Distribution, Abundance, and Coexistence of Two Species of Sucker (Catostomus) in Sagehen Creek, California and Their Status in the Western Lahontan Basin

MASTERS THESIS: In 1982 (the researcher) initiated a study to examine any differences in the distribution and abundance between mountain and Tahoe sucker and to determine how these two similar species coexist in Sagehen Creek. Early in the study (she) noticed that the relative abundance of these species had shifted dramatically when compared to earlier reports. IN addition to Sagehen Creek, four nearby streams were surveyed in 1982 to locate both species. At all sites mountain sucker were either absent or rare and only 10 individuals were eventually collected. The apparent scarcity of mountain sucker was perplexing; early records had shown mountain sucker were not only present and abundant but were also more numerous than the associated Tahoe sucker at these sites. (She) expanded the study to address the following objectives: 1. To determine if significant shifts in the relative abundance of suckers have occurred in Sagehen Creek since early surveys, 2. To determine if similar shifts have occurred elsewhere, 3. To distinguish differences in the distribution and abundance between the two species of sucker in Sagehen Creek where both species still exist, and 4. To determine how mountain and Tahoe sucker manage to coexist in a relatively small segment of stream.硕士学位论文：1982年，该女性研究者启动了一项研究，旨在探究山地吸口鱼（mountain sucker）与塔霍吸口鱼（Tahoe sucker）的分布与丰度差异，并阐明这两种近缘物种如何在赛真溪（Sagehen Creek）中共存。研究初期，该研究者注意到，相较于早期文献报道，这两种鱼类的相对丰度已发生显著变化。除赛真溪外，研究团队于1982年对周边四条溪流开展了调查，以搜寻这两个物种的踪迹。所有调查点位中，山地吸口鱼均未出现或极为稀少，最终仅采集到10尾个体。山地吸口鱼的显著稀缺性令人困惑：早期记录显示，在这些点位，山地吸口鱼不仅种群存续且数量丰沛，甚至比伴生的塔霍吸口鱼更为繁多。该研究者遂扩大研究范围，以达成以下研究目标：1. 明确自早期调查以来，赛真溪内吸口鱼的相对丰度是否已发生显著变化；2. 明确其他区域是否也出现了类似的丰度偏移；3. 在两种吸口鱼均存活的赛真溪河段，厘清二者在分布与丰度上的差异；4. 阐明山地吸口鱼与塔霍吸口鱼如何在长度相对有限的溪流片段中共存。