Daily salmon escapement counts from the OceanAK database, Alaska, 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 or near 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. This dataset contains salmon escapement data extracted from the Alaska Department of Fish and Game's OceanAK database, and contains data from multiple regions in Alaska.

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，允许一定数量的个体通过或逃脱设于淡水溪流入海口附近的鲑鱼渔业捕捞。
逃逸数据（escapement data）即对这些溯河洄游鱼类的计数结果，可作为对应溪流中产卵鲑鱼总丰度的衡量指标。此类数据对渔业管理具有重要意义，因为多数鲑鱼捕捞活动均发生在该洄游时段的淡水河流内及其周边区域。

逃逸数据的采集方式多样。固定式监测项目会安排观察员驻守淡水河道沿线，统计通过拦鱼堰或高架观测塔的溯河鲑鱼数量；布设於河道中的声呐设备也可开展固定式逃逸计数。此类计数通常仅为抽样结果，需经推算以代表24小时时段的总逃逸量。

逃逸数据也可通过航空调查采集，即由航空器上的观察员提供计数指标以估算逃逸量。总体而言，逃逸计数并不直接代表种群总丰度，仅为丰度的一项衡量指标。调查通常会安排在产卵高峰期开展，时段多为夏季；对于银大麻哈鱼（Coho salmon）而言，调查也可在秋季进行。

本数据集提取自阿拉斯加鱼类与野生动物部（Alaska Department of Fish and Game）的OceanAK数据库，涵盖阿拉斯加多个区域的鲑鱼逃逸数据。