ABSTRACT
Welfare of farmed fish has become of increasing concern for consumers, producers, interest groups and authorities. To improve fish welfare, it is necessary to find indicators that can identify stressful situations early enough so that an intervention can take place before detrimental effects occur. By using heart rate bio-loggers in freely swimming rainbow trout (Oncorhynchus mykiss), combined with plasma cortisol levels and a range of haematological and blood chemistry parameters, we assessed the severity of stress responses induced by a range of common aquaculture practices before and during harvest. Following surgery, transportation and reintroduction with conspecifics in the sea cage, it took ~4 days for heart rate to stabilize and for a clear circadian rhythm in heart rate to emerge (i.e. average circadian fluctuation in heart rate of ~25 to 27 beats min−1 ). The presence or absence of this circadian rhythm in heart rate could inform researchers in the aquaculture industry whether or not specific farming routines induce unnecessary and prolonged stress. The elevations in heart rate caused by common farming practises such as crowding and transportation (e.g. heart rate increased by ~8 and 9 beats min−1 above what would normally be expected for that time of day, respectively) corresponded well with increases in plasma cortisol levels. Stressful farming practises or events (indicated by elevated plasma cortisol levels) such as air exposure during brailing and aquatic hypoxia triggered a hypoxic bradycardia until fish were released back into oxygenated water whereupon heart rate significantly increased to repay the accumulated oxygen debt. Repeated stress induced by multiple farming practises (i.e. combined stressors of crowding, brailing and transportation) clearly had a cumulative and long-lasting effect as heart rate peaked at ~25 beats min−1 above what would normally be expected for that time of day. Heart rate also remained significantly elevated by ~9 beats min−1 the following morning, suggesting that if rainbow trout need to be subjected to multiple stressors during consequtive days, it is recommended that sufficient time for recovery is provided between stressors. This study demonstrates that heart rate monitoring can be useful to assess stress levels of freely swimming fish in sea cages. Moreover, the use of implantable bio-loggers opens up a broad range of possible applications that will allow researchers to investigate the effects of environmental and/or anthropogenic stressors on the welfare of fish under conditions more realistic to the aquaculture industry.
养殖鱼的福利越来越受到消费者、生产者、利益集团和机构的关注。为了改善鱼类福利，有必要找到能够及早识别压力情况的指标，以便在有害影响发生之前进行干预。通过在自由游动的虹鳟鱼(Oncorhynchusmykiss)中使用心率生物记录仪，结合血浆皮质醇水平和一系列血液学和血液化学参数，我们评估了一系列常见水产养殖实践引起的应激反应的严重程度在收获前和收获期间。在手术、运输和在海笼中重新引入同种动物后，需要约4天的时间才能使心率稳定下来，并使心率出现清晰的昼夜节律(即心率的平均昼夜波动约25-27次/min)。心率昼夜节律的存在或不存在，可以告知水产养殖业的研究人员是否会引起不必要的长期压力。由拥挤和交通等常见的农作活动引起的心率升高。心率增加8次和9次/min-1，比一天中的那个时候通常预期的高，分别与血浆皮质醇水平的增加相对应。应激性养殖实践或事件(通过升高的血浆皮质醇水平来指示)，如烧烤过程中暴露于空气和水中缺氧，引发缺氧性心动过缓，直到鱼被释放到含氧水中，心率显著增加以偿还累积的氧气债务。多种耕作方式引起的重复压力(即 当心率在25次/分钟时达到峰值，比一天中正常情况下的心率高出约25次/分钟时，就明显产生了累积和持久的影响。第二天早上，心率也保持显著升高，每分钟约9次，这表明如果彩虹鳟鱼在接下来的几天里需要被多重压力作用，建议在压力作用之间提供足够的恢复时间。这项研究表明，心率监测可用于评估自由游动的鱼在海笼子中的应激水平。此外，使用可植入的生物记录器开辟了厂泛的可能应用范围，这将使研究人员能够研究环境和/或人为压力因素对鱼类福利的影响，这些条件更接近水产养殖业的现实情况。
Keywords: Stress Teleost Cardiovascular Hormones Telemetry
关键词:压力，辐鳍鱼纲，心血管，激素，遥测
