DOI: 10.5061/dryad.9ghx3ffmg
title: Postrelease exploration and stress tolerance of landlocked and anadromous Atlantic salmon and their hybrids

description: Background We studied postrelease explorative behavior and stress
 tolerance of Landlocked and anadromous Atlantic salmon and their hybrids.
 For the research, we hybridized the Landlocked salmon of Lake Saimaa with
 a Baltic anadromous salmon from River Kymijoki, Southern Finland (strain
 originally from River Neva, Russia). These fish were hybridized in
 November 2017 and October 2018 in the Kainuu Fisheries Research Station,
 Paltamo, Kainuu, Finland (kfrs.fi).In the data the fish are treated as
 four strains (column 'Strain'): 1. Purebred Landlocked salmon
 (LLxLL), 2. hybrids, where the maternal population was landlocked salmon
 (LLxBA), 3. hybrids, where the maternal population was Baltic anadromous
 salmon (BAxLL) and 4. purebred Baltic anadromous salmon (BAxBA).
 Experiment 1. Post-release exploration In experiment 1., consisting of two
 separate trials, we studied post-release exploration of the fish in four
 circular seminatural streams. (Datasets 'Exploration2018.csv'
 & 'Exploration2020.csv', see also
 'Figure_1.jpg') Experiment 2. Stress tolerance In experiment 2.
 we studied the stress response and recovery of the fish (Dataset
 'Stress_BernoulliData.csv', see also 'Figure_2.jpg').
description: <strong>Experiment 1.
 </strong>'Figure_1.jpg' Datasets
 'Exploration2018.csv' &
 'Exploration2020.csv' In experiment 1., we
 studied post-release exploration of the hybridized salmon in four circular
 seminatural streams (column 'Pool'). All fish involved were
 identified using passive integrated transponders (column 'PIT').
 Movement, or explorative behavior, of the fish in the seminatural streams
 was followed using four evenly spaced antennae capable of reading the
 fish's PIT-tags. This movement data has been summarized in the
 columns 'Descending' (movement with the water stream, i.e.
 downstream movement), 'Ascending' (upstream movement) and
 'Total' (Total movement, i.e. Ascending & Descending).
 Units in these columns are rounds that the fish swam in the circular
 streams per hour (column 'Time.of.Day' and
 'Pseudotime' from the start to the end of the experiment).
 Centerline length of the circular streams was 26.15 m and therefore the
 rounds can be converted to meters by multiplying by 26.15. The experiment
 consisted of two separate seven-day (column 'Date') trials,
 conducted on 11–18 December 2018 ('Exploration2018.csv' ) and
 16–30 March 2020 ('Exploration2020.csv').
 <strong>Experiment 2.
 </strong>'Figure_2.jpg' Dataset
 'Stress_BernoulliData.csv' The fish used in
 experiment 2 were of two backgrounds (Column 'Background'):
 <br>Indoor fish ('Indoor') had experienced only standard
 aquaculture conditions, having been raised with food pellets at a density
 of 109 individuals/m<sup>2</sup> in indoor
 tanks.<br>Outdoor fish ('Outdoor') had spent 149 days in
 seminatural outdoor streams (during experiment 1. in winter 2018–2019, see
 above) at a density of 2.7 individuals/m<sup>2</sup>.
 <br>The latter fish were not fed during the outdoor-raising and they
 had thus gained experience in feeding on live invertebrate
 prey.<br>Again, all fish can be identified using passive integrated
 transponders (column 'PIT'). Experiment 2
 consisted of two parts: In <strong>part 1</strong>, the fish
 were subjected to a stress treatment and in <strong>part
 2</strong>, we observed their stress recovery for 12 hours, as
 reflected by the commencement of feeding activity. Before the experiments,
 we collected the fish from a storage tank into fasting cages (column
 'Fasting_cage'), where they remained for 18-23 hours prior to
 the stress treatment. The stress treatment
 (<strong>part 1</strong>) was conducted individually in four
 pale brightly lit channels with a rapidly changing water current (channel
 number is given in column 'Stress_channel'). During the
 treatment most fish settled to the bottom of the channels, refusing to
 move, but notes were made if the fish displayed 'escape
 behavior', i.e. started swimming against the water current at least
 once during the first (0–15 min from start) and/or second (15–30 min from
 start) half of the treatment. These notes are found in the column
 'Swimming_Activity' and range from 0 to 2. Control fish were
 subjected only to handling stress and were thus not exposed to the actual
 stress treatment (column 'Stress_Control').
 Immediately after the stress treatment the fish were moved
 individually into 24 dark, dimly lit plastic boxes (box number given by
 'ID_in_experiment'). The boxes contained 30 L of water
 oxygenated by aquarium oxygenators and within the box, the fish were
 provided with four <em>Lucilia sericata </em>fly larvae. The
 boxes were checked every three hours to see when the fish commenced
 feeding, i.e. started to recover from the stressful treatment
 (<strong>part 2</strong> of experiment). Starting and checking
 times are given in the columns 'Starting_Time' and
 'Checking_Time' (local clocktime as a decimal number).
 'Checking_Time_Absolute' is the time from the start of the
 experiment and 'Larvae_Eaten' is the number of larvae eaten at
 each checking time. Lengths and weights of the fish were measured after
 the stress experiments, on 21 July 2019. Temperature and Oxygen content of
 the incoming water are given, as measured each day. 
description: All data is given as .csv-tables (comma separeted values), where
 ';' serves as separator. <br><br>They can be opened
 using e.g. text editor, microsoft excel or R studio.