Effects of salmon lice on numbers and size distributions of Atlantic salmon populations returning to spawn in Norwegian rivers

Negative effects of salmon lice from salmon farms on wild salmonids have been a controversial issue for decades, and concerns are expressed from virtually all areas where salmon farming coexists with important fisheries for wild salmonids. A key question is to what extent lice infestation from farms reduces the number of wild mature salmon returning to spawn in the rivers. Here we study counts and recreational catches of small (< 3 kg), medium-sized (3 – 7 kg), and large mature salmon (> 7 kg) returning to spawn in Norwegian rivers, in association with lice burdens on out-migrating post-smolt recruits. The expected number of returning mature salmon was modelled as a function of theoretical smolt production in the rivers, river catches one generation back in time, size classes of returning salmon, year as a factor, a non-linear spatial effect, and parasite-induced mortality (PIM) of out-migrating post-smolts of salmon. PIM was attributed to small, medium-sized, and large salmon, as..., , # Effects of salmon lice on numbers and size distributions of Atlantic salmon populations returning to spawn in Norwegian rivers

Dataset DOI: [10.5061/dryad.m0cfxpphh](https://doi.org/10.5061/dryad.m0cfxpphh)

## Description of the data and file structure

The data was collected to explore the effects of salmon lice from salmon farms on the numbers and size distribution of wild Atlantic salmon returning to spawn in Norwegian rivers.

### Files and variables

#### File: Data.csv

**Description:** 

Empty cells are **not available data**

##### Variables

* river.id: River identifier. Variable Geo = numeric of first three digits
* year: Year for salmon population
* size: Small salmon (1SW), medium sized (2SW), large (3SW)
* percent.surv: Percentage of river surveyed for mature salmon
* method: Survey method
* in.data: Data in the main analyses indicated by 1, others 0
* pop: Adjusted count of salmon + catch
* count: Adjusted count of salmon
* count.nadj: Non-adjusted count of salmon
* ca...,