DTU Aqua, Section for Aquaculture, Technical University of Denmark, North Sea Science Park, 9850 Hirtshals, Denmark
DTU Vet, Division of Diagnostics & Scientific Advice - Fish Diseases, Technical University of Denmark, 2800 Lyngby, Denmark.
J Exp Biol. 2018 Apr 12;221(Pt 8):jeb174623. doi: 10.1242/jeb.174623.
Salmonid individuals show a relatively high variability in the time required to abandon the gravel nest where they hatch, the so-called 'emergence time'. Different behavioral and physiological traits have been shown to be associated with emergence time in wild salmonids. In general, early- and late-emerging fish have traits resembling those of proactive and reactive stress coping styles, respectively. Proactive fish are considered to be more resilient to stress and probably to disease, so it was hypothesized that fish with different emergence times have different abilities to resist repeated episodes of stress without suffering deleterious effects on their welfare or health status. In this study, rainbow trout eyed eggs were hatched and larvae were fractionated according to their emergence time (early fraction: first 20% of fish to emerge; intermediate fraction: mid 20%; late fraction: last 20%). When the fish were 4 months old, they were exposed to a daily repeated stress protocol for 15 days. The next day, both naïve and repeatedly stressed fish were exposed to an acute stress challenge. Different plasma (cortisol, glucose, lactate) as well as CNS (serotonergic activity) stress markers were assessed to evaluate the stress resilience of the different groups. Furthermore, an intraperitoneal infection challenge with was carried out to assess disease resilience. Altogether, the results showed that fish from different fractions displayed differences in activation of the hypothalamus-pituitary-inter-renal axis, indicating a higher stress resilience in the fish with early emergence times. However, those differences were not reflected in the ability of the different fractions to grow and perform well in terms of growth, or in the ability to overcome infection with bacteria, which was similar for all the emergence fractions. This suggests that discriminating fish according to emergence time would probably have little effect in improving the performance and the welfare of farmed fish.
鲑鱼个体在放弃孵化它们的砾石巢的时间（即所谓的“出壳时间”）上表现出相对较高的可变性。已经证明，在野生鲑鱼中，不同的行为和生理特征与出壳时间有关。一般来说，早期和晚期出壳的鱼具有类似于积极和消极压力应对方式的特征。积极的鱼被认为对压力和疾病更有弹性，因此有人假设，具有不同出壳时间的鱼在没有对其福利或健康状况产生不利影响的情况下，抵抗反复应激发作的能力不同。在这项研究中，虹鳟鱼的眼斑卵被孵化，幼鱼根据出壳时间（早期部分：前 20%出壳的鱼；中期部分：中间 20%；晚期部分：后 20%）进行分离。当鱼长到 4 个月大时，它们被暴露在每天重复的应激协议中 15 天。第二天，未受应激的鱼和反复应激的鱼都暴露在急性应激挑战中。评估了不同的血浆（皮质醇、葡萄糖、乳酸）和中枢神经系统（5-羟色胺能活性）应激标志物，以评估不同组的应激弹性。此外，还进行了腹腔内感染挑战，用 进行感染。总的来说，结果表明，来自不同部分的鱼在下丘脑-垂体-肾上腺轴的激活方面表现出差异，表明早期出壳的鱼具有更高的应激弹性。然而，这些差异并没有反映在不同部分的鱼在生长方面的生长和表现能力上，也没有反映在克服细菌感染的能力上，所有出壳部分的鱼的表现能力都相似。这表明，根据出壳时间来区分鱼可能对提高养殖鱼的性能和福利没有什么影响。
