Del Rio Annelise M, Davis Brittany E, Fangue Nann A, Todgham Anne E
Department of Animal Science, University of California Davis, Davis, CA, USA.
Department of Wildlife, Fish, and Conservation Biology, University of California Davis, Davis, CA, USA.
Conserv Physiol. 2019 Feb 18;7(1):coy078. doi: 10.1093/conphys/coy078. eCollection 2019.
Early life stages of salmonids are particularly vulnerable to warming and hypoxia, which are common stressors in hyporheic, gravel bed, rearing habitat (i.e. a 'redd'). With the progression of global climate change, high temperatures and hypoxia may co-occur more frequently within redds, particularly for salmonid species at their southern range limit. Warming and hypoxia have competing effects on energy supply and demand, which can be detrimental to energy-limited early life stages. We examined how elevated temperature and hypoxia as individual and combined stressors affected the survival, physiological performance, growth, and development of Chinook salmon (). We reared late fall-run Chinook salmon from fertilization to the fry stage in a fully factorial design of two temperatures [10°C (ambient) and 14°C (warm)] and two oxygen levels [normoxia (100% air saturation, 10 mg O/l) and hypoxia (50% saturation, 5.5 mg O/l)]. Rearing in hypoxia significantly reduced hatching success, especially in combination with warming. Both warming and hypoxia improved acute thermal tolerance. While rearing in hypoxia improved tolerance to acute hypoxia stress, warming reduced hypoxia tolerance. Hypoxia-reared fish were smaller at hatch, but were able to reach similar sizes to the normoxia-reared fish by the fry stage. High temperature and normoxia resulted in the fastest rate of development while low temperature and hypoxia resulted in the slowest rate of development. Despite improved physiological tolerance to acute heat and hypoxia stress, hypoxia-reared embryos had reduced survival and growth, which could have larger population-level effects. These results suggest that both warming and hypoxia are important factors to address in conservation strategies for Chinook salmon.
鲑科鱼类的早期生命阶段特别容易受到变暖和缺氧的影响，而这是潜流、砾石床、育幼栖息地（即“产卵砾坑”）中常见的应激源。随着全球气候变化的加剧，高温和缺氧可能在产卵砾坑中更频繁地同时出现，尤其是对于处于其分布范围南端的鲑科鱼类物种而言。变暖和缺氧对能量供应和需求具有相互竞争的影响，这可能对能量有限的早期生命阶段不利。我们研究了温度升高和缺氧作为单独及组合应激源如何影响奇努克鲑（）的存活、生理性能、生长和发育。我们在一个完全析因设计中，将秋末洄游的奇努克鲑从受精饲养至鱼苗阶段，该设计包含两种温度[10°C（环境温度）和14°C（温暖温度）]以及两种氧气水平[常氧（100%空气饱和度，10毫克O/升）和缺氧（50%饱和度，5.5毫克O/升）]。在缺氧环境中饲养显著降低了孵化成功率，尤其是在与升温相结合的情况下。变暖和缺氧均提高了急性热耐受性。虽然在缺氧环境中饲养提高了对急性缺氧应激的耐受性，但升温降低了缺氧耐受性。在缺氧环境中饲养的鱼苗在孵化时体型较小，但到鱼苗阶段时能够达到与在常氧环境中饲养的鱼苗相似的大小。高温和常氧导致发育速度最快，而低温和缺氧导致发育速度最慢。尽管对急性热应激和缺氧应激的生理耐受性有所提高，但在缺氧环境中饲养的胚胎的存活和生长有所降低，这可能会对种群水平产生更大的影响。这些结果表明，变暖和缺氧都是奇努克鲑保护策略中需要解决的重要因素。
