Pisces Conservation Ltd., IRC House, The Square, Pennington, Lymington, Hants. SO41 8G, UK.
Mar Pollut Bull. 2010;61(1-3):100-14. doi: 10.1016/j.marpolbul.2009.12.017. Epub 2010 Jan 13.
The species of fish and macro-crustacean living within the Severn Estuary are reviewed. The fish community is notably species rich and exceeds 100 species in total for the estuary. Standardised long-term sampling at Hinkley Point in Bridgwater Bay gives a total complement of 83 for a single locality and this number is increasing by about one new species every two years. Most of these new species are moving in from centres of population lying to the south of the estuary. Almost all species of fish and macro-crustacean living within the estuary undertake regular migrations so that they tend to move seasonally in waves up and down the estuary. For fish, both species richness and the total abundance reach a maximum in late summer and autumn. The timing of this peak varies between the upper and lower estuary. This seasonal maximum is primarily caused by the arrival of the new recruits which use the estuary as a nursery. In contrast, crustaceans tend to be at their most diverse and abundant in early to mid summer. Using a 30-year time series of fish and crustacean abundance collected at Hinkley Point it is shown that major changes in the structure of the community are now underway and there are considerable recent changes in the abundance. However, some abundant species, including sand goby, Pomatoschistus spp., whiting, Merlangius merlangus and sprat, Sprattus sprattus, the three most abundant species in the estuary, have shown no long-term trend. At present, approximately 20% of the fish and macro-crustaceans observed in Bridgwater Bay are undergoing rapid, typically exponential, change in abundance. For a numerically abundant, diverse, fauna composed of approximately 90 species such levels of change are unexpected and suggest that the system is presently far from equilibrium. In some cases, the observed changes can be related to recent warming and the North Atlantic Oscillation. The overall increase in fish abundance observed may reflect a general improvement in water quality and a reduction in other anthropogenic impacts such as mortality in cooling-water intakes. The potential impacts of tidal power generation in the Severn Estuary are reviewed. There is considerable potential for any major installation to impact the fish and crustacean populations as they migrate and also alter the nature of the habitat resulting in changes in community composition. A particular difficulty in predicting the future impact of harnessing tidal energy is that the present community is already changing rapidly. The ability of fish and crustaceans to pass through the turbines unharmed will be a key issue in an assessment of the impact of tidal power generation.
对生活在塞文河口的鱼类和大型甲壳类动物的物种进行了回顾。河口的鱼类群落物种丰富，总数超过 100 种。在布里斯托尔湾的欣克利角进行的标准化长期采样显示，单一地点的总补充量为 83 种，并且每隔两年就会增加一种新物种。这些新物种中的大多数都是从河口以南的人口中心迁移过来的。几乎所有生活在河口的鱼类和大型甲壳类动物都进行定期迁徙，因此它们往往会季节性地在河口上下游移动。对于鱼类来说，物种丰富度和总丰度在夏末和秋季达到最大值。这个高峰期的时间在上游和下游河口之间有所不同。这个季节性高峰主要是由新的幼鱼到达造成的，它们将河口用作育雏地。相比之下，甲壳类动物在初夏到中期最为多样和丰富。利用欣克利角收集的 30 年鱼类和甲壳类动物丰度时间序列，表明现在正在进行群落结构的重大变化，并且丰度最近发生了很大变化。然而，一些丰富的物种，包括沙鲷、Pomatoschistus spp.、鲷鱼、Merlangius merlangus 和鲱鱼、Sprattus sprattus，是河口最丰富的三种物种，它们没有长期趋势。目前，在布里斯托尔湾观察到的大约 20%的鱼类和大型甲壳类动物的数量正在迅速增加，通常呈指数增长。对于一个由大约 90 种丰富多样的动物组成的群落来说，这样的变化水平是出乎意料的，这表明该系统目前远未达到平衡。在某些情况下，观察到的变化可以与最近的变暖以及北大西洋涛动有关。观察到的鱼类数量增加可能反映了水质的普遍改善，以及冷却水进水口等其他人为影响的减少，如死亡率。对塞文河口潮汐能发电的潜在影响进行了回顾。任何大型设施在鱼类和甲壳类动物洄游时都有可能对其产生影响，并且还会改变栖息地的性质，从而导致群落组成的变化。在预测利用潮汐能的未来影响时，一个特别困难的问题是，目前的群落已经在迅速变化。鱼类和甲壳类动物是否能够安然无恙地通过涡轮机将是评估潮汐能发电影响的关键问题。
