1. The crucian carp Carassius carassius, a cyprinid fish characteristic of small ponds, is in decline throughout most of its European range, including in England where it is currently thought to be non‐native.
2. The present study, undertaken by the Norfolk Crucian Project, reports on reductions in pond populations of crucian carp in Norfolk, eastern England as well as the success of recent introduction/re‐introduction efforts in terms of crucian survival, recruitment and growth over the last 10 years.
3. A 72% decline in crucian carp distribution was observed between the 1950s–1980s and the 2010s. Of 18 crucian carp introductions/re‐introductions to restored and suitable existing ponds, 17 were successful in terms of survival, increasing the number of current crucian sites in Norfolk by 37%. Recruitment of young crucian carp was demonstrated for 12 of the 18 stocked ponds, with apparent elevated juvenile growth relative to other English and European populations.
4. Delays in, or a lack of, crucian recruitment in some ponds appeared to result from the presence of other fish species (especially threespine stickleback Gasterosteus aculeatus) with predation and interspecific competition possible contributory factors.
5. This study shows that, through combinations of pond rehabilitation and stocking, it has been possible to achieve a substantial recovery of crucian carp populations in the study region. Although the crucian carp is currently presumed to be non‐native within England, given other scientific studies that show a lack of adverse impacts of this species on native biota, and because it is greatly threatened in its native range, the call is sounded for more crucian carp conservation projects in other parts of England as well as in Europe more generally.

中文翻译：

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鱼Car体的恢复：英国保护项目的方法和早期结果

1. European鱼Car鱼（Carassius carassius）是一种小型池塘的鲤科鱼类，在整个欧洲大部分地区（包括目前被认为是非本土的英格兰）都在下降。
2. 这项由诺福克Cru鱼项目进行的研究报告了英格兰东部诺福克pond鱼池塘种群的减少，以及最近一次引进/再引入工作在recruitment鱼生存，招募和生长方面的成功经验。 10年。
3. 在1950年代至1980年代与2010年代之间，cru鱼的分布下降了72％。在18个cru鱼的引入/重新引入恢复和合适的现有池塘中，有17个在成活率方面取得了成功，使诺福克郡目前的cru鱼养殖场数增加了37％。在18个放养的池塘中，有12个显示了cru鱼的招募，与其他英国和欧洲种群相比，幼鱼的生长明显增加。
4. 某些池塘中cru鱼募集的延迟或缺乏，似乎是由于存在其他鱼类（尤其是三脊刺背le Gasterosteus aculeatus）造成的，而这种鱼类具有掠食性和种间竞争可能是造成这种情况的因素。
5. 这项研究表明，通过池塘修复和放养相结合，有可能使研究区域的recovery鱼种群大量恢复。尽管currently鱼目前在英国被认为是非本地的，但鉴于其他科学研究表明该on鱼对本地生物群没有不利影响，并且由于it鱼在其本地范围受到极大威胁，因此人们呼吁更多英格兰其他地区以及整个欧洲的鱼保护项目。