Experimental observation of the prior residence advantage in masu salmon in an experimental channel
Data files
Sep 05, 2025 version files 5.79 KB
-
Raw_data_(Data_S1).csv
2.58 KB
-
README.md
3.21 KB
Abstract
Stocking of hatchery-reared salmonids is still a common management strategy to supplement natural resources and improve recreational fishing catch. However, concerns have been raised about the effectiveness of stocking as there is evidence that stocked fish may replace prior resident fish or fail to settle at the intended stocking sites, resulting in downstream emigration, and may subsequently die. This study evaluated whether stocked masu salmon (Oncorhynchus masou masou), a species widely stocked in Japanese streams, displace prior resident fish or emigrate from the stocked site. Experimental stocking trials were conducted in an artificial channel with multiple pools where factors potentially affecting the interactions between residents and intruders can be controlled. We found that stocked intruder fish were more likely to move out of the artificial channel compared to prior resident fish. Our findings indicate that stocking of masu salmon may be ineffective in streams with prior resident fish and few available habitats, as most stocked fish are unable to settle at the site stocked. To optimize stocking efficiency for species that show prior residence advantage, such as masu salmon, stocking should only occur in situations where suitable, unoccupied habitats are available and where site fidelity of stocked fish can be expected.
Dataset DOI: 10.5061/dryad.mgqnk99bv
Description of the data and file structure
This dataset was collected to test the hypothesis that introduced non-anadromous hatchery-reared masu salmon are more likely to emigrate from stocked sites compared to prior residents. Experimental stocking trials were conducted in an artificial channel with multiple pools where potentially confounding factors could be controlled, allowing isolation of the effect of prior residence advantage. Young-of-the-year masu salmon were used as both prior resident and intruder fish; they were measured, individually marked to track movement, and then subjected to a two-stage stocking protocol (prior resident introduced first, acclimated 24 h, then intruder added). Movement outcomes were recorded 24 h after intruder addition and categorized into location categories based on final position. Six stocking trials were carried out between July and September 2018, resulting in 84 observations.
Files and variables
File: Raw_data_(Data_S1).csv
Description:
Raw dataset including trial number, whether the fish was assigned as a prior resident or an intruder fish, individual fish serial ID, fork length, stocked pool number, pool number at the end of the trial, and location category according to relative position between the pool where the fish was originally stocked and the pool number at the end of the trial. The location category values denote 1:” fish located in a pool upstream of the pool in which it was stocked”, 2: ”fish located in the pool in which it was stocked”, 3:” fish located in a pool downstream of the pool in which it was stocked”, and 4: ”fish moved out of the channel”. DC indicates s downstream container.
Variable list:
1. Trial
- Type/coding: Integer
- Description: Identifier for each stocking trial.
2. Fish category (Prior resident/intruder)
- Type/coding: Categorical / binary
- Description: Indicates whether the fish was the prior resident or the intruder.
3. Fish ID
- Type/coding: String / Integer
- Description: Unique individual identifier based on marking to track each fish.
4. Fork length (cm)
- Type/coding: Numeric
- Description: Fork length measured to the nearest 0.1 cm.
5. Stocked pool No.
- Type/coding: Integer
- Description: Pool number where the fish was originally stocked. Pools are arranged from upstream (No.1) to downstream (No.7).
6. Pool No. At the end of the trial
- Type/coding: String / categorical
- Description: Pool number where the fish was found at the end of the trial, or "DC" if the fish had moved out of the channel into the downstream container.
7. Location category
- Type/coding: Integer (1–4)
- Description: Final position relative to stocked pool, coded as: 1 = upstream pool, 2 = same pool, 3 = downstream pool, 4 = moved out of the channel.
Code/software
The raw data are provided in a .csv file. To view the data, any software capable of opening .csv files can be used.
No analysis code or script is included with this submission.