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Chum salmon escapement on Bonanza River in Norton Sound, Alaska

Citation

Bell, Jenefer (2021), Chum salmon escapement on Bonanza River in Norton Sound, Alaska, Dryad, Dataset, https://doi.org/10.5061/dryad.0k6djh9z4

Abstract

Bonanza River flows 40 rkm south from the Kigluaik Mountains and drains into Safety Sound approximately 39 km northeast of Nome, Alaska. Chum, pink, and coho salmon are the predominant species that return to the Bonanza River. A fixed-picket weir was installed  approximately 11 rkm above the Bonanza Bridge on the Nome-Council Highway (GPS coordinates 64°32.964ʹN, 164°35.812ʹW). The Bonanza River weir enumerated chum salmon for three seasons from 2018 to 2020. Chum salmon escapements were 7,903 in 2018; 8,824 in 2019; and 2,471 in 2020. In 2018 and 2019, high water delayed installation of the weir and therefore the beginning of the run may have been missed. Additionally, in 2019 high water forced weir operations to stop before the proposed end date, so it is likely the end of the chum salmon run was missed. In 2020, the weir went in according to schedule and counted the beginning of the run, but personnel issues, exacerbated by COVID-19 protocols, resulted in early termination of the project, and likely caused missed counting at the end of the run. High water that hindered counting on Bonanza River in 2018 and 2019 also hindered counting operations on other Subdistrict 1 rivers, and as a result aspects of Objectives 1 and 2 could not be completed for all project years. Age, sex, and length data were collected from chum salmon passing through the weir in all three years. Minimum sample size requirements to evaluate Objective 3 were met in 2018 and 2020, but not in 2019. In 2018, chum salmon were predominantly 4 years old and in 2020 chum salmon were predominantly 5 years old. This project indicated that using existing methods, such as weirs and aerial surveys, to estimate Bonanza River’s contribution to chum salmon abundance in Subdistrict 1 provide a reasonable approximation of chum salmon escapement in the absence of an enumeration project on Bonanza River.

Methods

Escapement data were collected by identifying salmon by species and counting them through a fixed picket weir on Bonanza River, Norton Sound, AK. Counts were conducted several times a day when the weir was ‘open’ to allow for fish passage. Escapement data is comprised of daily counts for each salmon species enumerated through the weir and summaries of cumulative count and cumulative proportion of run. 

Environmental data include water temperature and relative water height.  Water temperature was recorded using a handheld thermometer submerged in the river twice daily: once in the morning (8:00 am) and once in the evening (8:00 pm). Water temperature was also collected every 6 hours using a HOBO logger (Onset Computer Corporation) and data were downloaded at the end of the season.  Relative water height was recorded using a stream gauge (in decimal feet) at the same time water temperature was taken.  At the end of the season water height in decimal feet was converted to centimeters for reporting.  Relative water height was used to assess river height through a season and should not be compared between years because the water gauge was not located in the exact same spot each year. 

Age, sex, and length (ASL) data were collected predominately from chum salmon and other salmon species when time allowed.  Sex of the salmon was determined using external characteristics such as kype development and presence of an ovipositor.  Length was measured mid-eye to tail fork (METF) to the nearest millimeter. One scale was collected from each chum salmon for ageing.  Scales were placed on gum cards that were pressed into acetate sheets. A microfiche reader was used to age each readable scale and ages were reported following the European notation where the first digit refers to the freshwater age not including the year spent in the gravel and the second digit refers to the ocean age. Unreadable scales were assigned a code depending on the reason they were considered unreadable.

Usage Notes

Bonanza River escapements from 2018 to 2020 are not considered complete counts of chum salmon (or any other salmon species).

HOBO logger (Onset Computer Corporation) data include time when the logger was recording inside and outside air temperature - this reflects the time before the logger was placed in the river and after the logger was removed from the river but before downloading. 

In 2019, counting started on June 29 but ceased 4 days later due to high water.  Project operations resumed on July 9.

Funding

Alaska Sustainable Salmon Fund, Award: 51008