MaxN, which is the maximum number of individuals of a given taxon in a single frame (Cappo et al. 2006). Fork length was measured in stereo with individuals measured where they were well positioned relative to the camera and not occluded by other individuals. An Excel database was then created containing the identifications and measurements (where possible) of all animals.
All observations of individuals from the family Lethrinidae were extracted from this database. These observations were reanalysed using EventMeasure to determine frequency of different colour phases (number of individuals currently in each colour phase), physiological colour change (individuals actively displaying physiological colour change while in frame) and the association of physiological colour change with feeding behaviour (individuals displaying colour change while feeding or approaching to feed). Pictures taken from the videos were subsequently processed using Adobe Photoshop 22.2 adjusting brightness, saturation and contrast. Distinction was made between two different colour phases, light (silver/pale) and any form of dark colour (partly or fully dark). No quantitative differentiation of patterns among dark colour phases was made, however, different patterns were qualitatively described. Individuals displaying any form of dark colour phase were counted at the moment of MaxN (maximum number of individuals observed in the frame at one time) or the highest cumulative MaxN moment in which physiological colour change occurred or dark colour phases were present to avoid multiple counts of the same individuals. Individuals that showed active physiological colour change were also marked during dark phases.
README: Colour change and colour phases in Lethrinidae with insights into ecology
https://doi.org/10.5061/dryad.x69p8czqw
Column header | Explanation |
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Metadata Sheet Columns | |
New Opcode | Standardised naming convention, to keep consistency between expeds |
Exped | Place, year and season of survey |
Date | Date of deployment |
Year | Year of deployment |
Month | Month of deployment |
USE? | Will be YES if a sample was recorded, NO if rig was lost, camera died, etc. Used to separate “no fish” from “no sample”. At least 1 camera recording for at least an hour. |
Lat | Latitude of deployment |
Long | Longitude of deployment |
Time in | Time at which the BRUVS rig was deployed |
Time out | Time at which the BRUVS rig was retrieved |
Depth | Depth in metres |
Location | discrete locations within the survey. |
MaxN Sheet Columns | |
New Opcode | Standardised naming convention, to keep consistency between expeds |
Concate | A combination of New Opcode and binomial name of the relevant organism |
Exped | Place, year and season of survey |
Frame | Video frame in which the organism was recorded |
Time (mins) | Time at which the organism was recorded |
Period time (mins) | Time organism was recorded after the start of processing |
Family | Family classification of the organism |
Genus | Genus classification of the organism |
Species | Species classification of the organism |
Binomial | Scientific name of the relevant organism |
Common Name | Common name of the relevant organism |
MaxN | Maximum number of individuals of this organism in a single video frame |
Has fed | Whether or not the organism fed on the bait |
Depth (m) | Depth at which BRUV was deployed |
cat | Taxonomic level to which individual was identified |
Endemics | Whether the individual is endemic to the region |
Colour change | The presence or absence of colour change |
Light Phase | The presence of absence of light colour phase individuals |
Light Phase Length | Measured length of light phase individuals. "n/a" signifies that there were no individuals displaying this colour phase to be measured |
Dark Phase | The presence of absence of dark colour phase individuals |
Dark Phase Length | Measured length of dark phase individuals "n/a" signifies that there were no individuals displaying this colour phase to be measured |
Dark Phase Feeding | Feeding by dark phase individuals |
Active Change | Actively changing colour phase while in field of view |
Changing While Feeding | Actively changing colour phase while feeding |
Behaviour | Notes on behaviour for each record, where relevant. "null" signifies that no behaviour notes were made for this record |
Description of the data and file structure
The main metrics in this dataset are abundance (number of individuals), length (measured fork length of individuals), and colour phase (light or dark).
Abundance and length can be analysed at various scales within this dataset: they can be averaged by species, by individual BRUVS rig (labelled as "opcode"), by region (North West or Cocos), by season (month), or by year.
How to calculate mean abundance per sample in MS Excel:
- Create a pivot table including all relevant factors (MaxN, species, opcode, location, etc.)
- Calculate mean TA (sum of MaxN) per sample
- Create second pivot table using mean values
Determine species composition (of lethrinids)
- Create pivot table matrix of MaxN per Species per sample (opcode)
- Add in other factors, e.g. exped, year, etc.
- Calculate mean MaxN per species per sample (MaxN divided by no. of opcodes)