Very little is understood about the spawning habitat of endangered delta smelt Hypomesus transpacificus, which hinders ongoing recovery efforts such as wetland habitat restoration and spawning habitat augmentation. To address this, the spawning response of wild-caught H. transpacificus to different substrates and water velocities was examined across three experiments. In experiment 1, spawning response to dead wood, pebble, natural and artificial Schoenoplectus acutus, empty tray, and tank floor at water velocities of 1.4 and 8.8 cm/s was tested. Egg deposition on pebble at 8.8 cm/s velocity (78.1% of 7778 total eggs) was significantly greater than that on all other substrate-velocity combinations. In experiment 2, spawning response to natural S. acutus, dead wood, sand, pebble, cobble, and empty tray at velocities of 8.7 and 15.4 cm/s was tested. Egg deposition on pebble at 15.4 cm/s (61.5% of 36171 total eggs) was significantly greater than that on all substrate-velocity combinations except for sand at 15.4 cm/s. Sand at 15.4 cm/s (22.3%) contained significantly more eggs than all combinations except for pebble at 8.7 and 15.6 cm/s. In experiment 3, egg attachment to natural S. acutus, dead wood, sand, pebble, cobble, and empty tray when exposed to 14.6 cm/s velocity was tested. Egg loss on sand was significantly greater than that on empty tray and pebble, indicating that egg deposition on sand may have been underestimated in experiment 2. Together, these results indicate that H. transpacificus selects pebble and sand at higher water velocities for spawning under certain laboratory conditions. These findings are important, as they provide insight into the potential natural habitats that may be used for spawning and thereby inform ongoing habitat restoration efforts.

中文翻译：

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实验室条件下野生捕捞三角洲拟南芥下丘脑产卵微生境的选择

对于濒临灭绝的三角洲熔炼海带（Hypomesus transpacificus）的产卵栖息地知之甚少，这阻碍了正在进行的恢复工作，例如湿地栖息地的恢复和产卵栖息地的扩大。为了解决这个问题，我们在三个实验中检查了野生捕获的H. transpacificus对不同底物和水流速的产卵反应。在实验1中，测试了在1.4和8.8 cm / s的水速下对死木，鹅卵石，天然和人造Achotus，空盘和水箱底板的产卵响应。以8.8 cm / s的速度在卵石上的卵沉积（占7778个总卵的78.1％）显着大于所有其他底物速度组合的卵。在实验2中，产生自然响应测试了S. acutus，枯木，沙子，卵石，鹅卵石和空托盘，其速度分别为8.7和15.4 cm / s。以15.4厘米/秒的速度在卵石上的卵沉积（占36171个总卵中的61.5％）显着大于所有基质-速度组合上的卵，除了以15.4厘米/秒的速度沙子。15.4厘米/秒（22.3％）的沙粒比所有组合中包含的卵子要多得多，除了卵石分别为8.7和15.6厘米/秒。在实验3中，测试了当鸡蛋以14.6 cm / s的速度暴露时，鸡蛋附着在天然金黄色葡萄球菌，枯木，沙子，卵石，卵石和空托盘上的情况。沙子上的卵损失明显大于空托盘和卵石上的卵损失，这表明实验2中的卵在沙子上的沉积可能被低估了。加在一起，这些结果表明，H。transpacificus选择较高水速的卵石和沙子，以便在某些实验室条件下产卵。这些发现很重要，因为它们提供了可用于产卵的潜在自然栖息地的见识，从而为正在进行的栖息地恢复工作提供了信息。