Pasparakis Christina, Biefel Felix, De Castro Francine, Wampler Alexandra, Cocherell Dennis E, Carson Evan W, Hung Tien-Chieh, Connon Richard E, Fangue Nann A, Todgham Anne E
Department of Environmental Toxicology, University of California Davis, 1 Shields Ave., Davis, CA 95616, USA.
Bodega Marine Laboratory, University of California Davis, 2099 Westshore Rd., Bodega Bay, CA 94923, USA.
Conserv Physiol. 2024 Dec 14;12(1):coae081. doi: 10.1093/conphys/coae081. eCollection 2024.
Coastal estuaries globally, including the San Francisco Estuary (SFE), are experiencing significant degradation, often resulting in fisheries collapses. The SFE has undergone profound modifications due to population growth, industrialization, urbanization and increasing water exports for human use. These changes have significantly altered the aquatic ecosystem, favouring invasive species and becoming less hospitable to native species such as the longfin smelt (). With longfin smelt abundance declining to <1% of historical numbers, there is a pressing need for laboratory-based experiments aimed at investigating the effects of varying environmental conditions on their stress response and physiology. This study explored the impact of temperature (11 and 14°C) and turbidity maintained with algae (1, 4 and 11 nephelometric turbidity units (NTU)) on the physiological condition of juvenile longfin smelt. Fish were sampled after 2 and 4 weeks in experimental conditions and analysed for whole-body cortisol, glucose, lactate and protein. Condition factor was calculated using length and weight measurements. Critical thermal maximum trials were conducted to assess how prior rearing conditions affected upper thermal tolerance. Cortisol levels were significantly higher in fish held in low-turbidity conditions, whilst glucose levels were significantly greater at lower temperatures and higher turbidities. Protein-to-mass ratios were significantly greater in higher turbidity conditions, with a significant interaction between temperature and turbidity further influencing these ratios. Moreover, 14°C led to diminished condition factors but increased upper thermal tolerances (26.3 ± 0.05 vs 24.6 ± 0.18) compared to longfin smelt at 11°C, highlighting a potential trade-off between the induction of defense mechanisms and subsequent reductions in energy and growth. Data suggest that cooler temperatures (11°C) and elevated turbidities (11 NTU) can benefit juvenile longfin smelt by reducing stress and enhancing growth and energy. These findings hold significant implications for informing and optimizing future endeavours in the culturing and conservation of this species.
全球范围内的沿海河口，包括旧金山河口（SFE），正经历着严重的退化，常常导致渔业崩溃。由于人口增长、工业化、城市化以及人类用水导致的水资源出口增加，旧金山河口发生了深刻的变化。这些变化显著改变了水生生态系统，有利于入侵物种，而对诸如长鳍胡瓜鱼等本地物种则变得不那么适宜生存。随着长鳍胡瓜鱼数量降至历史数量的<1%，迫切需要开展基于实验室的实验，以研究不同环境条件对其应激反应和生理机能的影响。本研究探讨了温度（11和14°C）以及用藻类维持的浊度（1、4和11散射浊度单位（NTU））对幼年长鳍胡瓜鱼生理状况的影响。在实验条件下饲养2周和4周后对鱼进行采样，并分析其全身皮质醇、葡萄糖、乳酸和蛋白质含量。利用体长和体重测量值计算肥满度。进行临界热最大值试验，以评估先前的饲养条件如何影响热耐受性上限。在低浊度条件下饲养的鱼皮质醇水平显著更高，而葡萄糖水平在较低温度和较高浊度下显著更高。在较高浊度条件下蛋白质与质量比显著更高，温度和浊度之间的显著相互作用进一步影响了这些比例。此外，与11°C的长鳍胡瓜鱼相比，14°C导致肥满度降低，但热耐受性上限增加（26.3±0.05对24.6±0.18），突出了防御机制诱导与随后能量和生长减少之间的潜在权衡。数据表明，较低温度（11°C）和较高浊度（11 NTU）可通过减轻应激并促进生长和能量来使幼年长鳍胡瓜鱼受益。这些发现对于为该物种的养殖和保护提供信息以及优化未来工作具有重要意义。
