DOI: 10.5061/dryad.98sf7m0np
title: Afognak Lake Sockeye Salmon Monitoring Project (2020–2022)

description: The Afognak River (Litnik) has historically supported one of the largest
 sockeye salmon subsistence fisheries for Kodiak Archipelago residents. In
 the 2000s, the number of sockeye salmon returning to Afognak River had
 diminished substantially resulting in closures to commercial, sport, and
 subsistence fishing in Afognak Bay. Local subsistence users, represented
 by the Kodiak-Aleutians Regional Advisory Council, Kodiak Fish and Game
 Advisory Committee, and Kodiak Tribal Council, stressed the importance of
 the Afognak River system to local subsistence users and contended that
 continued closures would make it more difficult for local residents to
 meet their sockeye salmon needs and shift fishing efforts to small nearby
 sockeye salmon runs. The Afognak Lake Sockeye Salmon Stock Monitoring
 Project enumerates adult sockeye salmon into Afognak Lake through a weir
 located on the Afognak River, describes run-timing, or proportional daily
 passage, of sockeye salmon through the weir, estimates the age and sex
 composition of adult sockeye salmon returns, and estimates the average
 length (mm) by age and sex of sockeye salmon passing through the weir.
 Data collected from this project provide salmon management biologists the
 ability to make in-season decisions to execute commercial and sport
 fisheries. In addition, the information that is gathered from these
 projects refines the escapement goals and improves preseason run forecasts
 to allow for maximum sustainable yield and prevent unnecessary
 restrictions of federal and state subsistence fisheries.
description: <strong>Weir Installation and Adult Salmon
 Enumeration</strong> A 27 m long weir was
 installed perpendicular to the stream flow and consisted of 10 wooden
 tripods (each tripod consisting of three 4″ x 4″ x 8′ spruce timbers and
 2″ x 6″ x 6′ horizontal cat-walk supports), 33 aluminum pipes (2″ x 10′),
 44 picketed aluminum panels (1″ aluminum pipe with 1″ spacing totaling 30″
 x 6′), and 2 framed panel gates. All materials were secured with sandbags
 and lashed together to create a fish-tight structure that conformed to the
 contour of the stream channel. Two counting gates were
 placed between panels in the two deepest channels of the river enabling
 fish to be counted as they pass through the weir. A white flash panel was
 placed on the substrate beneath each gate to enhance visibility and
 species identification. Fish were counted by field technicians using hand
 tally denominators as fish migrated upstream through the gates. The
 counting gates remained closed until staff were present to count fish
 through the weir for escapement enumeration or when fish were being
 collected into the live trap for age, sex, and length sampling
 (ASL). <strong>Age, Sex, and Length
 Sampling</strong> An upstream “Scott live trap”
 (local name for a modified trap capable of capturing steelhead) was
 installed in front of the east bank gate, which acted as a sampling trap
 as well as a downstream steelhead trap. The trap consisted of 6 weir
 panels placed horizontally in the river in the form of a
 diamond. Adult
 sockeye salmon were sampled at the weir site throughout the adult
 escapement. Details and procedures for adult sampling are outlined in the
 Kodiak Management Area Sockeye Salmon Catch and Escapement Sampling
 Operational Plan, 2022. All scales, when possible, were collected from the
 preferred area of each fish. Scales were mounted on scale “gum” cards and
 returned to the Kodiak ADF&G office where impressions were made on
 cellulose acetate. Fish ages were determined by examining scale
 impressions for annual growth increments using a microfiche reader fitted
 with a 60X lens following designation criteria established by Mosher 1968.
 Ages were recorded using European notation, where a decimal separates the
 number of winters spent in fresh water (after emergence) from the number
 of winters spent in salt water (e.g., 2.3). The total age of the fish
 includes an additional year representing the time between egg deposition
 and emergence of fry. Length measurements were taken from mid-eye to tail
 fork to nearest 1 mm and sex was determined from external morphological
 characteristics. On days where escapement occurred
 but no samples were collected, proportions were estimated by linear
 interpolation between sampling events. The sample size was selected so
 that the proportion of each major age group (by stratum) was estimated
 within at least α=0.07 of its true value 95% of the time. Standard error
 of the age proportions was calculated as the square root of estimated
 variance of a proportion. Average length (unweighted) was calculated by
 age and sex.