Daily escapement counts from Tanada Creek and Long Lake weirs, Alaska, 1974-2014

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 salmon escapement data from Tanada Creek and Long Lake in the Copper River region of Alaska.

当鲑鱼从海洋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，即“逃逸”出通常设于淡水溪流入海口附近的鲑鱼渔业捕捞区域。逃逸量数据（escapement data）指对这些向上游洄游的鱼类进行计数所得的数据，可作为特定溪流中产卵鲑鱼总种群丰度的评估指标。这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道中。逃逸量数据的采集方式多种多样。固定站点项目会沿淡水廊道布设观测人员，计数经由堰坝或高架观测塔向上游洄游的鲑鱼；布设于河道中的声呐设备同样可完成固定式逃逸量计数。上述计数通常为抽样统计，需经推算以换算为完整24小时的总量。此外也可通过航空调查采集数据：由航空器上的观测人员提供评估指标以估算逃逸量。总体而言，逃逸量计数并非种群总丰度的直接统计结果，而是丰度的评估指标。调查通常会安排在产卵高峰时段开展，多为夏季；对于银大麻哈鱼（Coho salmon），则也可在秋季进行。此外还收录了部分非鲑鱼物种的相关数据。本数据集包含阿拉斯加铜河区域内塔纳达溪与长湖的鲑鱼逃逸量数据。