Seasonal Distribution of Humpback Whitefish in the Slana River

This study will describe the seasonal distribution of humpback whitefish Coregonus pidschian captured in the Slana River during fall. Humpback whitefish will be captured using electrofishing techniques during late September before the onset of spawning. One hundred adult humpback whitefish ≥320 mm FL will be surgically implanted with radio tags that will operate for ~25 months. Radiotagged humpbacked whitefish will be aerially tracked throughout the year to determine overall distribution, including overwintering, spawning, and summering areas, as well as migration timing among these locations. A fixed-tracking station will be used to track if/when humpback whitefish leave the Slana River drainage.

Operational Plan

The published Operational Plan for this study can be found at:

https://www.adfg.alaska.gov/FedAidPDFs/ROP.SF.3F.2024.08.pdf

Folder structure

/FDS_2025: FDS Report 2025 (to be published in 2026)

/FDS_2025/R

This folder consists of two R scripts for analyses pertaining to the FDS report to be published in 2026:

• 1_Slana_telemetry_fromobjectives.R contains all data import and analysis outlined in the Operational Plan objectives. The majority of the data manipulation consisted of handling the spatial river network describing the Slana river using the riverdist package, as well as defining observations as inside/outside Mentasta Lake and the principal spawning area. The majority of data analyses conducted here consisted of summary measures of migration distances and direction, and miniumum observed homeranges.

• 2_hiddenmarkov_survivalmod.R contains an exploration of a novel Bayesian Hidden Markov survival model using the longitudinal data available from this project.

Survival probability $\phi_{l,j}$ was assumed to vary according to each combination of location (Lake or River) and survey (number). Detection probability $p_{l,s}$ was assumed to vary according to location (Lake or River) and survival (Dead or Alive).

The model consisted of the following stochastic relationships:

• Survival $Y_{i,1} \sim Binom(\phi_{l,j},1)$ for the first survey after tagging, and
• Survival $Y_{i,j} \sim Binom(\phi_{l,j},Y_{i,j-1})$ thereafter; and,
• Observation $X_{i,j} \sim Binom(p_{l,s}, 1)$

for

• individual $i \in 1 \dots 100$
• survey $j \in 1 \dots 13$
• location $l \in {Lake, River}$
• survival $s \in {Dead, Alive}$

/FDS_2025/output_tables

This folder consists of a collection of output tables, written by the two R scripts found in /FDS_2025/R. All are exported from R directly as .csv files, and are combined in a single spreadsheet Slana_results_compiled.xlsx. All tables are described in further detail in /FDS_2025/Slana_results_annotation.Rmd.

/FDS_2025/flat_data

This folder consists of raw data to be imported by the R scripts found in /FDS_2025/R. Two .csv files (GIS.csv and tracker.csv) contain raw telemetry data, and slanacopper1.Rdata is an R workspace file containing the cleaned rivernetwork object defined as the regions of the Slana and Copper Rivers and tributaries relevant to spatial analyses.

/FDS_2025/raw_data

This folder consists of .xls and .jpg files provided by the project biologist, and is currently .gitignored.

Slana_results_annotation.Rmd

This R Markdown file provides annotation describing all tables found in /FDS_2025/output_tables, as well as some summary visualization.

/OP_2024: Operational Plan 2024

/OP_2024/Drafts

All drafts of the 2024 Operational Plan, currently .gitignored

/OP_2024/R

.R code associated with the Operational Plan:

• Visualizing the number of surviving tags over time, according to constant mortality
• Describing expected precision given the proposed sample size

/OP_2024/R_output

Tables and figures generated by the R code. Multiple versions of the same figure were saved.