Data from: Assessing fish movement and physiological traits along a salinity gradient by measuring stable oxygen isotope values in fish blood water and muscle water
Data files
Mar 27, 2025 version files 11.75 KB
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Amami_fish.csv
2 KB
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Amami_water.csv
1.16 KB
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Experimental_Japanese_eel.csv
1.42 KB
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Experimental_water.csv
679 B
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README.md
6.49 KB
Abstract
Variations in stable oxygen isotopes (δ18O) in the body water of animals reflect changes in δ18O values in environmental water and the animals’ physiological processes. Euryhaline/anadromous/catadromous fish species move across salinity gradients; changes in δ18O values in environmental water thus lead to changes in δ18O values in body water. Few studies have systematically evaluated the effect of salinity on δ18O values in fish body water. Accordingly, this study demonstrated a well-established approach to investigating the relationship between salinity and δ18O values in fish body water (blood water and muscle water). This study comprised two experimental designs. First, we implemented continual changes in salinity levels to assess the corresponding variations in δ18O values in the blood water of Japanese eels under controlled laboratory conditions. Second, field (river and estuary) studies were conducted for multiple fish species on Japan’s Amami Island. Samples of fish blood water and muscle water were analysed in accordance with a general headspace protocol to estimate δ18O values; this estimation was conducted using isotope ratio mass spectrometry, which involved an equilibration method for sample preparation. The data include the difference in δ18O values in fish blood water, muscle water and ambient water in the laboratory experiment involving changes in salinity and in the field collection from the Amami Island. Analysing δ18O values in environmental water, blood water, and muscle water is useful for monitoring the behaviours of regional migratory fish, such as temporary feeding in estuaries. Our analytical method is ideal for measuring δ18O values in fish body water because it enables analysing various organic tissues by using small amounts of body fluids, facilitating the examination of the ecology of aquatic animals.
Dataset DOI: 10.5061/dryad.fj6q5745h
Description of the data and file structure
We conducted two experiments to gain a more comprehensive understanding of the behaviour and physiology of migratory fish species. First, we changed the salinity levels of water under a controlled laboratory environment to monitor variations in δ18O values in the blood water and muscle water of Japanese eels (Anguilla japonica). Second, we collected wild fish specimens from the river and estuary to evaluate δ18O variations in their blood water and muscle water at different salinity levels.
Before blood sampling, 12-mL glass vials used for isotope analyses were flushed with a mixture of helium and 0.25 % reference CO2 with a known isotope value. Subsequently, three to four drops of each blood sample were injected into the flushed glass vials and stored in a fridge. Before the isotope analyses, the samples were incubated at 24 °C for 24 hours, ensuring δ18O equilibrium between sample and reference CO2. Headspace sampling was performed, and the obtained samples were analysed using the Delta V plus system (Thermo Fisher Scientific, Germany) equipped with Gasbench II (Thermo Fisher Scientific) at the Atmosphere and Ocean Research Institute, the University of Tokyo.
When fish samples were sacrificed or collected from the field, they were stored in the freezer immediately. After the fish samples were defrosted at room temperature, dorsal muscle (approximately 110 mg) was collected and soaked with a paper towel to avoid the contamination from other fluids, such as water and blood. Subsequently, the samples were placed in glass vials. The muscle samples were placed in glass vials and then treated in the same manner as the blood samples. Specifically, the muscle samples were flushed with a mixture of helium and CO2, incubated at 24 °C for 24 hours, and analysed using an IRMS system equipped with a GasBench system at the Atmosphere and Ocean Research Institute, the University of Tokyo.
Experimental_water.csv
| Column name | Description | Units | Data format | Missing data code |
|---|---|---|---|---|
| SampleID | The water sample is named according to the date of collection in the format (year.month.day). | - | Category | - |
| Salinity | The salinity of the experimental water. | PSU | Number | - |
| Day | The start date of the experiment. | - | Number | - |
| d18O | Stable oxygen isotope values in water. | ‰ | Number | - |
Experimental_Japanese_eel.csv
| Column name | Description | Units | Data format | Missing data code |
|---|---|---|---|---|
| PIT name | The ID number of pit tag | - | Category | - |
| Day | The start date of the experiment. | - | Number | - |
| Type | Sample types, such as blood or muscle. | - | Category | |
| d18O | Stable oxygen isotope values in blood water or muscle water. | ‰ | Number | - |
Amami_water. csv
| Column name | Description | Units | Data format | Missing data code |
|---|---|---|---|---|
| Name | The water sample is named according to the location of collection. | - | Category | - |
| Area | Sampling locations, including Shidokan Port, Shidokan River, and Yamato River. | - | Category | - |
| d18O | Stable oxygen isotope values in environmental waters. | ‰ | Number | - |
Amami_fish.csv
| Column name | Description | Units | Data format | Missing data code |
|---|---|---|---|---|
| Sample Name | The fish sample is named according to the location of collection. | - | Category | - |
| Species | Fish species. | - | Category | - |
| Area | Sampling locations, including Shidokan Port, Shidokan River, and Yamato River. | - | Category | - |
| b.d18O | Stable oxygen isotope values in blood water. | ‰ | Number | “NA” indicates the failure of blood extraction. |
| m.d18O | Stable oxygen isotope values in muscle water. | ‰ | Number | “NA” indicates the failure of muscle extraction (insufficient amount for isotope analyses). |