1. Conservation efforts have increased in response to global mussel declines, and effective surveys are a crucial step in assessing and monitoring mussel populations and in determining their conservation status. The burrowing behaviour of mussels can affect their detectability, and a better understanding of these behaviours would help to improve survey design and guidelines.
2. The burrowing depth of mussels may differ between seasons, habitat conditions, species, and individuals, and little is known about the burrowing behaviour of mussels in subtropical rivers.
3. Burrowing depth variation was examined and compared at three sites in the San Marcos, Guadalupe, and San Antonio river drainages in central Texas. In addition, laboratory experiments were used to determine whether observed differences between field sites and seasons could be linked to differences in substrate type and water temperature and to examine differences between species.
4. Seasonal variation in burrowing depth was found at all field sites, and water temperature was a significant factor for explaining variation in burrowing depth, but there was no clear relationship between burrowing depth and temperature in shorter term laboratory experiments, where individual variation was high and burrowing behaviour seemed to be solely a function of time.
5. Mussels burrowed significantly deeper in finer substrate (sand vs. gravel) in both field and laboratory experiments. Few significant differences between species were found in the field, but no differences were found in the laboratory experiments.
6. The results suggest that surveys may need to follow different guidelines depending on local conditions, such as substrate and water temperature. Surveys will be less efficient and may fail to detect larger proportions of populations in colder water temperatures. In addition, a larger proportion of burrowed mussels can be expected at sites with finer substrate, such as sand. Under these conditions, visual searches will not suffice, as a large part of the population or specific species may be overlooked.

中文翻译：

---

亚热带河流水体贻贝的穴居行为：对调查指南的启示

1. 随着全球贻贝数量的下降，保护工作有所增加，有效的调查是评估和监测贻贝种群并确定其保护状况的关键步骤。贻贝的穴居行为会影响其可检测性，对这些行为的更好理解将有助于改善调查设计和指南。
2. 贻贝的穴居深度在季节，栖息地条件，物种和个体之间可能有所不同，而对亚热带河流域贻贝的穴居行为知之甚少。
3. 在德克萨斯州中部的圣马科斯河，瓜达卢佩河和圣安东尼奥河三处的排水点，研究了挖深的变化并进行了比较。此外，还使用实验室实验来确定田间地点和季节之间观察到的差异是否可以与基质类型和水温的差异相关联，并检查物种之间的差异。
4. 在所有野外地点都发现洞穴深度的季节性变化，水温是解释洞穴深度变化的重要因素，但是在短期的实验室实验中，洞穴深度和温度之间没有明确的关系，因为个体间的变化很大且有洞穴现象。行为似乎仅仅是时间的函数。
5. 在野外和实验室实验中，贻贝在较细的基质（沙土与砾石）中的挖深明显更大。在田间几乎没有发现物种之间的显着差异，但是在实验室实验中没有发现差异。
6. 结果表明，根据当地条件（例如底物和水温），调查可能需要遵循不同的准则。调查的效率较低，可能无法在较冷的水温下发现较大比例的人口。此外，在底质较细的地方（例如沙子），预计会挖出更多的贻贝。在这种情况下，视觉搜索是不够的，因为可能会忽略大部分人口或特定物种。