Invasive species can have varying and unpredictable reproductive potential among native and invaded populations or along invasion fronts, potentially contributing to invasion success. Understanding the reproductive potential (fecundity and egg size) of low-density, leading-edge populations is important to inform the management of Silver Carp Hypophthalmichthys molitrix and Bighead Carp H. nobilis populations in the upper Mississippi River. Therefore, we compared batch fecundity and eggs/g of ovary subsample (an egg-size surrogate) of Silver Carp (n = 145) and Bighead Carp (n = 75) along a decreasing invasion gradient from Pool 20 (higher abundance) to Pool 17 (lower abundance) in the Mississippi River. Bighead Carp in Pools 17 and 18 (461 ± 22 eggs/g [mean ± SE]) had significantly fewer eggs/g than those in Pools 19 and 20 (higher abundance; 483 ± 13 eggs/g). Log-transformed batch fecundity for Bighead Carp was positively correlated to log-transformed fish length, and batch fecundity was higher in Pools 17, 18, and 19 than in Pool 20. The eggs/g values for Silver Carp, which have been previously shown to be independent of fish length, were similar among all pools (94 ± 11 eggs/g). Batch fecundity for Silver Carp was significantly higher in Pools 17–19 than in Pool 20, where densities are higher. Our results suggest that at lower densities, Bighead Carp produce more, larger eggs and Silver Carp produce more eggs, which collectively could increase their reproductive success along invasion fronts.

中文翻译：

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入侵前沿鳙鱼繁殖潜能的可塑性

入侵物种在本地种群和入侵种群之间或沿着入侵前沿可能具有不同且不可预测的繁殖潜力，这可能有助于入侵成功。了解低密度、前沿种群的繁殖潜力（繁殖力和卵大小）对于管理密西西比河上游的鲢​​鱼和鳙鱼种群非常重要。因此，我们比较了鲢鱼 ( n  = 145) 和鳙鱼 ( n = 75) 沿密西西比河中从 20 号池（丰度较高）到 17 号池（丰度较低）的入侵梯度递减。17 号和 18 号池中的鳙鱼（461 ± 22 枚卵/克 [平均值 ± SE]）的卵数/克明显少于 19 号和 20 号池中的鳙鱼（丰度更高；483 ± 13 枚卵/克）。鳙鱼的对数转换批次繁殖力与对数转换的鱼长呈正相关，池 17、18 和 19 的批次繁殖力高于池 20。独立于鱼的长度，在所有池中相似 (94 ± 11 eggs/g)。池 17-19 的鲢鱼批次繁殖力明显高于密度较高的池 20。我们的结果表明，在较低的密度下，鳙鱼产更多、更大的卵，而鲢鱼产更多的卵，