DOI: 10.7489/12394-2
title: Sea lice counts on wild sea trout

description: Data comprise sampling for wild sea trout from named sampling locations. The number of fish, individual fish fork length and the number and life cycle stage of any sea lice found are all recorded. 

Notes on temporal and spatial coverage

Data have been divided into 3 separate periods due to minor differences in spatial coverage, files covering 1997 – 2009 and 2011 – 2024 include available data covering all mainland west coast and western isles fisheries trusts regions. Data from 2010 features only data from mainland west coast fisheries trust regions (which includes some inner islands).
Column headings
“site” contains the sampling site name	
“region” contains information on the general region of Scotland within which the sample site is located. 
“date” contains the date that sampling point was undertaken	
“fish_id” contains a number to identify individual fish
“length” contains the fork length in mm of the individual sea trout		
“copepodid_chalimus” contains the number of this life cycle stage of lice found on the individual fish
“preadult_adult” contains the number of this life cycle stage of lice found on the individual fish
 “ovigerous_females” contains the number of this life cycle stage of lice found on the individual fish
Acknowledgements
This work was funded by Marine Scotland, and managed by Marine Scotland Science and Fisheries Management Scotland. Sampling was carried out by employees of the district fisheries trusts with the help of volunteers as required.

description: Sampling was undertaken between April and September, annually between 1997 and 2024. Each sampling event aims to catch at least 30 fish of either post-smolt and/or finnock life stage. 
Once caught, fish are anaesthetised using neutral-buffered MS222 (100 mgl-1) with the water poured through a 100µm sieve to catch any lice detached during the anaesthetising process. Fork length (to the nearest mm) was recorded during this process. For counting of lice, fish are placed in water against a light background with the number of lice present on the fish and the life cycle stages of the lice recorded as one of the following three categories:
Category 1: Early stages: attached copepodids and chalimus.
Category 2:  Mobile stages: pre-adults and adults including mature males and non-ovigerous females.
Category 3: Gravid stages: ovigerous females.
Further details on sweep netting method can be found at https://www.sfcc.co.uk/assets/files/SFCC%20Sweep%20Netting%20Protocol.pdf


Column headings
“site” contains the sampling site name	
"region" contains the wider region within which sampling sites are situated
“date” contains the date that sampling point was undertaken	
“fish_id” contains a number to identify individual fish
“length” contains the fork length in mm of the individual sea trout	
“lice_stage” contains the sea lice life cycle stage. Either "copepodid_chalimus", "preadult_adult" or "ovigerous_females"

In the column based resource, the following columns are included:
“copepodid_chalimus” contains the number of this life cycle stage of lice found on the individual fish
“preadult_adult” contains the number of this life cycle stage of lice found on the individual fish
 “ovigerous_females” contains the number of this life cycle stage of lice found on the individual fish

In the row based resource, the following columns are included:
"lice stage" describing the development stages detailed above
“count” contains the number of sea lice of the specified class on the fish

Acknowledgements
This work was funded by Marine Scotland, and managed by Marine Scotland Science and Fisheries Management Scotland. Sampling was carried out by employees of the district fisheries trusts with the help of volunteers as required.