Coho Distribution [ds326]

August 2025 Version. This dataset represents the "Observed Distribution" for coho salmon in California by using observations made only between 1990 and the present. It was developed for the express purpose of assisting with species recovery planning efforts. The process for developing this dataset was to collect as many observations of the species as possible and derive the stream-based geographic distribution for the species based solely on these positive observations. For the purpose of this dataset an observation is defined as a report of a sighting or other evidence of the presence of the species at a given place and time. As such, observations are modeled by year observed as point locations in the GIS. All such observations were collected with information regarding who reported the observation, their agency/organization/affiliation, the date that they observed the species, who compiled the information, etc. This information is maintained in the developer's file geodatabase (©Environmental Science Research Institute (ESRI) 2016). To develop this distribution dataset, the species observations were applied to California Streams, a CDFW derivative of USGS National Hydrography Dataset (NHD) High Resolution hydrography. For each observation, a path was traced down the hydrography from the point of observation to the ocean, thereby deriving the shortest migration route from the point of observation to the sea. By appending all of these migration paths together, the "Observed Distribution" for the species is developed. It is important to note that this layer does not attempt to model the entire possible distribution of the species. Rather, it only represents the known distribution based on where the species has been observed and reported. While some observations indeed represent the upstream extent of the species (e.g., an observation made at a hard barrier), the majority of observations only indicate where the species was sampled for or otherwise observed. Because of this, this dataset likely underestimates the absolute geographic distribution of the species. It is also important to note that the species may not be found on an annual basis in all indicated reaches due to natural variations in run size, water conditions, and other environmental factors. As such, the information in this dataset should not be used to verify that the species are currently present in a given stream. Conversely, the absence of distribution linework for a given stream does not necessarily indicate that the species does not occur in that stream. The observation data were compiled from a variety of disparate sources including but not limited to CDFW, USFS, NMFS, timber companies, and the public. Forms of documentation include CDFW administrative reports, personal communications with biologists, observation reports, and literature reviews. The source of each feature (to the best available knowledge) is included in the data attributes for the observations in the geodatabase, but not for the resulting linework. The spatial data has been referenced to California Streams, a CDFW derivative of USGS National Hydrography Dataset (NHD) High Resolution hydrography. Usage of this dataset: Examples of appropriate uses include: - species recovery planning, - Evaluation of future survey sites for the species, - Validating species distribution models. Examples of inappropriate uses include: - Assuming absence of a line feature means that the species are not present in that stream, - Using this data to make parcel or ground level land use management decisions, - Using this dataset to prove or support non-existence of the species at any spatial scale, - Assuming that the line feature represents the maximum possible extent of species distribution. All users of this data should seek the assistance of qualified professionals such as surveyors, hydrologists, or fishery biologists as needed to ensure that such users possess complete, precise, and up to date information on species distribution and water body location. Any copy of this dataset is considered to be a snapshot of the species distribution at the time of release. It is impingent upon the user to ensure that they have the most recent version prior to making management or planning decisions. Please refer to "Use Constraints" section below.2025年8月版。本数据集代表加利福尼亚州银大麻哈鱼（coho salmon）的观测分布（Observed Distribution），其数据仅来源于1990年至今的观测记录。本数据集专为协助物种恢复规划工作而构建。 本数据集的构建流程为：尽可能收集该物种的所有观测记录，并仅基于这些阳性观测结果，推导得到基于河流的物种地理分布范围。为本数据集之定义，观测指的是在特定时间与地点报告目击该物种，或获取其存在相关佐证的记录。据此，观测数据以观测年份为标识，以GIS中的点位置进行建模。 所有此类观测记录均附带相关元数据，包括观测报告人、其所属机构/组织/单位、观测该物种的日期、信息汇编人员等。该元数据存储于开发者的文件地理数据库（©环境系统研究所（ESRI）2016年版权所有）中。 为构建该分布数据集，将物种观测记录匹配至《加州河流》图层——该图层是美国地质调查局（USGS）国家水文数据集（National Hydrography Dataset, NHD）高分辨率水文数据的CDFW衍生产品。针对每一条观测记录，将从观测点沿水文网络向海洋方向追踪路径，由此推导得到从观测点至海域的最短洄游路线。将所有此类洄游路径合并后，即可得到该物种的观测分布范围。 需特别说明的是，本图层并未尝试模拟该物种的全部潜在分布范围，仅基于已被观测并报告的物种出现地点，呈现其已知分布情况。尽管部分观测记录确实代表了该物种的上游分布极限（例如在硬质障碍物处的观测），但绝大多数观测仅能反映该物种被采样或被目击的具体位置。因此，本数据集大概率低估了该物种的实际地理分布范围。 同时需注意，由于洄游种群规模、水文条件及其他环境因素的自然波动，该物种并非每年都会出现在所有标注的河段中。因此，本数据集的信息不应被用于验证某一河段中当前是否存在该物种。反之，某一河段未包含分布线要素，并不代表该物种不会出现在该河段中。 观测数据来源于多种不同渠道，包括但不限于CDFW、美国林务局（USFS）、国家海洋渔业局（NMFS）、木材公司及公众。相关记录形式包括CDFW行政报告、与生物学家的私人沟通记录、观测报告及文献综述。在地理数据库的观测记录数据属性中，会（基于现有可获取信息）标注每一条要素的来源，但最终生成的分布线要素并未附带该信息。 空间数据参考坐标系匹配至《加州河流》图层，即前述USGS NHD高分辨率水文数据的CDFW衍生产品。 本数据集适用场景包括： - 物种恢复规划 - 该物种未来调查点位的评估 - 物种分布模型的验证 不适用场景包括： - 假设某河段无分布线要素即代表该物种不存在于此河段 - 使用本数据进行地块或地面级土地利用管理决策 - 使用本数据集证明或支持任意空间尺度下该物种不存在 - 假设分布线要素代表该物种分布的最大潜在范围 所有使用本数据的用户，应根据需要咨询测量师、水文学家或渔业生物学家等合格专业人士，以确保自身掌握关于物种分布及水体位置的完整、精准且最新的信息。 本数据集的任何副本均被视为发布时刻的物种分布快照。用户有责任确保在进行管理或规划决策前，已获取本数据集的最新版本。请参阅下文的"使用限制"章节。