VERIFYING THE REPRODUCTIVE POTENTIAL OF TRIPLOID FARM ATLANTIC SALMON

大西洋鲑鱼是自然生态系统和人类社区的关键物种，但野生种群已下降约90%，达到历史最低水平。这种崩溃的原因之一是鲑鱼养殖，世界上增长最快的食物供应形式。地球上至少有95%的萨尔莫萨拉鱼现在都在农场饲养，但每年仍有成千上万的萨尔莫鱼逃到野外。这些逃脱者可以生存，分散数百英里，进入野生产卵种群，并最终繁殖。养殖鱼与野生鲑鱼不同，自20世纪70年代以来一直被强烈驯化，以便在笼子里快速生长和饲料转化。如果它们与野生鲑鱼繁殖，养殖鱼类会侵蚀和破坏野生适应的基因库，通过丧失重要的当地适应特性，如抗病性，物候和生长，造成生态不稳定。BBSRC-NERC称水产养殖的这种影响是“大西洋鲑鱼养殖中最具争议的当代问题”。“在一些野生鲑鱼产卵种群中发现了大量的农场鱼类，来自大西洋彼岸的证据表明，农场附近的河流野生鲑鱼数量下降最大，每一代下降约50%。我们建议科学地测试和验证一种解决农场x野生繁殖问题的潜在解决方案：三倍体绝育。通过施加压力使第二组母体染色体保留，对刚刚受精的鱼卵进行三倍体诱导，产生的鱼可能是生殖的死胡同。三倍体通常用于鳟鱼养殖，以防止放养的鱼类渗入非本地生态系统。虽然三倍体鱼尝试产卵，但大多数物种的配子发生通常被破坏，雌性通常不育。然而，三倍体诱导不一定使雄性不育。对欧鲽和丁鲷的详细研究表明，三倍体雄性产生的精子可以完全活动，几乎和二倍体的精子一样有效地使单倍体卵子受精。因此，在我们能够确信三倍体雄性对野生鲑鱼产卵种群不构成生殖威胁之前，必须在一个物种的两性中充分验证三倍体，包括在精子竞争下。即使三倍体不能产生可存活的后代，大量的逃逸也可能通过“占据”卵子和使野生雌性的生殖潜力绝育而影响野生鱼类。因此，我们将全面评估三倍体养殖大西洋鲑鱼的生殖功能，从而证明其生物安全性。我们知道，雄性三倍体鲑鱼表现出正常的繁殖行为，可以诱导雌性鲑鱼产卵，并释放鱼精。然而，关于三倍体鲑鱼的受精和繁殖潜力的信息还很缺乏。唯一一项关于三倍体成年大西洋鲑鱼繁殖的科学研究只检查了一条雄性鲑鱼，结果表明它是有生育能力的，但它的后代存活率很低。因此，我们将对三倍体男性生育力进行详细的科学试验，使用已建立的技术，在一系列相关条件下测量精子和卵子的性能，以测定三倍体生殖功能。我们将测试三倍体雄性在精子竞争中的表现（包括体外和竞争雄性之间），因为鲑鱼的交配模式是自然滥交的。我们的实验将产生有意义的结果，这将允许一个完整和详细的评估三倍体农场鲑鱼的繁殖影响时，他们逃到野生产卵种群。鲑鱼养殖业现在能够接受三倍体，因为研究表明，在正确的农场和饮食条件下，三倍体可以表现得和二倍体一样好。三倍体鲑鱼刚刚开始市场试验，所以我们的项目是完美的时间来评估这个解决方案，以农场x野生渐渗。我们将通过向公众，政策制定者，非政府组织和鲑鱼养殖者传播研究结果，确保我们的研究产生影响。

The Atlantic salmon is a keystone species for natural ecosystems and human communities, but wild stocks have declined by ~90% to their lowest recorded levels. One cause of this collapse is salmon farming, the world's fastest growing form of food provision. At least 95% of Salmo salar on our planet are now reared in farms, but hundreds-of-thousands escape each year to the wild. These escapees can survive, disperse hundreds of miles, enter wild spawning populations, and ultimately reproduce. Farm fish are different to wild salmon, having been intensely domesticated since the 1970s for rapid growth and feed conversion in cages. If they reproduce with wild salmon, farm fish erode and disrupt wild-adapted gene pools, causing ecological destabilisation through loss of important locally-adapted traits like disease resistance, phenology and growth. This impact from aquaculture is described by the BBSRC-NERC call as 'the most controversial contemporary issue in Atlantic salmon farming.' Big numbers of farm fish have been found in some wild salmon spawning populations, and evidence from across the Atlantic shows that rivers near farms have had the greatest wild salmon declines, by about 50% each generation.We propose to scientifically test and verify a potential solution to the problem of farm x wild reproduction: triploid sterilisation. Triploid induction of just-fertilised fish eggs, by applying pressure to cause retention of the second set of maternal chromosomes, produces fish that are likely to be reproductive dead-ends. Triploidy is routinely applied in trout farming, to prevent stocked fish from introgressing non-native ecosystems. Although triploid fish try to spawn, gametogenesis in most species is usually disrupted and females are often sterile. However, triploid induction does not necessarily sterilise males. Detailed studies on plaice and tench reveal that triploid males produce fully motile sperm that can fertilise haploid eggs almost as effectively as sperm from diploid equivalents. It is therefore essential that triploidy is fully verified in both sexes of a species, including under sperm competition, before we can be confident that triploid males pose no reproductive threat to wild salmon spawning populations. Even if triploids cannot produce viable offspring, large numbers of escapes could impact on wild fish by 'occupying' eggs and sterilising the reproductive potential of wild females. We will therefore fully evaluate the reproductive function of triploid farm Atlantic salmon, thereby proving biosecurity.We know that male triploid salmon show normal breeding behaviour, can induce females to spawn, and release milt. However, information on the fertilisation and reproductive potential of triploid salmon is lacking. The only scientific study of triploid adult Atlantic salmon reproduction examined just a single male, showing that it was fertile but its offspring had poor survival. We will therefore conduct detailed scientific trials on triploid male fertility, using established techniques that measure sperm and egg performance in a range of relevant conditions to assay triploid reproductive function. We will trial the performance of triploid males in sperm competitions (both in vitro and between competing males), because the salmon mating pattern is naturally promiscuous. Our experiments will generate meaningful results that will allow a full and detailed assessment of the reproductive impact of triploid farm salmon when they escape into wild spawning populations. The salmon farming industry is now in a position to embrace triploidy, since research reveals that triploids can perform as well as diploids under the right farm and diet conditions. Triploid salmon are just starting market trials, so our project is perfectly timed to assess this solution to farm x wild introgression. We will ensure that our research achieves impact, by disseminating findings to the public, policy-makers, NGOs, and salmon farmers.