Interagency Ecological Program San Francisco Estuary Smelt Larva Survey 2009 – 2023

The Interagency Ecological Program San Francisco Estuary Smelt Larva Survey was initiated by the California Department of Fish and Wildlife (CDFW) in 2009 to monitor the distribution and abundance of newly-hatched Longfin Smelt (Spirinchus thaleichthys) in the San Francisco Estuary. Surveys are conducted bi-weekly and sampling begins in December, and continues through March. The surveys sample at fixed locations, stations, from San Pablo Bay through Suisun Bay and into the Sacramento-San Joaquin River Delta. Napa River stations were added in 2014 and the San Pablo Bay expansion stations were added in December 2022. Each survey consists of 59 stations. At each station, one 10 minute stepped-oblique (bottom to top) tow is made following a prescribed tow schedule. The net is a conical 500 µm mesh lashed to a D shaped frame mounted on skis. Larval fish samples are preserved in the field in 10% Formalin and brought back to the CDFW Stockton Lab for identification to species and enumeration under a microscope. Several types of data are collected at each station in addition to the larval fish sample, including the volume of water sampled by the net, surface water temperature, surface and bottom specific conductance (EC normalized at 25˚C), Secchi disk depth, tow duration, tidal condition, and surface water turbidity.

跨机构生态项目旧金山河口胡瓜鱼幼体调查由加利福尼亚鱼类及野生动物部（CDFW）于2009年启动，旨在监测旧金山河口新孵化的长鳍胡瓜鱼（Spirinchus thaleichthys）的分布与丰度。调查每两周进行一次，采样工作始于12月，持续至次年3月。调查在固定站位开展采样，范围从圣巴勃罗湾经苏森湾延伸至萨克拉门托-圣华金河三角洲。纳帕河站位于2014年增设，圣巴勃罗湾扩展站位则于2022年12月新增。每次调查包含59个站位。每个站位按照规定的拖网计划进行一次10分钟的阶梯式斜向（自底至顶）拖网作业。所用网具为锥形500微米网目，固定于安装在滑橇上的D形框架。幼鱼样本在野外使用10%福尔马林固定，随后带回CDFW斯托克顿实验室，在显微镜下进行种类鉴定与计数。除幼鱼样本外，每个站位还收集多种数据，包括网具采样水量、表层水温、表层与底层电导率（25℃标准化电导率）、塞奇盘深度、拖网时长、潮汐状况及表层水浊度。