Wave-induced surge conditions are found in shallow marine ecosystems worldwide; yet, few studies have quantified how cyclical surges may affect free swimming animals. Here, we used a recently adapted respirometry technique to compare the energetic costs of a temperate fish species (Cymatogaster aggregata) swimming against a steady flow versus cyclical unidirectional and bidirectional surges in which unsteady swimming (such as accelerating, decelerating and turning) occurs. Using oxygen uptake (ṀO2) as an estimate of energetic costs, our results reveal that fish swimming in an unsteady (i.e. cyclical) unidirectional flow showed no clear increase in costs when compared to a steady flow of the same average speed, suggesting that costs and savings from cyclical acceleration and coasting are near equal. Conversely, swimming in a bidirectional cyclical flow incurred significantly higher energetic costs relative to a steady, constant flow, likely due to the added cost of turning around to face the changing flow direction. On average, we observed a 50% increase in ṀO2 of fish station holding within the bidirectional flow (227.8 mg O2 kg-1 h-1) compared to a steady, constant flow (136.1 mg O2 kg-1 h-1) of the same mean velocity. Given wave-driven surge zones are prime fish habitats in the wild, we suggest the additional costs fish incur by station holding in a bidirectional cyclical flow must be offset by favourable conditions for foraging and reproduction. With current and future increases in abiotic stressors associated with climate change, we highlight the importance of incorporating additional costs associated with swimming in cyclical water flow in the construction of energy budgets for species living in dynamic, coastal habitats.

中文翻译：

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双向周期性流动增加了站着的形状的游泳类鱼类（Cymatogaster aggregata）的能量消耗。

在全世界的浅层海洋生态系统中都发现了由波浪引起的浪涌条件。但是，很少有研究量化周期性的波动会如何影响自由游泳的动物。在这里，我们使用了最近采用的呼吸测定技术来比较温流鱼类（Cymatogaster aggregata）相对于稳定流量游泳与周期性单向和双向浪涌（其中不稳定游泳（如加速，减速和转向）发生）的能量消耗。使用摄氧量（ṀO2）作为能量消耗的估算值，我们的结果表明，与相同平均速度的稳定流量相比，在不稳定（即周期性）单向流动中游动的鱼没有明显增加成本。周期性加速和滑行所节省的费用几乎相等。反过来，相对于稳定，恒定的流量，在双向循环流中游泳会产生高得多的能量成本，这可能是由于转过身来面对不断变化的流向而产生的额外成本。平均而言，与稳定，恒定流量（136.1 mg O2 kg-1 h-1）的双向流量（227.8 mg O2 kg-1 h-1）相比，我们观察到鱼站内的ṀO2增加了50％。相同的平均速度。鉴于波浪驱动的浪涌区是野生的主要鱼类栖息地，我们建议，以双向周期性流动的水位保持的鱼类所产生的额外成本必须被觅食和繁殖的有利条件所抵消。随着当前和未来与气候变化相关的非生物应激源的增加，