Beginning in 2013, sites at the 128-m bottom depth contour were added to the sampling design of the annual Lake Michigan bottom trawl survey for prey fish, which has been conducted by the U.S. Geological Survey Great Lakes Science Center (GLSC) each fall since 1973, to better assess fish depth distributions in a changing ecosystem. The standard sampling design included bottom depths from 9 to 110 m, although the GLSC also sporadically conducted bottom trawl tows at the 128-m bottom depth contour during 1973–1988. Enactment of this new sampling design in 2013 revealed that mean biomass density of deepwater sculpins (Myoxocephalus thompsonii) at the 128-m depth exceeded the sum of mean biomass densities at shallower depths, indicating that the bulk of the deepwater sculpin population is residing in waters deeper than 110 m. Thus, our findings supported the hypothesis that the depth distribution of the deepwater sculpin population had shifted to deeper waters beginning in 2007, thereby explaining, at least in part, the marked decline in deepwater sculpin abundance since 2006 based on the standard sampling design. In contrast, our results did not support the hypothesis that the slimy sculpin (Cottus cognatus) population had shifted to deeper waters sometime after 2000. A portion of the burbot (Lota lota) population may have also shifted in depth distribution to waters deeper than 110 m after 2007, based on our results. Our findings have served as an impetus to further expand the range of depths sampled in our bottom trawl survey.

从 2013 年开始，美国地质调查局五大湖科学中心 (GLSC) 每年秋季在密歇根湖底拖网捕食鱼类调查的抽样设计中增加了 128 米底部深度等值线的地点。 1973 年，为了更好地评估不断变化的生态系统中的鱼类深度分布。标准抽样设计包括从 9 到 110 m 的底部深度，尽管 1973-1988 年期间 GLSC 也偶尔在 128 米的底部深度等值线处进行底部拖网拖网。2013 年实施的这一新采样设计揭示了深水杜鹃 ( Myoxocephalus thompsonii ) 的平均生物量密度) 在 128 米深度处超过了较浅深度处平均生物量密度的总和，这表明大部分深水杜鹃种群居住在 110 米以上的水域中。因此，我们的研究结果支持深水杜鹃种群的深度分布从 2007 年开始转移到更深水域的假设，从而至少部分解释了自 2006 年以来基于标准抽样设计的深水杜鹃丰度显着下降。相比之下，我们的结果不支持粘液杜鹃 ( Cottus cognatus ) 种群在 2000 年之后的某个时间转移到更深水域的假设。部分江豚 ( Lota lota) 根据我们的结果，在 2007 年之后，种群的深度分布也可能已经转移到深度超过 110 m 的水域。我们的发现推动了进一步扩大底拖网调查中采样的深度范围。