Effects of Temperature on Hatching and Growth Performance of Embryos and Yolk-Sac Larvae of a Threatened Estuarine Fish: Longfin Smelt

The longfin smelt (Spirinchus thaleichthys) population in the San Francisco Estuary has declined to less than 1% of historic numbers. It is crucial to identify the mechanisms that are driving the decline in order to implement species conservation plans. However, the low abundance and ever-declining population of longfin smelt limits access to research specimens. Developing a captive culture of longfin smelt would solve this issue while simultaneously gathering knowledge that could be used by conservation managers. To improve culture methods, we focused on the early life stages because it is the first major bottleneck in culturing the species. We measured the hatching and growth performance of longfin smelt embryos (ca. 15-28 days post-fertilization) and larvae (ca. 3-5 days post-hatch) and found that temperatures of 9�?? and 12�?? are appropriate culturing temperatures. These results demonstrate that the early life stages of longfin smelt require cooler water than delta smelt, another species of conservation concern that many California water management policies center around. While our study is useful for informing conservation efforts, the complexities surrounding the distribution of water resources in California may delay efforts to implement this knowledge into conservation plans