DOI: 10.5061/dryad.mgqnk99bv
title: Experimental observation of the prior residence advantage in masu salmon in an experimental channel

description: 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.
description: # Experimental observation of the prior residence advantage in masu salmon
 in an experimental channel Dataset DOI:
 [10.5061/dryad.mgqnk99bv](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.