Compiled age, sex, and length data for Alaskan salmon, 1922-2017

Age, sex and length (ASL) data provide population dynamics information that can indicate how population trends occur and may be changing. These data can help researchers estimate population growth rates, age-class distribution, and population demographics. Knowing population demographics, growth rates and trends is particularly valuable to fisheries managers who must perform population assessments to inform management decisions. These data are therefore important in valuable fisheries like the salmon fisheries of Alaska. This dataset includes age, sex and length data compiled from annual sampling of commercial and subsistence salmon harvests and research projects throughout Alaska from 1922-2017. It includes data on five salmon species: chinook, chum, coho, pink and sockeye. Age estimates were made by examining scales or bony structures (e.g. otoliths - ear bones). Scales were removed from the side of the fish; usually the left side above the lateral line. Scales or bony structures were then mounted on gummed cards and pressed on acetate to make an impression. The number of freshwater and saltwater annuli (i.e. rings) was counted to estimate freshwater and saltwater ages in years. Fish sex was determined by either examining external morphology (eg. head and belly shape) or internal sex organ. Length was measured in millimeters, generally from mid-eye to the fork of the tail. This data package includes a .csv of ASL data (ASL_master.csv) and .csv files defining project types (ASLProjectType.csv), gear types (gear.csv), length measurement types (length_type_lookup.csv), and locations (Locations_subdistricts_uniqueID.csv). The R Markdown file (ASL_processing.Rmd) details the data processing steps for the ASL data.

年龄、性别与体长（Age, sex and length, ASL）数据可提供种群动态信息，用以揭示种群趋势的发生与演变规律。此类数据可助力研究者估算种群增长率、年龄层级分布以及种群统计学特征。明晰种群统计学特征、增长率与变化趋势，对于需开展种群评估以制定管理决策的渔业管理者而言尤为重要。
因此，此类数据对于阿拉斯加鲑鱼渔业等具有高经济价值的渔业而言举足轻重。
本数据集涵盖1922年至2017年间，针对阿拉斯加全境商业性、自给性鲑鱼捕捞及相关研究项目开展年度采样所获取的年龄、性别与体长数据。
数据集涵盖5种鲑鱼：奇努克鲑（Chinook）、狗鲑（Chum）、银鲑（Coho）、粉鲑（Pink）与红鲑（Sockeye）。
年龄估算通过检视鳞片或骨质结构（如耳石（otoliths）——耳部骨骼）实现。
鳞片通常取自鱼体侧线以上的左侧区域。
随后将鳞片或骨质结构粘贴于涂胶卡片，并压印于醋酸纤维胶片以留存印痕。
通过计数淡水与海水环纹（即生长纹）的数量，以年为单位估算鱼类的淡水与海水生长年龄。
鱼类性别可通过两种方式判定：一是检视外部形态（如头部与腹部轮廓），二是解剖观察内部生殖器官。
体长以毫米为单位计量，通常测量起点为眼部中点，终点为尾鳍分叉处。
本数据包包含ASL主数据CSV文件（ASL_master.csv），以及用于定义项目类型（ASLProjectType.csv）、渔具类型（gear.csv）、体长测量类型（length_type_lookup.csv）与采样点位（Locations_subdistricts_uniqueID.csv）的配套CSV文件。
R Markdown文件（ASL_processing.Rmd）详细阐述了ASL数据的完整处理流程。