DOI: 10.5061/dryad.8cz8w9h1s
title: Enhancing reproducibility in stable isotope analysis (SIA) of fish eye lenses: A comparison between lamina number and diameter

description: Analyzing stable isotopes in archival tissues, such as fish eye lenses, is
 used to document shifts in feeding ecology, diet, habitat use, and to
 reconstruct life history. Fish eye lenses grow sequentially throughout
 their ontogeny, resulting in a structure of multiple layers, or laminae.
 These laminae represent the chronology of the fish's life, much like
 tree rings. Lenses are protein-rich, which makes them an ideal structure
 for analyzing light isotopes such as δ¹³C, δ¹⁵N, and δ34S. These light
 isotopes are primarily integrated into the lens tissue through the
 fish's diet. As research begins to emerge using eye lenses to
 reconstruct the life histories of fishes, the need for a reproducible
 method of delamination grows. For this study, two different researchers
 peeled lenses from each eye of the same adult Chinook salmon (Oncorhynchus
 tshawytscha) (n=10 fish). Lens lamina number, diameter (mm), and mass (mg)
 of each lamina were recorded. Laminae were then submitted for isotopic
 analysis of both δ¹³C and δ¹⁵N. Isotope values were used as a validation
 to compare delamination patterns between researchers. δ¹³C and δ¹⁵N values
 from the lenses were then plotted using both the assigned lamina number
 and lens diameter to compare the difference between researchers. Analyzing
 the laminae based on lamina number resulted in significant variability
 between researchers. However, when lens diameter was used instead of
 lamina number, isotope patterns throughout the lenses of the same fish
 were nearly identical. Using lens diameter removes subjectivity between
 researchers, thereby increasing the reproducibility of the technique and
 providing a more robust interpretation of the data.
description: Metadata of eye lens stable isotope data (CN) of 10 2018 fall run
 Chinook salmon. Fish-specific metadata (e.g., fork_length, site_id) is
 given and collected by CDFW. Lens-specific metadata (e.g., layer_no,
 lens_dm) is collected during sample processing. Isotope data is generated
 by the Stable Isotope Facility at the University of California,
 Davis. 
description: # Enhancing reproducibility in stable isotope analysis (SIA) of fish eye
 lenses: A comparison between lamina number and diameter
 [https://doi.org/10.5061/dryad.8cz8w9h1s](https://doi.org/10.5061/dryad.8cz8w9h1s) ## Description of the data and file structure Metadata of eye lens stable isotope data (CN) of 10 2018 fall run Chinook salmon. Fish-specific metadata (e.g., fork length, site) is given and collected by CDFW. Lens-specific metadata (e.g., layer number, lens diameter) is collected during sample processing. Isotope data is generated by the Stable Isotope Facility at the University of California, Davis.  ### Files and variables #### File: Lens\_Methods\_Metadata.csv **Description:** Fish eye lens isotope (C,N) data used in Chu and Li, et al.  A comparison between lamina number and diameter ##### Variables * lab_id: unique ID given to each individual fish * researcher: Researcher who processed the lens sample * layer_no: Lamina number assigned during dissection * lens_dm: Diameter of the lens (in millimeters, mm) measured using LAS X * lens_width_dm: Lamina width (in millimeters, mm), calculated as the difference in lens_dm between subsequent layer_no values * lens_mass: Lamina weight (in milligrams, mg) for each dissected lamina * site_id: Collection site identifier where fish were sampled * PFL: Whether the lamina is a partially formed layer (Y = yes, N = no) * fork_length: Fork length of the fish (in millimeters, mm) measured in the field * sex: Sex of the fish  * run: Run type of the fish (e.g., Fall, Winter) * capture_type: Species of the fish  * d15N: Nitrogen isotope value (in per mille, ‰) * d13C: Carbon isotope value (in per mille, ‰) Some samples were too small to be measured, resulting in `NA` values for their isotopic compositions (e.g., `d15N`, `d13C`). No width (`lens_width_dm`) is calculated, and no weight (`lens_mass`) is measured for `layer_no = 0`, as this represents the endpoint of sample processing. Remaining `NA` values in `lens_dm` reflect missing measurements during dissection, which in turn introduce `NA`s in the calculated `lens_width_dm` values.