Climate Change Shrinks and Fragments Salmon Habitats in a Snow‐Dependent Region

Abstract

The large majority of climate change research for aquatic organisms has focused on stream water temperature and discounted the importance of flow changes associated with evolving precipitation regimes. Using a high-resolution stream topographic map that supported a series of linked flow and fish habitat quality models, our research describes how observed historical flow reductions and projected future reductions affect local habitat quality, distributions, and connectivity for a salmon population. We demonstrated that as climate change continues to change flow regimes in snow-dependent regions, it will cause fragmentation and reduce the overall volume of available habitats in headwater streams where salmon and other cold-water fish species spawn and grow during early life stages.

Adult spawners: A critical period for subarctic Chinook salmon in a changing climate

“…For example, Pacific salmon can seek out thermal refugia along migration corridors via behavioral thermoregulation (Armstrong et al, 2016) that presumably results in little initial influence of warming on their survival, but as those thermal refugia disappear a dramatic influence on survival and reproductive success could emerge without warning. Moreover, the existence of thermal refugia alone may be insufficient if changes to hydrologic flow regimes results in fragmentation of available habitats (Tonina et al, 2022). The mainstem Yukon River does not appear to have thermal refugia (Eiler et al, 2022) and may help explain why Yukon River salmon have been particularly vulnerable to a warming climate.…”

Trends in Chinook salmon spawner abundance and total run size highlight linkages between life history, geography and decline

“…These recent declining trends have coincided with warming climate conditions in the marine and freshwater habitats of Chinook salmon with no historical analogue (Lindley et al, 2021; Schoen et al, 2017); including a marine heat wave, which has impacted marine ecosystems in the North Pacific since 2014 (DiLorenzo and Mantua 2016), increasing abundances of marine mammals that prey upon juvenile and adult salmon (Chasco et al, 2017; Nelson et al, 2019), and a period when the abundance of pink salmon ( O. gorbuscha ) in the North Pacific has peaked at over 500 million fish, creating the potential for cascading effects of competition between pink salmon and other pelagic predators (Ruggerone & Nielsen, 2004; Ruggerone & Irvine, 2018). Unprecedented variability in flow and river temperatures have also impacted Chinook and other salmon species (Crozier et al, 2019; Hinch et al, 2021; Tonina et al, 2022; von Biela et al, 2022). While climate‐driven disturbances and novel ecosystem conditions have likely contributed to negative trends across the regions we evaluated, California and Southern Oregon have been further impacted by a prolonged drought affecting freshwater systems (Kogan & Guo, 2015).…”

Fisheries Volume 48 Number 8 August 2023

“…It is anticipated that coolwater habitat will move upstream toward headwaters and become more isolated (e.g., Isaak et al 2010 ;Isaak and Rieman 2013 ;Tonina et al 2022 ). Two implications of this are (1) that removing barriers to fi sh migration or providing roundtrip passage facilities may be a priority, and (2) designated uses based on the presence of a species may change in the future.…”