A common goal of biological adaptation planning is to identify and prioritize locations that remain suitably cool during the summer. This implicitly devalues areas that are ephemerally warm, even if they are suitable most of the year for mobile animals. Here we develop an alternative conceptual framework, the growth regime, which considers seasonal and landscape variation in physiological performance, focusing on riverine fish. Using temperature models for 14 river basins, we show that growth opportunities propagate up and down river networks on a seasonal basis, and that downstream habitats that are suboptimally warm in summer may actually provide the majority of growth potential expressed annually. We demonstrate with an agent-based simulation that the shoulder-season use of warmer downstream habitats can fuel annual fish production. Our work reveals a synergy between cold and warm habitats that could be fundamental to support cold-water fisheries, and highlights the risk in conservation strategies that underappreciate warm habitats.

生物适应规划的一个共同目标是确定并优先考虑在夏季保持适当凉爽的地点。这隐含地贬低了短暂温暖的地区，即使它们在一年中的大部分时间都适合活动动物。在这里，我们开发了一个替代概念框架，即生长机制，它考虑了生理性能的季节性和景观变化，重点关注河流鱼类。使用 14 个流域的温度模型，我们表明增长机会会在季节性基础上沿河网向上和向下传播，而夏季次优温暖的下游栖息地实际上可能提供了每年表达的大部分增长潜力。我们通过基于代理的模拟证明，较温暖的下游栖息地的平季使用可以促进年度鱼类产量。