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Evaluating Methods to Describe Individual Substrate Size Classes in River Habitats

出版	Oregon Department of Fish and Wildlife, Conservation & Recovery Program, 2023
URL	http://books.google.com.hk/books?id=c3hr0AEACAAJ&hl=&source=gbs_api

註釋The Oregon Department of Fish and Wildlife's Aquatic Inventories Program has been developing methods that describe aquatic habitats across mainstem river environments that are generally not wadeable. During the summer of 2018 over the course of 16 survey days, we sampled over 65 kilometers of mainstem habitat in the Siletz River upstream of estuary and tidal influence. We identified seven distinct reaches and 389 independent habitat units. Sampling methods consisted of tributary stream techniques (wadeable) that rely on ocular observations and physical habitat measurements. We returned in the winter of 2019 and over the course of five days, resurveyed the same bounds of each defined reach using a 1199CI HD Humminbird side-scan sonar that was set to record continuous imagery. The images were visually assessed within the bounds of individual habitat units to describe streambed features using a modified Wolman Pebble Count. We summarized the results of each method at the reach scale to describe the efficiency and effectiveness of ocular estimation versus imagery from a side-scan sonar and the accuracy of streambed features captured from sonar imagery. We found that using a sonar to describe substrate size classes was a more efficient way to collect field data, but after including data processing and analysis time, both methods were similar in overall time. To assess the accuracy of sonar imaged streambed features, we used a simple linear regression to assess whether percent substrate from ocular estimates differed from sonar imagery. Individual substrate class adjusted R2 results across reaches ranged from 0.64 to 0.95 and p-values were all less than 0.05. When substrate classes were modeled within reaches, adjusted R2 results ranged from 0.50 to 0.99 and p-values were less than 0.05 in four out of the seven reaches. These findings suggest that the use of a side-scan sonar within river habitats describes individual substrate types consistent with results of ocular estimation with less effort in the field. The results of this report were used to create a key for describing individual substrate types when viewed on sonar imagery to improve future mainstem river survey accuracy and efficiency. We hope these methods will help integrate mainstem river habitat information with current data from tributary streams to give ODFW a complete picture of population-scale habitat availability and condition.