Impact of CO2 and salinity in aquaculture on physiology, growth and health of coho salmon

BBSRC: William Davison: BB/M009122/1（1921484）截至2017年，鲑鱼水产养殖每年价值220亿美元，其中英国贡献14亿美元，加拿大贡献9.88亿美元。然而，尽管联合国指示指出需要在2050年之前将产量翻一番，但公众的负面看法阻碍了增长。典型的鲑鱼养殖结合了陆地淡水孵化场和海栏养殖系统。虽然需要较低的维护成本，但海栏的使用增加了养殖鱼类患病的风险，并与野生鲑鱼种群中寄生虫过多有关，导致本地种群数量严重下降。因此，有必要缩短海洋生长阶段的持续时间，或完全过渡到陆地农场系统（称为循环水养殖系统- RAS），这在很大程度上避免了许多这些问题。然而，到目前为止，RAS养殖场的发展受到限制，因为与围栏相比，RAS的生长速度较慢，而且RAS的规模需要将鱼维持在收获尺寸。生长减少和不利的健康结果在很大程度上归因于与水化学有关的各种问题（例如CO2、盐度、pH等）。理查兹教授和布劳纳教授的实验室先前的研究确定了在RAS中生长银鲑的最佳盐度。研究发现，在与血液近似等渗的盐度下生长的鲑鱼，与在淡水到全浓海水等其他盐度下生长的鱼类相比，具有最快的生长速度和最低的食物转化率。这被假设为减少了渗透调节的能量消耗。然而，这项研究是在相对较低的ph值下进行的，这表明水中的呼吸二氧化碳积聚，这是一个在RAS中广泛存在的问题。由于渗透调节和鱼类的酸碱平衡之间的联系，任何环境二氧化碳的减少都可能通过减少在酸碱平衡上的能量消耗而有益于鱼类的健康和生长，因此与高二氧化碳环境下生长的鱼类相比，它们的生长速度更快。在这里，我们计划让鱼适应淡水（1 ppt）或等渗水（10 ppt），然后将它们暴露在大气中的二氧化碳水平或养鱼场中发现的升高的二氧化碳水平中。然后我们希望测量各种生理参数，如生长、酸碱平衡和免疫功能。然后，这些信息将用于确定最佳的水化学条件，以最大限度地提高水产养殖中鲑鱼的生长。

BBSRC : William Davison : BB/M009122/1 (1921484)As of 2017 salmonid aquaculture was worth $22 billion USD per year with the UK contributing $1.4 billion USD and Canada responsible for $988 million USD. However, despite UN directives stating a need to double production by 2050, growth is hampered by negative public perception. Typically salmonid aquaculture combines land-based freshwater hatcheries with sea-pen rearing systems. While requiring lower maintenance costs the use of sea-pens increases risk of disease in farmed fish and has been linked with parasite overspill into wild populations of salmon causing serious declines in native populations. As such there is a demand to reduce the duration of the marine grow out phase, or transition entirely to land based farm systems (referred to as recirculating aquaculture systems - RAS) which largely avoid many of these problems. However, thus far development of RAS farms has been limited due to reduced growth observed in RAS compared to pens, and the scale of RAS required to maintain fish up to harvest size. Reduced growth and adverse health outcomes have largely been attributed to various issues relating to water chemistry (e.g. CO2, salinity, pH etc.). Previous research from Prof. Richards and Prof Brauner's labs identified an optimal salinity for growing Coho salmon within RAS. Salmon grown at a salinity approximately isosmotic to blood were found to have the fastest growth rate and lowest food conversion ratio compare to fish grown at other salinities ranging from freshwater to full strength seawater. This has been hypothesised to be reduced energy expenditure for osmoregulation. However, that study was conducted at relatively low pHs indicative of a build-up of respiratory CO2 in the water, a problem that has been characterised extensively in RAS. Due to the link between osmoregulation and acid-base balance in fish, any reduction in environmental CO2 may therefore benefit fish health and growth by reducing energy expenditure on acid-base balance and therefore allow increased growth compared to fish grown at high CO2.Here we plan to acclimate fish to either freshwater (1 ppt) or isosmotic water (10 ppt) and then expose them to either atmospheric levels of CO2 or to the elevated levels of CO2 found within fish farms. We then hope to measure a variety of physiological parameters such as growth, acid-base balance and immune function. This information will then be used to determine optimal water chemistry conditions to maximise growth of salmon in aquaculture.