Compiled annual statewide Alaskan salmon escapement counts, 1921-2017

As salmon migrate from the marine environment to freshwater streams to spawn, a certain number are allowed to pass through, or '/escape/' the salmon fishery (frequently located near the mouth of the freshwater stream) as a management strategy to preserve the species. Escapement data are the enumeration of these migrating fish as they pass upstream, and represent an index of the total abundance of spawning salmon in that particular stream. These data are important for fisheries management, since most salmon harvest occurs in freshwater rivers during this migration. Escapement data are collected in a variety of ways. Stationary projects utilize observers stationed along freshwater corridors who count salmon as they pass upriver through weirs or past elevated towers. Sonar equipment placed in the river can also give a stationary escapement count. These counts usually represent a sample, and are expanded to represent a 24h period. Escapement data can also be collected using aerial surveys, where observers in an aircraft provide an index to estimate escapement. In general, escapement counts do not represent total abundance, but instead an index of abundance. Surveys are usually timed to coincide with peak spawning activity, generally in the summer, but in the case of Coho salmon in the fall as well. Some data about non-salmon species are also included. This dataset contains compiled annual data from multiple sources. The .Rmd merges all datasets, attaches location information from the escapement_locations.csv file, identifies and flags duplicate records, and performs quality assurance checks by filtering and graphing results.

当鲑鱼从海洋环境洄游至淡水溪流产卵时，作为保护该物种的管理策略，会允许一定数量的个体通过鲑鱼渔场（通常设于淡水溪流入海口附近），即所谓的‘逃逸’（escape）。逃逸量数据（escapement data）是对这些洄游鱼类溯河而上时的个体计数，可作为特定溪流中产卵鲑鱼总种群丰度的指标。此类数据对渔业管理至关重要，因为多数鲑鱼捕捞活动均发生在该洄游阶段的淡水河流中。

逃逸量数据的采集方式多种多样。固定站点监测项目会沿淡水河道布设观测人员，对通过拦鱼堰或高架观测塔的溯河鲑鱼进行计数。安装于河道内的声呐设备同样可完成固定站点的逃逸量计数。这类计数通常仅为抽样结果，需经外推得到24小时时段的总计数。

逃逸量数据也可通过航空调查采集，由航空器上的观测人员提供估算逃逸量的相关指标。总体而言，逃逸量计数并非种群总丰度的直接反映，而是丰度的替代指标。

调查时段通常与产卵高峰活动相契合，多集中于夏季，但对于银大麻哈鱼（Coho salmon）而言，秋季也会开展相关调查。本数据集还包含部分非鲑鱼物种的相关数据。

本数据集整合了多来源的年度汇编数据。其中的.Rmd文件用于合并所有数据集，附加来自escapement_locations.csv文件的位置信息，识别并标记重复记录，同时通过筛选与绘图结果开展质量保证校验。