1. Horseshoe crab population sizes and trends have been previously studied using surveys of spawning adults and counts of eggs from surface (top 5 cm) and deep (20 cm) sediment samples. The correlations between surface and deep eggs were studied at two locations, Delaware Bay and Jamaica Bay, USA, and the correlations between egg densities and spawning counts were examined in Jamaica Bay.
2. There were significantly higher densities of eggs in deep sediments than in surface sediments. Only about 10% of the variability in surface egg density was explained by deep egg density. The numerical patterns between surface and deep eggs were similar between Delaware Bay and Jamaica Bay and across sampling dates.
3. Nearly 20% of the deep samples in the combined data from Delaware Bay and Jamaica Bay with an egg density of ≥100,000 m⁻² had zero surface eggs. Therefore, the use of surface eggs as an indicator of habitat suitability and spawning intensity may seriously underestimate the importance of a beach for spawning horseshoe crabs.
4. When paired with nearest survey date, Jamaica Bay spawning indices did not predict deep or surface egg densities. This may be related to a temporal mismatch between survey methods, the extreme overdispersion (patchiness) of the eggs, and/or the dynamics of egg distribution after exhumation.
5. Both egg density and spawning surveys can provide useful data on habitat suitability for horseshoe crabs and can offer excellent opportunities for student and citizen scientist engagement. More labour is required for egg surveys than spawning surveys because of the time required to sample, sort, and enumerate the eggs.

中文翻译：

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产卵马蹄蟹与卵密度之间的关系：对种群和栖息地适宜性评估的建议

1. 马蹄蟹种群大小和趋势以前曾使用产卵成虫的调查和来自表面（顶部 5 厘米）和深层（20 厘米）沉积物样本的卵数进行研究。在美国特拉华湾和牙买加湾两个地点研究了表面和深层鸡蛋之间的相关性，并在牙买加湾检查了鸡蛋密度和产卵计数之间的相关性。
2. 深层沉积物中的卵密度明显高于表层沉积物。只有大约 10% 的表面鸡蛋密度变异性可以用深层鸡蛋密度来解释。特拉华湾和牙买加湾以及采样日期之间的表层和深层鸡蛋之间的数值模式相似。
3. 在来自特拉华湾和牙买加湾的鸡蛋密度≥100,000 m ^-2的组合数据中，近 20% 的深层样本的表面鸡蛋为零。因此，使用地表卵作为栖息地适宜性和产卵强度的指标可能会严重低估海滩对马蹄蟹产卵的重要性。
4. 当与最近的调查日期配对时，牙买加湾产卵指数不能预测深层或表面的鸡蛋密度。这可能与调查方法之间的时间不匹配、鸡蛋的极度过度分散（不均匀）和/或挖掘后鸡蛋分布的动态有关。
5. 卵密度和产卵调查都可以提供有关马蹄蟹栖息地适宜性的有用数据，并且可以为学生和公民科学家的参与提供极好的机会。与产卵调查相比，鸡蛋调查需要更多的劳动力，因为对鸡蛋进行采样、分类和计数需要时间。