Anthropogenic development of floodplains and alteration to natural hydrological regimes have resulted in extensive loss of off-channel habitat. Interest has grown in restoring these habitats as an effective conservation strategy for numerous aquatic species. This study developed a process to reproducibly identify areas of former stream meanders to assist future off-channel restoration site selections. Three watersheds in Iowa and Minnesota where off-channel restorations are currently being conducted to aid the conservation of the Topeka Shiner (Notropis topeka) were selected as the study area. Floodplain depressions were identified with LiDAR-derived digital elevation models, and their morphologic and topographic characteristics were described. Classification tree models were developed to distinguish relic streams and oxbows from other landscape features. All models demonstrated a strong ability to distinguish between target and non-target features with area under the receiver operator curve (AUC) values ≥ 0.82 and correct classification rates ≥ 0.88. Solidity, concavity, and mean height above channel metrics were among the first splits in all trees. To compensate for the noise associated with the final model designation, features were ranked by their conditional probability. The results of this study will provide conservation managers with an improved process to identify candidate restoration sites.

The Topeka shiner Notropis topeka is native to Iowa, Kansas, Minnesota, Missouri, Nebraska, and South Dakota and has been federally listed as endangered since 1998. Our goals were to determine the present distribution and qualitative status of Topeka shiners throughout its current range in Iowa and characterize the extent of decline in relation to its historic distribution. We compared the current (2016-2017) distribution to distributions portrayed in three earlier time periods. In 2016-2017 Topeka shiners were found in 12 of 20 HUC10 watersheds where they occurred historically. Their status was classified as stable in 21% of the HUC10 watersheds, possibly stable in 25%, possibly recovering in 8%, at risk in 33%, and possibly extirpated in 13% of the watersheds. The increasing trend in percent decline evident in earlier time periods reversed, going from 68% in 2010-11 to 40% in the most recent surveys. Following decades of decline, the status of Topeka shiners in Iowa appears to be improving. One potential reason for the reversal in the distributional decline of Topeka shiners in Iowa is the increasing number of oxbow restorations. Until a standardized monitoring program is established for Iowa, periodic status assessments such as this will be necessary to chronicle progress toward conserving this endangered fish species.

Pacific Lamprey (Entosphenus tridentatus) is an anadromous fish that provides many ecosystem services and is important to Native American tribes who harvest them for cultural uses. The largest harvest of adult Pacific Lamprey in North America occurs at Willamette Falls (“WF”; Oregon, USA). Lamprey have experienced conservation problems for decades and harvest numbers at WF have plummeted ~33‐fold, from a maximum of >500,000 during 1946 to an average of ~16,000 per year during 1969 – 1999. Recent harvest has dropped to <6,000 lamprey per year during 2000 – 2021. However, existing conservation plans do not provide a historical perspective on the lamprey harvest at WF and the cumulative threats to them in the Willamette basin that likely caused harvest reductions. Land development, river impoundment, and water pollution coincided with significant decreases in lamprey harvest at WF. These (and other) threats have resulted in reduced habitat for larval lamprey in the basin, and thus a reduction in the pheromones they release (which attract adults). Conservation plans do not identify specific, basin‐wide goals to increase the number of lamprey in general and to provide more lamprey for harvest in particular. Therefore, in this review paper we provide a conservation perspective on three topics to increase and monitor lamprey abundance at WF. We (1) provide an up‐to‐date history of the lamprey harvest and its regulation at WF, (2) recommend addressing the lack of basin‐wide, lamprey‐specific passage and habitat restoration to improve the quantity and quality of lamprey spawning and rearing habitats, and (3) identify research needs for monitoring the population(s) of lamprey at WF. We conclude that lamprey‐specific passage and habitat restoration throughout the Willamette basin above WF is necessary to bolster abundance.

No abstract