The file trap.csv contains the data on sea trout captures in the trap in the river Shieldaig that form the basis of the paper A 20-year study examining the effects of salmon lice on the return rate, time at sea, and marine growth of sea trout migrating from the river Shieldaig in Scotland.

The file is UTF-8-BOM encoded so can be read directly into Excel, or into R using the function read.csv with the argument fileEncoding = “UTF-8-BOM”.

The variables in the file are:

fish
Description: identifier of each trout
Unit:
Type: categorical
Levels: 17427
Note:

stock
Description: wild-origin or hatchery-origin trout
Unit:
Type: categorical
Levels: hatchery-origin, wild-origin
Note:

release_number
Description: identifies each capture and release of an individual trout from the downstream trap
Unit:
Type: integer
Range: 1, 4
Note: a release_number of 1 identifies the first time a trout was caught and released in the downstream trap; a release_number of 2 identifies the second time the trout was caught and released in the downstream trap; and so on. Most trout were only caught and released once.

release_lifestage
Description: the lifestage of the trout when released from the downstream trap
Unit:
Type: categorical
Levels: smolt, finnock, adult
Note:

release_date
Description: the date the trout was released from the downstream trap
Unit: YYYY-MM-DD
Type: date
Range: 1999-03-08, 2019-06-19
Note:

release_year
Description: the year the trout was released from the downstream trap
Unit: y
Type: discrete
Range: 1999, 2019
Note:

release_month
Description: the month the trout was released from the downstream trap
Unit:
Type: categorical
Levels: January, February, March, April, May, June, July, August, September, November
Note:

release_day
Description: the day of the year (from 1 January) that the trout was released from the downstream trap
Unit: d
Type: discrete
Range: 8, 331
Note:

release_length
Description: the length of the trout when released from the downstream trap
Unit: mm
Type: continuous
Range: 91, 414
Note:

release_weight
Description: the weight of the trout when released from the downstream trap
Unit: g
Type: continuous
Range: 8, 534
Note: measured from 2001 onwards

release_condition
Description: the condition of the trout when released from the downstream trap
Unit: dimensionless
Type: continuous
Range: -0.7, 0.91
Note: the residuals from a linear mixed model of log weight on log length (see the paper for details); available from 2001 onwards

infestation_presence
Description: a metric of sea lice infestation pressure based on presence / absence of lice
Unit: %
Type: continuous
Range: 0, 88.7
Note: the metric was based on electrofishing data from the lower reaches of the River Shieldaig in the year the trout was released from the trap; it was defined as the proportion of trout caught by electrofishing with at least one louse

infestation_threshold
Description: a metric of sea lice infestation pressure based on the lice threshold for harm
Unit: %
Type: continuous
Range: 0, 75.8
Note: the metric was based on electrofishing data from the lower reaches of the River Shieldaig in the year the trout was released from the trap; it was defined as the proportion of trout that met or exceeded the threshold for harm of 13 mobile lice; available from 2002 onwards

return_date
Description: the date the trout was recaptured (if it was)
Unit: YYYY-MM-DD
Type: date
Range: 1999-06-17, 2019-10-07
Note:

return_year
Description: the year the trout was recaptured
Unit: y
Type: discrete
Range: 1999, 2019
Note:

return_month
Description: the month the trout was recaptured
Unit:
Type: categorical
Levels: March, April, May, June, July, August, September, October, November
Note:

return_day
Description: the day of the year (from 1 January) that the trout was recaptured
Unit: d
Type: discrete
Range: 79, 321
Note:

return_direction
Description: whether the trout was recaptured in the upstream or downstream trap
Unit:
Type: categorical
Levels: downstream, upstream
Note: trout recaptured in the upstream trap were returning from sea; those recaptured in the downstream trap had evaded the upstream trap and were migrating to sea

return_length
Description: the length of the trout when recaptured
Unit: mm
Type: continuous
Range: 147, 448
Note:

return_weight
Description: the weight of the trout when recaptured
Unit: g
Type: continuous
Range: 22, 894
Note: measured from 2001 onwards

days_at_sea
Description: the number of days between release and recapture
Unit: d
Type: discrete
Range: 46, 193
Note: only provided for the releases and recaptures analysed in the paper; specifically, the first release and recapture of those trout used in the analysis of return rates (see return_analysis below) that were recaptured in the upstream trap in the same year as release

specific_growth_rate
Description: the specific growth rate between release and recapture
Unit: %/d
Type: continuous
Range: -0.83, 2.57
Note: only provided for the releases and recaptures analysed in the paper; specifically, the first release and recapture of those trout used in the analysis of return rates (see return_analysis below) that were recaptured in the upstream trap in the same year as release; available from 2001 onwards

return_analysis
Description: whether a release was used in the analysis of return rates
Unit:
Type: logical
Levels: TRUE (88%), FALSE (12%)
Note: identifies the releases used in the analysis of return rates in the paper; specifically, the first release of trout with length <= 212 mm

length_analysis
Description: whether a release was used in the quadratic discriminant analysis of length
Unit:
Type: logical
Levels: TRUE (3%), FALSE (97%)
Note: identifies the releases used in the quadratic discriminant analysis of length in the paper; specifically, the first and second releases of trout that were identified as smolts in their first release and were released for a second time the following year