Arctic Grayling Thymallus arcticus were once the dominant salmonid in the Big Manistee River, Michigan, but were extirpated from the watershed around 1900 and from the state of Michigan by 1936, likely due to overfishing, biotic interactions with introduced fish species, and habitat loss occurring largely around the turn of the 20th century. An interest in reestablishing native species by the Little River Band of Ottawa Indians led to an assessment of environmental conditions in a portion of the watershed encompassing 21 km of the Big Manistee River to determine whether suitable Arctic Grayling habitat remains. During summer in 2011–2013, abiotic habitat metrics, including water characteristics, substrate composition, channel profile, channel geomorphic unit, and stream velocity, were assessed across eight tributaries within the watershed. To assess whether abiotic conditions in these tributaries might support Arctic Grayling, the environmental conditions were compared to literature values from rivers where current or historical Arctic Grayling populations have been reported. This comparison, in conjunction with an assessment using a habitat suitability index for Arctic Grayling, indicated that important abiotic conditions were within ranges consistent with those associated with current and past populations of Arctic Grayling in North America. The results of this study will guide potential future reintroductions and indicate that suitable Arctic Grayling habitat does exist in portions of the Big Manistee River watershed, an assessment that will be further refined when coupled with biotic features of the environment. Received September 6, 2016; accepted February 28, 2017 Published online May 9, 2017
Restoration and enhancement of North American native freshwater fishes have for several decades been the subject of growing interest among fisheries biologists, natural resource managers, non‐governmental organizations, and the sportfishing public. The Little River Band of Ottawa Indians (LRBOI) and the Michigan Department of Natural Resources (MDNR), along with universities and public interest groups, are re‐examining the potential for re‐introduction of the Arctic Grayling Thymallus arcticus, a species that has been extirpated in Michigan since the 1930s. The Manistee River, Michigan, flows through the LRBOI's reservation and once supported the last known native Arctic Grayling population in the state's Lower Peninsula. The objectives of this study were to (1) identify potential biotic limitations, such as competition and/or predation from other fish species, that may interfere with Arctic Grayling re‐introduction in the Manistee River watershed; and (2) describe how instream habitat features currently relate to populations of potentially interacting species. Field surveys conducted during June–August 2012 in eight Manistee River tributaries identified suitable abiotic habitat for Arctic Grayling in 20 of 22 sampling reaches. However, high densities of Brown Trout Salmo trutta (a nonnative salmonid) may have influenced some of the habitat associations observed for Brook Trout Salvelinus fontinalis and Slimy Sculpin Cottus cognatus, two species that currently and historically co‐occurred in Arctic Grayling habitats. These two species were the most abundant in river reaches with Brown Trout densities less than 0.10 fish/m2. Based on habitat conditions and Brown Trout densities, there appear to be four distinct tributary regions for which management strategies could be developed to enhance the success of Arctic Grayling re‐introduction efforts. Re‐introduction of Arctic Grayling in the Manistee River watershed would support LRBOI and MDNR goals for native species restoration and would provide a unique and historic angling opportunity that has been absent in Michigan for nearly 100 years.
Natural sediment regimes of fluvial systems are variable and important to the biological and physical structures of rivers, yet watershed degradation has led to increased fine sediments entering and aggrading in rivers. As a result, quantifying substrate composition is important for targeting and monitoring restoration. Conventional methods for assessing substrate composition (e.g., pebble counts) can be time‐consuming and biased. We examined the use of the photogrammetric technique, structure‐from‐motion (SfM), as an alternative method by measuring streambed roughness. We expanded its application to submerged substrates in an artificial streambed to assess if roughness could predict pebble count substrate size percentiles across a range of manipulated levels of fine sediment aggradation. We then assessed the use of SfM in a free‐flowing river streambed. Results from the artificial streambed with coarse substrates (≤31% added fine sediment) revealed that repeated SfM models of the same streambed had a high degree of similarity (mean difference = 1 mm) and a strong relationship between SfM‐derived roughness and pebble counts (r2 > .95). This relationship was weaker (r2 < .66) and violated regression variance assumptions when substrates had up to 47% (55.7 kg) fines added, possibly due to SfM characterizing details not captured by pebble counts. In the natural streambed, there was a strong relationship between percentiles from the SfM model roughness and pebble count diameter (r2 = .96). SfM appears to be an efficient and appropriate alternative to direct substrate measurements across a broad range of streambed substrate compositions and thus a useful tool to model streambed morphology.
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