Delta Smelt Enclosure Studies, North Delta Arc of the upper San Francisco Estuary, CA, 2019 - 2024

This dataset comprises data from seven different enclosure studies, each of which used Delta Smelt reared by the UC Davis Fish Conservation and Culture Laboratory (FCCL). Each study had unique study questions and utilized slightly different methods. Enclosure Prototype (Rio Vista (RV) and Sacramento Deep Water Ship Channel (SDWSC)) – these studies, conducted January through February (RV) and March (SDWSC) of 2019, were designed to test different enclosure mesh sizes to assess their effects on Delta Smelt growth, survival, and feeding efficacy over a period of four weeks. Three different enclosure designs were deployed at two locations (Rio Vista and the Sacramento Deep Water Ship Channel), with 60 to 64 fish per enclosure and a control group of 30 fish at FCCL. See Baerwald et al, 2023 for details. - https://doi.org/10.1371/journal.pone.0286027 North Delta Pilot – This study, conducted in July and August of 2019, was implemented to test the feasibility of using enclosures to evaluate a flow action designed to improve food for Delta Smelt in the Yolo Bypass, and test upper thermal limits in field conditions for cultured Delta Smelt. Three enclosures were placed at Rio Vista and one enclosure was placed in the Yolo Bypass. Each enclosure held 60 fish. A control group of 90 fish was held at FCCL. The study lasted for four weeks; however, the Yolo Bypass enclosures were removed after three weeks following a heat wave that was lethal to all enclosure fish at that site. Suisun Marsh Pilot – This study, conducted in October and November of 2019, tested the feasibility of using enclosures to evaluate a flow action designed to improve low salinity habitat for Delta Smelt in Suisun Marsh. Three enclosures per site were placed at three locations (Suisun Marsh, Rio Vista, and the Yolo Bypass). Each enclosure held 60 fish, and a control group of 90 fish was held at FCCL. The study lasted for four weeks. Domestication/Behavior – This study, conducted in January and February of 2021, was designed to test the effect of domestication level on Delta Smelt survival and health in a naturalized environment. Nine enclosures, each holding 34 fish, were deployed at Rio Vista, with a control group of 40 fish held at FCCL; however, a high-wind storm event resulted in high mortality (93%) of field-deployed fish, limiting the available data from this experiment. Feeding Study – This study, conducted in February and March of 2022, was designed to test the effect of two different feeding strategies implemented at FCCL (dry-fed only, or acclimated to live-feed 30-days before the field trial) on survival, growth, and diets of fish transported to a naturalized environment. This study was designed to inform Delta Smelt supplementation strategies. Six enclosures, each holding 84 fish, were held at Rio Vista, and two control groups of 172 fish total were held at FCCL. During this study, subsamples of fish were collected and processed weekly from each enclosure and control group to provide deeper insight into fish condition and diet over time. The study ran for a total of four weeks. Biofouling Study – This study, conducted August through October of 2023, had the dual-purpose of testing: (1) Whether enclosures could be used to test the efficacy of a summer flow action to reduce salinity in Suisun Marsh and (2) Different methods for reducing biofouling on then enclosure, which in prior years had been noted as a potential confounding factor when utilizing enclosure studies during warmer months. Four enclosures were deployed at each of two locations (Rio Vista and Suisun Marsh) with each enclosure holding 70 fish. A control group of 24 fish was held at FCCL. Two of the enclosures at each field location were exchanged for clean enclosures every two weeks, while the other two enclosures at each location were scrubbed with a handheld brush once per week. The study ran for a total of six weeks. Suisun Marsh Salinity Control Gate Study – This study, conducted August and September of 2024, was designed to repeat the 2023 testing of the salinity action in Suisun Marsh to see if results were typical, though without the exchanging of enclosures. Four enclosures, each holding 70 fish, were deployed at each of two locations (Rio Vista and Suisun Marsh) for a total of four weeks. A control group of 70 fish was simultaneously held at FCCL. We had intended to run the study for six weeks; however, throughout the course of this study, the anchoring system securing the enclosures in Suisun Marsh repeatedly came loose. After the third failure, which occurred at four weeks, we made the decision to end the study.本数据集涵盖7项独立围隔实验的数据，所有实验所用的三角洲银汉鱼（Delta Smelt）均由加州大学戴维斯分校鱼类保护与养殖实验室（FCCL）繁育。每项实验均有独特的研究问题，并采用了略有差异的实验方法。 1. 围隔原型实验（里奥维斯塔（RV）与萨克拉门托深水航道（SDWSC））：本实验于2019年1-2月（里奥维斯塔）及3月（萨克拉门托深水航道）开展，旨在测试不同围隔网目尺寸，评估其对三角洲银汉鱼四周饲养周期内生长、存活与摄食效率的影响。实验在两个地点部署了3种不同的围隔设计，每个围隔放养60~64尾鱼，同时在FCCL设置对照组30尾。详细实验方案参见Baerwald等人2023年的研究：https://doi.org/10.1371/journal.pone.0286027。 2. 北三角洲先导实验：本实验于2019年7-8月开展，旨在验证围隔用于评估约洛摆渡道（Yolo Bypass）内改善三角洲银汉鱼食物资源的流量调控措施的可行性，并检测养殖三角洲银汉鱼在野外条件下的高温耐受上限。实验在里奥维斯塔布设3个围隔，在约洛摆渡道布设1个围隔，每个围隔放养60尾鱼；同时在FCCL设置对照组90尾。实验原计划持续4周，但约洛摆渡道的围隔在3周后因热浪导致所有围隔内鱼类死亡，遂提前移除。 3. 苏森沼泽先导实验：本实验于2019年10-11月开展，旨在验证围隔用于评估苏森沼泽内改善三角洲银汉鱼低盐生境的流量调控措施的可行性。实验在3个地点（苏森沼泽、里奥维斯塔、约洛摆渡道）各布设3个围隔，每个围隔放养60尾鱼；同时在FCCL设置对照组90尾，实验总时长为4周。 4. 驯化/行为实验：本实验于2021年1-2月开展，旨在测试驯化水平对自然化环境中三角洲银汉鱼存活与健康状况的影响。实验在里奥维斯塔部署9个围隔，每个围隔放养34尾鱼；同时在FCCL设置对照组40尾。但强风暴事件导致野外部署鱼类的死亡率高达93%，极大限制了本实验的可用数据量。 5. 摄食实验：本实验于2022年2-3月开展，旨在测试FCCL内实施的两种投喂策略——仅投喂配合饲料，或在野外试验前用活饵驯化30天——对转运至自然化环境的鱼类存活、生长与食性的影响，本实验旨在为三角洲银汉鱼的增殖放流策略提供科学参考。实验在里奥维斯塔布设6个围隔，每个围隔放养84尾鱼；同时在FCCL设置两个对照组，总放养量为172尾。实验期间，每周从每个围隔与对照组采集鱼体子样本进行处理，以深入解析鱼类随时间变化的健康状况与食性。实验总时长为4周。 6. 生物附着实验：本实验于2023年8-10月开展，兼具双重研究目标：（1）验证围隔能否用于测试夏季流量调控措施降低苏森沼泽盐度的效果；（2）测试不同的围隔生物附着抑制方法——此前多年研究发现，温暖月份开展围隔实验时，生物附着可能成为潜在的混杂因素。实验在里奥维斯塔与苏森沼泽两个地点各部署4个围隔，每个围隔放养70尾鱼；同时在FCCL设置对照组24尾。每个野外地点的4个围隔中，每两周更换一次清洁围隔，其余2个围隔每周用手持刷子刷洗一次。实验总时长为6周。 7. 苏森沼泽盐度控制闸门实验：本实验于2024年8-9月开展，旨在重复2023年苏森沼泽盐度调控措施的测试，以验证实验结果的可重复性，本次实验未进行围隔更换。实验在里奥维斯塔与苏森沼泽两个地点各部署4个围隔，每个围隔放养70尾鱼，原计划总实验时长为6周；同时在FCCL设置对照组70尾。但实验期间，苏森沼泽的围隔锚定系统多次松动，在第4周发生第3次锚定失效后，研究团队决定终止实验。