The data archived here were used to examine 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 data were collected between 1999 and 2020 and consist of a) fish captures in a trap at the mouth of the river Shieldaig with associated length and weight measurements; and b) fish captures by electrofishing in the area below the trap with associated salmon lice counts.
The data are 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. D J Morris, R J Fryer, J A Raffell, S J Middlemas, J D Godfrey, J D Armstrong. ICES Journal of Marine Science, Volume 83, Issue 1, fsag001 https://doi.org/10.1093/icesjms/fsag001.
Data and Resources
- Sea trout captures in the trap in the river Shieldaigcsv
The file trap.csv contains the data on sea trout captures in the trap in the...
Preview Download - Sea trout captures by electrofishing in the mouth of the river Shieldaigcsv
The file electrofishing.csv contains the data on sea trout captures by...
Preview Download
| Field | Value |
|---|---|
| Publisher | |
| Modified | 2026-06-11 |
| Release Date | 2026-06-11 |
| Identifier | 14949865-413d-4d04-9707-4dea1db8a713 |
| Spatial / Geographical Coverage Area | POLYGON ((-5.943603515625 57.54397714058, -5.943603515625 57.925195538185, -5.526123046875 57.925195538185, -5.526123046875 57.54397714058)) |
| Temporal Coverage | 1999-03-01 to 2020-03-31 |
| Language | English (United Kingdom) |
| License | UK Open Government Licence (OGL) |
| Data Dictionary | Migrating sea trout of both wild-origin and hatchery-origin were captured and tagged in a permanent weir-type fish trap installed approximately 120 m from the mouth of the river Shieldaig from March 1999 until March 2020. The trap allowed the non-lethal capture of trout smolts migrating downstream and adult recapture as they returned to the river from the sea. Downstream and upstream migrating fish were captured in separate holding boxes. On their downstream migration, captured fish were individually marked using paired Visible Implant (VI) tags in spring 1999 or, from 2000 onward, intra-peritoneally with Passive Integrated Transponder (PIT) tags. In addition, the length of each fish was recorded and from 2001 the fish were weighed. Fish missing the adipose fin were recorded as being of hatchery-origin, while those fish with an intact adipose fish were recorded as being of wild-origin. Fish caught in the trap when ascending the river (or on subsequent downstream migrations) were measured, the tag number recorded (if present), either visually for VI tags or using a hand-held PIT reader. Sea trout were electrofished in a consistent area of habitat of approximately 1100 m2 from above the high watermark to the trap during May and June from 1999 through 2019. The frequency of fishing was typically fortnightly in the early years of the study, becoming weekly later on. In 1999, 2000 and 2001 the presence (or absence) of any lice on each fish was recorded. Thereafter, sea lice stages were classified as attached (copepodid / chalimus), mobile (pre-adults or adults excluding ovigerous females) and ovigerous females and numbers of lice at each stage counted. In heavier infestations, when counting absolute numbers would be overly time-consuming, lice numbers were estimated by eye to prevent fish from being under anaesthetic for excessive periods. All procedures on fish were conducted under licence from the UK Home Office (licence numbers 60/2317, 60/2824, 60/4251, 70/8928) in accordance with ethical guidelines and regulations. |
| Contact Name | Marine Directorate, Scottish Government |
| Contact Email | |
| Public Access Level | Public |