When we think of salmon, we often associate them with cold, icy waters. However, a recent study has revealed that warm water plays a crucial role in the survival of these cold-water fish. The question remains: is salmon a warm water fish?
The study, published in Nature Climate Change, highlights the importance of warm river habitats in supporting the survival of salmon and trout. These habitats, typically found in lower parts of basins, provide pulses of growth potential during the spring and fall, also known as the shoulder seasons. During these periods, the rivers are not at peak summer temperatures, allowing the fish to grow and thrive.
Why Warm Water Matters
Warm water is essential for salmon and trout because it allows them to grow and store energy. This energy is critical for their survival, particularly during the summer months when they need to migrate to cooler parts of the river to reproduce. The synergy between cold water and warm water is vital, as it enables these fish to adapt to changing environmental conditions.
Conservation efforts often focus on protecting the coldest places, such as high mountain streams, which are already the most pristine parts of basins. However, this approach neglects the importance of warm water habitats, which are optimal for much of the year. By prioritizing cold-water habitat, we may be overlooking the critical role warm water plays in the life cycle of salmon and trout.
The Impact of Rising Temperatures
As the climate warms, the importance of warm water habitats becomes even more critical. Rising temperatures can have devastating effects on salmon and trout populations. For example, water heated to 68 degrees or more can be problematic for fish, causing them to slow down and become more susceptible to predators and infections. Extreme heat above 70 degrees can result in death, killing fish by the thousands.
In 2024, a heat wave and drought combination had a significant impact on sockeye salmon, with 99% of returning Snake River sockeye dying before they reached Idaho. This highlights the urgent need to consider the role of warm water in conservation strategies.
Salmon Farms and Sea Lice
Salmon farms, which rely on cool water in sea lochs to operate, are also affected by rising temperatures. As sea temperatures rise, the risk of parasitic sea lice outbreaks increases, posing a significant threat to wild fish populations. The life cycle of sea lice is highly temperature-dependent, and warmer waters allow them to complete their lifecycle more quickly, leading to increased infection pressure on Atlantic salmon farms.
The impact of sea lice on wild fish is not limited to the summer months. As winters get warmer, there is no reprieve for salmon from these parasites, and they can continue to proliferate throughout the year. This means wild salmonids will be at a greater risk to dangerous infestation pressure from farms for even longer periods of the year.
In conclusion, the answer to the question “Is salmon a warm water fish?” is not a simple yes or no. While salmon are often associated with cold water, warm water plays a critical role in their survival. By recognizing the importance of warm water habitats, we can develop more effective conservation strategies to protect these iconic species in a warming world.