Causes and Consequences of vateritic otoliths in hatchery-reared Coho salmon
Atkinson, J
2024-11-15
Goldstream River
The Goldstream River, located on Vancouver Island, British Columbia, Canada, hosts several species of salmon, including Chinook, Coho, and Chum salmon.The Goldstream River river covers an area of approximately 39 square kilometers (15 square miles). The Goldstream River river is located in a temperate rainforest region on Vancouver Island. It experiences a coastal temperate climate characterized by mild, wet winters and relatively dry summers. The region receives a significant amount of rainfall throughout the year, with the heaviest precipitation occurring during the fall and winter months. The Goldstream River itself is relatively short, with a length of about 16 kilometers (10 miles) from its headwaters to its confluence with the Strait of Juan de Fuca. However, it is important to note that the Goldstream River is just one part of the broader Goldstream river, which includes various tributaries and streams that contribute to its overall flow.
Goldstream River Hatchery
The Goldstream River Hatchery plays a vital role in the conservation and enhancement of salmon populations within the Goldstream River and to a lesser extent other small Coho rivers in the Saanich Pennisula area. The hatchery’s methods involve the collection of adult salmon returning to the river during their spawning runs. Female and male salmon are carefully selected, and their eggs and milt (sperm) are manually extracted, then fertilized and incubated in controlled environments. Once the salmon fry have hatched, they are reared in hatchery tanks, where water temperature, flow, and quality are closely monitored to ensure optimal conditions for growth. As the fry develop, they are gradually acclimated to the natural conditions of the river, preparing them for eventual release into the wild. Monitoring and tracking of released smolts play a crucial role in assessing the hatchery’s success and contribution to the overall health of the Goldstream River salmon populations.
Goldstream River coho returns typically begin mid-September but peak towards to beginning of November.
Goldstream River Study Area
The key loc_codes for the Goldstream River and the Bottlenecks Program is the Goldstream River Enhancement Hatchery located ~ 4 km from the ocean and the loc_codes of the mainstem PIT array located at tidewater (Figure. 1)
Figure 1. Goldstream River Study Map showing sampling and PIT antenna/array loc_code. Map is interactive
Goldstream River Juvenile Coho Outmigration Timing
A mainstem PIT array (comprised of two 20 ft HDPE Biomark Antennas) was installed in August of 2022 to detect outmigrating juvenile and returning adult Coho.
Figure 2. Goldstream River Coho Outmigration Detections 2023 and 2024.
Goldstream River Mainstem PIT Array Detection Efficiency for Adult Returns
The Goldstream River PIT array is comprised of two antenna transects that span the entire width of the river. Each transect is made up of 1 - 30 ft HDPE Biomark antenna. For return years 2022 and 2023 the array detection efficiency was calculated by unique tags detected on transect 1 compared to those detected on transect 2. These data were combined and then compared to PIT tags detected during mobile scanning and broodupdated_stock collection.
Table 2.Goldstream River Mainstem PIT Array Summary of Unique Detection’s and Detection Efficiency for Coho salmon 2023.
# Format the table using kable
knitr::kable(summary_system_Gold23,
caption = "",
format = "html",
table.attr = 'class="table table-bordered table-hover"') %>%
kable_styling(full_width = FALSE, bootstrap_options = c("striped", "hover", "condensed", "responsive")) %>%
row_spec(0, bold = TRUE) # Optional styling for the header row| Unique Tags Detected | Detection Efficiency | |
|---|---|---|
| Goldsttream Mainstem Lower | 210 | 0.86 |
| Goldstream Mainstem Upper | 232 | 0.95 |
Table 3.Goldstream River Mainstem PIT Array Summary of Unique Detection’s and Detection Efficiency for Coho salmon 2024.
# Format the table using kable
knitr::kable(summary_system_Gold23,
caption = "",
format = "html",
table.attr = 'class="table table-bordered table-hover"') %>%
kable_styling(full_width = FALSE, bootstrap_options = c("striped", "hover", "condensed", "responsive")) %>%
row_spec(0, bold = TRUE) # Optional styling for the header row| Unique Tags Detected | Detection Efficiency | |
|---|---|---|
| Goldsttream Mainstem Lower | 429 | 0.82 |
| Goldstream Mainstem Upper | 455 | 0.87 |
Goldstream River Migration Direction
In order to better inform whether fish were outmigrating versus returning, fish movements were assessed for directionality using PIT antenna detections. The approach involved identifying the very first detection of each fish after August 1st on each PIT antenna. This first detection was used to determine whether the fish moved upstream or downstream within a specified time window.
First, the dataset was sorted by tag_id_long (unique fish ID) and detection date, ensuring that the earliest detection for each fish was captured. Only detections after July 1, 2024, were included to focus on the current migration period. From there, the first detection at each PIT antenna (loc_code 11 and loc_code 12) was isolated for each fish.
Fish movement direction was then assessed by calculating the time difference between the first detection and any subsequent detections within 5 days. If a fish was first detected at loc_code 11 and subsequently detected at loc_code 12 within 5 days, it was classified as an upstream movement. Conversely, if the fish was first detected at loc_code 12 and then detected at loc_code 11 within the same 5-day window, it was classified as a downstream movement. Fish that did not exhibit detectable movement between the two antennas within 5 days were classified as having an unknown movement direction.
The movement results were categorized into three tagging_groups: “Upstream,” “Downstream,” and “Unknown,” and stored as a factor for further analysis. The final movement distribution was plotted, and a summary table was generated to report the counts and percentages of fish in each movement category. This method provided a clear understanding of the migratory behavior of fish in the Goldstream River, aiding in the distinction between outmigrating and returning individuals.
Figure 4. Directionality of Coho Detected on the Mainstem Array in Fall 2024
Table 2. Summary of Fish Movements (Upstream, Downstream, Unknown).
| Movement | Count | Percentage |
|---|---|---|
| Upstream | 273 | 49.9085923217550 |
| Downstream | 101 | 18.4643510054845 |
| Unknown | 173 | 31.6270566727605 |
Goldstream River Detections Through Time
Detections of tagged salmon movements within the Goldstream River are shown below (Table 3; Figure 4).These are movements of fish filtered to one distinct detection per day.
Figure 4. Detections Through Time at the Goldstream River Mainstem Array.
Goldstream River Coho Adult Returns
The figures in the below section summarize the age class and updated_stock composition of returned PIT tagged fish to the Goldstream River. These data only represent the data from the Bottlenecks to Marine Survival Program and do not represent the entire updated_stock composition of adult Coho returns.
Figure 18. Age class (right) and updated_stock composition (left) of returning adult Coho to the Goldstream River For Return Year 2022
Figure 19. Age class (right) and updated_stock composition (left) of returning adult Coho to the Goldstream River For Return Year 2023
Figure 20. Age class (right) and updated_stock composition (left) of returning adult Coho to the Goldstream River For Return Year 2024
Straying in the Goldstream River
Due to the large number of PIT tags being deployed in multiple rivers and salmon updated_stocks along the East Coast of Vancouver Island is the ability to detect straying of other updated_stocks into rivers where PIT arrays are located. Throughout the inaugural four years of the Bottlenecks Study a number of rivers have shown to have other updated_stocks entering and staying in non-natal rivers (Table 4)
Table 4. Non-Goldstream Species Detected at the Goldstream River Mainstem Array.
## `summarise()` has grouped output by 'outmigration_y', 'year_detected',
## 'species', 'updated_stock', 'river'. You can override using the `.groups`
## argument.| outmigration_y | year_detected | species | updated_stock | river | cohort | tally | groups |
|---|---|---|---|---|---|---|---|
| 2021 | 2022 | ck | Cowichan | cowichan | fall | 1 | drop |
| 2022 | 2022 | ck | Cowichan | cowichan | fall | 2 | drop |
| 2022 | 2023 | ck | Cowichan | cowichan | 1 | drop | |
| 2022 | 2024 | ck | Cowichan | cowichan | 1 | drop | |
| 2022 | 2024 | ck | Nanaimo fall | southern gulf | 1 | drop | |
| 2023 | 2023 | co | millstream | millstream | sm | 1 | drop |
| 2023 | 2024 | ck | southern gulf | 1 | drop | ||
| 2023 | 2024 | co | southern gulf | 2 | drop |
Goldstream River Coho Adult Return Timing
Developing clear return timing graphs, is important in understanding the influences of climate change and how long summer droughts may impacts the in-river timing of fish. Return timing graphs for Goldstream River Coho are presented in Figures
Figure 5. Goldstream River Coho Spawn Migration Detections and Escapement Curves.
Figure 5. Goldstream River Coho Spawn Migration Detections and Escapement Curves.
Figure 5. Goldstream River Coho Spawn Migration Detections and Escapement Curves.