DOI: 10.5061/dryad.gqnk98sn1
title: Age composition of subsistence harvests and total return of sockeye salmon from the Kvichak River

description: This project aged samples of sockeye salmon harvested in the subsistence
 fishery in the Kvichak River watershed in 2018 and 2019. Age data were
 vital to previously funded AKSSF Project #44362 ("Stock Composition
 of Subsistence Harvests and Total Return of Sockeye Salmon from the
 Kvichak River"). It was determined in that project’s first year that
 scale reabsorption necessitated using otoliths to age samples rather than
 scales. Ages from otolith reading combined with stock composition
 estimates from genetic mixed stock analysis were used to evaluate survival
 and productivity of brood years 2012–2015 at smolt and returning adult
 life stages. This project only produced the age reads from otoliths.
 Knowing the age composition of harvests permits reconstruction of the
 sockeye salmon return and examination of cohort returns and estimation of
 marine survival. This project dovetailed with AKSSF Project #44362 (Stock
 Composition of Subsistence Harvests and Total Return of Sockeye Salmon
 from the Kvichak River) by pairing age composition data with genetic stock
 composition data. Accurate age data are key to fisheries management.
 Harvests from in five communities along the Kvichak River were sampled
 (Kokhanok, Pedro Bay, Iliamna-Newhalen, Nondalton and Port Alsworth).
 Otoliths were collected during 2017, 2018, and 2019 to use to estimate the
 age.
description: Otolith collection and transfer to
 MTA Lab Otoliths were
 collected from sockeye salmon caught in subsistence fisheries in five
 communities in the Kvichak River watershed. During 2018, each pair of
 otoliths from one fish was stored in a coin envelope and paired with an
 axillary process for genetic analysis. During 2019, each pair of otoliths
 was stored in 96-cell genetics trays by site and date.  Otoliths were
 shipped to the MTA Lab in Juneau each year. Otolith cleaning and tray
 review Upon receipt,
 otoliths were cleaned with a 5% chlorine solution to remove any remaining
 tissue. Trays were then rinsed with 0.7% thiosulfate and water to stop the
 process. Data associated with each otolith pair, including number,
 species, life stage, statistical week, source, gear type, location, stream
 code, collectors, comments, shipping method, and number of otoliths were
 entered into the Mark, Tag, and Age Lab (Alaska Department of Fish and
 Game) Oracle database. Samples were tracked by bar-codes. Preparation for and ageing of
 otoliths Prior to estimating
 age of these sockeye salmon otoliths, readers studied examples of known
 age otoliths. Although we expected the estimated age of most fish would be
 one of four ages (1.2, 2.2, 1.3, and 2.3, most common ages, European age
 notation), all ages were studied. To estimate age, a reader placed a whole
 otolith on a petri dish sulcus side down and examined it under a
 dissecting microscope to count the annuli (Figure 2). Once a specimen was
 examined, age was entered in the database, and the otolith was returned to
 the tray. Quality Control/Quality Assurance
 First and Second
 Reads Because we did not have
 access to any known age otoliths from the Kvichak River watershed,
 laboratory personnel practiced estimating age of using samples from
 Southeast Alaska that either had a thermal mark or a scale age. Readers
 read these “known age” samples until their reader agreement was
 &gt; 90%. All sockeye salmon otoliths for this
 project were examined at least three times.  In other words, the age of an
 otolith was estimated by a reader, and then age was estimated for same
 otolith by a second and/or a third independent reader. Disagreements among
 readers were resolved by a final examination of the age by senior
 personnel (Final age; Fishery Biologist and/or Crew Leader). During the
 final read, the reader was aware of previous results. Read Assessment
 Methods For this project, we
 assessed reader reliability with: agreement matrices,<i> Kappa
 </i>statistics, mean coefficient of variation (CV), and percent
 error.
description: Description of data:  year: 2017,
 2018, 2019 SampSpec: sockeye salmon
 SURVEY_SITE: 5 sites in Kvichak River, AK*
 Final age: multiple READ_STATUS:
 completed * Kokhanok, Pedro Bay,
 Iliamna-Newhalen, Nondalton, Port Alsworth Questions?
 Contact Bev Agler: bev.agler@alaska.gov